The sources of stream water are important, for instance, for predicting floods. The connectivity between streams and different (ground-)water sources can change during rain events, which affects the stream water composition. We investigated this for stream water sampled during four events and found that stream water came from different sources. The stream water composition changed gradually, and we showed that changes in solute concentrations could be partly linked to changes in connectivity.

Fine-resolution lake temperature measurements (2 min, 15 depths) show different lake responses to atmospheric forcings: (1) continuous diurnal oscillations in the temperature in the first 5 m of the lake, (2) occasional diurnal oscillations in the temperature at depths from 7 to 20 m, and (3) occasional surface and internal seiches. Due to the sloped lake bottom, surface seiches produced the high-frequency oscillations in the lake temperatures with periods of 9 min at depths from 9 to 17 m.

Under rapid ongoing climate change, accurate quantification of natural greenhouse gas emissions in aquatic environments such as lakes and ponds is needed to understand regulation and feedbacks. Building on the rapid development in wireless communication, sensors, and computation technology, we present a low-cost, open-source, automated and remotely accessed and controlled device for carbon dioxide and methane fluxes from open-water environments along with tests showing their potential.

Vegetation optical depth (VOD) is a byproduct of the soil moisture retrieval from passive microwave instruments. This study demonstrates that VOD information can be utilized for improving land surface water budget and carbon conditions through data assimilation.

Projecting the changes in water resources under a no-analog future climate requires integrated hydrologic models. However, these models are plagued by several sources of uncertainty. A hydrologic model was forced with various resolutions of meteorological forcing (0.5 to 40.5 km) to assess its sensitivity to these inputs. We show that most hydrologic variables reveal biases that are seasonally and spatially dependent, which can have serious implications for calibration and water management.

Changes in snow affect the runoff seasonality, including summer low flows. Here we analyse this effect in 59 mountain catchments in Czechia. We show that snow is more effective in generating runoff compared to rain. Snow-poor years generated lower groundwater recharge than snow-rich years, which resulted in higher deficit volumes in summer. The lower recharge and runoff in the case of a snowfall-to-rain transition due to air temperature increase might be critical for water supply in the future.

We investigate why a conceptual hydrological model failed to correctly predict observed discharge changes in response to increasing precipitation and air temperature in 156 Austrian catchments. Simulations indicate that poor model performance is related to two problems, namely a model structure that neglects changes in vegetation dynamics and inhomogeneities in precipitation data caused by changes in stations density with time. Other hypotheses did not improve simulated discharge changes.

We present an automatic procedure based on wavelet ridge extraction to identify some characteristics of alternating morphological units (e.g., pools to riffles). We used four hydro-morphological variables (velocity, hydraulic radius, bed shear stress, local channel direction angle). We find that the wavelengths are consistent with the values of the literature, and the use of a multivariate approach yields more robust results and ensures a consistent covariance of flow variables.

Fresh groundwater can flow to oceans and seas, possibly adding nutrients and pollutants to coastal ecosystems. For the first time, three complementary (salinity-sensitive) geophysical methods are combined to delineate the outflow in a very dynamic coastal environment. This provides temporal and spatial information on the salt- and freshwater distribution on land, in the intertidal zone, and offshore and visualizes the fresh-groundwater discharge around the low-water line at De Westhoek, Belgium.

A modeling tool is developed to assess the vulnerability of coastal wetlands to climatic and water management changes. Applied to the case study of the Gialova lagoon (Greece), this tool highlights the reliance of the lagoon functionality on scarce freshwater sources already under high demand from agriculture. Climatic changes will likely increase lagoon salinity, despite efforts to improve water management.

In the case study presented in this paper, the GNSS-IR technique was used to monitor soil moisture during 66 d, from 3 December 2018 to 6 February 2019, in the installations of the Cajamar Centre of Experiences, Paiporta, Valencia, Spain. Two main objectives were pursued. The first was the extension of the technique to a multi-constellation solution using GPS, GLONASS, and GALILEO satellites, and the second was to test whether mass-market sensors could be used for this technique.

This paper is important for water resource management, being concerned with irrigation return flow causing hotspots in nitrate concentrations in groundwater and denitrification imprints where nitrate concentrations are reduced by denitrification although the dissolved oxygen concentration is not low. The work is highly significant for modelling of nitrate transport through soil–groundwater systems, for understanding denitrification processes, and for managing fertilizer application to land.

As frequently used precipitation products, Gauge, CPC, and CHIRPS presented different behaviors in describing precipitation on different spatial and temporal scales, yet these dissimilarities could be concealed in hydrological modeling by parameter calibration and validation. Parameter adjustment in hydrologic modeling, however, would yield different water balance components and thus alter hydrologic mechanisms, demonstrating the complexity in physically describing natural hydrologic processes.

Stable isotopes of soil water are an effective tool to reveal soil hydrological processes in irrigated agricultural fields. Flow mechanisms and isotopic patterns of soil water in the soil matrix differ, depending on the crop and irrigation practices. Isotope data supported the fact that unproductive water losses via evaporation can be reduced by introducing dry seasonal crops to the crop rotation system.

Remote sensing only provides snapshots of rapidly changing land surface variables; this limits its application for water resources and ecosystem management. To obtain continuous estimates of surface temperature, soil moisture, evapotranspiration, and ecosystem productivity, a simple and operational modelling scheme is presented. We demonstrate it with temporally sparse optical and thermal remote sensing data from an unmanned aerial system at a Danish bioenergy plantation eddy covariance site.

Freshwater availability is crucial for sustainable development across the Asian and eastern European regions. Our results indicate widespread decline in terrestrial water storage (TWS) over the region during 2002–2017, primarily due to the intensive over-extraction of groundwater and warmth-induced surface water loss. The findings provide insights into changes in TWS and its components over the Asian and eastern European regions, where there is growing demand for food grains and water supplies.

Our research has analyzed the surface water budget and atmospheric water vapour budget over western Canada from a set of convection-permitting regional climate simulations. The pseudo-global-warming simulation shows a great increase in evapotranspiration and an enhanced water cycle. We found that the orographic effect on the water vapour budget is significant over the Saskatchewan River basin, indicating the need for high-resolution regional climate modelling to reflect the effects.

A new way to downscale rainfall fields based on the notion of equal-volume areas (EVAs) is proposed. Experiments conducted on 100 rainfall events in the Netherlands show that the EVA method outperforms classical methods based on fixed grid cell sizes, producing fields with more realistic spatial structures. The main novelty of the method lies in its adaptive sampling strategy, which avoids many of the mathematical challenges associated with the presence of zero rainfall values.

We find that simulated runoff values are highly dependent on the accuracy of precipitation inputs. In contrast, simulated evapotranspiration is generally much less influenced in our comparatively wet study region. We also find that the impact of precipitation uncertainty on simulated runoff increases towards wetter regions, while the opposite is observed in the case of evapotranspiration.

We investigated the effects of the 2018 drought on water partitioning in a lowland catchment under grassland and forest in north-eastern Germany. Conditions resulted in drying up of streams, yield losses, and lower groundwater levels. Oak trees continued to transpire during the drought. We used stable isotopes to assess the fluxes and ages of water. Sustainable use of resource water requires such understanding of ecohydrological water partitioning.

In land surface models (LSMs), soil properties are inferred from soil texture. In this study, we use different input global soil texture maps from the literature to investigate the impact of soil texture on the simulated water budget in an LSM. The medium loamy textures give the highest evapotranspiration and lowest total runoff rates. However, the different soil texture maps result in similar water budgets because of their inherent similarities, especially when upscaled at the 0.5° resolution.

This study assesses the extent to which a land surface model can be optimized via the assimilation of leaf area index (LAI) observations at the global scale. The model performance is evaluated by the model-estimated LAI and five water flux/storage variables. Results show the LAI assimilation reduces errors in the model-estimated LAI. The LAI assimilation also improves the five water variables under wet conditions, but some of the model-estimated variables tend to be worse under dry conditions.

Our objective is to question the representation of the energy budget in surface–vegetation–atmosphere transfer models for the prediction of the convective fluxes in crops with complex structures (row) and under transient hydric regimes due to irrigation. The main result is that a coupled multiple energy balance approach is necessary to properly predict surface exchanges for these complex crops. It also points out the need for other similar studies on various crops with different sparsity levels.

Under a changing climate, reliable information on future hydrological conditions is necessary to inform water resource management. Here, we collaborated with a hydropower company that selected streamflow and energy demand indices. Using these indices, we identified stakeholder needs and used this to tailor the production of our climate change impact projections. We show that opportunities and risks for a hydropower company depend on a range of factors beyond those covered by traditional studies.

During the Pliocene, the Qaidam Basin on the Tibetan Plateau contained a mega-lake system. During the Pleistocene, it disappeared almost completely. Today, hyperarid climates prevail in the low-altitude parts of the basin. This study reveals that today's mean water balance of the Qaidam Basin is nearly zero and is positive during warmer, less dry years. The results explain how the mega-lake system could survive for a long time in the past and could eventually be restored in the future.

This paper was developed from PhD research focused on assessing the value of using hydrological datasets in water resource management. Previous studies have assessed how well data can help in predicting river flows, but there is a lack of knowledge of how well data can help in water allocation decisions. In our research, it was found that using seasonal streamflow forecasts improves the available water estimates, resulting in better water allocation decisions in a highly regulated basin.

To better understand the fate of methane (CH₄) and carbon dioxide (CO₂) in freshwaters, dissolved CH₄ and CO₂ need to be measured with a high temporal resolution. We developed the Fast-Response Automated Gas Equilibrator (FaRAGE) for real-time in situ measurement of dissolved gases in water. FaRAGE can achieve a short response time (CH₄: t_95 % = 12 s; CO₂: t_95 % = 10 s) while retaining a high equilibration ratio and accuracy.