March 21, 2014

Runoff estimation and water management for the Holetta river in Ethiopia – A glimpse at NBDC science

Posted by Ewen Le Borgne under Books and Chapters, CRP5, East Africa, Ethiopia, IWMI, NBDC, Nile, Nile 2, Presentation, Report, Water | Tags: , , , , , , |
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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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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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March 5, 2014

Hydrological modelling of a catchment using the SWAT model in the upper Blue Nile basin of Ethiopia – A glimpse at NBDC science

Posted by Ewen Le Borgne under Books and Chapters, CRP5, East Africa, Ethiopia, IWMI, NBDC, Nile, Nile 2, Presentation, Report | Tags: , , , , |
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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.

See the presentation:

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.

 

January 16, 2014

Hydrological modelling of sustainable land management interventions in the Mizewa watershed of the Blue Nile basin – A glimpse at NBDC science

Posted by Ewen Le Borgne under Books and Chapters, CRP5, East Africa, Ethiopia, IWMI, NBDC, Nile, Nile 4, Presentation, Report | Tags: , , , , , |
Leave a Comment 

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.

See the presentation:

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.

 

December 23, 2013

Understanding the dynamics of hydrological processes and rainfall runoff modeling in meja watershed – A glimpse at NBDC science

Posted by Ewen Le Borgne under Books and Chapters, CRP5, East Africa, Ethiopia, IWMI, NBDC, Nile, Nile 4, Presentation, Report | Tags: , , |
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Understanding the basic relationships between rainfall, runoff, soil moisture and ground water level are vital for an effective and sustainable water resources planning and management activities. But so far there is no hydrological study in Meja watershed that aims to understand the watershed characteristics and runoff generation processes.

This study was conducted to understand runoff generation processes and model rainfall runoff relationship in Meja watershed having a drainage area of 96.6 km2. The watershed is one of the three research sites of International Water Management Institute (IWMI) developed in early 2010 in the upper Blue Nile Basin of Ethiopia. In the study, primary data of soil moisture, shallow ground water level, rainfall and runoff were collected from the hydrological monitoring network in the watershed.

Hydrological models like HBV and RRL SMAR were configured to understand the relationship between rainfall and runoff in the watershed. Relationships between rainfall, soil moisture, shallow ground water level and discharge were developed to understand runoff generation processes in the watershed.

According to one year and three months data, there is no strong daily rainfall and runoff relationship (r2 <0.5) in Meja and Kolu which is a nested sub-watershed; this may be due to abstractions such as irrigation and human interventions in the watershed. There is a strong linear relationship of rainfall and monthly averaged volumetric soil moisture in most layers of Meja and its nested sub-watersheds. The general relationship between runoff and monthly averaged soil moisture at different layers in Meja watershed and Kolu is strong and linear. Analysis of rainfall runoff models indicated better performance of HBV than RRL SMAR model.

See the presentation:

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.