Cycle 1 (2011 Deadline)
Reducing soil loss through effective soil and water conservation practices using hydrologic considerations and farmers’ participation in the Blue Nile Basin
PI: Seifu Tilahun, Bahir Dar University
US Partner: Christopher Barrett, Cornell University
Project Dates: May 2012 - April 2015
Soil erosion decreases food production and hampers poverty reduction efforts in the highlands of eastern Africa. Although intensive efforts have been underway both to reduce sediment production and to halt land degradation since the 1980s, erosion continues unabated and the already low crop yields are deceasing even further. Shallow soils are becoming shallower and are often abandoned, and gullies are swallowing up productive cropland. Finally, some of the lost soil fills up reservoirs and silts up downstream irrigation canals. Current measures to reduce soil loss are ineffective, and new approaches that both consider the hydrology of the whole landscape (instead of the current plot based erosion research) and use traditional farmer’s knowledge for locating erosion control practices are required. The goal of the proposed research is to develop appropriate watershed and farmer-based erosion control practices for the Ethiopian highlands in order to replace the well minded imported and inappropriate technologies from foreign donors.
Tammo Steenhuis teaching the PhD students at Bahir Dar University. (Photo courtesy Dr. Tilahun).
Ali Yassin, 4th year undergrad student, building a weir, used as a measuring place for runoff and sediment concentration in the river (Photo courtesy Dr. Tilahun).
| Team members conducting a group walk and discussion with local community women on erosion in Debre Mawi watershed (Photo courtesy Dr. Tilahun).|
These researchers will instrument the Debre Mawi (5.27km2) and Bir (64km2) watersheds in the headwaters of Blue Nile and to continue monitoring another instrumented by the International Water Management Institute (IWMI), the Mizewa watershed (27km2). Their efforts will be aimed at identifying erosion hotspots by measuring spatially distributed runoff and soil loss (from periodically saturated areas in the valley bottoms and areas with exposed subsoil that are severely degraded) and by participatory watershed methods approach and sediment tracers. They will also study the relationship between nutrient loss and soil loss by measuring soil nutrients (N, P, K, Mg, and Ca). Perched water table levels will be measured in the Bir watershed (~64km2) to identify saturated areas. Gullies will be monitored through areal and satellite images in addition to field measurement in the Bir and Debre Mawi watersheds. By locating the hotspot areas within the watershed, they will propose effective conservation practices. A simple physically-based hydrology model will be applied to locate the practices on the vulnerable areas. Their predictions will be compared with farmers’ knowledge including the location of the traditional practices. Finally, practices will be designed with the participation of farmers. Within the project period and beyond, some of the proposed practices will be installed with the farmers’ help in the Debre Mawi and monitored after the project. This research project will be carried out by the School of Civil and Water Resource Engineering as part of the newly implemented PhD program and an existing master’s graduate program on hydrology in close cooperation with faculty and students of a NSF IGERT program at Cornell. Most importantly, the international partnership will train future scientists and managers for managing the soil and water resources in Ethiopia.
Summary of Recent Activities
During the months of July through September 2013, Dr. Tilahun and his research team continued their work at their different project sites. In the Debre Mawi Watershed, PhD student Dessalegn Chanie Dagnew has been recording rainfall data and monitoring hill erosion to evaluate the effectiveness of soil conservation measures. Stream depth, flow velocity, and suspended-sediment concentration and run-off volume measurements were conducted, and the collected sediment samples were filtered at the soil mechanics laboratory of Bahir Dar University. Measurement of spatial and temporal soil moisture dynamics in the selected fields has been ongoing, as have rill erosion measurements from 20 spatially distributed agricultural sites. Research and data collection efforts continued in the Bir Watershed as well. PhD student Getaneh Kebede Ayele collected rainfall data using two automatic and three manual rain gauges and amassed a total of 603 sediment liter samples. Gully rehabilitation involving community participation in this area shows significant improvement: high grass yield will soon be harvested, and significant amounts of sediment have been trapped as a result of using this conservation system. Rehabilitation returns will be calculated and the economic viability of rehabilitation works will be analyzed. At the same time, gully erosion during the rainy season continues to expand significantly in the Bir watershed study area. Research in the project’s third study area, the Mizwa Watershed, continues as well: rainfall data is being collected using an automatic rain gauge and 39 piezometers in 13 transects. In this area PhD student Mamaru Moges Ayalew also continues to collect water samples; measure water level, sediment, and water flow velocity; and make nutrient concentration calculations.
The gully rehabilitation demonstration shows improvement through community participation in physical and biological conservation. (Photo courtesy Dr. Tilahun).
At the same time gully erosion expansion is severe in the control area (Photo courtesy Dr. Tilahun).
| Graduate student Selamwit Damtew uses a surveying instrument to collect data for a cross-sectional profile of one of the gullies. (Photo courtesy Dr. Tilahun).|