Weathered basement aquifers are vital sources of drinking water in Africa. In order to better understand their role in the urban water balance, in a weathered basement aquifer in Kampala, Uganda, this study installed a transect of monitoring piezometers, carried out spring flow and high-frequency groundwater level monitoring, slug tests and hydrochemical analyses, including stable isotopes and groundwater residence time indicators. Findings showed a typical weathered basement aquifer with a 20–50-m thickness. Groundwater recharge was 3–50 mm/year, occurring during sustained rainfall. Recharge to a deep groundwater system within the saprock was slow and prolonged, while recharge to the springs on the valley slopes was quick and episodic, responding rapidly to precipitation. Springs discharged shallow groundwater, mixed with wastewater infiltrating from onsite sanitation practices and contributions from the deeper aquifer and were characterised by low flow rates (< 0.001 m³/s), low pH (<5), high nitrate values (61–190 mg/L as NO₃), and residence times of <30 years. The deeper groundwater system occurred in the saprolite/saprock, had low transmissivity (< 1 × 10⁻⁵ m²/s), lower nitrate values (<20 mg/L as NO₃), pH 6–6.5 and longer residence times (40–60 years). Confined groundwater conditions in the valleys were created by the presence of clay-rich alluvium and gave rise to artesian conditions where groundwater had lower nitrate concentrations. The findings provide new insights into weathered basement aquifers in the urban tropics and show that small-scale abstractions are more sustainable in the deeper groundwater system in the valleys, where confined conditions are present.

风化的地下含水层是非洲重要的饮用水源。为了更好地了解它们在城市水平衡中的作用，本研究在乌干达坎帕拉的一个风化地下含水层中安装了一段监测压力计，进行了泉水和高频地下水位监测、段塞试验和水化学分析，包括稳定同位素和地下水停留时间指标。调查结果显示了一个典型的风化地下含水层，厚度为 20-50 米。地下水补给量为 3-50 毫米/年，发生在持续降雨期间。岩层内深层地下水系统的补给缓慢而延长，而山谷斜坡上的泉水补给快速且间歇性，对降水反应迅速。泉水排放浅层地下水，³ /s)、低 pH (<5)、高硝酸盐值 (61–190 mg/L as NO ₃ ) 和 <30 年的停留时间。较深的地下水系统发生在腐泥土/腐岩中，具有低渗透率（< 1 × 10 ^-5  m ² /s），较低的硝酸盐值（<20 mg/L 作为 NO ₃），pH 6-6.5 和较长的停留时间（ 40-60 岁）。山谷中受限制的地下水条件是由富含粘土的冲积层造成的，并导致地下水硝酸盐浓度较低的自流条件。研究结果为城​​市热带地区风化的地下含水层提供了新的见解，并表明在存在受限条件的山谷中较深的地下水系统中，小规模的抽取更具可持续性。