Search

Due to surface water scarcity and variability in rainwater events in the Thies region, Senegal, farmers mostly rely on groundwater resources to improve yield production, although water quality in the hydrosystem and its suitability may be an issue. The objective of this study is to evaluate suitability of the Maastrichtian and Paleocene aquifers located the central western part of Senegal in the Thies region for irrigation purposes. For this purpose, chemical analyses were carried out on the major ions on the Maastrichtian and Paleocene aquifers through a network of 62 sample locations (39 from the Maastrichtian and 23 from the Paleocene) sampled in June 2019. Different water suitability assessment indices were used to evaluate the potential for irrigation, including sodium absorption ration (SAR), percentage of sodium (Na%), permeability index, Kelly ratio (RK), and salinity potential (SP) together with Wilcox and USSL diagrams as methods. The results indicate, that the Ca-Mg-HCO3 water type is dominant in the Maastrichtian aquifer, while in the Paleocene aquifer, HCO3-Ca-Mg and Cl-Ca-Mg are the main water types. The combination of these computed index values indicates that the percentage of suitable water for irrigation purposes accounts for 89.7% and 86.9% of the samples for the Maastrichtian and the Paleocene aquifers, respectively. On the other hand, water samples unsuitable for irrigation purposes range between only 10.3% and 13.1% for the two aquifers. [ABSTRACT FROM AUTHOR]

• Synthetically generated groundwater fluctuations and actual ET can be estimated from WTF method accurately. • Real measured actual ET can be estimated from groundwater fluctuations in a semiarid region of Senegal. • A decoupling depth of GW table between potential and actual ET was calculated. The use of diurnal or seasonal water table fluctuation (WTF) to estimate groundwater evapotranspiration (ET G) at different land uses and climate conditions is increasing applied in ecohydrological studies. In this study, we applied the WTF method for a shallow aquifer in an urbanized area in Senegal over the dry season 2000–2013.To analyze the applicability and validity of the WTF method for this site, and to understand the impact of the parameters used in this method, the unsaturated /saturated system was first simulated using the HYDRUS 1D model. The drawdown of the water table ranges from 18.1 to 113.2 cm and 10.4 to 101.9 cm for a bare soil and a perennial grass scenario and is highly related to the annual rainfall of the previous rainy season. The results indicate that the mean daily FAO-PM reference evapotranspiration rates for this area ranged from 2 to 4 mmd−1 and that the estimated actual evapotranspiration (ET a) from the HYDRUS 1D model ranged between 0.22 to 1.11 and 0.23 to 1.27 mmd−1 in bare soil and vegetative condition, respectively. ET a and ET G were well correlated for the vegetated scenario. However, the WTF method slightly overestimates ET a fluxes in the bare soil scenario. The study shows that the decline of ET a with water table depth can be simulated by an exponential function. The overall results indicate that higher ET a values were observed when the water table is shallow, suggesting that ET a is mainly driven by the water table depth at this site. [ABSTRACT FROM AUTHOR]