A hydrological model was used to compare different parameterisation strategies in view of predicting ecologically relevant streamflow indices in 33 Irish catchments. Compared for 14 different periods, a strategy fitting simulated and observed streamflow indices yielded better performance than fitting simulated and observed streamflow, but it also yielded a less consistent ensemble of parameter sets, suggesting that these indices may not be hydrologically relevant for model parameterisation.

We characterized the (dis)agreement between six evaporation methods from hourly to decadal timescales, focussing on the IJsselmeer region in the Netherlands. The projected changes in mean yearly water losses through evaporation between the years 2000 and 2100 range from 4 mm to 94 mm among the methods. We therefore stress that the choice of method is of great importance for water managers in their decision making.

Reliable forecasts of soil moisture conditions help water-related sectors to better prepare for drought and flooding events. This paper describes an approach in which monthly-to-seasonal soil moisture forecasts are developed and compared to remotely sensed observations from SMAP satellite. Our results reveal a promising skill in forecasting long-range soil moisture conditions, suggesting its great potential for real-time and practical applications.

We grouped 643 rivers from the United States into 10 behavioral groups based on their hydrological behavior (e.g., how much water they transport overall). Those groups are aligned with the ecoregions in the United States. Depending on the groups’ location and other characteristics, either snow, aridity or seasonality is most important for the behavior of the rivers in a group. We also find that very similar river behavior can be found in rivers far apart and with different characteristics.

How catchments store and release rain or melting water is still not well known. Now, it is broadly accepted that most of the water in streams is older than several months, and a relevant part may be many years old. But the age of water depends on the stream regime, being usually younger during high flows. This paper tries to provide tools for better analysing how the age of waters varies with flow in a catchment and for comparing the behaviour of catchments diverging in climate, size and regime.

Rapid warming in the Arctic is causing increased permafrost temperatures and ground ice degradation. To study the effects of ice degradation on water distribution, tracer was applied to two end members of ice-wedge polygons – a ubiquitous landform in the Arctic. End member type was found to significantly affect water distribution as lower flux was observed with ice-wedge degradation. Results suggest ice degradation can influence partitioning of sequestered carbon as carbon dioxide or methane.

Here we investigate the response of global evaporation to main climate modes, including the Indian Ocean Dipole (IOD), the North Atlantic Oscillation (NAO) and the El Niño–Southern Oscillation (ENSO). Our results indicate that ENSO is an important driver of evaporation for many regions, while the impacts of NAO and IOD are substantial. This study allows us to obtain insight about the predictability of evaporation and, hence, may help to improve the early-warning systems of climate extremes.

In this paper, recession flow analysis – assuming nonlinearized outflow from aquifers into streams – was used to quantify active groundwater storage in a headwater catchment with high glacierization and large-scale frozen ground on the Tibetan Plateau. Hence, this work provides a perspective to clarify the impact of glacial retreat and frozen ground degradation due to climate change on hydrological processes.

Recession analysis uses the receding streamflow following precipitation events to estimate watershed-average properties. Two methods for recession analysis use recession events individually or all events collectively. Using synthetic case studies, this paper shows that analyzing recessions collectively produces flawed interpretations. Moving forward, recession analysis using individual recessions should be used to describe the average and variability of watershed behavior.

There are many ways for water to join a river after a rainfall event, but they can be split into two categories: the quick ones that remain in the surface and the slow ones that use other trajectories. Thus, measured streamflow of a river can be split into two components: quickflow and baseflow. We present a new method to perform this separation, using only streamflow and rainfall data, which are generally broadly available. It is then used as an analysis tool of river dynamics over France.

Non-point source contaminations of aquifers are complex to model, predict and manage. This study uses numerical and stochastic methods to address the importance of key sources of spatial variability. We show that heterogeneity in recharge and contaminant loading does not significantly impact management metrics and could be simplified. Also, homogenizing physical properties has more impact on predictions, but can provide useful information on concentration statistics in a regional analysis.

Heavy precipitation events (HPEs), occurring around the globe, lead to natural hazards as well as to water resource recharge. Rainfall patterns during HPEs vary from one case to another and govern their effect. Thus, correct prediction of these patterns is crucial for coping with HPEs. However, the ability of weather models to generate such patterns is unclear. Here, we characterise rainfall patterns during HPEs based on weather radar data and evaluate weather model simulations of these events.

Quantifying crop water use at each field every day is challenging because of the complexity of the evapotranspiration (ET) process and the unavailability of data at high spatiotemporal resolutions. We fuse multi-satellite data and employ a sophisticated model to estimate ET at 30 m resolution and a daily interval. With validation against 86 site years of ground truth in the US Corn Belt, we are confident that our ET estimation is accurate and a reliable tool for water resource management.

To understand human vulnerability to flood and drought risk across large regions, researchers increasingly use large-scale hydrological models that convert climate to river flows. These models include the important effects of river regulation by dams but do not currently capture dam operators' use of flow forecasts to mitigate risk. This research addresses this problem by developing an approach to infer the forecast horizons contributing to the operations of a large sample of dams.

Fresh groundwater (GW) on barrier islands is affected by GW use and precipitation variability. Mean residence times (MRTs) of GW on a sand barrier island were determined. They ranged from 37 years to more than 150 years for tritium and had a much larger range (modern to 5000 years) for carbon-14. Perched aquifer systems in the unsaturated zone and peat formations around wetlands are the most likely cause of longer MRTs, as they have a significant impact on regional recharge and flow diversion.

During 18 May 2015, a storm event produced a flash flood in the municipality of Salgar (northwestern Colombian Andes), resulting in more than 100 human casualties and significant economic losses. Here we present a modeled process reconstruction of what happened during this event. For this, we only use radar rainfall estimations and a digital elevation model. Results show that with scarce data there is an opportunity to obtain acceptable tools for risk management and decision making.

The inundation of flood-prone areas can have crucial impacts on runoff generation and water quality. We investigate the variation of flooding in space and time along a small stream with long-term observations and numerical simulations. We demonstrate that the main reason for the flooding is the exfiltration of groundwater into local topographic depressions. However, only interplay with further influencing factors can explain all of the variability of the observed flooding patterns and dynamics.

This work relates total water storage (TWS) and rainfall to surface water inundation (SWI) using NASA satellite data. We determine whether TWS and/or rainfall control global SWI developments. Regression methods and cross-correlations were used to relate the measurements and correct for time differences among peaks. Results show TWS and rainfall control most global SWI developments. To our knowledge, this is the first global study on SWI controls and validates previous findings.

An automatic workflow is introduced to measure surface flow velocities in rivers. The provided tool enables the measurement of spatially distributed surface flow velocities independently of the image acquisition perspective. Furthermore, the study illustrates how river discharge in previously ungauged and unmeasured regions can be retrieved, considering the image-based flow velocities and digital elevation models of the studied river reach reconstructed with UAV photogrammetry.

The combined use of GRACE mass anomalies and observed river discharge for the first time allows us to quantify the water storage volumes drainable by gravity on global scales. Modelling of catchment and river network storages in a cascade with different dynamics reveals the time lag between total mass and runoff is caused by a non-zero river network storage. This allows catchment and river network storage volumes to be distinguished and is thus of great importance for water resources management.

The present work addresses the impact of climate change on the Water Highway project in Morocco. This project aims to transfer 860 × 106 m³ yr⁻¹ of water from the north to the south. As the project is very sensitive to the availability of water in the northern regions, we evaluate its feasibility under different future climate change scenarios: under a pessimistic climate scenario, the project is infeasible; however, under an optimistic scenario a rescaled version might be feasible.

Evapotranspiration (ET) links global water, carbon and energy cycles. We used 4 remote sensing models, 2 machine-learning algorithms and 14 land surface models to analyze the changes in global terrestrial ET. These three categories of approaches agreed well in terms of ET intensity. For 1982–2011, all models showed that Earth greening enhanced terrestrial ET. The small interannual variability of global terrestrial ET suggests it has a potential planetary boundary of around 600 mm yr^-1.

This study investigates the response of regional groundwater system to the climate change under three global warming levels (1.5, 2, and 3 °C) in a central German basin. A comprehensive uncertainty analysis is also presented. This study indicates that the variability of responses increases with the amount of global warming, which might affect the cost of managing the groundwater system.

Seasonal snowpack is an essential water resource in Mediterranean mountains. Here, we look at the role of water percolation in simulating snow mass (SWE), for the first time, in Mount Lebanon. We use SnowModel, a distributed snow model, forced by station data. The main sources of uncertainty were attributed to rain–snow partitioning, transient winter snowmelt, and the subpixel snow cover. Yet, we show that a process-based model is suitable to simulate wet snowpack in Mediterranean mountains.

We presented a global comparison between observed and simulated trends in a flood index over the 1971–2005 period using the Global Streamflow Indices and Metadata archive and six global hydrological models available through The Inter-Sectoral Impact Model Intercomparison Project. Streamflow simulations over 2006–2099 period robustly project high flood hazard in several regions. These high-flood-risk areas, however, are under-sampled by the current global streamflow databases.

Water resource allocation to various sectors requires an understanding of the hydrological cycle, where evapotranspiration (ET) is a key component. Satellite-derived products estimate ET but are hard to evaluate at large scales. This work presents an alternate evaluation methodology to point-scale observations in Africa. The paper enables users to select an ET product based on their performance regarding selected criteria using a ranking system. The highest ranked products are WaPOR and CMRSET.