Land Use/Cover Change and their Impacts on Streamflow in Kikuletwa Catchment of Pangani River Basin, Tanzania

Streamflow perturbation is highly prevalent in Kikuletwa catchment. However, little is known concerning land use/cover change (LULCC) with regard to streamflow perturbation in the catchment. This study aims to detect the historical and predict future LULCC and assess their impacts on streamflow amounts using the Soil and Water Assessment Tool (SWAT) model. Supervised classification of Landsat imagery data for 1985, 2000 and 2015 years was done in ERDAS 14 Imagine software. Future prediction of LULCC was done using Module for Land Use Change Evaluation (MOLUSCE) tool, a QGIS plug-in. An accuracy ranging from 79% to 82% was obtained for all steps. The results revealed that, from 1985 to 2000; 1985 to 2015; 1985 to 2030 and 1985 to 2050 the percentage of area change in cultivated land is +21.1%; +29.2%; +38.2% and +42.7%, respectively; forest is - 2.3%, -3.1%, -3.8% and -5.8%, respectively; and shrubland is -6.3%, -10%, -15.7% and - 16%, respectively. The performance of SWAT model during calibration were 0.74, 0.75, 0.51 and -0.5% for NSE, R2, RSR and PBIAS, respectively. The impacts of LULCC indicated that, between 1985 to 2000; 1985 to 2015; 1985 to 2030 and 1985 to 2050, the percentage increase in average simulated annual flow is 4.7%, 6.8%, 12.6% and 19.3%, respectively. Surface runoff increased from 25.2 mm (baseline) to 34.5 mm (36.9%); 36.2 mm (42.4%); 41.4 mm (64.3%) and 47.6 mm (88.9%), respectively. Base flow decreased marginally from 82.2 mm (baseline) to 79 mm (-3.8%); 77.8 mm (5.4%); 75.4 mm (-8.3%) and 73.9 mm (- 10.1%), respectively. Thus, apart from climate effects, streamflow perturbation in the catchment is also related to disturbances of catchment influences such as LULCC as revealed in this study. The study is useful for land planners and water resources managers and policy makers in managing resources sustainably.&nbsp

Spatial and Temporal Variation of Rainfall and Streamflow in the Kikuletwa Catchment of Upper Pangani Basin, Tanzania

Streamflow and rainfall records from 1980 to 2015 as a (common period for the analyzed stations) were used to analyze the variations of rainfall and streamflow in the Kikuletwa catchment. Also, the analysis of the longest time series available at each station up to 2015 (referred to as the whole series in this study) was conducted to relate past rainfall and streamflow changes, at the tributaries of Kikuletwa River located above the Rundugai natural springs as recommended from previous studies. Various methods such as simple statistics of the mean, standard deviation, coefficient of variance, and graphs were used to analyze intra-annual variations. Multi-year variability was analyzed by trends and change point tests using MannKendall and Pettitt tests respectively. The results of the study revealed the spatial variation of rainfall which was related to elevation differences. The streamflow amounts were found to vary from upstream to downstream. The whole time series analysis of annual rainfall and streamflow amounts revealed a decrease in rainfall and streamflow amounts for almost all stations though a significant decrease was only observed at two stations located on the upstream (for rainfall) and two stations located above the Rundugai natural springs (for streamflow). During 1980 – 2015, trends analysis indicated significant decreasing trends only in annual rainfall amounts at the two stations located on the upstream of the catchment with Z values of -3.20 and -2.68. In contrast, average annual flow trends analysis indicated significant decreasing trends at four stations out of five with Z values of -2.52, -2.28, -1.99 and -3.4 and, at one station insignificant decreasing trend was observed. The findings revealed the existence of other catchment influences to the streamflow changes other than rainfall during 1980-2015. The study provides very useful information that decides the necessity for separating the climate and human influences to the streamflow changes to find the most influencing factor

An Economic Comparison between Alternative Rice Farming Systems in Tanzania Using a Monte Carlo Simulation Approach

Tanzania is the second-largest producer of rice (Oryza sativa) in Eastern, Central, and Southern Africa after Madagascar. Unfortunately, the sector has been performing poorly due to many constraints, including poor agricultural practices and climate variability. In addressing the challenge, the government is making substantial investments to speed the agriculture transformation into a more modernized, commercial, and highly productive and profitable sector. Our objective was to apply a Monte Carlo simulation approach to assess the economic feasibility of alternative rice farming systems operating in Tanzania while considering risk analysis for decision-makers with different risk preferences to make better management decisions. The rice farming systems in this study comprise rice farms using traditional practices and those using some or all of the recommended system of rice intensification (SRI) practices. The overall results show 2% and zero probability of net cash income (NCI) being negative for partial and full SRI adopters, respectively. Meanwhile, farmers using local and improved seeds have 66% and 60% probability of NCI being negative, correspondingly. Rice farms which applied fertilizers in addition to improved seeds have a 21% probability of negative returns. Additionally, net income for rice farms using local seeds was slightly worthwhile when the transaction made during the harvesting period compared to farms applied improved varieties due to a relatively high price for local seeds. These results help to inform policymakers and agencies promoting food security and eradication of poverty on the benefits of encouraging improved rice farming practices in the country. Despite climate variability, in Tanzania, it is still possible for rice farmers to increase food production and income through the application of improved technologies, particularly SRI management practices, which have shown a promising future.Peer Reviewe

Seasonal profitability of soil and water conservation techniques in semi-arid agro-ecological zones of Makanya catchment, Tanzania

This research article published by Elsevier B.V., 2021Soil and water conservation techniques are known to be profitable and widely promoted in sub-Saharan Africa. However, how their profitability vary across cropping seasons has not been fully explored. Thus, farmers are often faced with the dilemma of which agricultural technique(s) and/or combination(s) thereof to implement in which cropping seasons, and for which crops to maximize profits. In this paper, we investigated the profitability of two soil and water conservation techniques (terraces and borders) and compared them against the conventional flat cultivation in Makanya catchment Tanzania. Farmers in the area grow maize, beans, lablab and cowpeas over three cropping seasons (locally called masika, vuli and chamazi/kipupwe). Based on field survey of 382 farmers in 2019, it was found that aggregate yields were generally higher on fields with intercrop than those with monocrop with more than 0.5 ton/ha of total grain yields. Borders were generally more profitable (399 USD/ha) than terraces and flat cultivation during all three cropping seasons while flat cultivation was more lucrative during the masika than vuli season. Terraces was only lucrative for rainfed beans with Benefit Cost Ratio of 1.5 (208.7 USD/ha) and 1.2 (90.5 USD/ha) in masika and vuli respectively. Beans grown on borders during chamazi season had the highest profitability with Benefit Cost Ratio of 1.9 (399 USD/ha) compared to terraces and flat cultivation in all three cropping seasons. Whereas it was more profitable to grow maize, beans and lablab on borders, farmers could still realize appreciable profits by growing these crops as purely rainfed on flat cultivation especially during the masika season. It was concluded that in semi-arid zones, soil and water conservation techniques used in combination with other auxiliary practices such as irrigation, intercropping with legumes, mulching and manure application could greatly enhance profitability, but that depends on cropping season and market factors

Optimizing System of Rice Intensification Parameters Using Aquacrop Model for Increasing Water Productivity and Water Use Efficiency on Rice Production in Tanzania

Producing more rice while using less water is among the calls in water scarce regions so as to feed the growing population and cope with the changing climate. Among the suitable techniques towards this achievement is the use of system of rice intensification (SRI), which has been reported as an approach that uses less water and has high water productivity and water use efficiency. Despite its promising results, the use of SRI practice in Tanzania is limited due to less knowledge with regard to transplanting age, plant spacing, minimum soil moisture to be allowed for irrigation, and alternate wetting and drying interval for various geographical locations. The AquaCrop crop water productivity model, which is capable of simulating crop water requirements and yield for a given parameter set, was used to identify suitable SRI parameters for Mkindo area in Morogoro Region, Tanzania. Using no stress condition on soil fertility, plant spacings ranging from 5 cm to 50 cm were evaluated. Results suggest that the yield and biomass produced per ha increase with decreasing spacing from 50 cm to 20 cm. Preliminary field results suggest that the optimum spacing is round 25 cm. However, the model structure does not take into consideration number of tillers produced. As such, the study calls for incorporation of the tillering processes into AquaCrop model

Challenges of optimal implementation of formal water rights systems for irrigation in the Great Ruaha River Catchment in Tanzania

In many countries around the world, increasing attention is being directed to the need to improve water rights systems. This paper is based on a recent study undertaken to investigate challenges facing optimal implementation of formal water rights systems for irrigation purposes in the Great Ruaha River Catchment in Tanzania. The study integrated social survey, hydrologic, water abstraction and water use data, and Geographical Information System techniques. The results showed that all the canals studied, except one, abstracted water throughout the year, provided there was water in the rivers irrespective of the conditions spelt out in their formal water rights. The formal water rights were also found to be problematic as the quantities to be abstracted were much higher compared to the actual water requirements and the actual river flows. This resulted in over-abstraction of water and increased water shortages for downstream users. The study concludes that although formal water rights are meant to control and regulate the use of water, they are also subject to abuse if not managed and monitored closely. The basin authorities in Tanzania therefore need to be equipped adequately and collaborate more closely with local water users in order to attain high levels of supervision and monitoring essential for optimal implementation of formal water rights systems.

Enhancing smallholders' capacity to cope with climate change : participatory action research and integrated soil fertility management

This document is one of a series of factsheets that aim to share practical experience of how Participatory Action Research (PAR) can be used to trigger technological, social and institutional innovation in Africa to enhance smallholders’ adaptive capacity in the face of climate change and increased climate variability. The uniqueness of this approach is the integration of the “what” (the technologies) with the “how” (PAR) and the “why” (increased capacity of smallholders to cope with climate change)

Pangani River Basin over time and space: On the interface of local and basin level responses

This research article published by Elsevier, 2011As the pressure on the water resources mounts within a river basin, institutional innovation may occur not as a result of a planned sequence of adjustments, but arising out of the interplay of several factors. By focusing on the basin trajectory this paper illustrates the importance of understanding how local-level institutional arrangements interface with national-level policies and basin-wide institutions. We expand Molle's typology of basin actors responses by explicitly introducing a meso-layer which depicts the interface where State-level and local-level initiatives and responses are played out; and focus on how this interaction finds expression in the creation and modification of hydraulic property rights. We subsequently apply this perspective to the case of Pangani River Basin in Tanzania. The Pangani River Basin development trajectory did not follow a linear path and sequence of responses. Attempts by the state government to establish ‘order’ in the basin by issuing water rights, levying water fees and designing a new basin institutional set-up have so far proven problematic, and instead generated ‘noise’ at the interface. So far water resources development in the Pangani has primarily focused on blue water, and the paper shows how investments in infrastructure to control blue water have shaped the relationship between water users, and between water user groups and the State. It remains unknown, however, what the implications will be of widespread investments in improved green water use throughout the basin – not only hydrologically for the availability of blue water, but also socially for the livelihoods of the basin population, and for the evolving relationships between green and blue water users, and between them and the State. The paper concludes with a question: will green water development engender a similar double-edged material-symbolic dynamic as blue water development has. The findings of this paper demonstrate that the expanded typology of basin actors’ responses helps to better understand the present situation. Such an improved understanding is useful in analysing current and proposed interventions