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Assessment of Physical Water Scarcity in Africa Using GRACE and TRMM Satellite Data

Department of Geography, State University of New York, Binghamton, NY 10002, USA
Hydrometeorology and Remote Sensing (HyDROS) Laboratory, Advanced Radar Research Center (ARRC), University of Oklahoma, Norman, OK 73019, USA
Geology Department, Faculty of Science, Damietta University, New Damietta 34518, Egypt
College of Atmospheric & Geographic Sciences, University of Oklahoma, Norman, OK 73019, USA
Author to whom correspondence should be addressed.
Remote Sens. 2019, 11(8), 904;
Received: 15 February 2019 / Revised: 10 April 2019 / Accepted: 11 April 2019 / Published: 13 April 2019
PDF [3794 KB, uploaded 13 April 2019]


The critical role of water in enabling or constraining human well-being and socioeconomic activities has led to an interest in quantitatively establishing the status of water (in)sufficiency over space and time. Falkenmark introduced the first widely accepted measure of water status, the Water Scarcity Index (WSI), which expressed the status of the availability of water resources in terms of vulnerability, stress, and scarcity. Since then, numerous indicators have been introduced, but nearly all adopt the same basic formulation; water status is a function of “available water” resource—by the demand or use. However, the accurate assessment of “available water” is difficult, especially in data-scarce regions, such as Africa. In this paper, therefore, we introduce a satellite-based Potential Available Water Storage indicator, PAWS. The method integrates GRACE (Gravity Recovery and Climate Experiment) satellite Total Water Storage (TWS) measurements with the Tropical Rainfall Measuring Mission (TRMM) precipitation estimates between 2002 and 2016. First, we derived the countries’ Internal Water Storage (IWS) using GRACE and TRMM precipitation data. Then, the IWS was divided by the population density to derive the PAWS per capita. Following the Falkenmark thresholds, 54% of countries are classified in the same water vulnerability status as the AQUASTAT Internal Renewable Water Resources (IRWR) method. Of the remaining countries, PAWS index leads to one or two categories shift (left or right) of water status. The PAWS index shows that 14% (~160 million people) of Africa’s population currently live under water scarcity status. With respect to future projections, PAWS index suggests that a 10% decrease in future water resources would affect ~37% of Africa’s 2025 population (~600 million people), and 57% for 2050 projections (~1.4-billion people). The proposed approach largely overcomes the constraints related to the data needed to rapidly and robustly estimate available water resources by incorporating all stocks of water within the country, as well as underscores the recent water storage dynamics. However, the estimates obtained concern potential available water resources, which may not be utilizable for practical, economic, and technological issues. View Full-Text
Keywords: Africa; GRACE; TRMM; water resources; water scarcity Africa; GRACE; TRMM; water resources; water scarcity

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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

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Hasan, E.; Tarhule, A.; Hong, Y.; Moore, B., III. Assessment of Physical Water Scarcity in Africa Using GRACE and TRMM Satellite Data. Remote Sens. 2019, 11, 904.

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