Browsing by Author "Lwimbo, Zuberi"

Now showing 1 - 3 of 3

Estimating groundwater recharge on the southern slope of Mount Kilimanjaro, Tanzania
(Springer Nature Switzerland AG., 2019-12-03) Lwimbo, Zuberi; Komakech, Hans; Muzuka, Alfred
This paper used three methods namely: water-table fluctuation (WTF), soil moisture balance (SMB), and chloride mass balance (CMB) to estimate groundwater recharge in a degraded Kahe catchment located on the southern slope of Mt. Kilimanjaro, Tanzania. Three methods yielded different groundwater recharge rates. Results of the WTF method showed that recharge in the catchment was about 248.4 million m3/year, whereas those of CMB and SMB methods were 156.0 and 132.1 million m3/year, respectively. The estimated recharge rates ranged between 132.1 and 248.4 million m3/year with an average of 191.34 ± 27.80 million m3/year. Differences in the estimated rates can be attributed to the scales of measurements, assumptions in each method, and the quality of the data used. Satellite images taken in between 2000 and 2017 were used to estimate the land-use changes and their impacts on groundwater recharge in the study catchment. Analyzed satellite images showed that over the 17-year period, natural forests and bushes and shrubs decreased by 3.6 and 4.1%, while agricultural land and built-up area increased by 12.8 and 0.8%, respectively. Using SMB method, we found that these land-use changes have contributed to a decrease in groundwater recharge of about 42% between 2000 and 2017 (i.e., from 227.8 to 132.1 million m3/year). The findings from this study are useful for assessing the potential impacts of land-use change on water resources in the catchment.
Groundwater recharge estimation and quality on the southern slopes of mount Kilimanjaro, Tanzania
(NM-AIST, 2021-07) Lwimbo, Zuberi
This study was undertaken to estimate groundwater recharge rates using three methods (water table fluctuation (WTF), chloride mass balance (CMB) and soil moisture balance (SMB), as well as assessing the impact use of the pesticides and fertilizers on groundwater quality in a Kahe catchment located on the Southern slope of Mt. Kilimanjaro, Tanzania. The estimated recharge rates of the WTF method yielded a higher value of about 248.4 million m 3 /year, whereas that of CMB and SMB methods was 156.0 and 132.1 million m 3 /year, respectively. The concentration of pesticide residues was below the detection limit, while, NO 3 - levels of sampled groundwater were averaged about 18.40 ± 4 and 7.6 ± 1.7 mg/l in the wet and dry season, respectively. An elevated level of nitrate (NO 3 - ), sulfate (SO 4 2- ), phosphate (PO 4 3- ), and ammonium (NH 4 + ) was found nearby the large-scale sugarcane farms. Generally, the groundwater chemistry was dominated by magnesium-sodium-bicarbonate (Mg-Na-HCO 3 ) water type. The cations levels were in the trend of Mg 2+ > Na + > Ca 2+ > K + , whereas anions were HCO 3 - > Cl - > SO 4 2- for both seasons. The heavy metals concentration of Pb, Cd, Fe, Mn, Zn and Cu for both seasons were averaged approximately 0.08 ± 0.03, 0.11 ± 0.03, 0.16 ± 0.02, 0.11 ± 0.01, 0.46 ± 0.05 and 0.55 ± 0.02 mg/l, respectively. Whereas the concentration was higher in shallow groundwater than deep boreholes and most of them were located around the western-eastern zone of the Kahe catchment. The findings from this study provided reliable data information for future monitoring programs of groundwater resources management in Kahe catchment, Tanzania.
Impacts of Emerging Agricultural Practices on Groundwater Quality in Kahe Catchment, Tanzania
(MDPI, 2019) Lwimbo, Zuberi; Komakech, Hans; Muzuka, Alfred
This paper assesses the impacts of farmers’ intensive use of agrochemicals (fertilizers and pesticides) on groundwater quality in the Kahe catchment. Samples were collected during the wet and dry seasons of the year 2018 and analyzed for the presence of agrochemicals in the water. Groundwater chemistry was dominated by magnesium-sodium-bicarbonate (Mg-Na-HCO3−). The cations levels were in the trend of Mg2+ >Na+ > Ca2+ > K+, whereas anions were HCO3− > Cl− > SO42− for both seasons. The NO3− had an average value of about 18.40 ± 4.04 and 7.6 ± 1.7 mg/L in the wet and dry season, respectively. Elevated levels of nitrate, sulfate, phosphate, and ammonium were found in water samples collected near the large-scale sugarcane plantation in the catchment. For both seasons, Pb, Cd, Fe, Mn, Zn and Cu concentrations averaged approximately 0.08 ± 0.03, 0.11 ± 0.03, 0.16 ± 0.02, 0.11 ± 0.01, 0.46 ± 0.05, and 0.55 ± 0.02 mg/L, respectively. On the other hand, the concentrations were higher in shallow wells than in the deep boreholes. Pesticides’ residues were below the detection limit in all sampled groundwater. The findings from this study provide important information for intervention in groundwater quality management in Kahe Catchment, Tanzania