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Title Hydrogeology of an urban weathered basement aquifer in Kampala, Uganda
Full text http://resolver.tudelft.nl/uuid:0ff94c74-7834-4c55-8c69-f9d2bd2c0892
Date 2022
Author(s) Nyenje, Philip M. (author); Ocoromac, Denis (author); Tumwesige, Stephen (author); Ascott, Matt J. (author); Sorensen, James P.R. (author); Tindimugaya, Callist (author); Kulabako, Robinah N. (author); Lapworth, Dan J. (author); Foppen, J.W.A. (author)
Abstract 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 3'50mm/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 (< 0.001m<sup>3</sup>/s), low pH (<5), high nitrate values (61'190mg/L as NO<sub>3</sub>), and residence times of <30years. The deeper groundwater system occurred in the saprolite/saprock, had low transmissivity (< 1 × 10<sup>âˆ'5</sup>m<sup>2</sup>/s), lower nitrate values (<20mg/L as NO<sub>3</sub>), pH6'6.5 and longer residence times (40'60years). 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. - Water Resources
Subject(s) Basement aquifer; Groundwater flow; Recharge; Uganda; Urban
Language en
Relation http://www.scopus.com/inward/record.url?scp=85131537784&partnerID=8YFLogxK; Hydrogeology Journal--1431-2174--742a1596-dbce-465c-8cde-a6f7bb344931
Type of publication journal article
Rights © 2022 Philip M. Nyenje, Denis Ocoromac, Stephen Tumwesige, Matt J. Ascott, James P.R. Sorensen, Callist Tindimugaya, Robinah N. Kulabako, Dan J. Lapworth, J.W.A. Foppen, More Authors
Identifier doi:10.1007/s10040-022-02474-9
Repository Delft - Technische Universiteit Delft
Added to C-A: 2022-07-14;07:14:08