Estimating the potential of small reservoir construction and groundwater pumping to reduce water stress and adapt to climate change for smallholder farmers in Senegal
Summary
In the past decades, Senegal has faced numerous droughts, and the frequency of these droughts is expected to increase due to the effects of climate change. Consequently, a large part of the population experiences food insecurity, as 70\% of the population relies on agriculture for their livelihood. To mitigate this problem, the construction of small reservoirs and groundwater pumping may offer a solution to increase water availability in the agricultural sector. This study aimed to identify suitable locations for reservoirs with dam heights of 3, 4, and 5 meters and an areal density of one reservoir per 5x5 or 10x10 cells in Senegal. The impact on water availability was modeled using the global hydrology model PCRGLOB-WB 2 at a spatial resolution of 30 arcseconds, incorporating new local datasets. Groundwater pumping was integrated to evaluate the combined effect on water availability using a two-layer groundwater model based on MODFLOW.
The results revealed that reservoirs with a dam height of 4 meters and an areal density of one reservoir per 5x5 cells show the greatest potential for enhancing water availability, particularly in the regions of Ziguinchor, Sédhiou, Kolda, and Kédougou. In the Fatick, Kaolack, and Kaffrine regions, the simulated impact of reservoir irrigation on increasing water availability was minimal, but the potential may increase with modifications in the modeling set-up. Furthermore, renewable groundwater resources have the capacity to fully meet irrigation demand in all of these regions, as well as in Tambacounda. However, tackling water availability alone does not fully solve the constraints on food security. Other factors such as water quality, soil degradation, market access, and investments in small-scale irrigation systems are also significant considerations.