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Application of Local Season-Ahead Precipitation Predictions for Reservoir Operations and Management in the Blue Nile Basin, Ethiopia

Background
Ethiopia’s predominately rain-fed agricultural society is greatly impacted by seasonal and inter-annual variability in precipitation, with 75% of precipitation occurring during one June-September rainy season (JJAS). However, reservoirs can capture water and allow for a second cropping season during October – May, potentially increasing yield and economic security in the region. Application of skillful season-ahead precipitation predictions may help inform reservoir operations and management decisions for greatest impact to the community.

Objective
Skillful season-ahead predictions conditioned on local and large-scale hydro-climate variables can provide valuable knowledge to farmers and reservoir operators, enabling informed water resource allocation and management decisions. In Ethiopia, the potential for advancing agriculture and hydropower management, and subsequently economic growth, is substantial. This work couples local precipitation predictions with reservoir characteristics for the Koga reservoir.

Initial Results
Results show how local precipitation predictions can be used to predict the volume of inflow to the reservoir during the JJAS season. Given the known state of the reservoir in May, this prediction provides indication in early June of whether the reservoir is expected to fill by the end of the dominant rainy season, an estimate of October reservoir volume. Prior indication of reservoir volume may assist agricultural decisions (e.g. preparation of land, seed allocation). Using a simple water balance iteration and reservoir characteristics, a relationship between JJAS precipitation and volume of JJAS inflow is determined, as a framework for implementation in water resource operations and management decisions.

Dissemination
Alexander, S., Block, P., and Wu, S. Development and Evaluation of Season-Ahead Precipitation Predictions for Sectoral Management in the Blue Nile Basin, Ethiopia. American Geophysical Union (AGU) Fall Meeting, New Orleans, LA, December 2017.

 

Figure 1. Observed JJAS precipitation (black) and probabilistic JJAS precipitation predictions results from locally-tailored statistical model issued June 1.

Figure 2. Reservoir application framework

Figure 3. Simulated October Koga reservoir volume based on observed precipitation (1981-2016) and distribution of precipitation predictions.

Research Team

Sarah Alexander, Graduate Research Assistant, Civil and Environmental Engineering, University of Wisconsin - Madison.

Paul Block, Assistant Professor, Civil and Environmental Engineering, University of Wisconsin-Madison.

Shu Wu, Assistant Researcher, Center for Climatic Research, University of Wisconsin - Madison.