+50 Years of Terrestrial Hydroclimatic Variability in Africa’s Transboundary Waters

Hasan, Emad; Tarhule, Aondover; Zume, Joseph T.; Kirstetter, Pierre‐Emmanuel

doi:10.1038/s41598-019-48813-x

Cited by 28 publications

(16 citation statements)

References 59 publications

(72 reference statements)

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“…Keen attention must be paid to areas that are more affected by water scarcity, such as the African continent [324,325], where water shortages may concern 37% of the 2025 population (~600 million people) and 57% in 2050 (~1.4 billion people), under the hypothesis of a decrease in water resources by 10%. Concerning water management, Biswas and Tortajada [326] point out unambiguously that "countries will have to manage their water significantly better, because they will have no other choice".…”

Section: Discussionmentioning

confidence: 99%

Satellite Remote Sensing of Precipitation and the Terrestrial Water Cycle in a Changing Climate

2019

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The water cycle is the most essential supporting physical mechanism ensuring the existence of life on Earth. Its components encompass the atmosphere, land, and oceans. The cycle is composed of evaporation, evapotranspiration, sublimation, water vapor transport, condensation, precipitation, runoff, infiltration and percolation, groundwater flow, and plant uptake. For a correct closure of the global water cycle, observations are needed of all these processes with a global perspective. In particular, precipitation requires continuous monitoring, as it is the most important component of the cycle, especially under changing climatic conditions. Passive and active sensors on board meteorological and environmental satellites now make reasonably complete data available that allow better measurements of precipitation to be made from space, in order to improve our understanding of the cycle’s acceleration/deceleration under current and projected climate conditions. The article aims to draw an up-to-date picture of the current status of observations of precipitation from space, with an outlook to the near future of the satellite constellation, modeling applications, and water resource management.

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Section: Discussionmentioning

confidence: 99%

Satellite Remote Sensing of Precipitation and the Terrestrial Water Cycle in a Changing Climate

2019

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“…The ARIMA model was selected to explore another statistical-based approach (deterministic statistic) to fill the missing record between GRACE and GRACE-FO. Currently, several ongoing research efforts are implementing either complex modeling tools [92], different explanatory variables from satellite or LSMs (i.e., precipitation, and temperature) [31,93], or independent geophysical datasets (i.e., Swarm satellite data) [94] to fill the one-year gap between GRACE and GRACE-FO. Herein, we present an alternative/easyto-apply approach to fill the one-year gap without any exogenous/independent variables/data.…”

Section: Arima Modelmentioning

confidence: 99%

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

Hasan¹,

Tarhule²,

Kirstetter³

2021

Preprint

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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.

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“…Then a fixed sample grid to GRACE CSR-M product was used to sample the corresponding trend value at a fixed spatial resolution of 1.0-degree grid. The associated uncertainty in each variable was expressed using standard deviations of the residual component following standardized approaches [7,39,69,79,80]. Table 1.…”

Section: Nile River Basinmentioning

confidence: 99%

“…The significance of the trend was tested using the Sen's slope method. These methods are widely used for trend estimation, and justification for their use appears in numerous publications [38,39,[90][91][92]. The Mann-Kendall statistic ( ) for a time series 1 , 2 , … , is calculated as,…”

Section: Trend Analysismentioning

confidence: 99%

“…These processes vary significantly over time and space, and the degree of variability increases as the study domain increases. Other studies have correlated interannual variability in GRACE anomalies to precipitation data [3], land surface model outputs [35][36][37][38][39], or explained how climate forcing, such as El Niño-Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD) drive GRACE anomalies in various basins [40][41][42][43].…”

Section: Introductionmentioning

confidence: 99%

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

Hasan¹,

Tarhule²

2019

Preprint

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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.

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+50 Years of Terrestrial Hydroclimatic Variability in Africa’s Transboundary Waters

Cited by 28 publications

References 59 publications

Satellite Remote Sensing of Precipitation and the Terrestrial Water Cycle in a Changing Climate

Satellite Remote Sensing of Precipitation and the Terrestrial Water Cycle in a Changing Climate

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

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

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