Evaluation of Lake Guiers’ (Senegal) water resources availability under climate change and human activities by using WEAP model

Abstract

This study assesses the future availability of water resources in Lake Guiers, Senegal, by 2050, under the combined impacts of climate change and human activities, using the WEAP (Water Evaluation and Planning) model. As the main freshwater reservoir of Senegal, Lake Guiers faces multiple threats, including intensive agriculture, aquatic plant proliferation, conflicting stakeholder interests, rising water demand, and the effects of climate change. Our methodology integrates original field data on water quality, hydrological flows, and agricultural water uses, combined with climate projections (SSP4.5 and SSP8.5). Future climate scenarios were downscaled and bias-corrected using CMHYD, Multiple Linear Regression (MLR), and the Mann-Kendall test. The WEAP model calibration yielded statistically robust results (NSE = 0.95; R² = 0.96). Climate projections (2015–2100) indicate a decline in precipitation of 0.66 mm/year (SSP4.5) and 1.71 mm/year (SSP8.5), alongside a temperature increase of 0.040°C/year and 0.080°C/year, respectively. Significant water losses were observed in the Taouey canal (6.32 m³/s, or 546,048 m³/day), while annual agricultural water withdrawals (79.33 million m³) exceed crop water requirements by 10.21 million m³/year, causing severe inefficiencies. Scenario analysis reveals that high water demand combined with SSP8.5 accelerates the lake’s volume depletion, with critical declines beginning as early as 2026, while a moderate demand increase (2%) under SSP4.5 could maintain water availability until 2050. The PREFERLO_Grand transfer project, requiring 556 million m³ annually, is incompatible with the lake's capacity, rapidly driving it toward the inactivity threshold of 149 million m³. This research provides critical insights for sustainable water resource management and policy development, offering practical guidance to address the growing climatic and anthropogenic challenges in the Lake Guiers region