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  <front>
    <journal-meta><journal-id journal-id-type="publisher">HESS</journal-id><journal-title-group>
    <journal-title>Hydrology and Earth System Sciences</journal-title>
    <abbrev-journal-title abbrev-type="publisher">HESS</abbrev-journal-title><abbrev-journal-title abbrev-type="nlm-ta">Hydrol. Earth Syst. Sci.</abbrev-journal-title>
  </journal-title-group><issn pub-type="epub">1607-7938</issn><publisher>
    <publisher-name>Copernicus Publications</publisher-name>
    <publisher-loc>Göttingen, Germany</publisher-loc>
  </publisher></journal-meta>
    <article-meta>
      <article-id pub-id-type="doi">10.5194/hess-22-5901-2018</article-id><title-group><article-title>Do users benefit from additional information in support of operational drought management decisions in the Ebro basin?</article-title><alt-title>Benefit of additional information for drought management
decisions</alt-title>
      </title-group><?xmltex \runningtitle{Benefit of additional information for drought management
decisions}?><?xmltex \runningauthor{C. Lin\'{e}s et al.}?>
      <contrib-group>
        <contrib contrib-type="author" corresp="yes" rid="aff1">
          <name><surname>Linés</surname><given-names>Clara</given-names></name>
          <email>c.lines@un-ihe.org</email>
        </contrib>
        <contrib contrib-type="author" corresp="no" rid="aff2">
          <name><surname>Iglesias</surname><given-names>Ana</given-names></name>
          
        <ext-link>https://orcid.org/0000-0002-3183-6658</ext-link></contrib>
        <contrib contrib-type="author" corresp="no" rid="aff3">
          <name><surname>Garrote</surname><given-names>Luis</given-names></name>
          
        <ext-link>https://orcid.org/0000-0001-9087-3638</ext-link></contrib>
        <contrib contrib-type="author" corresp="no" rid="aff2">
          <name><surname>Sotés</surname><given-names>Vicente</given-names></name>
          
        </contrib>
        <contrib contrib-type="author" corresp="no" rid="aff1 aff4">
          <name><surname>Werner</surname><given-names>Micha</given-names></name>
          
        <ext-link>https://orcid.org/0000-0003-4198-5638</ext-link></contrib>
        <aff id="aff1"><label>1</label><institution>Department of Water Science and Engineering, IHE-Delft, Delft, the Netherlands</institution>
        </aff>
        <aff id="aff2"><label>2</label><institution>Department of Agricultural Economics and Social Sciences, Technical University of Madrid, Madrid, Spain</institution>
        </aff>
        <aff id="aff3"><label>3</label><institution>Department of Civil Engineering: Hydraulics, Energy and Environment, Technical University of Madrid, Madrid, Spain</institution>
        </aff>
        <aff id="aff4"><label>4</label><institution>Department of Plant Production, Technical University of Madrid, Madrid, Spain</institution>
        </aff>
      </contrib-group>
      <author-notes><corresp id="corr1">Clara Linés (c.lines@un-ihe.org)</corresp></author-notes><pub-date><day>14</day><month>November</month><year>2018</year></pub-date>
      
      <volume>22</volume>
      <issue>11</issue>
      <fpage>5901</fpage><lpage>5917</lpage>
      <history>
        <date date-type="received"><day>2</day><month>May</month><year>2018</year></date>
           <date date-type="rev-request"><day>9</day><month>May</month><year>2018</year></date>
           <date date-type="rev-recd"><day>27</day><month>October</month><year>2018</year></date>
           <date date-type="accepted"><day>29</day><month>October</month><year>2018</year></date>
      </history>
      <permissions>
        
        
      <license license-type="open-access"><license-p>This work is licensed under the Creative Commons Attribution 4.0 International License. To view a copy of this licence, visit <ext-link ext-link-type="uri" xlink:href="https://creativecommons.org/licenses/by/4.0/">https://creativecommons.org/licenses/by/4.0/</ext-link></license-p></license></permissions><self-uri xlink:href="https://hess.copernicus.org/articles/22/5901/2018/hess-22-5901-2018.html">This article is available from https://hess.copernicus.org/articles/22/5901/2018/hess-22-5901-2018.html</self-uri><self-uri xlink:href="https://hess.copernicus.org/articles/22/5901/2018/hess-22-5901-2018.pdf">The full text article is available as a PDF file from https://hess.copernicus.org/articles/22/5901/2018/hess-22-5901-2018.pdf</self-uri>
      <abstract>
    <p id="d1e137">We follow a user-based approach to examine how information supports
operational drought management decisions in the Ebro basin and how these can
benefit from additional information such as from remote sensing data. First
we consulted decision-makers at basin, irrigation district and farmer scale
to investigate the drought-related decisions they make and the information
they use to support their decisions. This allowed us to identify the courses
of action available to the farmers and water managers, and to analyse their
choices as a function of the information they have available to them. Based
on the findings of the consultation, a decision model representing the
interrelated decisions of the irrigation association and the farmers was
built. The purpose of the model is to quantify the effect of additional
information on the decisions made. The modelled decisions, which consider the
allocation of water, are determined by the expected availability of water
during the irrigation season. This is currently informed primarily by
observed reservoir level data. The decision model was then extended to
include additional information on snow cover from remote sensing. The
additional information was found to contribute to better decisions in the
simulation and ultimately higher benefits for the farmers. However, the ratio
between the cost of planting and the market value of the crop proved to be a
critical aspect in determining the best course of action to be taken and the
value of the (additional) information. Risk-averse farmers were found to
benefit least from the additional information, while less risk-averse farmers
stand to benefit most as the additional information helps them take better
informed decisions when weighing their options.</p>
  </abstract>
    </article-meta>
  </front>
<body>
      

      <?xmltex \hack{\newpage}?>
<sec id="Ch1.S1" sec-type="intro">
  <title>Introduction</title>
      <p id="d1e149">Water managers and farmers regularly make decisions on how to make the most of the
available water resources. Information on the availability and variability of
the resource is essential to allow these decision-makers to choose among the
actions available to them, especially as water becomes scarce, for example
during drought events. Improved information on the availability of water can
then potentially lead to a more effective management and can therefore
contribute to the mitigation of the impacts of drought events.</p>
      <p id="d1e152">In situ meteorological and hydrological measurement networks have long served
to inform these decisions, often providing accurate water resources
observations at high temporal resolution. In addition, the potential of Earth
observation (EO) from satellites to support water management has also been
widely recognised <xref ref-type="bibr" rid="bib1.bibx11 bib1.bibx13" id="paren.1"/>. The
availability and quality of EO datasets has continuously improved during recent decades, providing an increasingly relevant source of globally
consistent data that can be used to complement in situ data.</p>
      <p id="d1e158">However, the increased quality and availability of information does not
necessarily translate directly into benefits due to better decisions. How the
information is used and distributed also plays a critical role
<xref ref-type="bibr" rid="bib1.bibx41" id="paren.2"/>. It is the capacity of the user of information to
change the course of action as a result of new information being available to
them that largely determines the value of that new information
<xref ref-type="bibr" rid="bib1.bibx24" id="paren.3"/>.</p>
      <?pagebreak page5902?><p id="d1e167"><?xmltex \hack{\newpage}?>A good understanding of the role that information plays or could play in
supporting decisions, as well as the resulting benefits, is useful both for
the users and the data providers and helps improve the connection between
these two groups. <xref ref-type="bibr" rid="bib1.bibx30" id="text.4"/> present a series of analyses on
the contribution of EO datasets in addressing environmental problems from a
policy point of view and conclude recommending more stakeholder-oriented
studies of the value of these data and the quantification of the benefits of
this data through comparisons with current tools. The assessment of the role
and impacts of remote sensing products is expected to help in fully achieving
the potential of the products, maximising the socio-economic and environmental
benefits, and contributing to justify the investment in developing and
improving the products.</p>
      <p id="d1e175">An example of a stakeholder-oriented approach to assess the value of
satellite-based information in support of water management is presented by
<xref ref-type="bibr" rid="bib1.bibx2" id="text.5"/>. They develop a framework to measure the benefits of
satellite-based observations. The framework, which is based on Bayesian
decision theory and expert consultation, is applied to water quality
management in the North Sea <xref ref-type="bibr" rid="bib1.bibx2" id="paren.6"/> and to coral reef
protection <xref ref-type="bibr" rid="bib1.bibx3" id="paren.7"/>.</p>
      <p id="d1e187"><xref ref-type="bibr" rid="bib1.bibx24" id="text.8"/> reviews studies on the value of information in Earth
science applications, classifying the techniques that are used or that are
potentially useful into three groups: studies that measure the value by gains
in output or productivity; studies based on hedonic pricing, in which the
value is inferred from models based on wages and housing prices; and studies
that consider the willingness to pay. The main example of the first group of
techniques are the studies that relate farm profits and weather information,
especially in relation to weather forecasts. Early studies explore simplified
cases of decisions such as whether to plant or to leave cultivable land
fallow <xref ref-type="bibr" rid="bib1.bibx4" id="paren.9"/>, or on what crop to plant
<xref ref-type="bibr" rid="bib1.bibx40" id="paren.10"/>.</p>
      <p id="d1e198">From the user's perspectives, the optimal choice for a decision to be made is
to take the course of action that results in the highest expected utility,
which is defined as the weighted sum of the outcomes of the possible actions
and the probability of a given state of nature such as a reduction in the
available water resource. Clearly this includes undesirable outcomes, where
an action is taken based on an expected state of nature that does not
materialise. Additional information is then considered to have value if it
can improve the advance knowledge on the probabilities of the different
possible states of nature occurring, thus allowing the user to make a better
informed decision. A commonly used approach to evaluate the value of advance
information, such as information provided through advanced warning, is the
cost–loss framework <xref ref-type="bibr" rid="bib1.bibx42 bib1.bibx28 bib1.bibx35 bib1.bibx39" id="paren.11"/>. Often used to evaluate the potential benefit of (flood)
warnings, this is the ratio of the costs of taking protective action to the
losses incurred if that action is not taken. This framework has also been
extended to water resources management decisions, such as in
<xref ref-type="bibr" rid="bib1.bibx33" id="text.12"/>, who analyse the value of climate projections to
decisions on applying measures to reduce water demand in the Ebro basin. The
cost–loss framework does assume a strictly rational behaviour of users in
weighing the costs and probability of losses, which is a limitation as
different users may make different decisions depending on their levels of
risk averseness. This can, however, be incorporated through a function of
risk aversion <xref ref-type="bibr" rid="bib1.bibx33 bib1.bibx26" id="paren.13"/>.</p>
      <p id="d1e210">The aim of our paper is to explore the value of information to drought
management decisions through a stakeholder-oriented analysis. We examine the
operational decisions that stakeholders such as farmers and reservoir
operators take within the context of water resources allocation during
droughts. The proposed framework first uses interviews to identify the
decisions stakeholders make, as well as the information they use to inform
those decisions. A decision model is then established and applied to emulate
the decision process and how additional information contributes to improving
the decisions made. Our work contributes to the developing field of
socio-hydrology <xref ref-type="bibr" rid="bib1.bibx36" id="paren.14"/> in that it explores the
co-evolution of the availability of water and the decisions made by humans
(in this case farmer and irrigation operators). While the emerging field of
socio-hydrology is broad <xref ref-type="bibr" rid="bib1.bibx27" id="paren.15"><named-content content-type="pre">see also the review of the first biennial of
the proclaimed IAHS Panta Rhei decade;</named-content></xref>, we consider our
work to be related most to that of the working group on drought in the
Anthropocene <xref ref-type="bibr" rid="bib1.bibx38" id="paren.16"/>, which explicitly addresses the
inefficiency of drought management due to poorly understood feedback between
people (and the decisions they make) and drought conditions.</p>
</sec>
<sec id="Ch1.S2">
  <title>Study area and approach</title>
<sec id="Ch1.S2.SS1">
  <title>The Ebro basin</title>
      <p id="d1e235">We explore the role of information in drought-related decisions in the Ebro
basin. The Ebro Basin is the largest in Spain (85 600 km<inline-formula><mml:math id="M1" display="inline"><mml:msup><mml:mi/><mml:mn mathvariant="normal">2</mml:mn></mml:msup></mml:math></inline-formula>) and is a
highly regulated basin with 125 reservoirs (<inline-formula><mml:math id="M2" display="inline"><mml:mrow><mml:mo>&gt;</mml:mo><mml:mn mathvariant="normal">1</mml:mn></mml:mrow></mml:math></inline-formula> Mm<inline-formula><mml:math id="M3" display="inline"><mml:msup><mml:mi/><mml:mn mathvariant="normal">3</mml:mn></mml:msup></mml:math></inline-formula>) and a total
storage capacity of approximately 8000 Mm<inline-formula><mml:math id="M4" display="inline"><mml:msup><mml:mi/><mml:mn mathvariant="normal">3</mml:mn></mml:msup></mml:math></inline-formula>. These reservoirs are used
primarily to supply water to more than 900 000 ha of irrigated agriculture
and 360 hydro-electrical plants <xref ref-type="bibr" rid="bib1.bibx8" id="paren.17"/>.</p>
      <p id="d1e278">The larger irrigation districts are located in the north-east of the basin
(Figure <xref ref-type="fig" rid="Ch1.F1"/>). We have selected one of these, the irrigation
district supplied by the Aragón and Cataluña channel (Canal de
Aragón y Cataluña, CAyC), to examine the decisions made at the
sub-basin scale.</p>

      <?xmltex \floatpos{t}?><fig id="Ch1.F1"><caption><p id="d1e285">Canal de Aragón y Cataluña: irrigated area and catchment.</p></caption>
          <?xmltex \igopts{width=241.848425pt}?><graphic xlink:href="https://hess.copernicus.org/articles/22/5901/2018/hess-22-5901-2018-f01.pdf"/>

        </fig>

      <p id="d1e294">Over 90 % of the water provided by CAyC is used for irrigation. The water
it supplies is sourced from three reservoirs (Barasona, San Salvador and
Santa Ana), and it is supplied to an irrigated area of around 98 000 ha.
Two zones can be distinguished in the irrigated area: an upstream zone that
can<?pagebreak page5903?> only be supplied from the Barasona reservoir as well as from the recently
inaugurated San Salvador reservoir, and a downstream zone that can be
supplied from all three reservoirs. These zones are 54 000 and 44 000 ha
in size, respectively. The main crops grown in the area are fruit orchard
(apple, pear, peach and nectarine) and extensive herbaceous crops, mainly
maize, alfalfa and barley. The area cropped with wine vine surface is
increasing, though it is still somewhat localised <xref ref-type="bibr" rid="bib1.bibx9" id="paren.18"/>.</p>
      <p id="d1e301">Three drought events that resulted in impacts to agriculture and other
sectors have been recorded for the 2000–2014 period: a short drought spell
in 2002, a multi-year event that lasted from the winter of 2004–2005 to the
spring of 2008, and another during the years 2011 and 2012
<xref ref-type="bibr" rid="bib1.bibx22" id="paren.19"/>. The impacts of the multi-year drought of 2004–2008 in
the Ebro basin have been widely studied. The north-eastern part of the basin
was the most impacted <xref ref-type="bibr" rid="bib1.bibx20" id="paren.20"/> and agriculture was the
most affected sector, with 540 million Euros of estimated losses to crop
production during the hydrological year 2004–2005 and further losses of 272
million in related industries <xref ref-type="bibr" rid="bib1.bibx31" id="paren.21"/>.</p>
</sec>
<sec id="Ch1.S2.SS2">
  <title>Approach</title>
      <p id="d1e319">As the utility of information strongly depends on the particular details of
the decisions and how information is used to support these, we first
consulted decision-makers at the basin (Confederación Hidrográfica
del Ebro, CHE), irrigation district (Comunidad de Regantes del Canal de
Aragón y Cataluña) and farmer scale to better understand their
decision processes, their information needs, and how they use information to
support the decisions they make. For this analysis we focused on decisions
regarding the allocation of water resources, in particular during drought,
when curtailments may be applied (Fig. <xref ref-type="fig" rid="Ch1.F2"/>). The methods
followed for the consultation and a summary of the outputs of the interviews
at each of the locations are provided in Sect. 3.</p>

      <?xmltex \floatpos{t}?><fig id="Ch1.F2"><caption><p id="d1e326">Research phases and spatial scales.</p></caption>
          <?xmltex \igopts{width=236.157874pt}?><graphic xlink:href="https://hess.copernicus.org/articles/22/5901/2018/hess-22-5901-2018-f02.pdf"/>

        </fig>

      <p id="d1e335">The findings of the consultation phase were used to build a model of the
decisions at irrigation district scale. The design of the model from these
findings is described in Sects. 4.1 (farmer decisions) and 4.2 (reservoir
operator decisions). The outputs of these components are the areas of
different crops that are planted during the irrigation season and the
curtailments applied. The crop yield is then calculated using the area of
each crop and observed meteorological data in open-source crop models
(introduced in Sect. 4.3).</p>
      <p id="d1e338">In order to test and quantify the effect that additional information has on
the operational drought management decisions analysed, the decision model was
run for two scenarios with different input information. The input data and
specific parameters used in these two runs are described in Sect. 5.</p>
      <p id="d1e342">The expected final results of the analysis are the relative values of
information in each of the tested scenarios. We calculate this based on the
total net benefit obtained by farmers during the whole period of analysis.
This benefit depends on the decisions made during each season, which in turn
depend on the information used to inform them. The results are described in
Sect. 6 and followed by discussion and conclusions.</p>
</sec>
</sec>
<sec id="Ch1.S3">
  <title>Stakeholder consultation</title>
<sec id="Ch1.S3.SS1">
  <title>Method</title>
      <p id="d1e357">The stakeholders we consider are the different groups that have the capacity
to modify the amount of water to be used for irrigation either by deciding on
the volume of water to be supplied, or by deciding on the area and type of
crops planted. This decision effectively also determines the irrigation
demand. We use semi-structured interviews to develop our understanding of the
decisions these stakeholders<?pagebreak page5904?> make in managing water resources and the
possible adjustments to those decisions that they may make in view of water
shortages. This method provides the possibility to discuss additional topics
not originally envisioned by the research team in the interview guideline
<xref ref-type="bibr" rid="bib1.bibx19" id="paren.22"/>. <xref ref-type="bibr" rid="bib1.bibx29" id="text.23"/> and
<xref ref-type="bibr" rid="bib1.bibx5" id="text.24"/> similarly apply semi-structured interviews to understand
water use and management practices. Participants were asked to describe their
own practices, as well as the practices of the groups they deal with in
relation to drought management. A set of questions had been previously
prepared, but was only used to guide the interviews and ensure that topics
not mentioned were addressed and that all required details about the decision
processes were collected.</p>
      <p id="d1e369">One interview session was held at each of the locations (the basin authority,
the irrigation association and the farm) with two or three people
participating in each. In the interview that was held at the basin authority,
the participants included the head of one of the basin's management units and
two members of the hydrological planning office, both with expertise in
drought management in the basin. In the interview at the Irrigation
Association, the participants were the head of the Irrigation Association and
the engineer in charge of the information service about current and expected
water availability. And in the interview at the farm level, two people
participated: the head of viticulture and the engineer responsible for the
information service.</p>
      <p id="d1e372">The information about the practices and attitudes of farmers in the study
area was to a great extent obtained from the interview with the staff at the
Irrigation Association who work in close collaboration with all the farmers
in the area and therefore have a wider view than individual farmers. We
acknowledge that the sample of interviews we held is small. Although
important to the assumptions made in the development of the decision model
that we constructed, we would readily agree that our representation of the
farmer behaviour and the diversity of responses across farmers may be over-simplified. A larger sample of interviews would reveal more information, but
we feel that is outside the scope of this paper.</p>
</sec>
<sec id="Ch1.S3.SS2">
  <?xmltex \opttitle{Confederaci\'{o}n Hidrogr\'{a}fica del Ebro}?><title>Confederación Hidrográfica del Ebro</title>
      <p id="d1e382">The main operational decisions that the Ebro river basin authority (CHE)
takes regarding drought are the declaration of drought conditions and the
allocation of water in emergency situations. To guide these decisions, CHE
defined a drought management plan in 2007 <xref ref-type="bibr" rid="bib1.bibx7" id="paren.25"/>, which was the
first of its kind in Europe. It is a very comprehensive plan and links
hydro-meteorological indicators to drought severity levels. The decision to
declare drought is informed by a set of indicators, derived from measurements
from a dense network of in situ automatic stations. The plan establishes the
main indicator to be used for each of the areas of the basin. Where
applicable, water stored in the reservoir is used as the main indicator, since it
is considered the most robust option. Otherwise 3-month discharge or
groundwater levels are used as indicators.</p>
      <p id="d1e388">In the opinion of those interviewed at CHE, the declaration of drought is currently well
informed and therefore they consider that additional information would be
more useful after the declaration, when conditions must be monitored closely
and decisions such as selecting the most cost-effective alternative sources
of water or how to secure sufficient water to guarantee environmental flows
must be taken. For these decisions timing is critical and they point out that
information should be available with a maximum delay of 1 week to be useful
for decisions. In addition, they showed particular interest in remote sensing
derived snow data to support the quantification of water availability in the
basin.</p>
</sec>
<sec id="Ch1.S3.SS3">
  <?xmltex \opttitle{Canal de Arag\'{o}n y Catalu\~{n}a (CAyC)}?><title>Canal de Aragón y Cataluña (CAyC)</title>
      <p id="d1e398">General Irrigation Associations such as Canal de Aragón y Cataluña
(CAyC) are responsible for the distribution of water from the reservoir to
the users. In drought situations they can decide to introduce restrictions to
irrigation water quotas. The decisions they make on the application of these
restrictions are informed by the availability of water in the reservoirs that
feed the irrigation canal system.</p>
      <p id="d1e401">The main decisions that CAyC make in relation to drought is to apply
restrictions (curtailments) to the maximum amount of water that irrigators
can request. They make this decision when they consider that the available
water resource is insufficient to reach the end of the irrigation season if
full irrigation supply to meet demand is maintained. They can also decide to
move water among the three reservoirs in the area. When restrictions are
necessary, these are applied to all users independently of the reservoirs
that they can be supplied from to ensure curtailments are applied equitably
across the district. However, when water is scarce, priority is given to
perennial crops such as fruit orchards and vines to ensure their survival.</p>
      <p id="d1e404">To make their decisions, the reservoir operators need information both on
water availability and the expected demand until the end of the season. In
the interviews, they indicated that they consider that they are well informed
on the availability of water given the levels in the reservoir. However, the
information on water demand is limited. The difficulty of knowing the demand
is due to the fact that they lack information on what crops farmers are
planning on cultivating that year, and especially if the farmers will decide
to plant a second crop, thus increasing the demand towards the end of the
season. Currently they use historic data to estimate the demand. They are
also conducting studies on the feasibility of obtaining this information from
remotely sensed NDVI data <xref ref-type="bibr" rid="bib1.bibx6 bib1.bibx32" id="paren.26"><named-content content-type="pre">described in</named-content></xref>, and although this will provide useful information on the
current crops, it will not provide information on the future plans of the
farmers.</p>
      <?pagebreak page5905?><p id="d1e412"><?xmltex \hack{\newpage}?>Unlike the managers at the basin scale, CAyC indicated that they consider
additional data on the snow cover in the headwaters to be of little use in
quantifying the available resource. They argue that they tend to be cautious
when accounting for snow in the estimation of total availability, since the
reservoir capacity is rather small and therefore the possibility to store
snowmelt runoff depends very much on the melt rate.</p>
</sec>
<sec id="Ch1.S3.SS4">
  <?xmltex \opttitle{Farmers in the Canal de Arag\'{o}n y Catalu\~{n}a irrigated area}?><title>Farmers in the Canal de Aragón y Cataluña irrigated area</title>
      <p id="d1e423">During the consultation, CAyC also provided details on the types of farmers
present in their supply area as well as on the decisions these farmers make
on what to plant. Typically, the proportion of crops planted is fruit
orchards and vines for roughly a third of the area, alfalfa for another
third, and annual crops for the remaining third. These annual crops are
mostly winter cereals and maize. The cropping schedule adopted by farmers is
mostly either a single crop of long-cycle maize or a winter cereal, or a
double crop in which a winter cereal is followed by short cycle maize. The
selection of one or the other by the farmers depends on the expected water
availability, and is currently mainly informed by the water level in the
reservoir. CAyC shares this information with them in the form of biweekly
reports. Conversely, the decisions farmers make in terms of what crop to
plant, and if they plan to plant a double crop, determine the demand for the
season, and will therefore also have an impact on the decision to apply
curtailments that are taken by the CAyC.</p>
      <p id="d1e426">A prominent farmer in the supply area of CAyC is the Raimat wine producer,
who also participated in the consultation process. They provided details of
their information use for water resources management. Their parcels extend
over 3200 ha and are highly technified, with extensive use of detailed
information. In addition to in situ measurements and meteorological station
data, they use Landsat satellite data and perform flight campaigns to acquire
spatial NDVI and thermal data. The thermal data are used to estimate the leaf
water potential and, together with temperature data, calculate a crop water
stress index. This information on crop condition is used to detect spatial
differences in the crops to make the most of the limited water, select the optimal moment
for irrigation and prevent plagues, as well as to ensure the production is as
uniform and controlled as possible.</p>
      <p id="d1e429">The decisions they make are already based on high-resolution data, and
therefore additional medium-resolution global data are not likely to be a
valuable contribution to this type of user. However, this extensive use of
information is not representative of all the farmers in the basin and other
farmers may indeed benefit from additional information.</p><?xmltex \hack{\newpage}?>
</sec>
</sec>
<sec id="Ch1.S4">
  <title>Decision model</title>
      <p id="d1e441">Two of the drought-related operational decisions described by the
stakeholders were selected to be modelled. These are the decisions of the
farmers on what to plant and the decision of the reservoir operators (part of
the irrigation association, CAyC) to apply curtailments to the amount of
water that farmers can request when this is considered necessary to avoid
depleting the supply before the end of the irrigation season. The model
represents both decisions as well as the interaction between the two. In the
year-to-year planning of water allocation and crops to plant, the basin
authority is of lesser relevance to the decision model as they are responsible for the longer-term
planning through the basin hydrological plan. They are also in charge of
developing the drought management plan, and although this plan provides
guidelines on the measures to be taken during drought, it does not go into
detail on the operational decisions to be taken on water allocation.</p>
      <p id="d1e444">The decision model was built in R <xref ref-type="bibr" rid="bib1.bibx34" id="paren.27"/>.</p>
<sec id="Ch1.S4.SS1">
  <title>Farmer decision: crop areas</title>
      <p id="d1e455">The farmers have a number of possible crop alternatives for each irrigation
season. In this part of the model we simulate the decision of the farmers to
follow one of the possible courses of action available to them. The result of
the decision is the planted area of the selected crops. Since fruit orchards,
vines and alfalfa crops are perennial crops and are typically planted for
several years, their approximate areal extent is known and is considered to
be constant in the model. The farmer decision model therefore focuses on
determining the variable areal extent of maize and winter cereal, as well as
the decision as to whether to plant a single crop or also a second crop. In the
model, barley is selected to represent the winter cereal crop since it is the
most common winter cereal crop in the area.</p>
      <p id="d1e458">The courses of action represented in the model consist of a series of
decisions made during the irrigation season. The possible actions are
depicted in Fig. <xref ref-type="fig" rid="Ch1.F3"/>, which shows the choices that can be
made at each decision stage in the calendar. At each of these decision
points, the option that farmers would prefer to take if they perceive there
are sufficient water resources available is indicated by a blue A. The
preferred decision(s) if there are insufficient resources is marked with a
red A. The choices and the calendar are based on the information provided by
the stakeholders we interviewed, supported by literature sources
<xref ref-type="bibr" rid="bib1.bibx10 bib1.bibx16 bib1.bibx23" id="paren.28"/>. We consider
two types of farmers in the model, with different options available to them:
technified farmers managing large plots and smaller-scale farmers. In the
model, technified farmers (marked with T1 in Fig. <xref ref-type="fig" rid="Ch1.F3"/>) can
support a double crop, and this is always their preferred option because of
its higher productivity. However, in years of low water availability (red A
in the figure) they may<?pagebreak page5906?> decide to leave the land fallow instead of planting a
second crop. Smaller-scale farmers (T2) can only manage a single crop and in
this case long-cycle maize is the most productive option. In years of low
water availability, their decision will depend on the level of risk they are
willing to take. We consider three levels of risk aversion (R1, R2 and R3 in
the figure). The safest option to secure a crop is to plant long-cycle barley
at the beginning of the season (R1), but they can also decide to wait for
conditions to improve, taking the risk of having to leave the land fallow if
there is no improvement (<inline-formula><mml:math id="M5" display="inline"><mml:mrow><mml:mi>R</mml:mi><mml:mo>&gt;</mml:mo><mml:mn mathvariant="normal">1</mml:mn></mml:mrow></mml:math></inline-formula>). If, however, water availability increases by
February, they can decide to plant long-cycle maize. If availability is still
low, they can secure a crop by planting a short-cycle barley (a less
productive option than the long-cycle version) (R2), or they can decide to
wait longer (R3). In April, they can still plant a long-cycle maize crop if
availability has improved, but, if it has not, then it is too late to plant
barley and they have no other option than to leave the land fallow.</p>

      <?xmltex \floatpos{t}?><fig id="Ch1.F3"><caption><p id="d1e482">Crop options considered in the model for farmers. Blue and red As
represent respectively good and poor water availability at the moment of the
decision. R1, R2 and R3 mark the different courses of action that farmers can
follow depending on the risk they are willing to take, with R1 being the most
risk averse and R3 the least risk averse. The lower case letters a–h indicate
the end points of the possible decision paths. The blue vertical line marks
the start of the irrigation season.</p></caption>
          <?xmltex \igopts{width=241.848425pt}?><graphic xlink:href="https://hess.copernicus.org/articles/22/5901/2018/hess-22-5901-2018-f03.pdf"/>

        </fig>

      <p id="d1e491">The choice of a particular course of action in the model is based on the
water availability at the moment of the decision and is used as an indicator
of the expected availability of water during the remaining season. For the
decisions made before the start of the irrigation season (November and
February), the availability is based on the observed volume in the reservoir
since these decisions have no influence on the level of the reservoir until
the actual start of the irrigation season. For the decisions after the start
of the irrigation season (decision points in April and May) a simulated
volume is used (Fig. <xref ref-type="fig" rid="Ch1.F4"/>). The simulated volume is
based on the observed volume at the beginning of the irrigation season and
the accumulated inflow from the beginning of the irrigation season until the
decision date. From the start of the irrigation season the decisions made
will have an influence on the level of the reservoir and therefore observed
levels are not representative as an input for further decisions. Note that
the barley crop is not irrigated and therefore does not pose a demand on the
available water resource. However, as can be seen in
Fig. <xref ref-type="fig" rid="Ch1.F3"/> the choice for planting a barley crop will have
implications for the available options later in the season and therefore
indirectly influences the irrigation demand.</p>

      <?xmltex \floatpos{t}?><fig id="Ch1.F4" specific-use="star"><caption><p id="d1e501">Model decisions, parameters that inform them and decision outputs. A
description of the abbreviations is included below. The period considered for
each parameter is given in between square brackets. The shapes indicate the
availability and source of the information. The parameters representing the
information that is exchanged between the two decision models are coloured in
green (crop surface, CS) and blue (curtailments, Cu). The grey boxes
represent different blocks of the decision models. The reservoir operation
decision has the same kind of input and output for each decision date, while
the farmer's decision has different inputs before and after the start of the
irrigation season. The white lines within the blocks represent the moments at
which decisions are made (time <inline-formula><mml:math id="M6" display="inline"><mml:mi>i</mml:mi></mml:math></inline-formula>).</p></caption>
          <?xmltex \igopts{width=341.433071pt}?><graphic xlink:href="https://hess.copernicus.org/articles/22/5901/2018/hess-22-5901-2018-f04.pdf"/>

        </fig>

</sec>
<sec id="Ch1.S4.SS2">
  <title>Reservoir operation decision: water restrictions</title>
      <p id="d1e523">Every 2 weeks during the irrigation season (March–October), the decision on
whether to apply curtailments to the maximum amount of water that irrigators
can request is re-examined. This decision requires an estimate of the total
amount of available water during the season and the total water demand. To
estimate the total amount of water that will be available during the season,
the inflow into the reservoir from the beginning of the hydrological year in
October up to the week of the decision (represented as <inline-formula><mml:math id="M7" display="inline"><mml:mrow><mml:msub><mml:mi>F</mml:mi><mml:mrow><mml:mo>[</mml:mo><mml:mi>h</mml:mi><mml:mo>:</mml:mo><mml:mi>i</mml:mi><mml:mo>]</mml:mo></mml:mrow></mml:msub></mml:mrow></mml:math></inline-formula> in
Fig. <xref ref-type="fig" rid="Ch1.F4"/>) is compared with the percentiles of historic
data. Data of accumulated inflow in the reservoir are preferred to reservoir
levels as input information for the reservoir operator decision model to
avoid the influence of the actual decisions of the managers and simulate them
independently. The percentile curve in which the value of the current year is
positioned is then used to sample from the climatological record a projection
of the inflow series into the reservoir until the end of the season.</p>
      <p id="d1e548">The total water demand for irrigation until the end of the season
(<inline-formula><mml:math id="M8" display="inline"><mml:mrow><mml:msub><mml:mi>D</mml:mi><mml:mrow><mml:mo>[</mml:mo><mml:mi>s</mml:mi><mml:mo>:</mml:mo><mml:mi>n</mml:mi><mml:mo>]</mml:mo></mml:mrow></mml:msub></mml:mrow></mml:math></inline-formula>) is calculated as the sum of the demand until the decision day
(<inline-formula><mml:math id="M9" display="inline"><mml:mrow><mml:msub><mml:mi>D</mml:mi><mml:mrow><mml:mo>[</mml:mo><mml:mi>s</mml:mi><mml:mo>:</mml:mo><mml:mi>i</mml:mi><mml:mo>]</mml:mo></mml:mrow></mml:msub></mml:mrow></mml:math></inline-formula>) and the expected demand from the decision day until the end of
the season (<inline-formula><mml:math id="M10" display="inline"><mml:mrow><mml:msub><mml:mi>D</mml:mi><mml:mrow><mml:mo>[</mml:mo><mml:mi>i</mml:mi><mml:mo>:</mml:mo><mml:mi>n</mml:mi><mml:mo>]</mml:mo></mml:mrow></mml:msub></mml:mrow></mml:math></inline-formula>). The first is the product of the crop surfaces
already planted (Cs<inline-formula><mml:math id="M11" display="inline"><mml:msub><mml:mi/><mml:mrow><mml:mo>[</mml:mo><mml:mi>i</mml:mi><mml:mo>-</mml:mo><mml:mn mathvariant="normal">1</mml:mn><mml:mo>]</mml:mo></mml:mrow></mml:msub></mml:math></inline-formula>), which is the output of the farmer decision
model, and the resulting crop demand (CD<inline-formula><mml:math id="M12" display="inline"><mml:msub><mml:mi/><mml:mrow><mml:mo>[</mml:mo><mml:mi>s</mml:mi><mml:mo>:</mml:mo><mml:mi>i</mml:mi><mml:mo>]</mml:mo></mml:mrow></mml:msub></mml:math></inline-formula>) obtained from the crop
models using observed meteorological data. The latter (<inline-formula><mml:math id="M13" display="inline"><mml:mrow><mml:msub><mml:mi>D</mml:mi><mml:mrow><mml:mo>[</mml:mo><mml:mi>i</mml:mi><mml:mo>:</mml:mo><mml:mi>n</mml:mi><mml:mo>]</mml:mo></mml:mrow></mml:msub></mml:mrow></mml:math></inline-formula>) is
unknown to the managers. In the model, an average demand per unit area of
crop calculated with the crop model data for the period 2000–2014 is used as
an estimate to inform their decision. This is a simplification, as the demand
to the end of season will depend on the expected climatological conditions
and the crop surfaces planted. The actual demand up to the decision day could
be used as an estimate of the expected demand until the end of the season.
However, while that could provide an indication of the climatological
conditions, the decisions made by farmers on which crops to plant at future
decision moments are unknown.</p>
      <p id="d1e668">When the estimated total amount of available water during the season is
insufficient to fulfil the total demand, curtailments are applied.
Conversely, if in a later week the expected total available water is found to
be enough to fulfil the total demand, restrictions are lifted.</p>
      <p id="d1e671">The output of the farmer model are the areas of each of the crops planted
each year by the farmers. These crop areas determine the demand in the
reservoir operator decision model.<?pagebreak page5907?> The outputs of the operator decision model
on the other hand are the curtailments posed on the water supplied to the
farmers until the end of the season, which is determined every 2 weeks. These curtailments may reduce the
yield of the crops if these are already planted and the demand cannot be
satisfied, but will also influence the farmer decisions within the irrigation
season. If curtailments are in force when the farmers are deciding what to
plant (April and May), then the model assumes that the farmers do not
consider water availability to be good, leading to decisions commensurate
with low water availability being made. These decisions will consequently
influence the demand.</p>
</sec>
<sec id="Ch1.S4.SS3">
  <title>Crop water demand and benefit</title>
      <p id="d1e681">AquaCrop-OS <xref ref-type="bibr" rid="bib1.bibx14" id="paren.29"/> was used to simulate barley and maize
yields. These crops are the main focus of the analysis and they require a
more detailed and flexible simulation to differentiate the different growing
cycles and planting dates. Default parameters for maize and barley were
adapted for the diverse cycles using data from <xref ref-type="bibr" rid="bib1.bibx23" id="text.30"/>,
<xref ref-type="bibr" rid="bib1.bibx16" id="text.31"/> and <xref ref-type="bibr" rid="bib1.bibx17" id="text.32"/>.</p>
      <p id="d1e696">CropWat 8.0 <xref ref-type="bibr" rid="bib1.bibx12" id="paren.33"/> was used for alfalfa and fruit orchards, the
crops that are considered to have a constant crop surface in the analysis.
Default parameters were used but were adapted to the cropping calendar in the
Ebro basin. Peach tree was selected as the representative fruit orchard crop.
An irrigation calendar of 14 days was selected to match the reservoir
operators' decision.</p>
      <p id="d1e702">The percentage of reduction in crop yield was calculated as the maximum
percentage of unsatisfied demand during the season. The reason for this is
that, when there is insufficient water, farmers prefer to stop watering a
part of the area, rather than apply insufficient water to the whole area.
These percentages were calculated using the same 2-week time step of the operator decision. The areas in which
irrigation was stopped were considered to have no yield and their
contribution was subtracted from the full supply yield values derived from
the crop models to obtain the final yield for each crop and year. Priority is
given to the perennial crops, with the curtailments then being applied to the
maize crops.</p>
</sec>
</sec>
<sec id="Ch1.S5">
  <title>Quantifying the effect of additional information</title>
      <p id="d1e712">Expected availability of water during the irrigation season is the main
variable used by both the reservoir operators and the farmers to inform their
decisions. Information on that<?pagebreak page5908?> availability can, however, be obtained from
different sources. Currently the main source of information that is used is
the volume stored in the reservoirs, obtained through observations of the
reservoir levels. Stakeholders indicated that they may also consider the
available water resource in the snowpack in the headwaters upstream of the
reservoirs, though there are currently no systematic observations of this
resource that are formally included in their decision processes. Satellite
images can, however, routinely provide estimates of this resource. Two
information scenarios were therefore simulated: the expected water resource
availability as informed by the reservoir levels alone, and the expected
availability based on the reservoir levels with the addition of satellite-based data on snow cover in the headwaters.</p>
      <p id="d1e715">Output benefit values using either of the two information scenarios were
evaluated against the value (Val) of uninformed decisions and decisions under
perfect information following the usual form of skill scores
<xref ref-type="bibr" rid="bib1.bibx37" id="paren.34"/>:

              <disp-formula id="Ch1.E1" content-type="numbered"><mml:math id="M14" display="block"><mml:mrow><mml:mstyle class="stylechange" displaystyle="true"/><mml:mi mathvariant="normal">RV</mml:mi><mml:mo>=</mml:mo><mml:mstyle displaystyle="true"><mml:mfrac style="display"><mml:mrow><mml:msub><mml:mi mathvariant="normal">Val</mml:mi><mml:mi mathvariant="normal">information</mml:mi></mml:msub><mml:mo>-</mml:mo><mml:msub><mml:mi mathvariant="normal">Val</mml:mi><mml:mrow><mml:mi mathvariant="normal">uninformed</mml:mi><mml:mspace width="0.125em" linebreak="nobreak"/><mml:mi mathvariant="normal">decision</mml:mi></mml:mrow></mml:msub></mml:mrow><mml:mrow><mml:msub><mml:mi mathvariant="normal">Val</mml:mi><mml:mrow><mml:mi mathvariant="normal">perfect</mml:mi><mml:mspace width="0.125em" linebreak="nobreak"/><mml:mi mathvariant="normal">information</mml:mi></mml:mrow></mml:msub><mml:mo>-</mml:mo><mml:msub><mml:mi mathvariant="normal">Val</mml:mi><mml:mrow><mml:mi mathvariant="normal">uninformed</mml:mi><mml:mspace width="0.125em" linebreak="nobreak"/><mml:mi mathvariant="normal">decision</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:mfrac></mml:mstyle><mml:mo>.</mml:mo></mml:mrow></mml:math></disp-formula></p>
      <p id="d1e773">The relative value (RV) is therefore a score between <inline-formula><mml:math id="M15" display="inline"><mml:mrow><mml:mo>-</mml:mo><mml:mi mathvariant="normal">∞</mml:mi></mml:mrow></mml:math></inline-formula> and 1, with
RV <inline-formula><mml:math id="M16" display="inline"><mml:mrow><mml:mo>=</mml:mo><mml:mn mathvariant="normal">1</mml:mn></mml:mrow></mml:math></inline-formula> meaning that the information is perfect and RV <inline-formula><mml:math id="M17" display="inline"><mml:mrow><mml:mo>≤</mml:mo><mml:mn mathvariant="normal">0</mml:mn></mml:mrow></mml:math></inline-formula> meaning
that the information does not contribute to improving the decisions made.</p>
      <p id="d1e806">The value of perfect information and uninformed decisions was calculated by
running the model for all possible courses of action represented in
Fig. <xref ref-type="fig" rid="Ch1.F3"/>. The value of perfect information was then
obtained by selecting for each season the best performing course of action,
while the value of the uninformed decisions was defined as the result of
selecting the course of action that performs best on average for all years.</p>
      <p id="d1e812">Analysing the pathways in Fig. <xref ref-type="fig" rid="Ch1.F3"/> results in seven
possible courses of action. These are summarised in
Table <xref ref-type="table" rid="Ch1.T1"/>, where the columns represent the four decision
points and the colours the course that is followed. Blue and red indicate that the
good or the poor water availability option is followed, respectively. The
points at which no decision is required are marked in yellow. This happens
when previous decisions already determine the course of action for later
months. Option 7 corresponds to the situation in which the availability of
water is good at the beginning of the hydrological year so farmers already
select to plant the most productive crops in November and no further
decisions are required in the following months. The other six options
correspond to situations in which the availability of water is not considered
to be good at the beginning of the hydrological year. In options 3 and 6, the
situation improves by February, so small-scale farmers decide to plant the
preferred option (long-cycle maize) at this point and do not require further
decisions. The difference between these two options results from the decision
taken by technified farmers on whether or not to plant a second crop in May.
They will do this if they consider the availability of water to be good
(option 6), otherwise they will leave the land fallow (option 3).</p>

<?xmltex \floatpos{t}?><table-wrap id="Ch1.T1"><caption><p id="d1e822">Possible paths for farmers. The paths are the result of the water
availability (red – poor availability, blue – good availability, yellow –
indifferent) at the four decision moments. The letters and coloured boxes in
the last four columns correspond to the courses of action in
Fig. <xref ref-type="fig" rid="Ch1.F3"/> for each of the farmer types given good or poor
availability at the four decision moments. The crops planted when following
each of the paths are indicated using the same colours as in Fig. <xref ref-type="fig" rid="Ch1.F3"/>.</p></caption>
  <?xmltex \igopts{width=241.848425pt}?><graphic xlink:href="https://hess.copernicus.org/articles/22/5901/2018/hess-22-5901-2018-t01.pdf"/>
</table-wrap>

<sec id="Ch1.S5.SS1">
  <title>Input data</title>
<sec id="Ch1.S5.SS1.SSS1">
  <title>Reservoir and meteorological data</title>
      <p id="d1e844">In situ data on reservoir levels were obtained from the automatic measurement
stations (SAIH, Automatic Hydrologic Information System). These data are
available from <uri>http://sig.mapama.es/redes-seguimiento/</uri> (last access:
12 November 2018).</p>
      <p id="d1e850">Reservoir volume data for Barasona reservoir and river flow data from the
stations at the upstream tributaries (stations located at Graus on the
Ésera river and at Capella on Isábena river, Fig. <xref ref-type="fig" rid="Ch1.F1"/>)
were used to estimate the availability of water during the season. We focus on
the Barasona reservoir as it is the levels in this reservoir that trigger the
restrictions in the area supplied by CAyC. SAIH provides data for the
Barasona reservoir from 1931 to September 2014, though there are some data
gaps in the first few decades. The reservoir was enlarged in 1972 to a capacity
of 84.71 hm<inline-formula><mml:math id="M18" display="inline"><mml:msup><mml:mi/><mml:mn mathvariant="normal">3</mml:mn></mml:msup></mml:math></inline-formula> and we therefore consider only the values after that year.</p>
      <p id="d1e864">In addition, daily precipitation and temperature data, as well as monthly
relative humidity data from the meteorological station located just outside
the basin at the University of Lleida (station 9771C), were used to provide
meteorological inputs to the crop model. Data from this station are available
from 1983 through 2014 and can be obtained from
<uri>https://opendata.aemet.es/centrodedescargas/productosAEMET</uri> (last
access: 12 November 2018).</p>
</sec>
<?pagebreak page5909?><sec id="Ch1.S5.SS1.SSS2">
  <title>Snow cover data</title>
      <p id="d1e876">MODIS 8-day snow cover 500 m grid data (MOD10A2; Hall, Salomonson, and Riggs
2006) were used to calculate the percentage of snow cover in the headwaters
of the reservoirs (Fig. 1) as an additional source of water availability
information. This dataset covers the period from 26 February 2000 to the end
of 2016 and was downloaded from the EartH2Observe Water Cycle Integrator
(<uri>http://wci.earth2observe.eu</uri>, last access: 12 November 2018).</p>
</sec>
</sec>
<sec id="Ch1.S5.SS2">
  <title>Model options</title>
<sec id="Ch1.S5.SS2.SSS1">
  <title>Availability thresholds</title>
      <p id="d1e894">Thresholds are needed to define at what reservoir level, or at what
combination of reservoir level and snow cover, the water availability is
regarded by the farmers as good. This judgement is made at each of the
decision points. If the availability is above the threshold, then the farmer
would follow the decision path associated with good expected availability of
water (this corresponds to following the paths marked with a blue A in
Fig. <xref ref-type="fig" rid="Ch1.F3"/>), while if it is below the threshold then the
alternative, poor expected availability path will be followed. These
thresholds are currently not formally defined, and may also differ between
farmers as individual farmers will assess water availability differently,
depending on how risk averse they are.</p>
      <p id="d1e899">In the first test we identified the thresholds that maximise the sensitivity
(rate of true positives) for all years analysed and for each of the farmers
decision moments (November, February, April, May). This is a measure of the
goodness of a binary classification that in this case refers to the points
correctly classified as having good availability of water. To assess the performance
of the classification the decisions made with perfect information are used
as a reference. This results in a set of four optimised thresholds, which may
be different for each of the decision points. The optimised threshold values
at each decision point are kept the same for all years analysed.</p>
      <p id="d1e902">In addition to the optimised set of thresholds, the model is run with 10
extra sets of thresholds to explore the sensitivity to these thresholds. In
this case, the thresholds are kept the same at each decision point, and the
values range from low (35 hm<inline-formula><mml:math id="M19" display="inline"><mml:msup><mml:mi/><mml:mn mathvariant="normal">3</mml:mn></mml:msup></mml:math></inline-formula>) to almost full capacity (80 hm<inline-formula><mml:math id="M20" display="inline"><mml:msup><mml:mi/><mml:mn mathvariant="normal">3</mml:mn></mml:msup></mml:math></inline-formula>).</p>
      <p id="d1e923">The effect of the additional snow cover information on the expected available
water resource is incorporated in the decision model by considering the
expected contribution of snowmelt to the available water resource. When the
snow cover is below a certain threshold, indicating lower than normal
expected runoff from snowmelt, the farmers would require the reservoir level
threshold to be higher to regard water availability as being good and thus
follow the higher water demanding path. The snow cover thresholds used for
this test are again determined using a goodness-of-fit measure of the binary
classification of the decision points correctly identified as having good or
poor availability. For the decisions made in May the snow information was
not considered since snow cover is already very limited in that period.</p>
</sec>
<sec id="Ch1.S5.SS2.SSS2">
  <title>Allocation factor</title>
      <p id="d1e932">An allocation factor is applied to the accumulated inflow in the reservoir to
obtain the proportion of the available resources that effectively reaches the
crops. This factor accounts for water supplied to other uses, water losses
due to evaporation, efficiency of the distribution network and releases from
the reservoir to the downstream river. The allocation factor determines the
amount of water that is available for irrigation and therefore has
significant influence on the decisions made by the farmers and operators. As
the true allocation factor is not known for the area, the sensitivity to this
factor is tested by running the model with different allocation factors,
considering perfect knowledge of the expected availability of water.</p>
      <p id="d1e935">The most profitable choices for farmers were identified for different
allocation factors under perfect information and are shown in
Table <xref ref-type="table" rid="Ch1.T2"/>. The first row (AF <inline-formula><mml:math id="M21" display="inline"><mml:mrow><mml:mo>=</mml:mo><mml:mn mathvariant="normal">1</mml:mn></mml:mrow></mml:math></inline-formula>) represents the
hypothetical situation in which all the water that enters the reservoir is
available to the farmers to irrigate the crops. The following rows represent
different levels of allocation of water for irrigation. The results show that
when more water is available, farmers already choose to plant the most
productive option in November or February (options 7 and 6 respectively).
When there is less water they select to plant less maize or nothing at all
(option 1). In years of water scarcity, such as 2005, we can see in the table
that this is the case even if 80 % of the total water is used for
irrigation.</p>

<table-wrap id="Ch1.T2"><caption><p id="d1e952">Most profitable choice for the farmers for each of the years of the
period 2001–2014 (represented in the columns) in function of the available
water determined by the allocation factor (AF). The numbers of the options
refer to the alternatives included in Table <xref ref-type="table" rid="Ch1.T1"/>. The
colours for the years represent the SPI-12 for the month of September for the
catchment area of Barasona and Santa Ana reservoirs, calculated with CHIRPS
precipitation data for the period 1981–2015.</p></caption>
  <?xmltex \igopts{width=241.848425pt}?><graphic xlink:href="https://hess.copernicus.org/articles/22/5901/2018/hess-22-5901-2018-t02.pdf"/>
</table-wrap>

      <p id="d1e962">An allocation factor of 0.55 was selected for the following tests, since it
is found to be a tipping point between good<?pagebreak page5910?> and poor availability for many of
the years in the tested period and therefore allows for a higher range of
represented situations. With this level of allocation, the area receives an
amount of water that would be able to satisfy the full demand of the most
productive alternative of crops in 10 out of the 14 years, with 4 years
experiencing water shortages, which reflects the number of drought events in
the 2000–2014 period.</p>
      <p id="d1e966">To calculate the crop demand an irrigation efficiency of 80 % is
considered.</p>
</sec>
<sec id="Ch1.S5.SS2.SSS3">
  <title>Farmer types</title>
      <p id="d1e975">The distribution of the types of farmer was kept constant for all the years
and runs. The proportions of technified and smaller-scale farmers was
established as the mid-range of the yearly ratio between farmers sowing
transgenic maize (considered to be technified) and farmers sowing conventional
maize (considered to be small-scale farmers) observed in the area for the period
2010–2015 <xref ref-type="bibr" rid="bib1.bibx10 bib1.bibx18" id="paren.35"/>. This resulted in
65 % of the area being exploited by farmers considered to be technified, and
35 % by small-scale farmers. The proportion of risk aversion used in the
model is R1 <inline-formula><mml:math id="M22" display="inline"><mml:mo>=</mml:mo></mml:math></inline-formula> 0.4, R2 <inline-formula><mml:math id="M23" display="inline"><mml:mo>=</mml:mo></mml:math></inline-formula> 0.3, R3 <inline-formula><mml:math id="M24" display="inline"><mml:mo>=</mml:mo></mml:math></inline-formula> 0.3, with R1 being the most
risk averse and R3 the most risk acceptant.</p>
      <p id="d1e1002">Different distributions of farmer types would result in different levels of
demand and therefore different optimal paths. The proportion between
technified farmers and smaller-scale farmers also gives more weight to
different decision moments. For example, the decision in May on whether to
plant a second crop is only relevant to the technified farmers.</p>
</sec>
<sec id="Ch1.S5.SS2.SSS4">
  <title>Costs and benefits</title>
      <p id="d1e1011">Planting costs and selling prices were used to calculate the value of the
yield for the variable crops. The planting costs considered are
496 EUR ha<inline-formula><mml:math id="M25" display="inline"><mml:msup><mml:mi/><mml:mrow><mml:mo>-</mml:mo><mml:mn mathvariant="normal">1</mml:mn></mml:mrow></mml:msup></mml:math></inline-formula> for barley and 1807 EUR ha<inline-formula><mml:math id="M26" display="inline"><mml:msup><mml:mi/><mml:mrow><mml:mo>-</mml:mo><mml:mn mathvariant="normal">1</mml:mn></mml:mrow></mml:msup></mml:math></inline-formula> for maize
<xref ref-type="bibr" rid="bib1.bibx25" id="paren.36"/> and the selling prices are EUR 159 per 1000 kg for
barley and EUR 171.3 per 1000 kg for maize
<xref ref-type="bibr" rid="bib1.bibx1" id="paren.37"/>. Average yields are
2349.75 kg ha<inline-formula><mml:math id="M27" display="inline"><mml:msup><mml:mi/><mml:mrow><mml:mo>-</mml:mo><mml:mn mathvariant="normal">1</mml:mn></mml:mrow></mml:msup></mml:math></inline-formula> for rainfed barley and 12 179.34 kg ha<inline-formula><mml:math id="M28" display="inline"><mml:msup><mml:mi/><mml:mrow><mml:mo>-</mml:mo><mml:mn mathvariant="normal">1</mml:mn></mml:mrow></mml:msup></mml:math></inline-formula> for
irrigated maize <xref ref-type="bibr" rid="bib1.bibx25" id="paren.38"/>. No differences in price or cost between
the varieties of a same crop type were considered, although the higher
productivity of long-cycle varieties results in these varieties being more
profitable in the model.</p>
</sec>
</sec>
</sec>
<sec id="Ch1.S6">
  <title>Results</title>
<sec id="Ch1.S6.SS1">
  <title>Selection of optimal thresholds</title>
      <p id="d1e1085">We first ran all possible decisions paths and identified the decisions that
result in the highest benefits to the farmers for each season. These
decisions are represented in Fig. <xref ref-type="fig" rid="Ch1.F5"/> by the
coloured points, with the volume of the reservoir on the <inline-formula><mml:math id="M29" display="inline"><mml:mi>y</mml:mi></mml:math></inline-formula> axis. If the
point is red, then the best decision is for the farmer to follow the path
marked with a red A in Fig. <xref ref-type="fig" rid="Ch1.F3"/>. If it is blue, then it is
best to follow the blue A path. If the point is yellow, then it does not
matter which of the paths is followed.</p>

      <?xmltex \floatpos{t}?><fig id="Ch1.F5"><caption><p id="d1e1101">The position of the points represents reservoir levels <bold>(a)</bold>
and snow cover <bold>(b)</bold> for the period 2001–2014. The points are
coloured according to the decisions made with perfect information at those
decision points, which are considered to be the “optimal course”, and refer to
the paths illustrated in Fig. <xref ref-type="fig" rid="Ch1.F3"/>. The individual
thresholds mark the threshold for reservoir level or snow cover when
considered independently, while the combined thresholds are the modified
thresholds for reservoir level for years in which the snow cover threshold is
not reached.</p></caption>
          <?xmltex \igopts{width=241.848425pt}?><graphic xlink:href="https://hess.copernicus.org/articles/22/5901/2018/hess-22-5901-2018-f05.pdf"/>

        </fig>

      <p id="d1e1118">We use the optimal decisions based on perfect information to establish a
threshold for the reservoir level to divide between good and poor water
availability. A perfect threshold would be selected such that all the red
points are below and all the blue points are above the threshold. This
perfect threshold would always allow the farmer to make the decision that
results in a higher benefit at the end of the season.</p>
      <p id="d1e1121">However, as can be seen in Fig. <xref ref-type="fig" rid="Ch1.F5"/>, it is not
possible to obtain a perfect classification of the reservoir levels with a
single threshold. The dashed lines mark the thresholds that maximise the
points correctly classified. The fact that the classification cannot be
perfect means that the reservoir level alone does not provide enough
information on what is the best decision to make. Additional information
will be valuable if it contributes to improving the classification and,
therefore, results in the decision that maximises the benefits being made
more often. In this case the additional information we consider is the snow
cover data. This is shown in the lower part of the figure. The coloured
points again indicate the decision<?pagebreak page5911?> path that would be taken based on perfect
information. Again the figure shows that it is not possible to select a
threshold value (dashed lines) where all the red points are below the
threshold, and all blue points are above the threshold. This again indicates
that this information alone does not lead to a perfect classification either.</p>
      <p id="d1e1127">This is different when the combined information of reservoir level and snow
cover extent is used to inform the expectation of water availability. We
incorporate this additional information by amending the threshold of the
reservoir level. This is the solid line in the figure for the months
November, February and April. Snow cover is not considered in May as that is
too late in the season for snow to be of significance. When snow covers an
area larger than the threshold coverage (dashed line in the lower plot), then
the original threshold for the reservoir level is used. However, when the
snow cover is smaller than the identified threshold, and therefore the future
contribution to the reservoir volume from snowmelt is expected to be low, a
second, more conservative threshold for the reservoir level is used (solid
line). With the second threshold some of the red points incorrectly
classified above the original threshold are now classified below the
threshold.</p>
      <p id="d1e1130">The optimised thresholds for the reservoir level were established at
62 hm<inline-formula><mml:math id="M30" display="inline"><mml:msup><mml:mi/><mml:mn mathvariant="normal">3</mml:mn></mml:msup></mml:math></inline-formula> for November, February and April, and 82 hm<inline-formula><mml:math id="M31" display="inline"><mml:msup><mml:mi/><mml:mn mathvariant="normal">3</mml:mn></mml:msup></mml:math></inline-formula> for May; the
thresholds for snow cover were set at 25 %, 35 % and 15 % for
November, February and April respectively, while the increase in the
reservoir level threshold for the years that are below the snow threshold was
set at 20 hm<inline-formula><mml:math id="M32" display="inline"><mml:msup><mml:mi/><mml:mn mathvariant="normal">3</mml:mn></mml:msup></mml:math></inline-formula>.</p>
<sec id="Ch1.S6.SS1.SSS1">
  <title>Value of additional information for the decisions</title>
      <p id="d1e1165">The value of information is assessed here in terms of the total and relative
benefit for the farmers during the whole period of analysis in each of the
information scenarios. Figure <xref ref-type="fig" rid="Ch1.F6"/> shows the total
benefits obtained considering the two information scenarios with each of the
10 sets of thresholds. The benefits obtained using the optimised set
identified in the previous step is also included (labelled as 62 in the
figure). The columns are coloured to show the net benefit in terms of total
gain (above 0) or loss (below 0) of each of the years in the period. The
black dot represents the net benefit taken over the whole period.</p>
      <p id="d1e1170">The two reference scenarios are included in the first two columns. These show
the net benefits using the uninformed decision and decisions made using
perfect information, which are independent of the thresholds.</p>

      <?xmltex \floatpos{t}?><fig id="Ch1.F6"><caption><p id="d1e1175">Total benefit for decisions informed by reservoir level alone (R)
and with the addition of snow information (S) for the 10 sets of thresholds
and the optimized thresholds (labelled as 62). The total benefit for
uninformed decisions (A) and perfect information (P) is included as a
reference. The colours indicate the yearly benefit while the points represent
the total benefit for the period (total gains – total losses).</p></caption>
            <?xmltex \igopts{width=241.848425pt}?><graphic xlink:href="https://hess.copernicus.org/articles/22/5901/2018/hess-22-5901-2018-f06.pdf"/>

          </fig>

      <p id="d1e1184">The difference between the perfect information (column labelled P) and the no
information (labelled A) reference scenarios shows the potential value of
using information, as the use of uncertain information is expected to scale
between these two extreme situations. However, as can be seen in the
following columns that represent the net benefits of the informed scenarios
as a function of the threshold (labelled R for information from reservoir
levels only and S for information from both reservoir levels and snow cover),
the use of non-perfect information in this case results in losses for some of
the years. This is particularly so for the lower thresholds, as water
availability is often judged to be good when in fact it is poor.</p>
      <p id="d1e1188">Figure <xref ref-type="fig" rid="Ch1.F7"/> presents the relative value of the decisions
using each of the two tested sources of information with respect to the
decisions informed by perfect information and the uninformed decisions
(Eq. 1). This shows that the relative values for the total benefits are
negative for almost all thresholds, both when using only reservoir levels as
well as when also using additional information on snow cover. This means
that, for the period as a whole, selecting a course of action based on the
expected availability informed by these datasets does not result in higher
benefits than when following the path that performs best on average every
year. The reason for this lies in the large losses incurred when failing to
recognise a poor-availability year and as a consequence planting more than
what can be irrigated. This is the case for the years with a negative benefit
represented in Fig. <xref ref-type="fig" rid="Ch1.F6"/>. These high losses also result
in higher thresholds showing a better relative value, since these thresholds
lead to more years being regarded as poor-availability years, thus leading to
lower areas being planted.</p>

      <?xmltex \floatpos{t}?><fig id="Ch1.F7"><caption><p id="d1e1197">Total Relative Value for the period 2001–2014 for decisions
informed by reservoir level alone (R) and with the addition of snow
information (S) for the 10 sets of thresholds and the optimized thresholds
(labelled as 62).</p></caption>
            <?xmltex \igopts{width=241.848425pt}?><graphic xlink:href="https://hess.copernicus.org/articles/22/5901/2018/hess-22-5901-2018-f07.pdf"/>

          </fig>

      <p id="d1e1206"><?xmltex \hack{\newpage}?>Still, the results show that the additional information does help to reduce
the losses in some of the years and for all thresholds a better relative
value is obtained when using the additional dataset on snow cover. This can
be seen by the net benefit for the period 2001–2014 (represented by black
dots in Fig. <xref ref-type="fig" rid="Ch1.F6"/>) being higher for all thresholds when<?pagebreak page5912?>
the snow-cover information is used.</p>
</sec>
</sec>
<sec id="Ch1.S6.SS2">
  <title>Quantifying the effect of additional information</title>
      <p id="d1e1219">The high losses in some of the years are the result of the limited profit
margin between the cost of planting and the selling price of the products. To
illustrate further the effect of the profit margin in the decision and the
value of information, we have run a series of additional simulations where
the costs of planting are reduced by 50 %, 75 % and 100 % (which
is the same as zero cost). The relative value of information for these
simulations (shown in Fig. <xref ref-type="fig" rid="Ch1.F8"/>) indicates there is a gradual
increase in the relative value of the informed decisions as the ratio of the
benefits from the crop yield to the cost of planting increases. The fully
detailed gains and losses for these simulations can be found in the
Supplement (Fig. S1). Relative values are still low, however, even when there
is no cost for planting. This is because the uninformed decision used as a
reference also improves with the reduction in the cost of planting. The
course of action that performs better on average, in which the uninformed
decision is based, is path 3 for the full reported cost, path 4 for the
reduced costs and path 5 when no cost is considered. This means that with
lower or no investment costs for planting it is better on average to plant
the more water-demanding crops. These results also show that as the ratio
between the profit made from the crop yield and the costs of planting
increases, the relative value of the informed decisions for the years in
which the optimal path is followed is also reduced.</p>

      <?xmltex \floatpos{t}?><fig id="Ch1.F8"><caption><p id="d1e1226">Relative value (RV) with different levels of cost for planting for
decisions informed by reservoir level alone (R) and with the addition of snow
information (S) for the 10 sets of thresholds and the optimized thresholds
(labelled as 62).</p></caption>
          <?xmltex \igopts{width=241.848425pt}?><graphic xlink:href="https://hess.copernicus.org/articles/22/5901/2018/hess-22-5901-2018-f08.pdf"/>

        </fig>

      <p id="d1e1235">At the reduced costs it also appears that the added value of the information
from snow cover reduces and in some cases is even detrimental, particularly
at the higher reservoir level thresholds. This is likely caused by the
uncertainty in the relationship between snow cover and available water
resources, which will be elaborated further in the discussion.</p>
</sec>
</sec>
<sec id="Ch1.S7" sec-type="conclusions">
  <title>Discussion</title>
      <p id="d1e1245">To answer the question posed in the title on whether users would benefit from
additional information on available water resources in drought conditions, we
adopt an approach that starts with a stakeholder consultation to be able to
understand the decisions users make and how they use information to support
those decisions. This is followed by a model of the decisions to quantify how
additional information can be used to inform and influence the decision
process.</p>
      <p id="d1e1248">The consultation was performed by semi-structured interviews with key
stakeholders. The advantage of this method is that it encourages discussion
<xref ref-type="bibr" rid="bib1.bibx21" id="paren.39"/>, although the main limitations are the small sample
size, which means that only a partial view is obtained of the plurality of
the stakeholders that make these decisions. Despite this limitation, the
responses of the interviews provided a detailed description of the possible
choices to deal with water shortages in the Ebro basin, and the interaction
and feedbacks between water management strategies at basin, irrigation
district and local farmer scales. This knowledge was used to build a model of
the interrelated decisions of farmers and water managers at the irrigation
district scale. The decisions modelled are informed by the expected water
availability during the irrigation season, which is currently derived mainly
from the reservoir levels. In this case we test the use of additional
information of remotely sensed snow cover, as this is information users
currently may consider, but further research on the value of different
datasets that inform the expectation of the available water resource could be
conducted using the model.</p><?xmltex \hack{\newpage}?>
<?pagebreak page5913?><sec id="Ch1.S7.SS1">
  <title>Potential value of additional information</title>
      <p id="d1e1260">Decisions made with perfect or no information were used as reference cases.
The difference in the net benefit between these two cases reveals the
potential improvements that information can bring with respect to the
uninformed decisions. With perfect information, losses can be avoided in
seasons of water scarcity and benefits maximised when enough water is
available. It should be noted that the paths for perfect information in the model maximise the benefit of the whole group of
farmers, rather than that of individual farmers. In reality, the benefits and losses are not shared by the group,
and individual farmers would try to optimise their individual benefit
instead, though community collaboration in the form of the established user
associations in the basin ensures that to an extent farmers do make decisions
that contribute to a common good and the tragedy of the commons does not
arise.</p>
      <p id="d1e1263">The uninformed case follows a conservative approach considering that for
every year the available water will be limited. Although this results in high
losses being avoided, the benefits are well below the potential. Using
additional information to inform decisions is expected to help the decision-makers in characterising each season in terms of the water availability and
selecting what and when to plant, and accordingly increasing their benefits.
As additional information we test a medium-resolution snow cover product
derived through remote sensing. <xref ref-type="bibr" rid="bib1.bibx15" id="text.40"/> show the value of
this product in providing snow cover information at the Pyrenees range scale.
Our analysis shows that the information from this product also has value at
the basin headwater scale, showing improvements in the decisions made when
compared to decisions informed by reservoir levels alone.</p>
      <p id="d1e1269">Detailed analysis of the years where there is benefit in using the additional
information shows that this arises mainly from the reduction in the losses in
those years in which the optimal decision to make is more uncertain. In these
the years the classification of the water resource as being good or bad is
difficult, and the additional information on the snow cover adds value by
making it more difficult for a bad year to look good. Losses occur in 2002,
2006, 2011 and 2012 (see Fig. S2 for yearly relative value plots), which
match the years for which drought impacts in irrigation agriculture have been
reported <xref ref-type="bibr" rid="bib1.bibx22" id="paren.41"/>. They are the consequence of an inappropriate
course of action being chosen, as a result of the expected availability of
water being too high, compounded by the high cost of planting relative to the
return on investment of the crops planted.</p>
      <p id="d1e1275">To test the robustness of the observed effect of the additional information,
the model was run 10 times with randomly sampled values of snow cover at each
of the decision points. The results of these runs (included in Fig. S3) show
that the improvement then also follows a more random pattern and in some
cases the additional information is detrimental, thus
supporting the hypothesis that the improvements in the decisions are indeed
caused by the additional information on snow cover.</p>
      <p id="d1e1279">However, the results of the model indicate that selecting the option that
performs better on average, as is done in the uninformed case, leads to
higher benefits than when using the information on reservoir levels (either
alone or supported by the MODIS snow cover information). This is in
contradiction with the current practice, in which the reservoir-level
information is used to support the decision and different choices are made
each year. One reason that farmers do not follow this strategy may lie in the
fact that not all the losses are assumed by the farmers, since there are
subsidies for certain crops or for losses incurred in disastrous years. These
subsidies are often based on planted surface and influence the ratio between
the return from the crop yield and the investment costs incurred when
planting. Additionally, the actual farmer decision on what to plant is
influenced not only by water availability, but also by the market prices of
the crops. Maize has a high cost of production and therefore, when its
selling price is low, farmers tend to select other crops with lower
production cost <xref ref-type="bibr" rid="bib1.bibx10" id="paren.42"/>. In the model, however, the
planting costs and selling prices were kept constant for all the years to
better observe the effect of information on the selection of the crops.</p>
</sec>
<sec id="Ch1.S7.SS2">
  <title>Effect of the cost of planting on the value of information</title>
      <p id="d1e1291">The effect of the cost of planting and the profit margins on the usefulness
of the information was explored by running the model for different planting
costs. Changing the cost of planting modified the course of action both for
the informed and uninformed decisions. The reduction in the costs results in
higher relative values for the informed decisions for the period as a whole,
caused again by the reduction in the net losses. The ratio between the cost
of planting and the return on investment on the crop is similar to the
cost–loss ratio used in evaluating the benefit of flood warnings
<xref ref-type="bibr" rid="bib1.bibx39" id="paren.43"/>. Where the cost–loss ratio is high, the cost of
taking an action in vain (false alarm) is also high, and significant losses
may be incurred. This may even result in the information being detrimental,
since it does contain uncertainty and may therefore lead to wrong choices
being made. Larger losses than if that information is simply ignored and the
business-as-usual action is taken may then be incurred. For users with a
lower cost–loss ratio, explored here by lowering the cost of planting,
additional (uncertain) information becomes increasingly valuable as these
users become more tolerant of making a wrong decision. The role of
uncertainty in the link between the information used (reservoirs levels and
snow) and the realisation of the available water resource is not directly
explored in this study through for example a hydrological model, though
explicitly considering the uncertainty can add further value to the
information. Several authors <?pagebreak page5914?><xref ref-type="bibr" rid="bib1.bibx35 bib1.bibx39" id="paren.44"/> have
shown that the value of information from forecasts is always higher when
these are probabilistic. In the application presented here, the relation
between the reservoir levels and the available water resources is more
certain than the relation between the snow cover and the available water.
This may also explain the poorer performance when using snow cover
information than when using only reservoir levels. This occurs in 2006.
In this year the snow cover at the start of the year (February) was
exceptionally high, leading to an expectation of good water resource
conditions. However, this was due to widespread snowfall at the end of
January just before the decision point in February. This snow melted rapidly
and the snow cover in April was anomalously low, with low water resource
availability for the rest of the season.</p>
</sec>
<sec id="Ch1.S7.SS3">
  <title>Value of the information for the different types of farmers</title>
      <p id="d1e1307">The value of the additional information is not equal to each of the different
types of farmers identified. The additional information on the expected water
resource provided by the snow cover is found to be relevant only to the
decisions that are made in February. For the technified farmers the
information is therefore of little value, as the main decisions made by them
fall in November and in May, respectively, before the snow accumulation period
and after the snowmelt period.</p>
      <p id="d1e1310">For the small-scale farmers, the additional information can be relevant for
the decisions that are made when there is snow cover, primarily those made in
February, but also those made in April. These small-scale farmers have only
one crop. Once a decision is made to plant a crop, there is no further value
to information as there is no further decision to be made. However, the
benefit is again not evenly distributed. Small-scale farmers were divided
here into three groups of decreasing risk averseness (R1, R2 and R3). We find
that the additional information benefits the group of farmers that is willing
to take more risk most. These are the farmers that decide to take the risk to
wait for a possible improvement when the water availability is classified as
not being good at the decision point, instead of taking the safe bet and
securing a crop by planting a barley crop, which does not depend on
irrigation and possible curtailments. The most risk-averse small-scale
farmers (R1) do not even wait for any information on water availability and
already plant barley in November. For them there is no value in the
additional information. For the slightly less risk-averse farmers (R2) there
is limited value in the additional information. If in January the water
resource situation is expected to be good, then they will choose to plant
maize, but at the first sign of it being bad they will forfeit the possible
higher profits from maize and opt to take the safe bet by planting barley.
The most risk-acceptant small-scale farmers benefit the most from the
additional information, as it will help them make the choice between taking
the gamble of waiting for the water resource availability to become better so
that they can plant maize, or plant a cereal to avoid the risk of having to
leave the land fallow if it does not. In this case these results show that
the additional information may be beneficial to improved equity across the
farmers in the irrigation district as it is most beneficial to small-scale
farmers, provided they are willing to take a gamble to improve their
benefits.</p>
      <p id="d1e1313">In this paper we model the distribution of risk averseness using only a
simple percentile distribution. A more realistic distribution of risk
averseness can be developed using for example the constant absolute risk
aversion utility function <xref ref-type="bibr" rid="bib1.bibx26 bib1.bibx33" id="paren.45"/>, though this
will require extensive survey data to determine how risk averseness is
distributed among farmers.</p>
</sec>
</sec>
<sec id="Ch1.S8" sec-type="conclusions">
  <title>Conclusions</title>
      <p id="d1e1326">An approach that combines stakeholder consultation and decision modelling was
followed, allowing a comprehensive analysis of the role of information on
drought management decisions in the area. Consultation with the different
decision-makers in the Ebro basin provided useful insight into the
operational decisions they make in managing water resources when scarce, and
their information needs and use. This allowed us to identify the courses of
action available to the farmers and water managers, and to analyse their
choices as a function of the information they have available to them.
Feedbacks between the decisions made by farmers and the reservoir operators
at irrigation district level were identified: curtailments imposed at
irrigation district level as a result of water scarcity influences the
decision farmers make on the planting of crops, which in turn influence
demand and consequently water scarcity.</p>
      <p id="d1e1329">Based on the findings of the consultation, a decision model representing
these interrelated decisions was built with the aim of quantifying the effect of
additional information on the decisions. The modelled decisions, which
consider the allocation of water, are taken based on the expected
availability of water during the irrigation season. This is currently
informed primarily by observed reservoir-level data. When levels are above a
defined threshold at the time of the decision, water resources availability
is classified as good, whereas when levels are below the threshold and
expected demand is high it is classified as poor and curtailments to water
allocations are applied. Farmers decide on the crop to be planted based on their
expectation of water resources availability, and whether curtailments are in
force. The decision model was then extended from considering only reservoir
levels to include additional information on snow cover in the basin
headwaters obtained from MODIS remote sensing data to inform the expectation
of water resources availability.</p>
      <p id="d1e1332">Our simulations with the decision model show the additional information can
contribute to better decisions and ultimately to higher benefits for the
farmers. However, the ratio between the cost of planting and the market value
of the crop<?pagebreak page5915?> proved to be a critical aspect in determining the best course of
action to be taken and the value of the (additional) information. When there
is little room for error due to small margins, then any information used to
inform the decision may even be detrimental to any benefits being made.
However, even in this case the additional information on snow cover can
provide benefit over using the reservoir levels alone. Tests with reduced
planting costs, and thus increasing margins, does lead to a higher benefit when
using the additional information from snow cover. Nevertheless uncertainty in
the relationship between good snow cover and water resource availability may
lead to overestimation of the expected resources and consequent losses.</p>
      <p id="d1e1335">A key finding of our research is that farmers can benefit when the
operational decisions they make consider the additional information. To what
extent they benefit does, however, depend to a great extent to their level of
risk averseness. Risk-averse farmers will decide to take the safe option
early on, with information on the available water resource then having no
value. Farmers that are less risk averse do benefit as the information helps
them weigh the options between planting a crop with a higher return or having
to leave the land fallow.</p>
</sec>

      
      </body>
    <back><notes notes-type="codedataavailability">

      <p id="d1e1342">All in situ and remote sensing data used in this
research are openly available. The sources are mentioned in Sect. 5.1. The
crop models, Aquacrop-OS and Cropwat, are open-source and available from
<uri>http://aquacropos.com/download-2/</uri> (last access: 12 November 2018) and
<uri>http://www.fao.org/land-water/databases-and-software/cropwat/en/</uri> (last
access: 12 November 2018) respectively. The code for the decision model may
be made available by request to the corresponding author.</p>
  </notes><app-group>
        <supplementary-material position="anchor"><p id="d1e1352">The supplement related to this article is available online at: <inline-supplementary-material xlink:href="https://doi.org/10.5194/hess-22-5901-2018-supplement" xlink:title="pdf">https://doi.org/10.5194/hess-22-5901-2018-supplement</inline-supplementary-material>.</p></supplementary-material>
        </app-group><notes notes-type="authorcontribution">

      <p id="d1e1361">CL, AI, LG and MW conceived the idea and designed the analysis. CL, AI, LG and VS performed
the interviews. CL developed the model, performed the analysis and prepared
the paper with advice and contributions from all authors.</p>
  </notes><notes notes-type="competinginterests">

      <p id="d1e1367">The authors declare that they have no conflict of
interest.</p>
  </notes><ack><title>Acknowledgements</title><p id="d1e1373">The authors would like to thank CHE, CAyC and Raimat for their collaboration
in the consultation phase of this research.</p><p id="d1e1375">This research received funding from the European Union Seventh Framework
Programme (FP7/2007–2013) under grant agreement no. 603608, “Global Earth
Observation for integrated water resource assessment”: eartH2Observe. This
work is a contribution to the Hymex Drought and Water Resources Science
Team.<?xmltex \hack{\newline}?><?xmltex \hack{\newline}?> Edited by: Hilary McMillan
<?xmltex \hack{\newline}?> Reviewed by: two anonymous referees</p></ack><ref-list>
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    <!--<article-title-html>Do users benefit from additional information in support of operational drought management decisions in the Ebro basin?</article-title-html>
<abstract-html><p>We follow a user-based approach to examine how information supports
operational drought management decisions in the Ebro basin and how these can
benefit from additional information such as from remote sensing data. First
we consulted decision-makers at basin, irrigation district and farmer scale
to investigate the drought-related decisions they make and the information
they use to support their decisions. This allowed us to identify the courses
of action available to the farmers and water managers, and to analyse their
choices as a function of the information they have available to them. Based
on the findings of the consultation, a decision model representing the
interrelated decisions of the irrigation association and the farmers was
built. The purpose of the model is to quantify the effect of additional
information on the decisions made. The modelled decisions, which consider the
allocation of water, are determined by the expected availability of water
during the irrigation season. This is currently informed primarily by
observed reservoir level data. The decision model was then extended to
include additional information on snow cover from remote sensing. The
additional information was found to contribute to better decisions in the
simulation and ultimately higher benefits for the farmers. However, the ratio
between the cost of planting and the market value of the crop proved to be a
critical aspect in determining the best course of action to be taken and the
value of the (additional) information. Risk-averse farmers were found to
benefit least from the additional information, while less risk-averse farmers
stand to benefit most as the additional information helps them take better
informed decisions when weighing their options.</p></abstract-html>
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