| dc.description.abstract | In the present study, a 42-year record of rainfall and temperature from Airport and a 43-year
rainfall record from Kizimbani meteorological station were analyzed to understand how these
climatic variables are affecting groundwater resources on the Island of Zanzibar, Tanzania.
Water table fluctuation, abstraction volume and different Physico-chemical parameters such
as chlorinity, nitrate, electrical conductivity and total dissolved solids were also studied. The
balance between groundwater recharge and water abstraction rates and assess the impact of
groundwater pumpage on water quality on the island of Zanzibar was estimated. Through the
use of the water table fluctuation (WTF) method, this study estimated the local sustainable
yield (SY) and integrated water balance (IWB) in Zanzibar. Rainfall records showed that
Zanzibar Island receives a total mean annual rainfall of 1673 mm out of which 7%
(equivalent to 1.79 x 10
6
m
3
/y) recharges the groundwater. Temperature variations indicated
an incremental trend accompanied by low rainfall. The average estimated local sustainable
yield was 0.72% while the integrated water balance showed a deficit of 39%. Furthermore,
the total groundwater abstraction rate in the studied area was 2.49 x 10
6
m
3
/y, which is higher
than the rate of recharge. This means that the groundwater resources are currently overexploited
and
if
immediate
action
is
not
taken,
the
groundwater
aquifers
may
be
subjected
to
pollution,
collapse,
and
seawater
intrusion.
The
effects
of
over-pumping
are
being
manifested
by
the
levels
of
EC,
Cl
-
, TDS, total hardness (TH) and nitrate that have shown an increasing
trend with time. Due to the high variation of temperature, a controlled infiltration of
harvested rainwater is suggested as a sustainable solution for salt intrusion as well the balance
way of recharge and abstraction rate in Zanzibar and other islands. | en_US |
