Terrestrial Water Storage Variations Research Articles

The role of groundwater in the Amazon water cycle: 3. Influence on terrestrial water storage computations and comparison with GRACE

AbstractWe explore the mechanisms whereby groundwater influences terrestrial water storage (TWS) in the Amazon using GRACE observations and two contrasting versions of the LEAF‐Hydro‐Flood hydrological model: one with and the other without an interactive groundwater. We find that, first, where the water table is shallow as in northwestern Amazonia and floodplains elsewhere, subsurface stores (vadose zone and groundwater) are nearly saturated year‐round, hence river and flooding dominate TWS variation; where the water table is deep as in southeastern Amazonia, the large subsurface storage capacity holds the infiltrated water longer before releasing it to streams, hence the subsurface storage dominates TWS variation. Second, over the whole Amazon, the subsurface water contribution far exceeds surface water contribution to total TWS variations. Based on LEAF‐Hydro‐Flood simulations, 71% of TWS change is from subsurface water, 24% from flood water, and 5% from water in river channels. Third, the subsurface store includes two competing terms, soil water in the vadose zone and groundwater below the water table. As the water table rises, the length of vadose zone is shortened and hence the change in groundwater store is accompanied by an opposite change in soil water store resulting in their opposite phase and contributions to total TWS. We conclude that the inclusion of a prognostic groundwater store and its interactions with the vadose zone, rivers, and floodplains in hydrological simulations enhances seasonal amplitudes and delays seasonal peaks of TWS anomaly, leading to an improved agreement with GRACE observations.

A simple groundwater scheme in the TRIP river routing model: global off-line evaluation against GRACE terrestrial water storage estimates and observed river discharges

Abstract. Groundwater is a non-negligible component of the global hydrological cycle, and its interaction with overlying unsaturated zones can influence water and energy fluxes between the land surface and the atmosphere. Despite its importance, groundwater is not yet represented in most climate models. In this paper, the simple groundwater scheme implemented in the Total Runoff Integrating Pathways (TRIP) river routing model is applied in off-line mode at global scale using a 0.5° model resolution. The simulated river discharges are evaluated against a large dataset of about 3500 gauging stations compiled from the Global Data Runoff Center (GRDC) and other sources, while the terrestrial water storage (TWS) variations derived from the Gravity Recovery and Climate Experiment (GRACE) satellite mission help to evaluate the simulated TWS. The forcing fields (surface runoff and deep drainage) come from an independent simulation of the Interactions between Soil-Biosphere-Atmosphere (ISBA) land surface model covering the period from 1950 to 2008. Results show that groundwater improves the efficiency scores for about 70% of the gauging stations and deteriorates them for 15%. The simulated TWS are also in better agreement with the GRACE estimates. These results are mainly explained by the lag introduced by the low-frequency variations of groundwater, which tend to shift and smooth the simulated river discharges and TWS. A sensitivity study on the global precipitation forcing used in ISBA to produce the forcing fields is also proposed. It shows that the groundwater scheme is not influenced by the uncertainties in precipitation data.

Continental-Scale Basin Water Storage Variation from Global and Dynamically Downscaled Atmospheric Water Budgets in Comparison with GRACE-Derived Observations

Abstract Since 2002, the Gravity Recovery and Climate Experiment (GRACE) has provided gravity-derived observations of variations in the terrestrial water storage. Because of the lack of suitable direct observations of large-scale water storage changes, a validation of the GRACE observations remains difficult. An approach that allows the evaluation of terrestrial water storage variations from GRACE by a comparison with those derived from aerologic water budgets using the atmospheric moisture flux divergence is presented. In addition to reanalysis products from the European Centre for Medium-Range Weather Forecasts and the National Centers for Environmental Prediction, high-resolution regional atmospheric simulations were produced with the Weather Research and Forecast modeling system (WRF) and validated against globally gridded observational data of precipitation and 2-m temperature. The study encompasses six different climatic and hydrographic regions: the Amazon basin, the catchments of Lena and Yenisei, central Australia, the Sahara, the Chad depression, and the Niger. Atmospheric-related uncertainty bounds based on the range of the ensemble of estimated terrestrial water storage variations were computed using different configurations of the regional climate model WRF and different global reanalyses. Atmospheric-related uncertainty ranges with those originating from the GRACE products of GeoForschungsZentrum Potsdam, the Center for Space Research, and the Jet Propulsion Laboratory were also compared. It is shown that dynamically downscaled atmospheric fields are able to add value to global reanalyses, depending on the geographical location of the considered catchments. Global and downscaled atmospheric water budgets are in reasonable agreement (r ≈ 0.7 − 0.9) with GRACE-derived terrestrial mass variations. However, atmospheric- and satellite-based approaches show shortcomings for regions with small storage change rates (<20–25 mm month−1).

A Simple Groundwater Scheme for Hydrological and Climate Applications: Description and Offline Evaluation over France

Abstract Despite their potential influences on surface water and climate, groundwater processes are generally not represented in climate models. Here, a simple groundwater scheme including two-dimensional flow dynamics and accounting for groundwater–river exchanges is introduced into the global Total Runoff Integrated Pathways (TRIP) river routing model coupled to the Météo-France climate model. This original scheme is tested in offline mode over France at high () and low (0.5°) resolution against a dense network of river discharge and water table observations over the 1970–2010 period, and is compared to the fine-tuned Système d’Analyze Fournissant des Renseignements Atmosphériques à la Neige (SAFRAN)–Interactions between Soil, Biosphere, and Atmosphere (ISBA) coupled hydrometeorological model (MODCOU). In addition, the simulated terrestrial water storage (TWS) variations are compared to the TWS estimates from the Gravity Recovery and Climate Experiment (GRACE) satellite mission. The aquifer basins over France are defined using the World-wide Hydrogeological Mapping and Assessment Programme (WHYMAP) groundwater resources map, a simplified French lithological map, and the International Geological Map of Europe (IGME). TRIP is forced by daily runoff and drainage data derived from a preexisting simulation of the ISBA land surface scheme driven by the high-resolution SAFRAN meteorological analysis. Four simulations are carried out with or without groundwater at both resolutions. Results show that the groundwater scheme allows TRIP to better capture the spatiotemporal variability of the observed river discharges and piezometric heads. Summer base flows are particularly improved over the main rivers of France. Decreasing the horizontal resolution has a limited impact on the simulated discharges, while it slightly degrades the simulation of water table variations.

Investigation of temporal characteristics of terrestrial water storage changes and its comparison to terrestrial mass changes

AbstractThis study investigates the dominant component of terrestrial water storage (TWS) and its contribution ratio at both seasonal and interannual time‐scales on a global‐scale, using a land‐surface hydrological model, and estimates the climatological mean mass changes. The largest annual range of the four components of TWS, namely soil moisture, snowpack, river channel water storage, and shallow groundwater storage, and the range ratio of the largest annual range among the four components to that of TWS at both seasonal and interannual time‐scales on a global‐scale are investigated using the land‐surface hydrological model. Although soil moisture covers most areas as the largest annual range at the monthly time‐scale, the three other components show unique geographical distributions. At the interannual time‐scale, geographical distribution is basically similar to that of the monthly time‐scale except for the replacement of snowpack to soil moisture in high latitudinal regions. These results provide qualitative information about which component is important for a certain region. In addition, mass changes, namely mineral dust and sediment transports as natural phenomena, crude oil, coal, and natural gas, iron, and bauxite mining as anthropogenic phenomena, are estimated. Comparison of the mass changes with the TWS variability show that it takes a long time for the mass changes to become equivalent to the interannual variability of TWS in magnitude in most regions or fields. Detectability of the mass changes by a satellite gravity mission is examined and the mass decreases due to mineral dust and sediment transports and mining are detectable in regions with large signals within 20 years under ideal conditions. These results provide basic but new information about hydrological features of TWS and mass changes. Copyright © 2012 John Wiley & Sons, Ltd.

Satellite based estimates of terrestrial water storage variations in Turkey

In recent years, the Gravity Recovery and Climate Experiment (GRACE) has provided a new tool to study terrestrial water storage variations (TWS) at medium and large spatial scales, providing quantitative measures of TWS change. Linear trends in TWS variations in Turkey were estimated using GRACE observations for the period March 2003 to March 2009. GRACE showed a significant decrease in TWS in the southern part of the central Anatolian region up to a rate of 4cm/year. The Global Land Data Assimilation System (GLDAS) model also captured this TWS decrease event but with underestimated trend values. The GLDAS model represents only a part of the total TWS variations, the sum of soil moisture (2m column depth) and snow water equivalent, ignoring groundwater variations. Therefore, GLDAS model derived TWS variations were subtracted from GRACE derived TWS variations to estimate groundwater storage variations. Results revealed that decreasing trends of TWS observed by GRACE in the southern part of central Anatolia were largely explained by the decreasing trends of groundwater variations which were confirmed by the limited available well groundwater level data in the region.

Accuracy of scaled GRACE terrestrial water storage estimates

We assess the accuracy of global‐gridded terrestrial water storage (TWS) estimates derived from temporal gravity field variations observed by the Gravity Recovery and Climate Experiment (GRACE) satellites. The TWS data set has been corrected for signal modification due to filtering and truncation. Simulations of terrestrial water storage variations from land‐hydrology models are used to infer relationships between regional time series representing different spatial scales. These relationships, which are independent of the actual GRACE data, are used to extrapolate the GRACE TWS estimates from their effective spatial resolution (length scales of a few hundred kilometers) to finer spatial scales (∼100 km). Gridded, scaled data like these enable users who lack expertise in processing and filtering the standard GRACE spherical harmonic geopotential coefficients to estimate the time series of TWS over arbitrarily shaped regions. In addition, we provide gridded fields of leakage and GRACE measurement errors that allow users to rigorously estimate the associated regional TWS uncertainties. These fields are available for download from the GRACE project website (available at http://grace.jpl.nasa.gov). Three scaling relationships are examined: a single gain factor based on regionally averaged time series, spatially distributed (i.e., gridded) gain factors based on time series at each grid point, and gridded‐gain factors estimated as a function of temporal frequency. While regional gain factors have typically been used in previously published studies, we find that comparable accuracies can be obtained from scaled time series based on gridded gain factors. In regions where different temporal modes of TWS variability have significantly different spatial scales, gain factors based on the first two methods may reduce the accuracy of the scaled time series. In these cases, gain factors estimated separately as a function of frequency may be necessary to achieve accurate results.

Terrestrial water variations in the North China Plain revealed by the GRACE mission

Using eight years of time-variant gravity measurements from the GRACE gravity satellite mission, we estimate monthly terrestrial water storage variations in the North China Plain between August 2002 and August 2010. We find that during this period, the water storage is not constant but accelerate at a rate of −1.1 cm/yr over time. The study confirms that the relatively long-term trend of water storage in the North China Plain (by 13-point moving average) is consistent well with that by linear fitting. Two hydrological models, CPC and GLDAS, are adopted in calculating surface water variations, with results indicating that they agree with those of GRACE. Furthermore, rates of −0.6 cm/yr for surface water variations and −0.5 cm/yr for groundwater variations are found in the North China Plain during the study period. Decrease of rainfall and the groundwater over-exploitation are possibly the main causes for groundwater depletion in the North China Plain. The results will be helpful for better understanding climatic changes and provide reference for the management of water resources and the establishment of policies on preventing and alleviating natural hazards.

Annual and interannual variations in terrestrial water storage during and following a period of drought in South Carolina, USA

Summary The goal of this research is to quantify variations in both space and time of water stored in the terrestrial environment within South Carolina during and following a period of drought. We use a water balance approach that synthesizes observed and modeled hydrologic fluxes for sub-watersheds defined by the drainage area between streamflow gaging stations. We apply the approach for the period 1998–2007 to study the impact of a drought that occurred during the early part of this time period on terrestrial water storage within the state. Results from the analysis provide evidence of distinct annual and interannual variation in water storage for different regions of the state, with the fall season having a water surplus and spring season exhibiting a water deficit. The impact of the drought varied for different regions of the state depending in part on hydrogeological conditions including soil type and depth to the groundwater level. Comparing estimates of rate of change in terrestrial water storage with observed groundwater levels, as an independent validation of the terrestrial water storage estimations, shows that many of the sub-watersheds within the state exhibited similar patterns between variation of rate of change in terrestrial water storage estimates and observed groundwater levels during the period of analysis, as expected. However, some sub-watersheds did not follow general annual and interannual variations in groundwater level or in estimated rate of change in terrestrial water storage relative to neighboring sub-watersheds. We speculate that these abnormalities may be related to human influences that alter local water storage trends within specific sub-watersheds of the state, however future work is needed to further investigate this possible explanation. We conclude through this study that the water balance approach presented is a simple yet valuable means for estimating variations in water availability at a regional spatial scale by synthesizing existing observations and model output data within a geospatially-explicit context.

Water Storage, Net Precipitation, and Evapotranspiration in the Mackenzie River Basin from October 2002 to September 2009 Inferred from GRACE Satellite Gravity Data

Abstract Gravity Recovery and Climate Experiment (GRACE) satellite gravity data are used to determine the variability of terrestrial water storage within the Mackenzie River basin from October 2002 to September 2009. During that period, it is estimated that there is no significant (7 yr) linear trend in the water storage after having accounted for postglacial rebound using the ICE-5G (VM2) ice sheet and Earth viscosity model. Errors in this model may alter this conclusion. The GRACE gravity data are also combined with precipitation and river discharge datasets to estimate trends in net precipitation and evapotranspiration in the basin. Net precipitation is seen to have a significant trend with a corresponding increase in river discharge. Evapotranspiration was found to be constant over the study period.

New diagnostic estimates of variations in terrestrial water storage based on ERA‐Interim data

AbstractTerrestrial water storage is an important component of the climate system as it determines the partitioning of the water and energy fluxes at the land surface. Since in situ measurements are scarce, there is a strong need for alternative validation data sources.Here we present a new dataset of monthly basin‐scale terrestrial water storage changes (TWSC) derived with the combined atmospheric‐terrestrial water‐balance approach, also referred to as basin‐scale water‐balance (BSWB) approach. It is diagnosed from observation‐constrained reanalysis data for the atmospheric fields and observed streamflow. A previous BSWB dataset derived from the European Center for Medium‐Range Weather Forecasts (ECMWF) reanalysis ERA‐40 provided reasonable estimates of TWSC for mid‐latitude basins. The here presented BSWB dataset is derived from the latest ECMWF reanalysis ERA‐Interim, which is available in real time. The potential real‐time availability of TWSC derived from ERA‐Interim is of great relevance for several agricultural, hydrological, and climate applications.An uncertainty analysis of the derived TWSC highlights the importance of the atmospheric moisture flux convergence fields from the reanalysis for the resulting product uncertainty. We find that the BSWB estimates have a relative uncertainty of about 4–6% in basins larger than 1·5 × 106 km2 compared with the mean seasonal cycle. The ERA‐Interim based dataset compares better with in situ soil moisture, snow depth, and groundwater measurements in the Ob basin and Illinois than the previous ERA‐40 based dataset. We further compare the BSWB datasets to retrievals from the Gravity Recovery And Climate Experiment (GRACE), scatterometer data from the European Remote Sensing (ERS) satellites, and land surface model output from the second phase of the Global Soil Wetness Project (GSWP). We find a better correlation between ERS and the BSWB data than between GRACE and the BSWB data, which might be related to the relatively coarse resolution of GRACE. GSWP model output and the BSWB datasets compare well in most of the studied river basins. Copyright © 2010 John Wiley & Sons, Ltd.

Past terrestrial water storage (1980–2008) in the Amazon Basin reconstructed from GRACE and in situ river gauging data

Abstract. Terrestrial water storage (TWS) composed of surface waters, soil moisture, groundwater and snow where appropriate, is a key element of global and continental water cycle. Since 2002, the Gravity Recovery and Climate Experiment (GRACE) space gravimetry mission provides a new tool to measure large-scale TWS variations. However, for the past few decades, direct estimate of TWS variability is accessible from hydrological modeling only. Here we propose a novel approach that combines GRACE-based TWS spatial patterns with multi-decadal-long in situ river level records, to reconstruct past 2-D TWS over a river basin. Results are presented for the Amazon Basin for the period 1980–2008, focusing on the interannual time scale. Results are compared with past TWS estimated by the global hydrological model ISBA-TRIP. Correlations between reconstructed past interannual TWS variability and known climate forcing modes over the region (e.g., El Niño-Southern Oscillation and Pacific Decadal Oscillation) are also estimated. This method offers new perspective for improving our knowledge of past interannual TWS in world river basins where natural climate variability (as opposed to direct anthropogenic forcing) drives TWS variations.

Terrestrial water budget of the Eurasian pan‐Arctic from GRACE satellite measurements during 2003–2009

We assess the controls of the terrestrial water budget over the Eurasian pan‐Arctic drainage region from 2003 to 2009 by combining observations from the Gravity Recovery and Climate Experiment (GRACE) with reanalysis estimates of net precipitation and observations of river discharge from gauges. Of particular interest are the expansive permafrost regions. Thawing permafrost has been implicated to contribute to the observed discharge increases through the melting of excess ground ice. We show that terrestrial water storage (TWS) over large areas of the Eurasian pan‐Arctic region has increased during 2003–2009. However, significant interannual TWS variability is present and most TWS increases occur over nonpermafrost regions in the Ob and Yenisei basins. Over the central Lena basin, which is mostly underlain by permafrost, TWS steadily increased until 2007 but has slightly declined since. By combining GRACE observations of TWS anomalies with discharge and net precipitation, we show that the terrestrial water budget is at least qualitatively closed over the Eurasian Arctic basins. The observed TWS and discharge increases over the study time period were driven by increased atmospheric moisture fluxes. Therefore, we conclude that melting of excess ground ice in permafrost regions did not act as a source to observed changes in discharge. Nonetheless, the signature of significant TWS increases points to ongoing thickening of the active layer in particular over the discontinuous permafrost regions in the central Lena basin.

Evaluating terrestrial water storage variations from regionally constrained GRACE mascon data and hydrological models over Southern Africa – preliminary results

A concentration of surface mass has a distinct, localized signature in Gravity Recovery and Climate Experiment (GRACE) K-band range rate (KBRR) data. This fact is exploited in the regional solutions for mass concentration parameters (mascons) made at the Goddard Space Flight Center (GSFC). In this paper we explore an experimental set of regionally constrained mascon blocks over Southern Africa where a system of 1.25° × 1.5° and 1.5° × 1.5° blocks has been designed. The blocks are divided into hydrological regions based on drainage patterns of the largest river basins, and are constrained in different ways. We show that the use of regional constraints, when solving mascon parameters of different hydrological regions independently, yields more detail and variation than comparable spherical harmonic solutions and mascon solutions using isotropic constraints. We validate our results over Lake Malawi with water level from altimetry. Results show that weak constraints across regions in addition to intra-regional constraints are necessary, to reach reasonable mass variations.

Global Evaluation of the ISBA-TRIP Continental Hydrological System. Part II: Uncertainties in River Routing Simulation Related to Flow Velocity and Groundwater Storage

Abstract In the companion paper to this one (Part I), the Interactions between Soil, Biosphere, and Atmosphere–Total Runoff Integrating Pathways (ISBA-TRIP) continental hydrological system of the Centre National de Recherches Météorologiques is evaluated by using river discharge measurements and terrestrial water storage (TWS) variations derived from three independent datasets of the Gravity Recovery and Climate Experiment (GRACE). One of the conclusions is that the river reservoir simulated by TRIP at the global scale seems to be one of the main sources of TWS and/or discharge errors. Here, the authors study these uncertainties in river routing processes, such as flow velocity and groundwater storage. For this purpose, a simple groundwater reservoir depending on a time delay factor and a variable streamflow velocity calculated via Manning’s formula are added to TRIP following the approach of Arora and Boer. The previous and the new TRIP are then compared, and two studies of the sensitivity to the groundwater time delay factor and to the flow velocity are performed. Using the same experiment design as in Part I, the authors show that the effect of this flow velocity and of the groundwater time delay factor on the ISBA-TRIP simulation is potentially significant. Nevertheless, over tropical and temperate basins, a competition between the two processes implies a slight difference between the previous and the new TRIP compared to both the GRACE and the discharge signals. The global results underline that simulating a realistic streamflow velocity is a key process for global-scale application.

Global Evaluation of the ISBA-TRIP Continental Hydrological System. Part I: Comparison to GRACE Terrestrial Water Storage Estimates and In Situ River Discharges

Abstract In earth system models, the partitioning of precipitation among the variations of continental water storage, evapotranspiration, and freshwater runoff to the ocean has a major influence on the terrestrial water and energy budgets and thereby on simulated climate on a wide range of scales. The evaluation of continental hydrology is therefore a crucial task that requires offline simulations driven by realistic atmospheric forcing to avoid the systematic biases commonly found in global atmospheric models. Generally, this evaluation is done mainly by comparison with in situ river discharge data, which does not guarantee that the spatiotemporal distribution of water storage and evapotranspiration is correctly simulated. In this context, the Interactions between Soil, Biosphere, and Atmosphere–Total Runoff Integrating Pathways (ISBA-TRIP) continental hydrological system of the Centre National de Recherches Météorologiques is evaluated by using the additional constraint of terrestrial water storage (TWS) variations derived from three independent gravity field retrievals (datasets) from the Gravity Recovery and Climate Experiment (GRACE). On the one hand, the results show that, in general, ISBA-TRIP captures the seasonal and the interannual variability in both TWS and discharges. GRACE provides an additional constraint on the simulated hydrology and consolidates the former evaluation only based on river discharge observations. On the other hand, results indicate that river storage variations represent a significant contribution to GRACE measurements. While this remark highlights the need to improve the TRIP river routing model for a more useful comparison with GRACE [Decharme et al. (Part II of the present study)], it also suggests that low-resolution gravimetry products do not necessarily represent a strong additional constraint for model evaluation, especially in downstream areas of large river basins where long-term discharge data are available.

Variations of Terrestrial Water Storage in the Yangtze River Basin under Climate Change Scenarios

In this study, the water balance-based Precipitation-Evapotranspiration-Runoff (PER) method combined with the land surface model Variable Infiltration Capacity (VIC) was used to estimate the spatio...

Role of rivers in the seasonal variations of terrestrial water storage over global basins

The role of rivers in total terrestrial water storage (TWS) variations is evaluated in 29 basins. The contribution of individual storage components to total TWS is investigated by using ensemble hydrological simulations with river routing. The observed Gravity Recovery And Climate Experiment (GRACE) TWS data are used to validate model simulations. It is found TWS simulations are more accurate when river storage is taken into account except for dry basins. Rivers play different roles in various climatic regions as indicated by two new indices quantifying the significance of each TWS component and their interactions. River storage, which effectively includes downslope movement of shallow groundwater, explains up to 73% of TWS variations in Amazon. It also acts as “buffer” which smoothes TWS seasonal variations particularly in snow‐dominated basins. Neglecting river storage may lead to mismatch in the amplitude and phase of TWS seasonal variations compared to the GRACE observations.

Remote sensing: hydrology

Satellite remote sensing is a viable source of observations of land surface hydrologic fluxes and state variables, particularly in regions where in situ networks are sparse. Over the last 10 years, the study of land surface hydrology using remote sensing techniques has advanced greatly with the launch of NASA’s Earth Observing System (EOS) and other research satellite platforms, and with the development of more sophisticated retrieval algorithms. Most of the constituent variables in the land surface water balance (eg, precipitation, evapotranspiration, snow and ice, soil moisture, and terrestrial water storage variations) are now observable at varying spatial and temporal resolutions and accuracy via remote sensing. We evaluate the current status of estimates of each of these variables, as well as river discharge, the direct estimation of which is not yet possible. Although most of the constituent variables are observable by remote sensing, attempts to close the surface water budget from remote sensing alone have generally been unsuccessful, suggesting that current generation sensors and platforms are not yet able to provide hydrologically consistent observations of the land surface water budget at any spatial scale.

Analysis of seasonal terrestrial water storage variations in regional climate simulations over Europe

Land‐surface processes play a major role in the climate system, and their validation is crucial to improve current climate models. Here we investigate the seasonal evolution of terrestrial water storage (TWS) (includes all water stored on land) in an ensemble of 30‐year‐long climate simulations from the PRUDENCE archive (9 regional and 2 global models), representing current and future climatic conditions. For validation purposes we employ a recently published basin‐scale water‐balance (BSWB) data set of diagnosed monthly TWS variations, where the term variations refers to monthly changes in TWS. The analysis is conducted in five large‐scale European domains composed of major river basins. This analysis shows that the climatology of most models lies within the interannual variability of the BSWB data set in the investigated regions, but the different models sometimes display considerable discrepancies in the seasonal evolution of TWS. In particular, we find that all models suffer from a considerable underestimation of interannual TWS variability. The deviations of the individual models from the BSWB data set can be linked to biases in the hydrological fluxes (i.e., precipitation, runoff, evapotranspiration). The simulated future changes for the Intergovernmental Panel on Climate Change (IPCC) A2 scenario suggest an enhancement of the seasonal cycle of TWS, with drier soils in summer. Mainly in the Central European domain, several models show a reduction of the year‐to‐year variability of summer TWS variations, indicating an exhaustion of the models' soil water reservoirs by the end of summer under future climatic conditions.