Browsing by Author "Muzuka, Alfred"

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Distribution of organic carbon: possible causes and impacts in the Pangani River Basin ecosystem, Tanzania
(CSIRO PUBLISHING, 2018-06-08) Selemani, Juma; Zhang, Jing; Muzuka, Alfred; Wu, Ying; Njau, Karoli; Zhang, Guosen; Mzuza, Maureen; Maggid, Arafa; Zhang, Miao; Qi, Lijun
There is limited information on organic carbon in African rivers, especially from the eastern side. Here, we report distribution and impacts of total suspended matter (TSM), and dissolved and particulate organic carbon (DOC & POC) in the Pangani River Basin (PRB) ecosystem together with their fluxes to the Indian Ocean. δ13C was also used to trace sources of carbon in the basin. Results showed that the basin is supplied with carbon from allochthonous sources dominated by C3 plants, with higher levels of TSM and DOC in the wet season than in the dry season. Several factors, including altitude, temperature, rainfall, lithology and anthropogenic activities, have a significant influence on the seasonal and spatial distribution of organic carbon in the basin. High discharge in the wet season mobilised terrestrial organic carbon to elevate concentrations of DOC, POC and TSM. Mean concentrations of DOC, dissolved inorganic carbon (DIC), POC and TSM in PRB were in ranges comparable to that in other tropical rivers but their fluxes were lower than in most tropical rivers around the world. Diverting water from the river for irrigation and hydroelectric power production was one of the factors that reduced the flux of carbon. Observed hypoxic conditions in the reservoir indicates that the quality of water for human and aquatic ecosystem health is possibly threatened by a high level of organic carbon; furthermore, the trends of increasing population, deforestation, temperature and rainfall will likely increase the concentration of organic carbon in the future. Better management of waste, afforestation and reforestation are recommended to restore degraded natural forest, so as to reduce uptake of organic carbon from the terrestrial environment.
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.
Evidence of climate change impacts on water, food and energy resources around Kilimanjaro, Tanzania
(Springer Nature Switzerland AG., 2019-11-08) Said, Mateso; Komakech, Hans; Munishi, Linus; Muzuka, Alfred
This review presents research evidence of climate change and anthropogenic impacts on the slopes of Mt. Kilimanjaro and its implications on water, food and energy production (WFE nexus). While there exist divided scholarly opinions on the impacts of climate change on the Mt. Kilimanjaro glacier, consistent decreases in precipitation amounts are evident throughout the existing literature. The 2050 projections indicate increases in the precipitation amounts by approximately 16–18%. However, it is also stated that there will be a concomitant increase in water deficit of about 71%, 27% and 1% in agriculture, hydropower and livestock production respectively. Despite a large number of researches on impacts of climate and anthropogenic pressure on WFE along Mt. Kilimanjaro slopes, there are still limited long-term, good-quality and high-resolution altitudinal precipitation, temperature records and observation network. Moreover, there is limited information on groundwater recharge areas and their stability under changing environment. It is not clear how the interdependence and interaction between climate change, irrigation, vegetation and river discharges affect groundwater recharge process. Also, there is scarce information on future land use/cover changes. Very limited studies focused on fog water deposition for Mt. Kilimanjaro forest and East Africa, despite its relevance as the water tower of the mountain streams. The review further highlights how both climate and anthropogenic impacts may affect ecosystem services in the region. There is a need for developing adaptive strategies for responding to climate change and anthropogenic impacts on the slopes of Mt. Kilimanjaro now and into the future.
Hydrogeochemical characteristics and spatial distribution of groundwater quality in Arusha well fields, Northern Tanzania
(Springer, 2018-07-09) Chacha, Nyamboge; Njau, Karoli; Lugomela, George; Muzuka, Alfred
Arusha aquifers have been exploited intensively serving as the main source of domestic water supply in the city. But the quality of groundwater is not clearly documented for future planning and management. Hydrogeochemical assessment was carried out to establish groundwater quality and its spatial distribution with the aid of geostatistical techniques. Groundwater samples were collected and analyzed for major cations and anions using conventional methods of water analysis. Well lithology and geological map were considered for hydrogeological interpretation of the area. The results of piper diagram revealed Na–K–HCO3 water type with sodium and bicarbonate ions dominating in all samples. High fluoride concentrations and general groundwater chemistry are mainly controlled by aquifer lithology than anthropogenic activities. The levels of anthropogenic pollution indicators such as nitrate, chloride and sulfate in deep wells are generally low and most likely coming from natural sources. The geological sections indicate two potential aquifers (volcanic sediment and weathered/ fractured formation) both yield water containing significant concentration of fluoride. Fluoride concentrations were higher than WHO guidelines (1.5 mg/l) and Tanzanian standards (4.0 mg/l) by 82 and 36% of the analyzed groundwater samples, respectively. The southern part of the study area yields groundwater of better quality for human consumption than northern zones which is at high elevation on the foot of Mt. Meru. With exception of fluoride, the quality of groundwater in the study area is generally suitable for drinking purpose and other socioeconomic uses.
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
Seasonal water chemistry variability in the Pangani River basin, Tanzania
(Springer, 2017-09-17) Selemani, Juma; Zhang, Jing; Muzuka, Alfred; Njau, Karoli; Zhang, Guosen; Maggid, Arafa; Mzuza, Maureen; Jin, Jie; Pradhan, Sonali
The stable isotopes of δ18O, δ2H, and 87Sr/86Sr and dissolved major ions were used to assess spatial and seasonal water chemistry variability, chemical weathering, and hydrological cycle in the Pangani River Basin (PRB), Tanzania. Water in PRB was NaHCO3 type dominated by carbonate weathering with moderate total dissolved solids. Major ions varied greatly, increasing from upstream to downstream. In some stations, content of fluoride and sodium was higher than the recommended drinking water standards. Natural and anthropogenic factors contributed to the lowering rate of chemical weathering; the rate was lower than most of tropical rivers. The rate of weathering was higher in Precambrian than volcanic rocks. 87Sr/86Sr was lower than global average whereas concentration of strontium was higher than global average with mean annual flux of 0.13 × 106 mol year−1. Evaporation and altitude effects have caused enrichment of δ18O and δ2H in dry season and downstream of the river. Higher d-excess value than global average suggests that most of the stations were supplied by recycled moisture. Rainfall and groundwater were the major sources of surface flowing water in PRB; nevertheless, glacier from Mt. Kilimanjaro has insignificant contribution to the surface water.We recommend measures to be taken to reduce the level of fluoride and sodium before domestic use.