Abstract
Groundwater quantity and quality may be affected by climate change through intricate direct and indirect mechanisms. At the same time, population growth and rapid urbanization have made groundwater an increasingly important source of water for multiple uses around the world, including southern Africa. The present study investigates the coupled human and natural system (CHANS) linking climate, sanitation, and groundwater quality in Ramotswa, a rapidly growing peri-urban area in the semi-arid southeastern Botswana, which relies on the transboundary Ramotswa aquifer for water supply. Analysis of long-term rainfall records indicated that droughts like the one in 2013–2016 are increasing in likelihood in the area due to climate change. Key informant interviews showed that due to the drought, people increasingly used pit latrines rather than flush toilets. Nitrate, fecal coliforms, and caffeine analyses of Ramotswa groundwater revealed that human waste leaching from pit latrines is the likely source of nitrate pollution. The results in conjunction indicate critical indirect linkages between climate change, sanitation, groundwater quality, and water security in the area. Improved sanitation, groundwater protection and remediation, and local water treatment would enhance reliable access to water, de-couple the community from reliance on surface water and associated water shortage risks, and help prevent transboundary tension over the shared aquifer.
Highlights
Groundwater supports about 75% of the Sub-Saharan African (SSA) population as well as industry and some crop irrigation (Calow and MacDonald 2009; Villholth 2013; Niang et al 2014), and water insecurity across SSA results from a complex interplay of natural and social systems (Howard and Bartram 2010)
This work demonstrated the indirect effect of climate change on groundwater quality in Ramotswa, Botswana
The drought led to water restrictions, inducing people with flush toilets to use pit latrines
Summary
Groundwater supports about 75% of the Sub-Saharan African (SSA) population as well as industry and some crop irrigation (Calow and MacDonald 2009; Villholth 2013; Niang et al 2014), and water insecurity across SSA results from a complex interplay of natural and social systems (Howard and Bartram 2010). Pit latrines are the most common means of human waste disposal, often in areas where communities rely on groundwater for drinking (Cronin et al 2007; Lapworth et al 2017). Unlined pit latrines leach to the groundwater, threatening groundwater quality and human health with pollutants like nitrate (NO3−) and pathogens (Cronin et al 2007; Graham and Polizzotto 2013). In studies of pit latrine impacts on groundwater quality, NO3− is the most commonly detected pollutant (Graham and Polizzotto 2013). Though safe levels of NO3− for humans in drinking water are still debated (Schullehner et al 2018), it is clear that this is a critical and widespread pollutant.
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