An Integrated Perspective for Urban Water Management 55
difficult and may result in over-abstraction of the aquifer (Foster et al., 2010b). Localized groundwater abstraction in urban areas presents significant groundwater quality challenges that need to be addressed when planning for current and future water supplies. Wastewater infiltration from poorly maintained latrines can pollute aquifers, hence groundwater protection and improved wastewater management and sanitation are connected issues (Foster et al., 2006). Additionally, groundwater quality concerns are more acute in coastal areas where the lack of control of aquifer pumping can cause salinity problems due to seawater intrusion.
Box 2.9
An Innovative Approach Leads to the Discovery of the Kimbiji Aquifer, a Potentially Important Water Supply Source for Dar es Salaam, Tanzania The Kimbiji Aquifer System, a previously unknown aquifer, was discovered in 2006 as part of Dar es Salaam (Tanzania) Future Water Source Masterplan Development, under the World Bank–funded Dar es Salaam Water Supply and Sanitation Project. Twenty-six supply options (including on-stream and off-stream dams, interbasin transfers, shallow and deep groundwater, and desalination) were reviewed but only two were further investigated: the deep Kimbiji Aquifer and Kidunda Dam. The groundwater study concluded that the Kimbiji Aquifer System is an important potential source of water to cover Dar es Salaam water demand through 2030. It is estimated to cover an area of 10,000 square kilometers and have a storage volume of approximately 1 million liters (or megaliter—Ml). Average annual recharge rate is estimated to be about 1,000 Ml/year—an enormous potential water source compared to the city’s estimated additional 2030 water demand of around 200 Ml/day. The existing water supply for the city comes from the Ruvu River, a surface water source to the north. The Kimbiji Aquifer is located south of the city. With adequate management and protection, this large natural reservoir will remain a strategic water source for the rapidly growing area. Conjunctive use and management of surface and groundwater can offer the Dar es Salaam Water Supply and Sewerage Authority the flexibility to effectively respond to hydrological variability during periods of drought. Moreover, the Kimbiji Aquifer (as a naturally buffered system) offers resilience from the impacts of climate change on the city’s water supply. Sources: Hirji, 2012; Ruden, 2007.
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