INTEGRATED WATER RESOURCES ASSESSMENT AND MANAGEMENT IN A DROUGHT-PRONE WATERSHED IN THE ETHIOPIAN HIGHLANDS
Food production shortfalls and accelerated land degradation are common in the semi-arid Ethiopian highlands. Both issues can be addressed to a significant extent by better water management. This dissertation presents four studies in eastern Amhara that examined effectiveness of a range of water management practices. An on-farm study tested effectiveness of subsoiling, open and tied ridges, no till, and conventional maresha tillage to mitigate impact of dry spells on crops and to protect the soil. Tillage performance varied with seasonal rainfall distribution and intensity and land gradient. Ridges significantly increased soil moisture and grain yield and reduced soil loss. Subsoiling moderately increased grain yield and root growth, but led to higher soil loss than conventional tillage. No till minimized soil loss, but reduced yield during one season. A second study measured plot and catchment hydrologic responses with and without conservation measures. Results show that severe erosion in the watershed occurred during few erratic storms rather than steadily across all seasons. Gently-sloped cropland generated over twice the seasonal runoff and sediment yield compared with steep rangeland. Plot runoff consistently exceeded catchment discharge demonstrating a scale effect. Catchment rehabilitation resulted in reduced peak discharge and longer duration streamflow compared to a catchment without these measures. A third study examined hydrological and land cover changes in a wetland through remote sensing, hydrological measurements, rainfall records, and a residents? survey. All evidence indicated limited flooding and dense woody vegetation cover in the wetland 40 years ago and a trend towards current conditions of no living trees/bushes, extensive flooding, and heavy sedimentation. Results suggest changes are a consequence of increasing runoff from the catchment and higher population pressure that decreased potential of rainwater to infiltrate. A fourth study surveyed households to assess what water resources they accessed and their water concerns. Each household relied on over 3 different water sources to assure daily supplies of 5-12 liters per person. Females assured most domestic water while male participation increased for livestock water and sources farther from home. Concerns included unhealthy water quality, unreliable year-round supply, and long up to 5 hours daily walking distances.
Tammo S. Steenhuis, Erick C.M. Fernandes, Parfait M. Eloundou-Enyegue
watershed management; Ethiopia; runoff; erosion; infiltration; conservation tillage; subsoiling; tied ridge; wetland hydrology; perception; remote sensing; soil loss; soil moisture; drought mitigation; community water resources; Africa; sorghum yield; catchment hydrology; gully rehabilitation
dissertation or thesis