Development of future water source strategies for Dar Es Salaam

The sources of water within the DWSSP area are the Ruvu river, Kizinga river, shallow wells and boreholes. The total potential production capacity of 272,000m3/day is from surface water plus 36,000m3/day from ground water. The present water supply is inadequate to meet the increasing demand of the city and is prone to high levels of un accounted for water amounting to 50%. The objectives of this study included: to establish water augmentation required from new sources: to examine the impact of a fully implemented demand management system on the projected demands: to evaluate current source options and formulate development strategies and to identify other factors aggravating water scarcity in Dar Es Salaam and propose measures. The population within the study area was derived from the results of both Gauff 2004 Consumer survey and House Count. The 2004 population was estimated as 1,879,551. The assessment results were found to be about 2% lower than the 2002 Census figures when compared on similar administrative areas. Present and long term water demand for water users in the study area was assessed for a maximum horixon of 11 years. Based on average per capita consumptions for the various consumer categories as indicated in the Gauf 2003 Design Criteria Report, the 2004 net domestic demand within the supply area was calculated as 149,593 m3/day. These computed domestic demands were used together with those for2004 non-domestic demands obtained from the consumer survey to determine an estimation of the 2004 total net water demand within the study area. It was estimated as 194,511 m3/day. The present system transmission and distribution physical losses were incorporated into the 2004 total net water demand to establish the 2004 Total average daily water demand it was estimated as 398,023 m3/day. The 2004 peak demand was established using a peaking daily factor of 1.15. It was established as 418,200 m3/day. The population was projected using a simplified model of exponential growth and the application of Gauff 2003 annual growth rates. The water demand was projected based on the projected population. Two scenarios were established. Scenario A considered universal metering alone while scenario B, additionally considered introduction of block Tariff structure. The present supply was projected taken into account the effects of a progressive leak reduction program. The demand v/s supply projections indicated that an immediate augmentation from new sources of 91,000 m3/day under scenario A and 52,000 m3/day under scenario B were required to cope with peak daily demand within the study area until year 2015. The study showed with the implementation of demand management 45.5% of the present supply can be saved in the year 2015. This is more than the 2004 water demand for medium income household. Also the study showed demand management will provide early balance between supply and total net demand in year 2005, and postpones the necessity of new sources required in 2011 to at least after 2015 to meet total net demand. In addition, demand management balances average daily and supply during years (2007 – 2010) of the design horizon and thus postponing the neccessity of new sources immediately to balance supply and 2010 average demand. Furthermore, with demand management, the peak daily demand is balanced in year 2008 of the design horizon and as such the new source is needed after 2008. The current sources identified based on previous studies were initially qualitatively screened based on the potential of staging the required infrastructure and a further preliminary assessment was based on estimated threshold lead time to develop the source, potential yield of the source and storage efficiency. This assessment was used to formulate three development strategies that give incremental increases in supply in line with the expected growth in demands. The three strategies developed included: palaeo-channel aquifer of the Ruvu river by a diversion from Rufiji catchments. The study identified apart from ever increasing demand levels; water scarcity in Dar es Salaam is also aggravated by other three factors; reluctance to treat water as an economic as well as a public good, environmental degradation of water sources, in particular, reduced water quality and quantity due to pollution from urban or land based activities and inadequate use of alternative water sources. Alternative water sources other than ground water and surface water are rarely explored. In the view of the above, the study proposes a Dar Es Salaam integrated water management strategy that should move towards, water audits, demand management, integrated urban water resource management (IUWRM), Dar Es Salaam watersheds and water kiosk supplies. In conclusion, for reliability of Dar es Salaam water supply, integrated source development and staged development of the preferred source option is needed.