Browsing by Author "Melchioly, Simon Rwekiza"

Now showing 1 - 1 of 1
  • Thumbnail Image
    Item
    Assessment of groundwater resources in coastal aquifers of Kilwa district
    (University of Dar es Salaam, 2018) Melchioly, Simon Rwekiza
    The main objective of this research was to carry out an assessment of groundwater resources status of coastal aquifers in Kilwa District. The study area covered KilwaMasoko town, KilwaKivinje, KilwaKisiwani Island, Singino village, and Nangurukuru. The major findings of the reseach include; the water demand (based on population) for the study area is obtained as 1.583 x 106 m3/yr while supply is 1.262 x 106 m3/yr and hence the deficit of water for the study area is 0.321 x 106 m3/yr. Groundwater recharge in the study area has been obtained as 159.63 mm/yr which is equivalent to 16.44189 x 106 m3/yr. Annual groundwater abstraction is estimated as 1.583 x 106 m3/yr. The water balance estimates an average sustainable yield of 6.58 x 106 m3/yr (estimated as 40% of annual groundwater recharge). These results show clearly that the aquifer in the study area is sustainably exploited. Aquifer hydraulic parameters obtained are such that the transmissivity (T) and hydraulic conductivity (K) for Mpara aquifer system are 39.3 m2/day and 1.3 m/day respectively while transmissivity (T) and hydraulic conductivity (K) for KilwaMasoko aquifer system are 25.55 m2/day and 0.852 m/day respectively. The land use and /or land cover changes in the area for the period 2006 to 2013 show that for KilwaKisiwani Island, the area covered by Mangroves along the seashore has increased by 17%. Similarly, settlement areas increased by 11% while areas covered by forest decreased by 9.8%. For the case of KilwaMasoko town and its neighbourhood, vegetation cover has decreased by 13% for that same period. The land acquired for farming increased by 11% while the urbanised areas increased by 16%. Geophysical resistivity results show that there are potential aquifers with resistivity values ranging from 11.68 Ωm to 33.45 Ωm while formations with saline water as well as clayey formations have resistivity values ranging from 3.89Ωm to 1.56Ωm. Drilling depths at KilwaMasoko should be limited to 66 meters below ground surface. For KilwaKisiwani Island the recommended maximum drilling depths for potential sites vary from 15 m to 30 m below ground surface.The groundwater quality classification shows that the dominant group is the Mg-Cl water type, followed by no dominant water type, the MgHCO3 water type and finally the Na-Cl water type. The pH values ranges from 5.06 to 8.6 while electrical conductivity (EC) has moderate to high values as compared to TZS 789: 2008 standards. The groundwater in the study area is suitable for both drinking and irrigation.