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Groundwater is the major source for drinking water in Sub-Saharan Africa. However, there is lack of reliable and timely information on the status of groundwater supplies fundamental to groundwater drought planning and adaptation. Moreover, the methodological approach used for determining climate-groundwater relationship needs advanced technology which can be highly costly for poor resource settings. This study determined long term climate change trends and its impacts on groundwater dynamics (recharge) by using simpler and quicker approach to easy early detection of impacts.
A cross-sectional study was conducted in Nzega District Tanzania from March to June 2010. Both quantitative (borehole and household surveys) and qualitative community survey (participatory village meetings and key-informants interview) methods were employed. Detailed analyses of climate data from 1925 to 2008 were done using spreadsheet. Recharge rates were estimated by empirical methods, surveys by SPSS program and qualitative data through structural and content analysis. Two scenarios were used to compare change in temperature i.e. past (1960-1989) and current (1990-2008) while rainfall-recharge were compared in three scenarios, .i.e., past (1925-1955), middle (1956-1985) and current (1986-2008). Climate has changed by both increased temperature (79%, N=100, increased monthly average minimum and maximum temperatures, and annual average maximum & minimum temperature also increased by 1.3 and 1.2oC respectively from past to present. Per decadal rise by 0.3oC were computed); and decreased rainfall (61%, N=100). These contributed to increased depth of groundwater excavation and increased frequency and duration of shallow wells drying. Rainfall used to cease from mid-April, but currently starts to cease in early March. Moreover, in the past, district experienced two peaks of maximum rainfall (December and Mid-April), currently only one maximum peak is observed in December. Total annual rainfall decreased by 11.8 mm (1.5%) from past to present resulting into decreased annual groundwater recharge rate by 2.3%. It can be concluded that climate has changed from past to present and impacting groundwater recharge negatively; therefore, there is the need to continuously monitor groundwater system and recharge in an integrated manner. |
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