Basin-scale Water Balance Research Articles

Baseflow index assessment for agriculture-industry led Ramganga river basin

The baseflow index is a crucial parameter in basin-scale water balance studies. However, it has frequently been neglected for various reasons, viz. near-impossible direct measurement, simplification of the model, and non-existence of the hydro-meteorological data. Hence, baseflow is computed for the Ramganga river basin in the present study, for which a scientific assessment had not been done previously. The classified-archived-observed river discharge data are obtained from Central Water Commission (CWC) and are applied in an analytical filter to assess the baseflow index (BFI) at all exiting CWC hydro-meteorological sites in the Ramganga river basin. The average values of BFIs for the CWC sites vary between 27% and 38%. The results are found to be consistent and showed significance with the hydrological characteristics of the basin. The results have also been discussed to account for various possible anthropogenic effects, which are assessed as having no significant impact.

A global terrestrial evapotranspiration product based on the three-temperature model with fewer input parameters and no calibration requirement

Abstract. Accurate global terrestrial evapotranspiration (ET) estimation is essential to better understand Earth's energy and water cycles. Although several global ET products exist, recent studies indicate that ET estimates exhibit high uncertainty. With the increasing trend of extreme climate hazards (e.g., droughts and heat waves), accurate ET estimation under extreme conditions remains challenging. To overcome these challenges, we used 3 h and 0.25∘ Global Land Data Assimilation System (GLDAS) datasets (net radiation, land surface temperature (LST), and air temperature) and a three-temperature (3T) model, without resistance and parameter calibration, in global terrestrial ET product development. The results demonstrated that the 3T model-based ET product agreed well with both global eddy covariance (EC) observations at daily (root mean square error (RMSE) = 1.1 mm d−1, N=294 058) and monthly (RMSE = 24.9 mm month−1, N=9632) scales and basin-scale water balance observations (RMSE = 116.0 mm yr−1, N=34). The 3T model-based global terrestrial ET product was comparable to other common ET products, i.e., MOD16, P-LSH, PML, GLEAM, GLDAS, and Fluxcom, retrieved from various models, but the 3T model performed better under extreme weather conditions in croplands than did the GLDAS, attaining 9.0 %–20 % RMSE reduction. The proposed daily and 0.25∘ ET product covering the period of 2001–2020 could provide periodic and large-scale information to support water-cycle-related studies. The dataset is freely available at the Science Data Bank (https://doi.org/10.57760/sciencedb.o00014.00001, Xiong et al., 2022).

Global Evapotranspiration Datasets Assessment Using Water Balance in South America

Evapotranspiration (ET) connects the land to the atmosphere, linking water, energy, and carbon cycles. ET is an essential climate variable with a fundamental importance, and accurate assessments of the spatiotemporal trends and variability in ET are needed from regional to continental scales. This study compared eight global actual ET datasets (ETgl) and the average actual ET ensemble (ETens) based on remote sensing, climate reanalysis, land-surface, and biophysical models to ET computed from basin-scale water balance (ETwb) in South America on monthly time scale. The 50 small-to-large basins covered major rivers and different biomes and climate types. We also examined the magnitude, seasonality, and interannual variability of ET, comparing ETgl and ETens with ETwb. Global ET datasets were evaluated between 2003 and 2014 from the following datasets: Breathing Earth System Simulator (BESS), ECMWF Reanalysis 5 (ERA5), Global Land Data Assimilation System (GLDAS), Global Land Evaporation Amsterdam Model (GLEAM), MOD16, Penman–Monteith–Leuning (PML), Operational Simplified Surface Energy Balance (SSEBop) and Terra Climate. By using ETwb as a basis for comparison, correlation coefficients ranged from 0.45 (SSEBop) to 0.60 (ETens), and RMSE ranged from 35.6 (ETens) to 40.5 mm·month−1 (MOD16). Overall, ETgl estimates ranged from 0 to 150 mm·month−1 in most basins in South America, while ETwb estimates showed maximum rates up to 250 mm·month−1. ETgl varied by hydroclimatic regions: (i) basins located in humid climates with low seasonality in precipitation, including the Amazon, Uruguay, and South Atlantic basins, yielded weak correlation coefficients between monthly ETgl and ETwb, and (ii) tropical and semiarid basins (areas where precipitation demonstrates a strong seasonality, as in the São Francisco, Northeast Atlantic, Paraná/Paraguay, and Tocantins basins) yielded moderate-to-strong correlation coefficients. An assessment of the interannual variability demonstrated a disagreement between ETgl and ETwb in the humid tropics (in the Amazon), with ETgl showing a wide range of interannual variability. However, in tropical, subtropical, and semiarid climates, including the Tocantins, São Francisco, Paraná, Paraguay, Uruguay, and Atlantic basins (Northeast, East, and South), we found a stronger agreement between ETgl and ETwb for interannual variability. Assessing ET datasets enables the understanding of land–atmosphere exchanges in South America, to improvement of ET estimation and monitoring for water management.

Estimating seasonal water budgets in global lakes by using multi-source remote sensing measurements

The seasonal change in lake water storage (LWSsc) reflect periodic fluctuations of the basin-scale water balance. However, the role of LWSsc in regulating the water budget at the global scale has not yet been investigated based on straight-forward observations. Quantifying LWSsc is necessary, especially under the context of global change. Available in-situ measurements of lake water levels and volumes are still scarce. Therefore, the Global Surface Water datasets of Joint Research Centre and multi-source satellite altimetry datasets through mathematical statistics methods are used in this study to address this issue. We estimate the LWSsc of 463 lakes and reservoirs worldwide with areas greater than 10 km2, which represent nearly 64% of the total global lake area and 93% of the total lake volume capacity. Results show that the global seasonal water storage variation of these examined water bodies is 1390.91 ± 78.91 km3, comprising 869.44 ± 67.35 km3 from lakes and 521.46 ± 41.11 km3 from reservoirs. The relatively large estimates of LWSsc are concentrated in North American and African basins. Among the watersheds, the seasonal fluctuations of lakes in the North American Lawrence basin make up the most substantial magnitude of 10.76% of the global LWSsc. The latitudinal direction zonality of LWSsc is relatively significant. The LWSsc is concentrated between 30° N and 60° N in the northern hemisphere and between the equator and 30° S in the southern hemisphere. Considering the geographic similarity and climatological zonality, the global LWSsc estimates are also extrapolated to other lakes without direct satellite altimetry observations on the basis of the average rate of the examined lakes distributed in the same Köppen − Geiger Climate Classification zones. The LWSsc is calculated with a consequence of 488.23 ± 14.72 km3 for these extrapolated lakes, indicating an estimate of 1357.67 ± 68.94 km3 for the LWSsc of the global natural lakes (>10 km2). This initial estimation of LWSsc at a global scale will greatly help the improvement of our understanding of the seasonal behavior of lakes and reservoirs in regulating global and regional water cycles and the contribution of terrestrial water storage to sea level rise.

Water scarcity-risk assessment in data-scarce river basins under decadal climate change using a hydrological modelling approach

Basin-scale water scarcity, an adverse consequence of the imbalance between the available fresh water and water demands, is an alarming situation in many countries worldwide. This necessitates for analyzing the risk of water scarcity forced with the changing climate, land-use alterations, growing population, and industrialization to pave a way for sustainable water resources systems planning and management. This study advocates a hydrological model-based evaluation approach employing Soil Water Assessment Tool (SWAT) to identify the dominating drivers on the decadal streamflow patterns and other basin-scale water balance components, viz., blue water flow (BWF), green water storage (GWS), and green water flow (GWF) in the Brahmani and Baitarani River basins of eastern India. The results reveal that, in these basins, the climate change effect has relatively a higher impact on streamflow than the land-use change. This study surmises that the Brahmani and Baitarani River basins can be categorized under the high- and moderate-risk water scarcity zones, respectively. The developed approach of assessing the water scarcity risk under the non-availability of basin-scale sectoral water demands could be a reliable tool for many data-scarce river basins worldwide.

Impact of flooded rice paddy on remotely sensed evapotranspiration in the Krishna River basin, India

AbstractEvapotranspiration (ET) is one of the major water exchange processes between the earth's surface and the atmosphere. ET is a combined process of evaporation from open water bodies, bare soil and plant surfaces, and transpiration from vegetation. Remote sensing‐based ET models have been developed to estimate spatially distributed ET over large regions, however, many of them reportedly underestimate ET over semi‐arid regions (Jamshidi et al., Journal of Hydrometeorology, 2019, 20, 947–964). In this work, we show that underestimation of ET can occur due to the open water evaporation from flooded rice paddies ignored in the existing ET models. To address the gap in ET estimation, we have developed a novel approach that accounts for the missing ET component over flooded rice paddies. Our method improved ET estimates by a modified Penman‐Monteith algorithm that considered the fraction of open water evaporation from flooded rice paddies. Daily ET was calculated using ground based meteorological data and the MODIS satellite data over the Krishna River Basin. Seasonal and annual ET values over the Krishna Basin were compared with two different ET algorithms. ET estimates from these two models were also compared for different crop combinations. Results were validated with flux tower‐based measurements from other studies. We have identified a 17 mm/year difference in average annual ET over the Krishna River Basin with this new ET algorithm. This is very critical in basin scale water balance analysis and water productivity studies.

Integrated water resources management and modeling: A case study of Bow river basin, Canada

Abstract This paper introduces a comprehensive modeling framework for Integrated Water Resources Management (IWRM). The model incorporates water demands, allocation, and uses under various climate, population, and economic scenarios as well as management strategies. Model outputs include crop yields, municipal water use, power generation, recreational reservoir uses, and environmental flows. Further, a novel indicator integrates many key model outputs for social, economic, and environmental assessment based on the basin-scale water balance, and provides a comprehensive and clear representation of basin conditions to improve the understanding of IWRM trade-offs. When applied to the Bow River Basin, Canada, as a practical example, this Bow River Integrated Model (BRIM) revealed through a set of modeling scenarios that (1) only the industrial demands exceeded the water license in the high-water demand and reference scenarios due to population growth and economic development; (2) increased cooling tower shares for thermal power plants was the most effective policy in managing industrial demand; and (3) the new indicator reflected both basin-scale conditions and sectoral water stresses. Finally, model results from three gaming scenarios showed socio-economic and environmental trade-offs clearly, providing users with guidance in developing a comprehensive view of basin-scale water security, and hands-on experience to support IWRM. Therefore, the modeling framework and novel indicator can improve an understanding of IWRM concepts and strategic trade-offs in efforts towards basin water sustainability.

English

Under conditions of high pressure on water resources, it is essential to quantify the water balance. There are tools to perform the water balance, but unfortunately, they are expensive and  hardly accessible in developing countries. The objective of this study was to quantify the water balance using a low-cost lysimeter (LCL). Rainfall was measured using rain gauge. Soil water content (SWC) and infiltration were measured in the LCL, which was out in the open. The site of study was a place in La Malinche volcano (Mexico). Evaporation was calculated using the water balance equation. In order to evaluate the LCL efficiency, measurements were registered for two years (2015-2016). The distribution of the rainfall data was assessed using Kolmogorov-Smirnov test (K-S). The Mann-Whitney test (M-W) was used to compare rainfall, SWC and infiltration for the two years. HYDRUS-1D software was used to simulate soil water storage (SWS) in the LCL. The efficiency of HYDRUS-1D was evaluated with Nash-Sutcliffe test (N-S). The total annual rainfall was 992.1 mm for 2015 and 1025.1 mm for 2016. The K-S test showed that rainfall data had exponential distribution in both years. The M-W test evidenced that rainfall, SWC and infiltration were not significantly different (p>0.05) for the two years. Rainwater infiltration was 6.4% for 2015 and 5.9% for 2016. Most of the rainfall was evaporated, reaching percentages around 94%. N-S test showed that there was a good simulation of the LCL by HYDRUS-1D software. The water balance indicated that currently, La Malinche recharge area is insufficient to compensate the water consumption of Puebla and Tlaxcala. The use of low cost lysimeter would be of great help in expanding basin-scale water balance studies.  Key words: La Malinche volcano, low-cost lysimeter, water balance, HYDRUS-1D. &nbsp

The Neogene de-greening of Central Asia

Abstract There remains substantial debate concerning the relative roles of tectonics and global climate in driving the evolution of climate in Central Asia. Today, interior Asia—including the Taklamakan, Gobi, and Ordos Deserts—is exceptionally arid and is surrounded by distinct rainfall boundaries, such as those generated by the Asian monsoon systems to the east and south and those generated by high topography to the north and west. Determining how and why these boundaries have varied over the Neogene is hindered by the lack of a single proxy that can be broadly applied through space and time. We construct isoscapes of pedogenic carbonate δ13C (δ13Cc) over the Neogene in Asia by combining a compilation of 2236 published measurements with new data from three localities in northern Central Asia. Pedogenic carbonate δ13C records local aridity—excepting localities impacted by C4 grasslands and during large changes in atmospheric pCO2—through variations in soil respiration, depth of carbonate formation, and the effect of water stress on plant δ13C. Together, these effects reflect changes in both primary productivity and mean annual precipitation. Throughout the Neogene, we find consistent and exceptionally high δ13Cc in interior Asia with a ring of lower δ13Cc that demarcates higher precipitation. This persistent ring of lower δ13Cc corresponds in the south and east with the influence of the Asian monsoon systems; in the west and north, it reflects both orographic rainfall due to uplift of the Tian Shan and to moisture delivery by the mid-latitude westerlies. Finally, δ13Cc and, hence, aridity increases regionally in the latest Neogene, reflecting the effects of Northern Hemisphere glaciation and cooling. This widespread “de-greening” would have increased regional albedo and modified basin-scale water balances, resulting in greater dust fluxes due to reduced vegetative cover and precipitation.

Evaluation of Satellite Precipitation Products with Rain Gauge Data at Different Scales: Implications for Hydrological Applications

Rain gauge and satellite-retrieved data have been widely used in basin-scale hydrological applications. While rain gauges provide accurate measurements that are generally unevenly distributed in space, satellites offer spatially regular observations and common error prone retrieval. Comparative evaluation of gauge-based and satellite-based data is necessary in hydrological studies, as precipitation is the most important input in basin-scale water balance. This study uses quality-controlled rain gauge data and prevailing satellite products (Tropical Rainfall Measuring Mission (TRMM) 3B43, 3B42 and 3B42RT) to examine the consistency and discrepancies between them at different scales. Rain gauges and TRMM products were available in the Poyang Lake Basin, China, from 1998 to 2007 (3B42RT: 2000–2007). Our results show that the performance of TRMM products generally increases with increasing spatial scale. At both the monthly and annual scales, the accuracy is highest for TRMM 3B43, with 3B42 second and 3B42RT third. TRMM products generally overestimate precipitation because of a high frequency and degree of overestimation in light and moderate rain cases. At the daily scale, the accuracy is relatively low between TRMM 3B42 and 3B42RT. Meanwhile, the performances of TRMM 3B42 and 3B42RT are highly variable in different seasons. At both the basin and pixel scales, TRMM 3B43 and 3B42 exhibit significant discrepancies from July to September, performing worst in September. For TRMM 3B42RT, all statistical indices fluctuate and are low throughout the year, performing worst in July at the pixel scale and January at the basin scale. Furthermore, the spatial distributions of the statistical indices of TRMM 3B43 and 3B42 performed well, while TRMM 3B42RT displayed a poor performance.

Runoff coefficient and average yearly natural aquifer recharge assessment by physiography-based indirect methods for the island of Sardinia (Italy) and its NW area (Nurra)

Summary Runoff estimation and water budget in ungauged basins is a challenge for hydrological researchers and planners. The principal aim of this study was the application and validation of the Kennessey method, which is a physiography-based indirect process for determining the average annual runoff coefficient and the basin-scale water balance. The coefficient can be calculated using specific physiographic characteristics (slope, permeability and vegetation cover) and a parameter that defines climatic conditions and does not require instrumental data. One of the main purposes of this study was to compare the average annual runoff coefficient obtained using the Kennessey method with the coefficients calculated using data from 30 instrumented drainage basins in Sardinia (Italy) over 71 years (from 1922 to 1992). These measurements represent an important and complete historical dataset from the study area. Using the runoff coefficient map, the method was also applied to assess the effective annual recharge rate of the aquifers of the Calich hydrogeological basin in the Nurra Plain (Alghero, NW Sardinia-Italy). The groundwater recharge rate was compared with rates calculated using the standard water balance method. The implementation of the method at the regional and basin scales was supported by GIS analyses. The results of the method are promising but show some discrepancies with other methodologies due to the higher weights given to the physiographic parameters than to the meteorological parameters. However, even though the weights assigned to the parameters require improvements, the Kennessey method is a useful tool for evaluating hydrologic processes, particularly for water management in areas where instrumental data are not available.

Physical Mechanisms Related to Climate-Induced Drying of Two Semiarid Watersheds in the Southwestern United States

Abstract Water managers across the United States face the need to make informed policy decisions regarding long-term impacts of climate change on water resources. To provide a scientifically informed basis for this, the evolution of important components of the basin-scale water balance through the end of the twenty-first century is estimated. Bias-corrected and spatially downscaled climate projections, from phase 3 of the Coupled Model Intercomparison Project (CMIP3) of the World Climate Research Programme, were used to drive a spatially distributed Variable Infiltration Capacity (VIC) model of hydrologic processes in the Salt–Verde basin in the southwestern United States. From the suite of CMIP3 models, the authors select a five-model subset, including three that best reproduce the historical climatology for the study region, plus two others to represent wetter and drier than model average conditions, so as to represent the range of GCM prediction uncertainty. For each GCM, data for three emission scenarios (A1B, A2, and B1) were used to drive the hydrologic model into the future. The projections of this model ensemble indicate a statistically significant 25% decrease in streamflow by the end of the twenty-first century. The primary cause for this change is due to projected decreases in winter precipitation accompanied by significant (temperature driven) reductions in storage of snow and increased winter evaporation. The results show that water management in central Arizona is highly likely to be impacted by changes in regional climate.

Distinguishing water conservation from water savings in the western USA

Chronic water shortages are a serious and growing concern in the western USA. Water conservation is among the key strategies promoted to help affected communities bring their water demands into better balance with current and projected supplies. The term ‘water conservation’, however, has different meanings to different people at different times, and the muddled and inconsistent interpretation of associated terms – including ‘water efficiencies’, ‘water savings’, and ‘water use’ – can confuse and even impede progress towards intended conservation goals. The importance of evaluating proposed water conservation measures by considering the relevant water pathways, the basin-scale water balances, and applicable water law is discussed, and assessments of several typical water conservation actions are provided as examples. To help planners and policy-makers ensure that proposed water conservation measures are likely to achieve desired conservation objectives, this paper identifies the key aspects to take into account when evaluating specific water conservation strategies and options.

On the contribution of groundwater storage to interannual streamflow anomalies in the Colorado River basin

Abstract. We assess the significance of groundwater storage for seasonal streamflow forecasts by evaluating its contribution to interannual streamflow anomalies in the 29 tributary sub-basins of the Colorado River. Monthly and annual changes in total basin storage are simulated by two implementations of the Variable Infiltration Capacity (VIC) macroscale hydrology model – the standard release of the model, and an alternate version that has been modified to include the SIMple Groundwater Model (SIMGM), which represents an unconfined aquifer underlying the soil column. These estimates are compared to those resulting from basin-scale water balances derived exclusively from observational data and changes in terrestrial water storage from the Gravity Recovery and Climate Experiment (GRACE) satellites. Changes in simulated groundwater storage are then compared to those derived via baseflow recession analysis for 72 reference-quality watersheds. Finally, estimates are statistically analyzed for relationships to interannual streamflow anomalies, and predictive capacities are compared across storage terms. We find that both model simulations result in similar estimates of total basin storage change, that these estimates compare favorably with those obtained from basin-scale water balances and GRACE data, and that baseflow recession analyses are consistent with simulated changes in groundwater storage. Statistical analyses reveal essentially no relationship between groundwater storage and interannual streamflow anomalies, suggesting that operational seasonal streamflow forecasts, which do not account for groundwater conditions implicitly or explicitly, are likely not detrimentally affected by this omission in the Colorado River basin.

Estimating basin scale evapotranspiration (ET) by water balance and remote sensing methods

AbstractEvapotranspiration (ET) is an important hydrological process that can be studied and estimated at multiple spatial scales ranging from a leaf to a river basin. We present a review of methods in estimating basin scale ET and its applications in understanding basin water balance dynamics. The review focuses on two aspects of ET: (i) how the basin scale water balance approach is used to estimate ET; and (ii) how ‘direct’ measurement and modelling approaches are used to estimate basin scale ET. Obviously, the basin water balance‐based ET requires the availability of good precipitation and discharge data to calculate ET as a residual on longer time scales (annual) where net storage changes are assumed to be negligible. ET estimated from such a basin water balance principle is generally used for validating the performance of ET models. On the other hand, many of the direct estimation methods involve the use of remotely sensed data to estimate spatially explicit ET and use basin‐wide averaging to estimate basin scale ET. The direct methods can be grouped into soil moisture balance modelling, satellite‐based vegetation index methods, and methods based on satellite land surface temperature measurements that convert potential ET into actual ET using a proportionality relationship. The review also includes the use of complementary ET estimation principles for large area applications. The review identifies the need to compare and evaluate the different ET approaches using standard data sets in basins covering different hydro‐climatic regions of the world. Copyright © 2011 John Wiley & Sons, Ltd.

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.

LISFLOOD: a GIS‐based distributed model for river basin scale water balance and flood simulation

In this paper we describe the spatially distributed LISFLOOD model, which is a hydrological model specifically developed for the simulation of hydrological processes in large European river basins. The model was designed to make the best possible use of existing data sets on soils, land cover, topography and meteorology. We give a detailed description of the simulation of hydrological processes in LISFLOOD, and discuss how the model is parameterized. We also describe how the model was implemented technically using a combination of the PCRaster GIS system and the Python programming language, and discuss the management of in‐ and output data. Finally, we review some recent applications of LISFLOOD, and we present a case study for the Elbe river.

A Revised Hydrology for the ECMWF Model: Verification from Field Site to Terrestrial Water Storage and Impact in the Integrated Forecast System

Abstract The Tiled ECMWF Scheme for Surface Exchanges over Land (TESSEL) is used operationally in the Integrated Forecast System (IFS) for describing the evolution of soil, vegetation, and snow over the continents at diverse spatial resolutions. A revised land surface hydrology (H-TESSEL) is introduced in the ECMWF operational model to address shortcomings of the land surface scheme, specifically the lack of surface runoff and the choice of a global uniform soil texture. New infiltration and runoff schemes are introduced with a dependency on the soil texture and standard deviation of orography. A set of experiments in stand-alone mode is used to assess the improved prediction of soil moisture at the local scale against field site observations. Comparison with basin-scale water balance (BSWB) and Global Runoff Data Centre (GRDC) datasets indicates a consistently larger dynamical range of land water mass over large continental areas and an improved prediction of river runoff, while the effect on atmospheric fluxes is fairly small. Finally, the ECMWF data assimilation and prediction systems are used to verify the effect on surface and near-surface quantities in the atmospheric-coupled mode. A midlatitude error reduction is seen both in soil moisture and in 2-m temperature.

Topographic Impacts on Solar Radiation for Basin Scale Water Balance

Topographic Impacts on Solar Radiation for Basin Scale Water Balance

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.