Nitrate contamination of urban groundwater and heavy rainfall: Observations from Dakar, Senegal

In low-income urban areas of major cities in Africa, sanitation provision derives primarily from onsite systems often comprising septic tanks and pit latrines. Such rely upon the ability surrounding soil substratum to attenuate contaminants like nitrate pathogenic microorganisms wastewater. Here, we assess soil–water solute dynamics Quaternary aeolian sands underlying a densely populated suburb (Keur Massar) Dakar (Senegal) using high-frequency monitoring vadose zone modeling (Hydrus-1D). Observations rainfall intensity, moisture content, shallow groundwater-level fluctuations concentrations were carried out at an experimental site adjacent tank supplied by toilets used primary school. Rapid rises content episodic recharge contributions observed groundwater levels caused heavy (>10 mm h−1) extreme (>20 are well modeled (R2 = .79–.83; RMSE 0.012–0.019) pore-matrix flow unsaturated Darcy–Richards equation. Spot sampling around most intense 2020 (45 reveals fivefold rise fall concentration (∼500 ∼2,500 mg L−1). These measurements provide new insight into hydrological which is grossly contaminated (>500 L−1) through flushing wastewater vast estimated network over 250,000 this Dakar.