The world‘s human population is increasing at an unprecedented rate with much of this growth
taking place in towns and cities of developing countries. Dar es Salaam in United Republic of
Tanzania is one of the fastest growing cities in Africa with a population of more than 4.5 million
people. The study was carried in the populous district Temeke, one of the three districts within
Dar es Salaam City. The district is accommodating 30% of total population of Dar es Salaam
(estimated to reach 1.4 million people). Approximately, less than 15% of Temeke residents
supplied with surface water from DAWASCO water supply system. The rest 90% rely on
groundwater as their main source of potable water supplied through public and private deep
boreholes or shallow wells. The illegal and improper dumping of solid waste, leakage of effluent
from industries, poor management of sewage from domestic and commercial activities are major
common pollution sources identified in the area. The main objective of this study was to assess
the impact of rapid expansion of the urban settlements on groundwater vulnerability in Temeke
District. The study assessed the spatial and temporal changes of land use and land cover changes
in the area, identified and assessed the groundwater quality status. The study further investigated
and mapped groundwater vulnerability areas to pollution using the DRASTIC Model. Land use
and land cover analysis of the study area through GIS and Remote Sensing application using
Landsat imagery TM and ETM of 1989, 1998, 2009 and 2014 under supervised classification was
applied. Results showed large expansion of built up area by 62% due to urbanization from 1989 to
2014. Population increase caused expansion of built up area and reduction of the open land from
47% to 13% and woodland cover from 33% to 18%. The high expansion of built-up area with
rapid emerging of informal settlements and urban slums and use of onsite sanitation threatened the
water quality in the area. In assessing the groundwater quality status of Temeke District, the area
was divided into four categories namely; industrial areas (Keko, Changómbe and Kurasini),
residential areas (Mbagala Kuu, Mtoni and Kurasini), agricultural areas (Changómbe) and
commercial areas (Tandika). Groundwater samples from boreholes and shallow wells in the
selected sampling sites in the study area were analysed for physico-chemical and microbiological
parameters. The parameters were analysed using standard methods. Faecal coliforms increased in
concentration from 0 CFU/100 ml at Keko, Mbagalla Kuu and Tandika in the dry season to 170
CFU/100 ml at Changómbe during wet season. The mean value measured was 26 ±37 CFU/100ml
in the dry season and 56 ± 64 CFU/100ml during the wet season. The total coliform count
measured in the dry season ranged from 5 CFU/100ml to 257 CFU/100ml while in the wet season
it ranged from 10 CFU/100ml to 310 CFU/100ml). The mean total coliform count ranged from 67± 95 CFU/100ml in the dry season to 115 ± 110 CFU/100ml in the wet season. Statistical results
from ANOVA indicated significant difference of faecal coliforms among sampling sites and
between seasons at significant level p = 0.05 (f = 10.036, p = 0.001). A Tukey Post-hoc Test
confirmed the significant differences between Tandika and Changómbe (p = 0.001), Mtoni and
Changómbe (p = 0.003) Kurasini and Changómbe (p = 0.021), Keko and Changómbe (p = 0.001)
and Mbagalla Kuu and Changómbe (p = 0.005). Analysis of variance showed statistical significant
differences of total coliforms count among sites and between season at significant level p <
0.05(f=20.447, p < 0.000. The Tukey Post hoc Test discovered the statistical significant
differences of the total coliforms means between Tandika and Changómbe (p = 0.000), Mtoni and
Changómbe (p = 0.000) Kurasini and Changómbe (p = 0.001), Keko and Changómbe (p = 0.000)
and Mbagalla Kuu and Changómbe (p = 0.000) at significant level p < 0.05. Results revealed also
high concentration in turbidity, total dissolved solids, nitrate, iron, manganese, faecal coliforms
and total coliforms exceeded the Tanzanian Standards and World Health Organization (WHO)
permissible limits for drinking water. The rapid population increase in the area coupled with high
usage of on-site sanitary facilities (pit latrines and septic tanks) and poor waste management all
contribute to elevated levels of some of the groundwater quality parameters. The DRASTIC
method for mapping intrinsic aquifer vulnerability was applied to identify and delineate the
groundwater vulnerable area to pollution based on hydrogeological parameters of the study area.
Results from DRASTIC Model revealed that, about 49.39% of the total area in Temeke District
found to lie between moderate to extreme high vulnerable of groundwater pollution. These were
all areas characterized with high population density with high use of onsite sanitary facilities
mostly pit latrines, septic tanks, improper dumping of solid waste and sewage from industries,
commercial and residential areas. Also, hydrogeological parameters of the area like high porosity
and permeability (influencing hydraulic conductivity) of the existing alluvial sandy aquifer, high
recharge from surface pollution sources lowered the capacity of this aquifer to attenuate all the
contaminants. The study recommends the need to have regular monitoring of groundwater in
Temeke District and that intrinsic vulnerability maps should be incorporated into urban landuse
planning and decision making to minimise the risk of groundwater contamination from pollution
load.