Assessing the efficiency of indigenous soil and water conservation methods used in Mountainous regions of Uganda (case study of Nyamiyaga village Kisoro District)

Abstract

Water and soil are basic natural resources that support life in all forms. These resources are scarce to meet the increasing demands of man, which calls for their conservation. The purpose of the study was therefore to assess the efficiency of indigenous/traditional practices of soil and water conservation (SWC) in mountainous regions of Uganda, case of Nyamiyaga village Kisoro District and design appropriate SWC measures for sustainable management of these resources. The specific objectives of the study were; Assessing the farmers’ perspective on causes and effects of soil erosion in the study area, examining indigenous SWC practices and designing appropriate measures for SWC in moutaineous regions utilising the local knowledge. Primary data was collected using slit trap experiments, taking measurements of existing SWC structures and using a structured questionnaire, while secondary data was obtained from Uganda National Meteorological Authority, United States Geological Survey and literature. Analysis was done using Excel, SPSS and Arc GIS 10.5. Soil Conservation Service (SCS) method was used to determine total annual runoff volume while soil erosion potential was assessed using the Revised Universal Soil Loss Equation. The study revealed that average annual soil erosion rate for the micro catchments was 318 tons ha- 1 yr-1 (classified as very severe), while averege annual runnoff volume at a 2 year return period was estimated at 1,497m3. This affects the design, construction and operation of hydraulic structures (such as dams, reservoirs and waterways to manage water resources for domestic and agriculture), watershed management (such water quality and quantity management, flood control, and sustainable use of natural resources), environmental impact assessment of development projects (such as roads, housing, mines, and industrial facilities) and agricultural productivity of farmers, in absence of improved SWC measures. Major traditional practices of SWC were identified as soil erosion control fences, terrace with fanya juu, water retention trenches, erosion control stone bunds, fallowing and rainwater harvesting tanks. Using slit traps, the study examined the efficiency of the the major indigenous SWC structures and came up with improved structural designs of these structures to enhence their performance. Modifications made include; introducing a foundation trench for stone bunds of 15cm and adjusting their cross sectional area from 0.07m2 to 0.10m2, reducing the spacing between stakes for erosion fences from 4m to 3m and introducing fodder trees between them, increasingxiii the cross sectional area of water retention trenches from 0.16m2 to 0.25m2, increasing cross sectional area of a bench terrace from 0.12m2 to 0.18m2 and increasing the capacity of a RWHT from 3m3 to 7.5m3. The efficiency of the improved measures was found to be 95% as compared to 75% of the indigenous methods. Finally, the study recommended similar studies on other slopes of Kisoro and Uganda in general, studies on gender in relation to SWC and studies into factors affecting the adoption of modern methods of SWC in the catchment.