Assessment the Impacts of Reuse Wastewater for Irrigation on Soil: Case study: Dakar Niayes Zone

Abstract

Urban agriculture in Dakar occurs within the Niayes region, which possesses highly conducive climatic and hydrological conditions for this practice. As a result of the gradual increase in salinity in the groundwater, agricultural practitioners started employing untreated wastewater from aging drainage pipelines for the purpose of irrigating their fields. This research aims to assess the impacts of irrigation with treated water on physical and chemical properties of groundwater and soil in Niayes zone, Senegal, using Irrigation Water Quality Index (IWQI) and indices for water irrigation quality. for sampling method 30 water and 74 soil samples were collected into 4 different areas for irrigation: Technopole of Pikine, Patte d’oie, Maristes and Sangalkam our control zone. The physical and chemical water parameters were analyzed and IWQI and indices like SAR, PS, MH, RSC, PI and % Na were calculated for assessing the quality of water for irrigation. Groundwater samples show higher salinity levels than wastewater due to overexploitation for irrigation, leading to salinization and contamination of water tables, posing risks to coastal regions. While wastewater irrigation helps mitigate yield reductions from saline groundwater, concerns arise regarding magnesium hazard and sodium carbonate levels, potentially leading to soil alkalinization and decreased agricultural productivity. The Irrigation Water Quality Index suggests caution in using these waters for irrigation without proper soil permeability conditions. Groundwater quality is compromised by excessive salts and elements, contributing to overall declines in water quality indices. Continuous reuse of low-quality wastewater adversely impacts soil fertility and groundwater quality, emphasizing the need for improved wastewater management strategies for sustainable agriculture and water security.