As snow cover becomes patchy during snowmelt, energy is advected from warm snow-free surfaces to cold snow-covered surfaces. This paper proposes a simple sensible and latent heat advection model for snowmelt situations that can be coupled to one-dimensional energy balance snowmelt models. The model demonstrates that sensible and latent heat advection fluxes can compensate for one another, especially in early melt periods.

Few studies focused on the direct solution of the ADE for 3-D DFNs. The study is the first to solve the ADE and focus on assessing the velocity uncertainty in 3-D DFNs. The velocity uncertainty shows a limited range of influence close to the mean diameter of a fracture. The information is useful for engineering designs at sites with fractured rocks. We quantified that the tracer test in wells might lead to the overestimation of mean concentration and induce high uncertainty in fractured media.

Complex water management activities challenge hydrologic modeling. We evaluated how different representations of reservoir operation and agricultural irrigation affect streamflow simulations in the Yakima River basin. Results highlight the importance of the inclusion of reliable reservoir and irrigation information in watershed models for improving watershed hydrology modeling. Models used here are public and hold the promise to benefit water assessment and management in other basins.

We developed a new tracer-aided hydrological model for karst catchments. This model captured the flow and tracer dynamics within each landscape unit quite well, and we could estimate the storage, fluxes and age of water within each. Such tracer-aided models enhance our understanding of the hydrological connectivity between different landscape units and the mixing processes between various flow sources. It is an encouraging step forward in tracer-aided modelling of karst catchments.

We investigate the seasonal memory properties of a large sample of European rivers in terms of high and low flows. We compute seasonal correlations between peak and low flows and average flows in the previous seasons and explore the links with various physiographic and hydro-climatic catchment descriptors. Our findings suggest that there is a traceable physical basis for river memory which in turn can be employed to reduce uncertainty and improve probabilistic predictions of floods and droughts.

In this study, we explore the use of an underground superconducting gravimeter as a new source of in situ observations for the evaluation of radar-based precipitation estimates. The comparison of radar and gravity time series over 15 years shows that short-duration intense rainfall events cause a rapid decrease in the measured gravity. Rainfall amounts can be derived from this decrease. The gravimeter allows capture of rainfall at a much larger spatial scale than a traditional rain gauge.

Floods often affect a whole region and not only a single location. When estimating the rarity of regional events, the dependence of floods at different locations should be taken into account. We propose a simple model that considers the dependence of flood events at different locations and the network structure of the river system. We test this model on a medium-sized catchment in Switzerland. The model allows for the simulations of flood event sets at multiple gauged and ungauged locations.

The root zone storage capacity (S_r) of the vegetation is an important hydrological parameter. This study used a relatively new method based on climate data to estimate S_r values in boreal regions, instead of using soil data. The study shows that the climate-derived S_r values are not only linked to climate, but can also be directly linked to vegetation characteristics, and that the (non-)coincidence of snow melt and potential evaporation can have a large influence on the derived S_r values.

Managed aquifer recharge allows increasing water resources and can be used to improve water quality. We assess the degradative capabilities of infiltrating pollutants by mapping the composition of microbial communities linked to periods of infiltration/drought. From samples of soil, surface and groundwater, we found some microbial species involved in the nitrogen and carbon cycles. Furthermore, we found that, during infiltration, microbial abundance rises, increasing degradative capabilities.

We investigated seasonal changes in sediment transport activities following forest harvesting in a humid periglacial area. Removal of the forest canopy by forest harvesting alters the type of winter soil creep. Winter creep velocity of the ground surface sediment in the harvested site was significantly higher than that in the non-harvested site. Meanwhile, sediment flux on the hillslopes decreased in the harvested site because of capture of sediment by branches of harvested trees.

We evaluated the uncertainty propagation from the inputs (forcings) and parameters to the predictions of groundwater travel time distributions (TTDs) using a fully distributed numerical model (mHM-OGS) and the StorAge Selection (SAS) function. Through detailed numerical and analytical investigations, we emphasize the key role of recharge estimation in the reliable predictions of TTDs and the good interpretability of the SAS function.

This paper provides a process-based assessment of the impact of spatial model resolution on future projections of European soil moisture changes. In central-western Europe, simulated future drying is more severe and starts earlier in the season at higher global resolution compared to conventional resolution simulations. The enhanced drying suggests that future projections of central-western European drying by conventional resolution global climate models have been potentially underestimated.

We conducted a comprehensive evaluation of 26 precipitation datasets for the US using the Stage-IV gauge-radar dataset as a reference. The best overall performance was obtained by MSWEP V2.2, underscoring the importance of applying daily gauge corrections and accounting for reporting times. Our findings can be used as a guide to choose the most suitable precipitation dataset for a particular application.

A hydrological model is used in combination with thermal measurements to investigate the effect of restoration actions in an artificial island of the Upper Rhine river. The injection of water in a newly built channel is efficient as it enhances overall hydrologic dynamics of the system with possible benefits for water quality and biodiversity. The combined use of the model and thermal measurements is also proven to be a relevant tool to study the effect of restoration on hydrological systems.

This study investigates the value of assimilating coarse-resolution remotely sensed soil moisture data into high-resolution land surface models for improving soil moisture and runoff modeling. The soil moisture estimates in this study, with complete spatio-temporal coverage and improved spatial resolution from the assimilation, offer a new reanalysis product for the monitoring of surface soil water content and other hydrological fluxes at 3 km resolution over Europe.

How long does it take for raindrops to become streamflow? Here I propose a new approach to this old problem. I show how we can use time series of isotope data to measure the average fraction of same-day rainfall appearing in streamflow, even if this fraction varies greatly from rainstorm to rainstorm. I show that we can quantify how this fraction changes from small rainstorms to big ones, and from high flows to low flows, and how it changes with the lag time between rainfall and streamflow.

To localize the source of a contaminant in the subsurface, based on concentration observations at some wells, we propose to test different possible locations and minimize the misfit between observed and simulated concentrations. We use a global optimization technique that relies on an expected improvement criterion, which allows a good exploration of the parameter space, avoids the trapping of local minima and quickly localizes the source of the contaminant on the presented synthetic cases.

This paper explains why forecasts of river flow in Europe for a time between 1 and 7 months have skill. The forecasts were produced with a water model. The model reacts to forecasts of weather variables like precipitation, which tend to have little skill and hence hardly contribute to the skill in the forecasts of river flow. The paper shows when and where these forecasts have skill; this is mostly due to knowledge of the amount of water in the soil at the time the forecasts are made.

Do experts attach the same meaning as laypeople to terms often used in hydrology such as "river", "flooding" and "downstream"? In this study a survey was completed by 34 experts and 119 laypeople to answer this question. We found that there are some profound differences between experts and laypeople: words like "river" and "river basin" turn out to have a different interpretation between the two groups. However, when using pictures there is much more agreement between the groups.

The relationship among glacier melt, groundwater, and streamflow remains highly uncertain, especially in tropical glacierized watersheds in response to climate. We implemented a multi-method approach and found that melt contribution varies considerably and may drive streamflow variability at hourly to multi-year timescales, rather than buffer it, as commonly thought. Some of the melt contribution occurs through groundwater pathways, resulting in longer timescale interactions with streamflow.

Groundwater supplies the most freshwater for industrial and agricultural production and domestic use in the arid northwest of China. This research uses environmental tracers to enhance one's understanding of groundwater, including aquifer recharge sources and groundwater mean residence times in the alluvium aquifers. The results provide valuable implications for groundwater resources regulation and sustainable development and have practical significance for other arid areas.

Low-flow events are little dynamic in space and time. Thus, it is hypothesized that models can be found, based on simple statistical relationships between low-flow metrics and meteorological states, that can help identify potential low-flow drivers. In this study we assess whether such relationships exist and whether they can be applied to predict future low flow within regional climate change impact assessment in the northwestern part of Germany.

This study is an effort for a better understanding and quantification of the water cycle and related processes in the Mediterranean region, by dealing with satellite products and their uncertainties. The aims of the paper are 3-fold: (1) developing methods with hydrological constraints to integrate all the datasets, (2) giving the full picture of the Mediterranean WC, and (3) building a model-independent database that can evaluate the numerous regional climate models (RCMs) for this region.

Subseasonal streamflow forecasts have received increasing attention during the past decade, but their performance in alpine catchments is still largely unknown. We analyse the effect of a statistical correction technique applied to the driving meteorological forecasts on the performance of the resulting streamflow forecasts. The study shows the benefits of such hydrometeorological ensemble prediction systems and highlights the importance of snow-related processes for subseasonal predictions.

We estimate the phase lag of surface states and heat fluxes to incoming solar radiation at the sub-daily timescale. While evapotranspiration reveals a minor phase lag, the vapor pressure deficit used as input by Penman–Monteith approaches shows a large phase lag. The surface-to-air temperature gradient used by energy balance residual approaches shows a small phase shift in agreement with the sensible heat flux and thus explains the better correlation of these models at the sub-daily timescale.

We reviewed research perspectives and ambitions of connectivity scientists in order to improve joint connectivity research across disciplinary boundaries. We demonstrated the wide diversity of approaching science in the community. We introduced a shared mental model approach with an exploratory case study as a way to overcome persistent barriers in understanding by identifying gaps and overlaps of individual researchers' perspectives, which improves collaboration in interdisciplinary science.

Our study shows that there is declining coupling between sediment concentration and discharge from daily to annual scales for gauges across the Yellow River basin (YRB). Not only the coupling, but also the magnitude of sediment response to discharge variation decreases with long-term mean discharge. This emergent stationarity can be related to sediment retardation by vegetation, suggesting the shift of dominance from water to vegetation as mean annual discharge increases.

In this study, we quantified the holistic impacts of food trade on food security and water–land savings and revealed that the MENA region saved significant amounts of national water and land based on the import of barley, maize, rice, and wheat within the period from 2000 to 2012. In addition, the MENA region focused more on increasing the volume of virtual water imported during the period 2006–2012, yet little attention was paid to the expansion of connections with country exporters.

The description of pharmaceutical fate and transport introduced into a watershed is a challenging topic, especially because of the possible adverse effects on human health. In addition, an accurate estimation of solute sources and routes is still missing. This study uses a new promising modeling approach to predict pharmaceutical concentrations in rivers. Results show an interesting relationship between solute concentrations in waters and touristic fluxes.

This paper assesses the potential of satellite precipitation estimates (SPEs) for precipitation measurement and hydrological and snow modelling. A total of 12 SPEs is considered to provide a global overview of available SPE accuracy for users interested in such datasets. Results show that, over poorly monitored regions, SPEs represent a very efficient alternative to traditional precipitation gauges to follow precipitation in time and space and for hydrological and snow modelling.

This paper projects future changes in drought characteristics under different warming levels over a semiarid watershed based on hydroclimate simulations. Despite large uncertainties from climate models, we find that less frequent but more severe hydrological drought events would occur in the near future, suggesting that different aspects of hydrological droughts should be carefully investigated when assessing the impact of global warming.