Managing climate risks in agriculture and hydropower by coupling prediction and multi-purpose reservoir models in the Blue Nile Basin, Ethiopia
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The Blue Nile Basin in Ethiopia is a critical water resource for the nation and continent, subject to spatial and temporal variations in climate that adversely impact local communities. Extreme conditions, e.g. drought and flood, threaten livelihoods causing direct hydrologic, economic, and social implications. To reduce vulnerability and enhance economic security in the region, predictive information is coupled with operational reservoir models to issue advance prediction of dominant rainy season conditions and inform sectoral decision-making. Advance predictions of seasonal precipitation may provide information to aid water resource management decisions in various sectors. Yet, a disconnect between the spatial scale upon which skillful predictions are issued and the sectoral decision-making scale renders current predictive information inadequate in many cases. This work explores season-ahead precipitation prediction skill for a local region in the Blue Nile basin, Ethiopia, to better understand how model structure may serve to provide more skillful and valuable predictive information to the end-user. Statistical downscaling of global dynamic and regional empirical models as well as development of a high resolution, locally-tailored statistical model indicate that model structure and prediction skill are inextricably linked. Statistical approaches specific to the local region show higher prediction skill at the sectoral decision-making scale compared with dynamic approaches, offering the potential to aid local communities in many regions that are currently vulnerable to highly variable spatial and temporal precipitation patterns. Predictive hydroclimate information may be further enhanced by integrating with sectoral models, to provide actionable information for communities by explicitly addressing climate risks. In this work, local-scale, statistical streamflow forecasts are coupled with a multi-purpose reservoir model to explore benefits and tradeoffs to hydropower and agriculture production for the Finchaa – Amerti system in the Blue Nile basin of Ethiopia. Strategies to meet agriculture demand and maximize hydropower result in increased hydropower production and agriculture water allocation using this framework. The resulting increase in resilience and decrease in vulnerability across sectors provides a concrete example of how hydroclimate prediction can be translated to actionable information to guide water resources management and bridge the existing disconnect between prediction and decision-making scales.