Browsing by Author "Kashaigili, J.J."

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Effects of land use/ cover changes on flow regime of the Usangu wetland and the Great Ruaha River in Tanzania
(SUA, 2010) Kashaigili, J.J.
The Usangu wetland (Ihefu) is a wetland of great importance for its biodiversity and acts as regulator for downstream flows for the Great Ruaha River through the Ruaha National Park. While recognizing the importance of this wetland, little is known about the effects of land use and cover changes on the wetland itself and the flow regime of the Great Ruaha River in the downstream. Recognizing that, a study was conducted using remote sensing and GIS techniques to inventory land use/cover changes in the watershed over the years. Hydrological data were analyzed to reveal the alterations and trends at three periods (pre-1974, 1974-1975 and post 1985) from 1958 to 2004. It was revealed that there was a steady increase in cultivated area, from 121.2 km2 to 874.3 km2 between 1973 and 2000 while the woodland area decreased significantly over years. The minimum dry season area of the wetland declined significantly, with more changes occurring between 1984 and 2000 at 67% reduction. The river was found to be sensitive to land use/ cover changes and highly variable on an intra annual (seasonal) and inter-annual (year to year) basis. There was a slight shift in the peaking for the post-1985 period with high flows attained earlier in February instead of April. The Q50 flow progressively declined from 19.23m3s-1 in the pre-1974 to 16.51 m3s-1 and 9.04 m3s-1 for 1974-1975 and post-1985 period respectively. The Q95 (low flow) declined from 2.84 m3s-1 to 0.11 m3s-1 and 0.0 m3s-1 for pre-1974, 1974-1975 and post-1985 period respectively. The study concludes that the modification of the land use and cover has resulted into changes in time distribution of runoff within the catchment. The study highlights the effects of land use /cover changes on ecosystems and water resources for an informed decision on proper catchment planning and management.
Evaluation of water productivity for maize under drip irrigation
(2010) Silungwe, F.R.; Mahoo, H.F.; Kashaigili, J.J.
A drip system operating under deficit irrigation was used to evaluate water productivity (WP) of TMV-1 maize variety in Morogoro, Tanzania. A block was divided into four sub-blocks; and each randomly assigned with deficit treatment (T1, T2, T3 and T4 as 60%, 40%, 20% and 0% irrigation water deficits, respectively). Three replications were used producing randomized block design. Each sub block biomass, grain yield and harvest index were determined. Biomass development and grain yield were significantly (0.1
Failure of the Mtera-Kidatu reservoir system in the Early 1990s
(SUA, 2003) Yawson, D.K.; Kachroo, R.K.; Kashaigili, J.J.
Four possible causes for the failure of the Mtera-Kidatu Reservoir System within the Rufiji River Basin in Tanzania in the early 1990s were investigated. These were sudden decrease in inflows, sudden increase in losses, sudden increase in hydropower generation, and unnecessary spills; or a combination of these, and it was found out that unaccounted for and unnecessary spillage was the main cause. This paper proposes that consideration of the flows that are generated within the intervening catchment (i.e. catchment between Mtera and Kidatu) and the operational policy that maximum power is produced at Kidatu most of the time must be the core in the management of the reservoir system. If this was the case in the past then the Mtera Reservoir should not have gone dry in the 1991-1994 period. The validity of this assertion was tested with the TALSIM 2.0 model and an efficiency of 95% was achieved, indicating a very good correlation with the investigative techniques employed in this study.
Hydrological modelling to assist water management in the Usangu wetlands, Tanzania
(JRBM, 2008) McCartney, M.P.; Kashaigili, J.J.; Lankford, B.A.; Mahoo, H. F.
The Usangu wetlands, containing the Ihefu swamp, are one of the most valuable inland wetlands in Tanzania. Over the last decade, outflow from the swamp has ceased for extended periods in the dry season. This has had severe consequences for downstream ecosystems, including the Ruaha National Park. Results from a simple hydrological model developed for the Ihefu swamp indicate that, between 1958 and 2004, dry season inflows declined by approximately 60% and the dry season area of the swamp decreased by approximately 40% (i.e. from 160 km2 to 93 km2 ). The model also shows that to maintain minimum downstream environmental flows requires a minimum inflow of 7 m3 s−1 , which is approximately 65% greater than occurs currently. There is significant potential for improving water use efficiency. However, given the socio-economic importance of current levels of water withdrawal, this inflow may be difficult to achieve. Consequently consideration needs to be given to other options, including upstream storage and water management within the wetland itself. This paper highlights that a simple model supplying relatively low-confidence, but indicative, results can provide a useful basis for contemplating water management options.
Local knowledge on the influence of land use/cover changes and conservation threats on avian community in the Kilombero wetlands, Tanzania
(Scientific Research Publishing Inc., 2014) Ntongani, W.A.; Munishi, P.K.T.; More, S.R.; Kashaigili, J.J.
Local knowledge of the history and ecology of wetland ecosystems is very useful in wetland re- sources management, especially when other historical ecological information is not available and can be integrated with scientific knowledge to introduce better management of resources. The aims of this paper were to assess existing local knowledge on land use/cover changes in the Ki- lombero wetlands, thereafter investigate local knowledge on its effect on avian population in the wetland and identify factors influencing local knowledge on such changes in the study area. Ran- dom sampling was used to obtain representative sample population for this study. Structured questionnaire and focus group discussions were used to extract information from local people in six villages. Study results from multi-response analysis showed that natural forests had been con- verted into cropland and bushed grassland, grassland to crop land, grassland to grazed land, for- est to settlement and grassland to settlement. Land use change was singled out as primary cause of decrease in avian community in the wetland. Threats to the conservation of avian species were identified as livestock grazing, drought, use of poison, traps and bush meat hunting for food. Age and education level were seen as determinants of household’s knowledge on the ecological changes. This pool of existing knowledge is important among wetland users and stakeholders in order to generate conservation strategies of the wetland ecosystem.
Modelling the Mtera-Kidatu reservoir system to improve integrated water resources management
(Hydro Africa, 2003) Yawsona, D.K.; Kashaigili, J.J.; Kachroo, R.K.; Mtalo, F.W.
Failure of the Mtera-Kidatu Reservoir System within the Rufiji River Basin in Tanzania in the early 1990s is investigated by considering four possible causes (i.e. sudden decrease in inflows, sudden increase in losses, sudden increase in hydropower generation or unnecessary spills; or a combination of these) and it was found out that unaccounted spillage seems to be the main cause. Consequently, the system’s simulation model has been proposed in this paper that takes into consideration the flows that are generated in the intervening catchment (i.e. catchment between Mtera and Kidatu) with the operational policy that maximum power is produced at Kidatu most of the time because Kidatu has higher head for greater power generation than at Mtera. The paper shows that if this proposed model had been in place then the Mtera Reservoir should not have gone dry in the 1991-1994 period. The validity of the proposed model is tested with the TALSIM 2.0 Model and the regression analysis of the water levels at Mtera Reservoir produced by the models had an efficiency of 95%, indicating a very good correlation. The proposed model operates the reservoir system in an integrated manner by considering the flows into the Mtera Reservoir as well as accounting for the flows generated by the intervening catchment.