Hydroclimatic Extremes Evaluation Using GRACE/GRACE-FO and Multidecadal Climatic Variables over the Nile River Basin

Zemede M Nigatu,Assefa M Melesse,Wei You,Dongming Fan

doi:10.3390/rs13040651

Abstract

Hydroclimatic extremes such as droughts and floods triggered by human-induced climate change are causing severe damage in the Nile River Basin (NRB). These hydroclimatic extremes are not well studied in a holistic approach in NRB. In this study, the Gravity Recovery and Climate Experiment (GRACE) mission and its Follow on mission (GRACE-FO) derived indices and other standardized hydroclimatic indices are computed for developing monitoring and evaluation methods of flood and drought. We evaluated extreme hydroclimatic conditions by using GRACE/GRACE-FO derived indices such as water storage deficits Index (WSDI); and standardized hydroclimatic indices (i.e., Palmer Drought Severity Index (PDSI) and others). This study showed that during 1950–2019, eight major floods and ten droughts events were identified based on standardized-indices and GRACE/GRACE-FO-derived indices. Standardized-indices mostly underestimated the drought and flood severity level compared to GRACE/GRACE-FO derived indices. Among standardized indices PDSI show highest correlation (r2 = 0.72) with WSDI. GRACE-/GRACE-FO-derived indices can capture all major flood and drought events; hence, it may be an ideal substitute for data-scarce hydro-meteorological sites. Therefore, the proposed framework can serve as a useful tool for flood and drought monitoring and a better understanding of extreme hydroclimatic conditions in NRB and other similar climatic regions.

Highlights

The Nile is the world’s longest river with a drainage area of about 3.2 million km2, which is nearly 10% of the African continent’s landmass
Gravity Recovery and Climate Experiment (GRACE)/GRACE-FO time series and standardized indices over Nile River Basin (NRB) during 1950–2019. This framework incorporates groundwater, agricultural, and meteorological droughts and flood severity based on respective indices
Our results indicate that the GRACE/GRACEFO derived indices can adequately capture the drought and flood events that agree reasonably well with Palmer Drought Severity Index (PDSI), SPI, Standardized Precipitation Evapotranspiration Index (SPEI), SSI, MSDIp, MSDIe, and, though differences occur owing to inherent differences among indices

Summary

Introduction

The Nile is the world’s longest river with a drainage area of about 3.2 million km , which is nearly 10% of the African continent’s landmass. The agricultural system [1,2], economic development [3,4], food security, and increasing population [5] makes the basin extremely vulnerable. The basin demands a suitable method to determine its spatiotemporal patterns of floods and droughts. A drought or flood is an event characterized by a land-water deficit or excess that significantly affects agriculture, ecosystems, and socioeconomic development [6,7].

Methods

Discussion

Conclusion