scholarly journals Twentieth and Twenty-First Century Water Storage Changes in the Nile River Basin from GRACE/GRACE-FO and Modeling

2021 ◽  
Vol 13 (5) ◽  
pp. 953
Author(s):  
Emad Hasan ◽  
Aondover Tarhule ◽  
Pierre-Emmanuel Kirstetter
Keyword(s):  
River Basin ◽  
Land Surface ◽  
Water Storage ◽  
Model Performance ◽  
Dry Season ◽  
Nile River ◽  
Surface Model ◽  
Wet Season ◽  
Distribution Fitting ◽  
Nile River Basin

This research assesses the changes in total water storage (TWS) during the twentieth century and future projections in the Nile River Basin (NRB) via TWSA (TWS anomalies) records from GRACE (Gravity Recovery and Climate Experiment), GRACE-FO (Follow-On), data-driven-reanalysis TWSA and a land surface model (LSM), in association with precipitation, temperature records, and standard drought indicators. The analytical approach incorporates the development of 100+ yearlong TWSA records using a probabilistic conditional distribution fitting approach by the GAMLSS (generalized additive model for location, scale, and shape) model. The model performance was tested using standard indicators including coevolution plots, the Nash–Sutcliffe coefficient, cumulative density function, standardized residuals, and uncertainty bounds. All model evaluation results are satisfactory to excellent. The drought and flooding severity/magnitude, duration, and recurrence frequencies were assessed during the studied period. The results showed, (1) The NRB between 2002 to 2020 has witnessed a substantial transition to wetter conditions. Specifically, during the wet season, the NRB received between ~50 Gt./yr. to ~300 Gt./yr. compared to ~30 Gt./yr. to ~70 Gt./yr. of water loss during the dry season. (2) The TWSA reanalysis records between 1901 to 2002 revealed that the NRB had experienced a positive increase in TWS of ~17% during the wet season. Moreover, the TWS storage had witnessed a recovery of ~28% during the dry season. (3) The projected TWSA between 2021 to 2050 unveiled a positive increase in the TWS during the rainy season. While during the dry season, the water storage showed insubstantial TWS changes. Despite these projections, the future storage suggested a reduction between 10 to 30% in TWS. The analysis of drought and flooding frequencies between 1901 to 2050 revealed that the NRB has ~64 dry-years compared to ~86 wet-years. The exceedance probabilities for the normal conditions are between 44 to 52%, relative to a 4% chance of extreme events. The recurrence interval of the normal to moderate wet or dry conditions is ~6 years. These TWSA trajectories call for further water resources planning in the region, especially during flood seasons. This research contributes to the ongoing efforts to improve the TWSA assessment and its associated dynamics for transboundary river basins.

scholarly journals Using GRACE/GRACE-FO, Data-Driven, and Modeling to Assess the Twentieth and Twenty-first Century Water Storage Changes in the Nile River Basin

2021 ◽  
Author(s):  
Emad Hasan ◽  
Aondover Tarhule ◽  
Pierre-Emmanuel Kirstetter
Keyword(s):  
Water Resources ◽  
River Basin ◽  
Land Surface ◽  
Water Storage ◽  
Data Driven ◽  
Nile River ◽  
Surface Model ◽  
Distribution Fitting ◽  
Duration Magnitude ◽  
Nile River Basin

This research assesses the changes in the total water storage (TWS) during the twentieth century and their future projections in the Nile River Basin (NRB) via TWSA (TWS anomalies) records from GRACE (Gravity Recovery and Climate Experiment), GRACE-FO (Follow-On), data-driven-reanalysis TWSA and land surface model (LSM), in association with precipitation, temperature records, and standard drought indicators. The analytical approach incorporates the development of 100+ yearlong TWSA records using a probabilistic conditional distribution fitting approach by the GAMLSS (Generalized Additive Model for Location, Scale, and Shape) model. The drought and flooding severity, duration, magnitude, frequencies, and recurrence were assessed during the studied period. The results showed, 1- The NRB between 2002 to 2020 has transited to substantial wetter conditions. 2- The TWSA reanalysis records between 1901 to 2002 revealed that the NRB had experienced a positive increase in TWS during the wet and dry seasons. 3- The projected TWSA between 2021 to 2050 indicated slight positive changes in TWSA during the rainy seasons. The analysis of drought and flooding frequencies between 1901 to 2050 indicated the NRB has ~64 dry-years compared to ~86 wet-years. The 100+ yearlong TWSA records assured that the NRB transited to wetter conditions relative to few dry spells. These TWSA trajectories call for further water resources planning in the region especially during flood seasons. This research contributes to the ongoing efforts to improve the TWSA assessment and its associated dynamics for transboundary river basins. It also demonstrates how an extended TWSA record provides unique insights for water resources management in the NRB and similar regions.

scholarly journals Integrating GRACE products and land surface models to estimate changes in key components of terrestrial water storage in the Nile River Basin

2020 ◽  
Author(s):  
Zemede M. Nigatu ◽  
Dongming Fan ◽  
Wei You
Keyword(s):  
Time Series ◽  
Soil Moisture ◽  
River Basin ◽  
Land Surface ◽  
Signal To Noise Ratio ◽  
Water Storage ◽  
Nile River ◽  
Terrestrial Water Storage ◽  
Terrestrial Water ◽  
Nile River Basin

Abstract The Nile River Basin (NRB) is facing extreme pressure on its water resources due to an alarmingly increasing population that is extremely vulnerable in aspects of irrigation and hydropower. The NRB ascends itself to remotely sensed approaches with high resolution of spatial and temporal coverage as disparate to ground-based in-situ observations due to its size and limited access from basin countries. The Gravity Recovery and Climate Experiment (GRACE) allow a unique opportunity to investigate the changes in key components of Terrestrial Water Storage (TWS). Differences in tuning parameters and processing strategies result in GRACE TWS solutions with regionally specific variations and error patterns. We explored the spatiotemporal changes of the TWS time series, trend, uncertainties, and signal-to-noise ratio (SNR) among different GRACE TWS. We had also investigated the key terrestrial water storage components (surface water, soil moisture, and groundwater storage changes). The results show that the uncertainty of GRACE spherical harmonic (SH) solutions are higher than the mass concentration (mascon) over the NRB, and the Center for Space Research-mascons (CSR-M) noted the first best performance. Substantially, significant long-term (2003–2017) negative groundwater and soil moisture trend demonstrates a potential depletion over NRB. Despite an increase in precipitation and TWS time series, the rate of decline noted to increase rapidly from 2008, thus indicating the possibility of human-induced change ( e.g., for irrigation purposes). Thus, the result of this study provides a guiding principle for future studies in TWS change-related hydro-climatic change over NRB and similar basins.

scholarly journals Trend Dynamics of GRACE Terrestrial Water Storage in the Nile River Basin

2019 ◽  
Author(s):  
Emad Hasan ◽  
Aondover Tarhule
Keyword(s):  
Soil Moisture ◽  
Population Density ◽  
River Basin ◽  
Goodness Of Fit ◽  
Water Storage ◽  
Least Square ◽  
Nile River ◽  
Terrestrial Water Storage ◽  
Terrestrial Water ◽  
Nile River Basin

GRACE-derived Terrestrial Water Storage Anomalies (TWSA) continue to be used in an expanding array of studies to analyze numerous processes and phenomena related to terrestrial water storage dynamics, including groundwater depletions, lake storage variations, snow, and glacial mass changes, as well as floods, droughts, among others. So far, however, few studies have investigated how the factors that affect total water storage (e.g., precipitation, runoff, soil moisture, evapotranspiration) interact and combine over space and time to produce the mass variations that GRACE detects. This paper is an attempt to fill that gap and stimulate needed research in this area. Using the Nile River Basin as case study, it explicitly analyzes nine hydroclimatic and anthropogenic processes, as well as their relationship to TWS in different climatic zones in the Nile River Basin. The analytic method employed the trends in both the dependent and independent variables applying two geographically multiple regression (GMR) approaches: (i) an unweighted or ordinary least square regression (OLS) model in which the contributions of all variables to TWS variability are deemed equal at all locations; and (ii) a geographically weighted regression (GWR) which assigns a weight to each variable at different locations based on the occurrence of trend clusters, determined by Moran’s cluster index. In both cases, model efficacy was investigated using standard goodness of fit diagnostics. The OLS showed that trends in five variables (i.e., precipitation, runoff, surface water soil moisture, and population density) significantly (p<0.0001) explain the trends in TWSA for the basin at large. However, the models R2 value is only 0.14. In contrast, the GWR produced R2 values ranging between 0.40 and 0.89, with an average of 0.86 and normally distributed standard residuals. The models retained in the GWR differ by climatic zone. The results showed that all nine variables contribute significantly to the trend in TWS in the Tropical region; population density is an important contributor to TWSA variability in all zones; ET and Population density are the only significant variables in the semiarid zone. This type of information is critical for developing robust statistical models for reconstructing time series of proxy GRACE anomalies that predate the launch of the GRACE mission and for gap-filling between GRACE and GRACE-FO.

A study on implementing catchment-scale rootzone water storage capacities, derived from climatic parameters, in the HTESSEL land surface scheme

2020 ◽  
Author(s):  
Fransje van Oorschot ◽  
Andrea Alessandri ◽  
Ruud van der Ent ◽  
Markus Hrachowitz
Keyword(s):  
Land Surface ◽  
Storage Capacity ◽  
Water Storage ◽  
Land Surface Model ◽  
Dry Season ◽  
Surface Model ◽  
Catchment Scale ◽  
Land Surface Scheme ◽  
Storage Reservoir ◽  
Surface Scheme

<p>Evaporation is a key flux in both Earth’s water and energy balances. It is largely controlled by the transport of water from the subsurface to the atmosphere, through the roots of vegetation. The water storage capacity in the rootzone is a key parameter in predicting evaporation fluxes in land surface models. Drought predictions are of particular interest because the size of the rootzone-storage-reservoir determines how long into the dry season vegetation is able to evaporate. Whereas climate is the major driver of root development, the storage in the rootzone in the HTESSEL land surface scheme is only dependent on soil type and model soil depth. Moreover, the model describes root parameters by tables based on observations of individual plants that do not represent ecosystem scales. This research analyses the effect of implementing rootzone water storage capacities estimated with catchment-scale mass balances, in the land surface model HTESSEL on water and energy fluxes for 15 Australian river catchments.</p><p>This study found that the storage capacity in the vegetation’s rootzone represented in HTESSEL is larger than the mass-balance derived estimates. This leads to an underestimation of river discharge and overestimation of evaporation fluxes by the model, with significantly larger errors in the dry season. Implementation of the climate-based rootzone storage estimates in the current HTESSEL scheme leads to small model improvements regarding long term mean discharge predictions, but larger improvements in dry season discharge predictions. Transpiration fluxes in the dry season are directly linked to the size of rootzone water storage reservoir. The results indicate that inadequate rootzone representation could result in errors in modelled discharge and evaporation fluxes in the land surface model HTESSEL.</p><p>This study shows that investigating uncertainties in the representation of the rootzone in the HTESSEL land surface model is paramount. Future research is required to improve the representation of the rootzone in climate models.</p>

scholarly journals Assimilation of GRACE Terrestrial Water Storage Data into a Land Surface Model: Results for the Mississippi River Basin

2008 ◽  
Vol 9 (3) ◽  
pp. 535-548 ◽  
Author(s):  
Benjamin F. Zaitchik ◽  
Matthew Rodell ◽  
Rolf H. Reichle
Keyword(s):  
River Basin ◽  
Mississippi River ◽  
Land Surface ◽  
River Flow ◽  
Water Storage ◽  
Land Surface Model ◽  
Surface Model ◽  
Mississippi River Basin ◽  
Terrestrial Water Storage ◽  
Terrestrial Water

Abstract Assimilation of data from the Gravity Recovery and Climate Experiment (GRACE) system of satellites yielded improved simulation of water storage and fluxes in the Mississippi River basin, as evaluated against independent measurements. The authors assimilated GRACE-derived monthly terrestrial water storage (TWS) anomalies for each of the four major subbasins of the Mississippi into the Catchment Land Surface Model (CLSM) using an ensemble Kalman smoother from January 2003 to May 2006. Compared with the open-loop CLSM simulation, assimilation estimates of groundwater variability exhibited enhanced skill with respect to measured groundwater in all four subbasins. Assimilation also significantly increased the correlation between simulated TWS and gauged river flow for all four subbasins and for the Mississippi River itself. In addition, model performance was evaluated for eight smaller watersheds within the Mississippi basin, all of which are smaller than the scale of GRACE observations. In seven of eight cases, GRACE assimilation led to increased correlation between TWS estimates and gauged river flow, indicating that data assimilation has considerable potential to downscale GRACE data for hydrological applications.

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