Browsing by Author "Mjemah, Ibrahimu C."

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Influence of meteorology on ambient air quality in Morogoro, Tanzania
(International Journal of Enviromental Science., 2011-03) Mkoma, Stelyus L.; Mjemah, Ibrahimu C.
The influence of meteorological parameters on air quality was investigated for a rural background site in Morogoro. Precipitation, temperature, relative humidity and wind speed were measured during wet and dry seasons of 2005 and 2006 period and their relationship with reported mass of particles of aerodynamic diameter smaller than 10 μm (PM10) for the site was assessed. The results show that higher PM10 mass concentrations (45μg/m 3 ) were obtained during the 2005 dry season and the lowest (13 μg/m 3 ) during the 2006 wet season. It is interpreted that reasons for the higher levels of the particulate matter mass in the dry season are due to temperature inversions and absence of rain washdown. The observed particulate matter levels are also affected by the variations in sources strengths and in meteorological conditions such as mixing height, precipitation, relative humidity, wind speed and direction as supported by air mass trajectories.
Investigating seawater intrusion due to groundwater pumping with schematic model simulations: The example of the Dar es Salaam coastal aquifer in Tanzania
(Elsevier, 2014) Camp, Marc Van; Mtoni, Yohana; Mjemah, Ibrahimu C.; Bakundukize, Charles; Walraevens, Kristine
Water supply requirements in Dar es Salaam city (Tanzania) are rising rapidly by population growth and groundwater is increasingly used to fullfill the needs. The groundwater is taken from the Dar es Salaam Quaternary coastal aquifer (DQCA), stretching inland from the coastline. As thousands of wells have been drilled in the coastal strip and pumping rates are uncontrolled, seawater intrusion is deteriorating the quality of fresh groundwater. To investigate the response of the fresh/salt water interface to coastal pumping, simulations with a schematic two-dimensional cross-sectional model have been done. Depending on the depth of the wells in the 150 m thick DQCA and their distance from the coastline, different pathways of seawater intrusion and shifts of the interface can be recognized. The local presence of a semi-pervious layer can have a significant impact on the fresh/salt water distribution. Although the modeled section is not related to a specific location along the coastline but rather represents an average aquifer buildup, the results of the simulations can be used to formulate recommendations when drilling new wells and for a better monitoring of the salinisation process along the coast. It proves that even simple schematic models can give meaningful contributions
Nitrate pollution of Neogene alluvium aquifer in Morogoro Municipality, Tanzania.
(International Formulae Group, 2011-02) Kibona, Irene; Mkoma, Stelyus L.; Mjemah, Ibrahimu C.
Concern over nitrate pollution of groundwater in integrated water quality management has been growing recently. The levels of nitrate in wells from septic tanks and urban agriculture with nitrogen fertilizers application may increase the potential groundwater pollution by nitrate. The purpose of this study was to determine the concentrations and spatial distribution of nitrate (NO 3 − ) in groundwater in Morogoro Municipality. Groundwater samples were collected from 20 wells during wet season period in March-April 2010 in 6 wards namely Kihonda, Mji Mpya, Mafisa, Saba Saba, Boma and Kilakala. The spectrophotometer was used to measure the NO 3 − concentration in water samples. The minimum and maximum nitrate levels were 1.4 and 32.5 mg/L respectively in the wards studied with an average of 7.76 mg/L. These results showed that all of the groundwater samples have NO 3 − concentration below the Tanzania Bureau of Standards upper limit value and World Health Organization guideline of 75 mg/l and 50 mg/l respectively. Also, the level of nitrate concentration tend to decrease with depth for most of the places due to the anoxic condition that is available at the higher depth which facilitates the utilization of nitrate by anaerobic microorganisms.
Predicting land use/cover changes and its association to agricultural production on the slopes of Mount Kilimanjaro, Tanzania
(Taylor & Francis Group, 2021) Said, Mateso; Hyandye, Canute; Komakech, Hans C.; Mjemah, Ibrahimu C.; Munishi, Linus K.
Increasing demand for food production results in Land use and land cover (LULC) changes, which afflicts the provision of ecosystem services in high mountain areas. This work used time-series LULC and selected spatial metrics to predict the LULC changes for Kikafu-Weruweru-Karanga (KWK) watershed (on the southern slopes of Mt. Kilimanjaro) for the next decade. LULC maps were generated by classifying time-series satellite images. We further predicted the implications for selected staple crop production over the next decade. The simulated LULC shows expansion in built-up (by 32.55%/27.04 km2) and agriculture (by 39.52%/52.0 km2) areas from 2018 to 2030. These results suggest that urbanization is likely the next biggest threat to water availability and food production. Grasslands and wetlands are expected to decrease by 57.24% and 39.29%, respectively. The forest area is likely to shrink by 6.37%, about 9.82 km2, and 1.26 km2 being converted to agriculture and built-up areas, respectively. However, expansion in agricultural land shows very little increase in staple food crop production records, suggesting that farm size plays a minor role in increasing crop production. Predicting the near future LULC around KWK is useful for evaluating the likelihood of achieving development and conservation targets that are set locally, nationally and internationally.
Saltwater intrusion in the quaternary aquifer of the Dar es Salaam region, Tanzania
(GEOLOGICA BELGICA, 2012) Mtoni, Yohana; Mjemah, Ibrahimu C.; Msindai, Kristoko; Van Camp, Marc; Walraevens, Kristine
A description of the occurrence of the salt water intrusion from seawater close to the coastline of Dar es Salaam Region is presented. The present status of intrusion in two pilot areas located between Mlalakuwa and Msimbazi Rivers (locality I) and Msimbazi and Kizinga Rivers (locality II) is evaluated. The causes, effects, remedial measures and future possibility of intrusion are discussed. An investigation on the hydrodynamics of the phenomenon and analysis of the formations as well as the interfacial transition zone is currently being performed. Water samples from Mikocheni, Oysterbay, Msasani, Masaki and City Centre areas show elevated chloride, sulphate and sodium concentrations. Using Stuyfzand (1986) water classification method, about 60 percent of the samples are classified as fresh-brackish to salt and 30 percent as extremely hard. Groundwater was classified into several categories by subtype, i.e., Sodium-Chloride, Sodium-Bicarbonate, Calcium-Bicarbonate, Magnesium-Bicarbonate, Sodium-Mix and Calcium-Mix. The growing human population in and around the investigated areas has had an adverse impact on the water in the shallow aquifer through, among other factors, indiscriminate abstraction of water without knowledge of the aquifer’s capacity.
The use of the DRASTIC-LU/LC model for assessing groundwater vulnerability to Nitrate contamination in Morogoro municipality, Tanzania.
(MDPI Earth, 2022-11-07) Mkumbo, Neema J.; Mussa, Kassim R.; Mariki, Eliapenda E.; Mjemah, Ibrahimu C.
Groundwater is a useful source of water for various uses in different places. The major challenge in the use of this resource is how to manage and protect it from contamination. The current study was conducted in Morogoro Municipality to identify vulnerable groundwater areas by using DRASTIC-LU/LC model. The study applied eight input parameters, i.e., depth to water table, net recharge, aquifer media, soil media, topography, impact of vadose zone, hydraulic conductivity and land use/land cover patterns, which were overlaid in GIS to generate groundwater vulnerable map. The model used rating (R = 1–10) and weighting (W = 1–5) techniques to assess the effect of each parameter on groundwater contamination. The DRASTIC-LU/LC Vulnerability Index map was classified into low- (area = 29.2 km 2 ), moderate- (area = 120.4 km 2 ) and high-vulnerability zones (area = 124.4 km 2 ). Nitrate analysis was conducted using the cadmium reduction method (DR 890) to assess the validity of the model and it was observed that 55%, 15% and 50% of the samples with unacceptable (>50 mg/L), high (29–50 mg/L) and moderate (14–28 mg/L) nitrate concentrations, respectively, fall into the high-vulnerability zone. Furthermore, 45%, 70% and 50% of the samples with unacceptable, high and moderate nitrate concentrations, respectively, fall into the moderate- vulnerability zone. In the low-vulnerability zone, only 15% of samples were found with a high nitrate concentration.