Rainfall-discharge relationship and water balance over the past 60 years within the Chari-Logone sub-basins, Lake Chad basin

Study Region: Chari-Logone River basin, Lake Chad basin. Study Focus: The objective of this study was to better understand the hydrological functioning of the Chari-Logone basin under the effect of the high variability of rainfall which has affected the Sahel during the last sixty years. The study is based on hydro-climatic data for the period between 1960 and 2015 obtained from the national and international institutions. This work based on the following steps: 1) Average hydrological balances were estimated for different geographical areas, to identify the most productive parts of the basin. 2) The rainfall-runoff relation was compared for the wettest and driest decades of the study period, to identify the areas that contribute most to the amplification of the hydrological response to variations in rainfall. 3) The long-term period stability of the rainfall-runoff relation was evaluated for climatic conditions close to the average situation, in order to detect potential evidence of the anthropogenic impact. New Hydrologic Insights for the Region: During the period 1960-2015, the average water flow in the Chari-Logone basin (42 mm/year) represented only 5% of precipitation. Between the two climatically most contrasted wet (1960-1971) and dry (1982-1997) periods, the average flow differed by 75 % against a decrease of 15 % of precipitation. Our hydroclimatic data show no clearly detectable evidence of an anthropogenic impact responsible for a decrease in flows or a modification of the hydrological regime in the Chari-Logone basin.

Automated summary

This study aimed to understand the hydrological functioning of the Chari-Logone basin under the high variability of rainfall which has affected the Sahel region in the last sixty years. The results showed that the water flow in the basin represented only 5% of precipitation, with significant variations in flow during wet and dry periods, but no clear evidence of anthropogenic impact on flow or hydrological regime modification.