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On-site sanitation density and groundwater quality: Evidence from remote sensing and in situ observations in the thiaroye aquifer, Senegal

Diaw, MT; Cissé-Faye, S; Gaye, CB; Niang, S; Pouye, A; Campos, LC; Taylor, RG; (2020) On-site sanitation density and groundwater quality: Evidence from remote sensing and in situ observations in the thiaroye aquifer, Senegal. Journal of Water Sanitation and Hygiene for Development , 10 (4) pp. 927-939. 10.2166/washdev.2020.162. Green open access

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Abstract

© 2020 The Authors. In rapidly urbanising low-income towns and cities, there remains an absence of scientific evidence and regulatory structures to sustain the quality and quantity of groundwater used for low-cost water supplies and to reconcile this with continued use of the subsurface for low-cost sanitation. Here, we analyse the relationship between the density of on-site sanitation and shallow groundwater quality in the Thiaroye aquifer of Quaternary sands in Dakar, Senegal. On-site sanitation was mapped using object-oriented classification and visual interpretation of high-resolution, optical satellite images and ground-truthing surveys. Groundwater quality was assessed over a three-year period (2017–2019) from a network of 61 sources comprising boreholes, dug-wells, hand tubewells and piezometers. More than 253,000 on-site sanitation facilities are identified over an area of 520 km2 with densities ranging from 1 to 70 per hectare. A moderate, statistically significant linear relationship (r2 = 0.55, p « 0.01) is found between the density of on-site sanitation facilities and nitrate concentrations in sampled groundwater sources. Groundwater contamination beyond the WHO drinking-water guideline value (50 mg/L) occurs where densities of on-site sanitation facilities exceed 4 (±4) per hectare, a threshold commonly surpassed in peri-urban areas underlain by the Thiaroye aquifer of Dakar.

Type: Article
Title: On-site sanitation density and groundwater quality: Evidence from remote sensing and in situ observations in the thiaroye aquifer, Senegal
Open access status: An open access version is available from UCL Discovery
DOI: 10.2166/washdev.2020.162
Publisher version: http://dx.doi.org/10.2166/washdev.2020.162
Language: English
Additional information: This is an Open Access article distributed under the terms of the Creative Commons Attribution Licence (CC BY 4.0), which permits copying, adaptation and redistribution, provided the original work is properly cited (http://creativecommons.org/licenses/by/4.0/).
Keywords: faecal contamination and remote sensing, groundwater quality, on-site sanitation density, urban and peri-urban area, water supply
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Civil, Environ and Geomatic Eng
UCL > Provost and Vice Provost Offices > UCL SLASH
UCL > Provost and Vice Provost Offices > UCL SLASH > Faculty of S&HS
UCL > Provost and Vice Provost Offices > UCL SLASH > Faculty of S&HS > Dept of Geography
URI: https://discovery.ucl.ac.uk/id/eprint/10119282
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