IWMI


The hydrology of Holetta River and its seasonal variability is not fully studied. In addition to this, due to scarcity of the available surface water and increase in water demand for irrigation, the major users of the river are facing a challenge to allocate the available water.

Therefore, the aim of this research was to investigate the water availability of Holetta River and to study the water management in the catchment. Soil and Water Assessment Tool (SWAT) modelled the rainfall runoff process of the catchment. Statistical (coefficient of determination [R2], Nash- Sutcliffe Efficiency Coefficient [NSE] and Index of Volumetric Fit [IVF]) and graphical methods used to evaluate the performance of SWAT model.

The result showed that R2, NSE and IVF were 0.85, 0.84 and 102.8, respectively for monthly calibration and 0.73, 0.67 and 108.9, respectively, for monthly validation. These indicated that SWAT model performed well for simulation of the hydrology of the watershed. After modelling the rainfall runoff relation and studying the availability of water at the Holetta River, the water demand of the area assessed. CropWat model and the survey analysis performed to calculate the water demand in the area. The total water demand of all three major users was 0.313, 0.583, 1.004, 0.873 and 0.341 MCM from January to May, respectively. The available river flow from January to May obtained from the result of SWAT simulation. The average flow was 0.749, 0.419, 0.829, 0.623 and 0.471 MCM from January to May respectively. From the five months, the demand and the supply showed a gap during February, March and April with 0.59 MCM.

Therefore, in order to solve this problem alternative source of water supply should be studied and integrated water management system should be implemented.

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This paper was first presented at the Nile Basin Development Challenge Science meeting. The NBDC Science meeting was held on 9 and 10 July 2013 at the ILRI-Ethiopia campus, with the objectives to exchange experiences and research results across NBDC scientists involved in the NBDC projects and to discuss challenges and possible solutions.

Over the past five decades, gullying has been widespread and has become more severe in the Ethiopian highlands. Only in very few cases, rehabilitation of gullies has been successful in Ethiopia due to the high costs.

The objective of this paper is to introduce cost effective measures to arrest gully formation. The research was conducted in the Debre-Mewi watershed located at 30 km south of Bahir Dar, Ethiopia.

Gullying started in the 1980s following the clearance of indigenous vegetation and intensive agricultural cultivation, leading to an increase of surface and subsurface runoff from the hillside to the valley bottoms. Gully erosion rates were 10–20 times the measured upland soil losses. Water levels, measured with piezometers, showed that in the actively eroding sections, the water table was in general above the gully bottom and below it in the stabilized sections.

In order to develop effective gully stabilizing measures, we tested and then applied the BSTEM and CONCEPT models for their applicability for Ethiopian conditions where active gully formation has been occurring. We found that the model predicted the location of slips and slumps well with the observed groundwater depth and vegetation characteristics.

The validated models indicated that any gully rehabilitation project should first stabilize the head cuts. This can be achieved by regrading these head cuts to slope of 40 degrees and armoring it with rock. Head cuts will otherwise move uphill in time and destroy any improvements. To stabilize side walls in areas with seeps, grass will be effective in shallow gullies, while deeper gullies require reshaping of the gullies walls, then planting the gully with grasses, eucalyptus or fruit trees that can be used for income generation. Only then there is an incentive for local farmers to maintain the structures.

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See the full proceedings of the NBDC Science meeting


This paper was first presented at the Nile Basin Development Challenge Science meeting. The NBDC Science meeting was held on 9 and 10 July 2013 at the ILRI-Ethiopia campus, with the objectives to exchange experiences and research results across NBDC scientists involved in the NBDC projects and to discuss challenges and possible solutions.

The Nile Basin

The Nile Basin

As the Nile Basin Development Challenge (NBDC) comes to an end this short document from the CGIAR Challenge Program on Water and Food offers a summary of research conducted in the past four years.

It covers:

  • What the NBDC was about
  • The main challenges addressed
  • The eight key messages identified in 2013
  • Some outcomes and lessons

As much NBDC work is slowly integrated into CGIAR research programs on Water, Land and Ecosystems and on Integrated Systems for the Humid Tropics, this summary is a neat and short introduction to some essential issues that NBDC has left as a legacy to improve land and water management in Ethiopia and the wider Nile Basin.

Read the full Nile Basin Summary

Most soil erosion studies conducted in Ethiopia are focused on quantification of sediment and lack specific information on temporal and spatial variability of sediment and its associated plant nutrients loss. This study was therefore quantified and characterized runoff and sediment along with estimated the on-site financial cost of erosion in terms of its concomitant crop yield loss due to the nitrogen and phosphorus lost in consequence of erosion.

Data on discharge and runoff samples for sediment concentration and nutrient content was collected at three monitoring stations (Melka, Galesssa and Kollu) in Meja watershed in Jeldu district, in the Ethiopian part of the Blue Nile Basin. Daily samples collected during the rainy season were analysed in the laboratory of Ambo University for sediment content of runoff, particle size distribution of the sediment and nitrogen and phosphorus content of both the sediment and runoff. Preliminary results indicate that both runoff volume and sediment concentration vary with space and time. While the maximum runoff volume was recorded in the middle of the rainy season, sediment concentration decreased towards the end of the rainy season in response to increased ground cover. The average suspended sediment concentration during the rainy season was 3.0 ± 1.1, 2.2 ±1.3 and 1.4 ± 0.9 g L-1 while the total sediment yield ranged from 74 t km-2, 248 t km-2 and 604 t km-2 at Melka, Galesssa and Kollu, respectively. The financial cost of erosion was estimated at 595, 510 and 2475 ETB ha-1 from Melka, Kollu and Galessa, respectively.

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See the full proceedings of the NBDC Science meeting


This paper was first presented at the Nile Basin Development Challenge Science meeting. The NBDC Science meeting was held on 9 and 10 July 2013 at the ILRI-Ethiopia campus, with the objectives to exchange experiences and research results across NBDC scientists involved in the NBDC projects and to discuss challenges and possible solutions.

The current paper discusses the use of hydrological modelling tool to understand sustainable land management interventions in the Blue Nile basin of Ethiopia.

A micro-watershed named Mizewa with a drainage area of 27 km2 in Fogera district was selected and instrumented with hydrological cycle observation networks in the year 2011. The SWAT hydrological modelling tool was used to simulate landscape-wide Soil and Water Conservation (SWC) investments.

Simulations of the selected investments modelled in this analysis suggest that improvements in infiltration, decreases in surface runoff and decreases in erosion are achievable in the watershed. Further simulations suggest that a landscape-wide approach of terrace and bund construction has the greatest effect in terms of decreasing surface runoff, decreasing sediment yield and increasing groundwater flow and shallow aquifer recharge.

A comprehensive landscape investment of terraces on slopes greater than 5% and bunds maintained on slopes less than 5% would decrease surface flow by almost 50%, increase groundwater flow by 15% and decrease sediment yield from erosion by 85%. However, constructing terraces in areas with greater than 5% slope (without constructing bunds in areas under 5% slopes) has a similar effect whereby surface flow and sediment yield decreases by 45 and 83%, respectively and groundwater flow increases by 13%. Residue management also has a significant effect on surface flow and erosion in the Mizewa watershed. Average annual surface flow decreased 17 when adopting residue management on all agricultural land and 26% when coupling terracing on steep slopes with residue management in mid-range slopes.

These analyses provide the foundation for understanding feasible outcomes given a more comprehensive investment strategy. Results stemming from the current work can be paired with household level socio-economic data in order to assess program investment alternatives taking into account household constraints to Sustainable Land and Watershed Management (SLWM) investment and maintenance on private and public lands.

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This paper was first presented at the Nile Basin Development Challenge Science meeting. The NBDC Science meeting was held on 9 and 10 July 2013 at the ILRI-Ethiopia campus, with the objectives to exchange experiences and research results across NBDC scientists involved in the NBDC projects and to discuss challenges and possible solutions.

This paper examines the advance time of furrow irrigation at Koga.

Koga irrigation scheme was developed to irrigate about 7004 ha. Furrow irrigation is the recommended method for the distribution of water. However, furrow irrigation has inherent inefficiencies due to deep percolation on the upper end and runoff at the lower end of the furrow. These losses depend on furrow length, furrow gradient, surface roughness, stream size and cutoff time. These factors play significant role to influence the advance time of irrigation and the operation rule of the scheme.

The experiment was conducted during 2012 irrigation season in two periods (February and April). The advance time of irrigation was monitored at three discharge rates and four furrow gradients at 90–110 m furrow length. The required discharge was measured using RBC flume. The average advance time at respective discharge rates of 0.3, 0.6 and 0.8 litre/sec range from 290–460 min, 150–437 min and 100–294 min during 1st irrigation; and 115–370 min, 78–189 min and 43–217 min during 2nd irrigation. The advance time vary greatly among the discharge rates when the furrow length increases. The advance time of water at 0.5, 1.0, 2.0 and 2.5 % gradients was 236, 181, 197 and 398 min at 1st irrigation and 163, 175, 220 and 88 min at 2nd irrigation respectively. Furrow gradients and surface irregularities result in great variation of advance time. The advance time becomes shorter when the field gets smoother during 2nd irrigation. Under non-levelled and irregular field conditions, 0.6–0.8 litre/sec application rate can be suggested to irrigate 30–40 m furrow lengths in order to improve application efficiency above 60% and to optimize the daily operation rule of the overall scheme.

The result of this study indicates the relevance of examining the furrow length, discharge and application time recommended in the feasibility study of irrigation schemes.

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See the full proceedings of the NBDC Science meeting


This paper was first presented at the Nile Basin Development Challenge Science meeting. The NBDC Science meeting was held on 9 and 10 July 2013 at the ILRI-Ethiopia campus, with the objectives to exchange experiences and research results across NBDC scientists involved in the NBDC projects and to discuss challenges and possible solutions.

Mixed crop–livestock farming system is a major livelihood strategy in most sub-Sahara African countries. Low water use efficiency and water scarcity characterize the dominant rainfed agricultural production system in the densely populated highlands of Ethiopia. Improving water productivity in the rainfed system is among the ways of overcoming the water scarcity challenge.

This study was conducted in Meja watershed, located in Jeldu district, West Shewa in the Ethiopian part of the Blue Nile Basin to estimate economic crop water productivity based on agro-ecology and crop management practices. The watershed was classified into three landscape positions (local agro-ecologies) and major crops representing at least 70% of each landscape position were identified through discussion with farmers and development agents.

Five farmer fields were randomly selected for each major crop and crop management practices implemented by the farmers were monitored and yield (grain or tuber and straw) was measured at harvest. The local market value of the crops and the production cost was estimated based on the local market value for labour and other inputs. CROPWAT model was used to estimate effective precipitation based on weather data generated using NewLocClim and crop characteristics.

The result indicated that the landscape positions, crop variety and management practices significantly influenced the net economic water productivity. The net economic crop water productivity for barley, wheat, tef, sorghum and maize grains and fresh potato tubers were 3.31, 2.45, 3.09, 3.01 and 5.20 and ETB 13.56 m-3, respectively. Similarly, physical water productivity of the crops ranged from 0.47 for teff to 9.98 kg m-3 for fresh potato tubers. Hence, farmers can enhance economic benefit from the land and water resources they are endowed with rainfed by using improved agronomic practices that could raise grain/tuber and biomass yield. Enhancing improved input use, improving access to market for outputs and integrating livestock with crops may further augment the benefit at system scale.

Read the paper

See the full proceedings of the NBDC Science meeting


This paper was first presented at the Nile Basin Development Challenge Science meeting. The NBDC Science meeting was held on 9 and 10 July 2013 at the ILRI-Ethiopia campus, with the objectives to exchange experiences and research results across NBDC scientists involved in the NBDC projects and to discuss challenges and possible solutions.

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