Abstract
This Areai, as shown in Fig. 3, has a basin structure, surrounded by faults or Precambrian basement rocks.
The basin is fflled by alluvium deposits chiefly composed of sands, gravels, clays and calcareous deposits, with some amounts of lavas and pyroclastic rocks originated from Kilimanjaro Volcan. These deposits which are roughly estimated at more than 130m in thickness in the south and seem to become thicker toward north are major aquifers in this area.
As shown in Fig. 9 the total quantity of water recharged in the Kahe-Miwaleni groundwater basin is estimated to be 300, 000, 000m3/year and the quantity of water consumed by surface runoff (mainly from the Miwaleni Spring) and pumping works is estimated 110, 000, 000m3/year. About half the quantity of recharge may be regarded as the object of the future groundwater exploitation. However, it is still dangerous to think that all of 190, 000, 000m3/year can be expoited in future. It is technically impossible to pump out all the potential quantity due to hydrogeological restrictions and power limit of the pumping facilities. The quantity of water that can be practically drawn up should be estimated at most 50, 000, 000m3/year, less than half the potential quantity.
