Enhancing Protection of Dar es Salaam Quaternary Aquifer: Groundwater Recharge Assessment

Mtoni, Yohana Enock; Mjemah, Ibrahimu Chikira; Camp, Marc Van; Walraevens, Kristine

doi:10.1007/978-3-642-19902-8_35

Cited by 8 publications

(8 citation statements)

References 3 publications

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“…It can be concluded that there is possible common source of nitrogen compounds (NO3-N, NH3-N, NH4 + and NH3) during wet season as there is moderate to strong correlations among them (Zhou et al,2019). The possible source of these nutrients in surveyed areas are decomposition of organic matter, percolation of organic wastes and discharge of wastewater from onsite sanitation systems, urban agriculture, urban runoff and general poor waste management practices which ultimately percolates to the groundwater (Mjemah et al, 2011, Mtoni et al, 2011Mtoni, 2013;Sappa et al, 2015 andElisante et al, 2017). Pearson correlation showed moderate positive correlations between nitrate nitrogen concentrations measured during dry and wet seasons with r = 0.524.…”

Section: Correlation Among Nutrient Analyzed During Wet Seasonsmentioning

confidence: 99%

Occurrence of Elevated Nitrogenous and Phosphorus in Groundwater Sources Used in Unplanned Settlements, Dar Es Salaam - Tanzania

2022

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Groundwater in unplanned settlements is stressed by multiple pollution sources threatening health of consumers. Elevated nitrogen and phosphorus affect the quality of groundwater as they leach through the soil to groundwater. This study aimed at establishing variations of nitrogenous and phosphorus compounds in 75 boreholes used in 8 unplanned settlements in Dar es Salaam, Tanzania. Laboratory analysis using Spectrophotometer DR/4000 was conducted at Ardhi University. Principal Component Analysis was conducted by using Paleontological Statistics (PAST) software, version 3.08 and statistical significance set at p < 0.05. Results indicated that about 84% and 73.3% of sampled boreholes during wet and dry seasons, respectively had nitrate nitrogen greater than WHO recommendations for drinking water quality standards. Concentration of NO2-N showed that 12% and 14.7% of sampled boreholes during wet and dry seasons, respectively were greater than 0.9 mg/L TZS (574:2016) recommended guidelines. Phosphate concentration was greater than 2.2 mg/L TZS (574:2016) recommended guidelines in 49.3% and 12% of sampled boreholes during both wet and dry seasons, respectively. These results indicated that consuming such polluted water may be unsafe to infants and older people and therefore alternative drinking water source is recommended.

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Section: Correlation Among Nutrient Analyzed During Wet Seasonsmentioning

confidence: 99%

Occurrence of Elevated Nitrogenous and Phosphorus in Groundwater Sources Used in Unplanned Settlements, Dar Es Salaam - Tanzania

2022

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“…The study site is located in Dar es Salaam city, Tanzania (Figure 1). The area is densely populated (population density of 14,250/km 2 ), with an average temperature of 22°C and an average rainfall of 117 and 253 mm for short and long rains respectively (Mtoni et al 2012). The site was surveyed to identify existing domestic wells and wastewater systems (pit latrines) and collect information such as construction method, size, depth, age of pit latrine, and sewage discharge schedule.…”

Section: Study Area and Data Collectionmentioning

confidence: 99%

“…Additionally, we obtained official well records from the Drilling and Dam Construction Agency (DDCA) that included soil profiles and well logs. Groundwater recharge rates and rainfall patterns were obtained from the literature (Mjemah et al 2009;Mtoni et al 2011). Hydraulic head and groundwater flow direction data were calculated using the well log information provided and digital elevation model (DEM) data.…”

Section: Study Area and Data Collectionmentioning

confidence: 99%

“…Two main aquifers underlie the city: an upper unconfined sand aquifer and a lower semi-confined sand aquifer that are separated by a clay aquitard (Mtoni et al 2012). The majority of the city including the study area overlays a clay aquitard and a sand aquifer, which are the main sources of groundwater (Mjemah et al 2009).…”

Section: Hydrogeologymentioning

confidence: 99%

“…Vertical and horizontal hydraulic conductivity anisotropy values were estimated to be 4 and 1 respectively (Mualem 1984;Chapuis & Gill 1989). The starting head was set at 60 m. The average annual recharge value for Dar es Salaam is 184 mm/year (0.0005 m/day) (Mtoni et al 2011). Hydrogeological properties used were soil types, hydraulic conductivity, porosity, and observed hydraulic heads.…”

Section: Hydrogeologymentioning

confidence: 99%

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Improving safe sanitation practices using groundwater transport modelling and water quality monitoring data

Ngasala

Phanikumar

Masten

2021

Water Science and Technology

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In many developing countries, poorly constructed pit latrines are the primary source of groundwater contamination. Approaches are needed to identify site-specific separation distances between domestic wells and pit latrines. In this study, tracer transport simulations are combined with water quality monitoring data to identify separation distances in peri-urban Dar es Salaam. Bivariate correlation and linear regression models were used to find the relationships between (1) simulated tracer and distances from the wells to the nearest pit latrines (2) simulated tracer and observed contaminants (nitrate, E. coli, and total dissolved solids). The results showed a strong correlation between tracer with nitrate and E. coli, with Pearson coefficient (r) values of 0.80 and 0.79, but a weak correlation with TDS (r=0.23). A strong correlation between tracer and distance for shallow and deep wells (r=−0.96, −0.76) was found. Based on the soil type and aquifer properties in the area, wells must be placed at least 34 m from a pit latrine to minimize contamination. With recent advances in sensor technologies and the availability of low-cost sensors, linking simulated tracer with observed contaminant levels may provide an alternative first approach to quickly assess human health risks associated with groundwater contamination.

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Saltwater intrusion and nitrate pollution in the coastal aquifer of Dar es Salaam, Tanzania

et al. 2013

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Dar es Salaam Quaternary coastal aquifer is a major source of water supply in Dar es Salaam City used for domestic, agricultural, and industrial uses. However, groundwater overdraft and contamination are the major problems affecting the aquifer system. This study aims to define the principal hydrogeochemical processes controlling groundwater quality in the coastal strip of Dar es Salaam and to investigate whether the threats of seawater intrusion and pollution are influencing groundwater quality. Major cations and anions analysed in 134 groundwater samples reveal that groundwater is mainly affected by four factors: dissolution of calcite and dolomite, weathering of silicate minerals, seawater intrusion due to aquifer overexploitation, and nitrate pollution mainly caused by the use of pit latrines and septic tanks. High enrichment of Na+ and Cl- near the coast gives an indication of seawater intrusion into the aquifer as also supported from the Na-Cl signature on the Piper diagram. The boreholes close to the coast have much higher Na/Cl molar ratios than the boreholes located further inland. The dissolution of calcite and dolomite in recharge areas results in Ca-HCO3 and Ca-Mg-HCO3 groundwater types. Further along flow paths, Ca2+ and Na+ ion exchange causes groundwater evolution to Na-HCO3 type. From the PHREEQC simulation model, it appears that groundwater is undersaturated to slightly oversaturated with respect to the calcite and dolomite minerals. The results of this study provide important information required for the protection of the aquifer system

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Enhancing Protection of Dar es Salaam Quaternary Aquifer: Groundwater Recharge Assessment

Cited by 8 publications

References 3 publications

Occurrence of Elevated Nitrogenous and Phosphorus in Groundwater Sources Used in Unplanned Settlements, Dar Es Salaam - Tanzania

Occurrence of Elevated Nitrogenous and Phosphorus in Groundwater Sources Used in Unplanned Settlements, Dar Es Salaam - Tanzania

Improving safe sanitation practices using groundwater transport modelling and water quality monitoring data

Saltwater intrusion and nitrate pollution in the coastal aquifer of Dar es Salaam, Tanzania

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