Abstract:
Dar es Salaam City is highly depending on
groundwater resources since 1997. The resulting overex-
ploitation is entailing the risk of seawater intrusion. This
problem has been systematically investigated for the first
time, and appears to be wide-spread. Determining the depth
of the fresh–salt water interface was deemed crucial in the
view of sustainable exploitation of the Dar es Salaam
quaternary coastal aquifer system. Vertical electrical
soundings (VES) and horizontal resistivity profiles have
shown a decrease of resistivity with depth and toward the
coastline. Cross sections have shown the presence of salt
water in the aquifer near the coastline, and the boundary
between fresh and saline waters is mapped. The surface
prospection resistivity data showed comparable results as
reflected in hydrochemical/lithological cross sections and
resistivity well logs. Salt water was found mostly in the
area within 2 km of the coastline, and the depth to the
interface in this zone is ranging from 1.3 to 20 m. Away
from the coastline, the interface (if present) is at greater
depth. VES executed at Kurasini (4 km from the sea) showed the fresh–salt water interface at a greater depth
(43 m).
