Browsing by Author "Nakawuka, Prossie"

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    Assessing soil erosion risk in a peri‑urban catchment of the Lake Victoria basin
    (Modeling Earth Systems and Environment, 2022) Ssewankambo, Gyaviira; Kabenge, Isa; Nakawuka, Prossie; Wanyama, Joshua; Zziwa, Ahamada; Bamutaze, Yazidhi; Gwapedza, David; Tally Palmer, Carolyn; Tanner, Jane; Mantel, Sukhmani; Tessema, Bezaye
    Soil erosion and sedimentation contribute to deteriorating water quality, adverse alterations in basin hydrology and overall ecosystem biogeochemistry. Thus, understanding soil erosion patterns in catchments is critical for conservation planning. This study was conducted in a peri-urban Inner Murchison Bay (IMB) catchment on the northern shores of Lake Victoria since most soil erosion studies in Sub-Saharan Africa have been focused on rural landscapes. The study sought to identify sediment sources by mapping erosion hotspots using the revised universal soil loss equation (RUSLE) model in appendage with field walks. RUSLE model was built in ArcGIS 10.5 software with factors including: rainfall erosivity, soil erodibility, slope length and steepness, land cover and support practices. The model was run, producing an erosion risk map and field assessments conducted to ground-truth findings and identify other hotspots. The percentage areas for RUSLE modelled erosion rates were: 66.8% for 0–2 t ha− 1 year− 1; 10.8% for 2–5 t ha− 1 year− 1; 10.1% for 5–10 t ha− 1 year− 1; 9% for 10–50 t ha− 1 year− 1 and 3.3% for 50–100 t ha− 1 year− 1. Average erosion risk was 7 t ha− 1 year− 1 and the total watershed erosion risk was 197,400 t year− 1, with croplands and steep areas (slope factor > 20) as the major hotspots (> 5 t ha− 1 year− 1). Field walks revealed exposed soils, marrum (gravel) roads and unlined drainage channels as other sediment sources. This study provided the first assessment of erosion risk in this peri-urban catchment, to serve as a basis for identifying mitigation priorities. It is recommended that tailored soil and water conservation measures be integrated into physical planning, focusing on identified non-conventional hotspots to ameliorate sediment pollution in Lake Victoria.
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    Assessing the Effect of Irrigation Water Management Strategies on Napier Productivity—A Review
    (Agricultural Sciences, 2021) Ntege, Ivan; Kiggundu, Nicholas; Wanyama, Joshua; Nakawuka, Prossie
    Napier, a fast growing and perennial grass has a dry matter (DM) yield potential of 78 tons/ha/yr. However, under water availability constraints Napier’s yield potential reduces to 62 tons/ha/yr. In an effort to attain Napier’s yield potential, irrigation management strategies have been integrated into its production to provide the highest productivity. This review assesses the effect of irrigation water management strategies on Napier productivity and also looks at future perspectives. Application of these strategies i.e. , precision irrigation, deficit irrigation, and application of biophysical models, can increase Napier’s yield potential to 112 tons/ha/yr. Review findings revealed that there is a need to close the knowledge gap on response of Napier productivity to different irrigation water management strategies. The future perspective explores the potential of the FAO AquaCrop model in provision of pre-season decision-making on irrigation strategies due to its relatively low cost and simplifications required in parameterization.
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    Assessment of irrigation water distribution using remotely sensed indicators: A case study of Doho Rice Irrigation Scheme, Uganda
    (Smart Agricultural Technology, 2023) Wamala, Fawaz; Gidudu, Anthony; Wanyama, Joshua; Nakawuka, Prossie; Bwambale, Erion; Chukalla, Abebe D.
    The rising competition for scarce land and water resources and the need to satisfy the global food demand from an ever-growing population necessitates novel methods to monitor irrigation scheme performance for improved water use efficiency. The traditional methods employed in sub-Saharan Africa to assess irrigation performance are point-based, expensive, and time-consuming, making monitoring and evaluation of these capital-intensive projects difficult. This study aimed at employing satellite data with high spatial and temporal resolution in assessing the performance of Doho Rice Irrigation Scheme through estimations of actual evapotranspiration. Actual evapotranspiration (ETa) was modelled from Landsat 7 imagery using the surface energy balance system algorithm on five clear days between January and April 2020. Using equity and adequacy metrics, the derived ETa was used to assess the irrigation performance of the scheme. Results showed that the equity indicator was generally fair, with the coefficient of variation between 0.11 and 0.08, close to the 0.10 threshold implying irrigation water is fairly distributed within the scheme. The average adequacy was 0.87, above the 0.65 threshold, indicating adequate water supply throughout the scheme. The study’s findings can be used in future research and benchmarking with other irrigation schemes to address the country’s water resource management challenges.