Addressing water availability and climate change issues in the Cordillera Blanca, Peru through technical analysis and community building strategies

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Read, Laura K.

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Accelerated tropical glacial melt on the order of 15-18 meters per year since the 1980's in Peru's Cordillera Blanca region is alarming rural communities and urban authorities, causing them to seek technical support for risk management and adaptation actions. Melting glaciers coupled with changing seasonal rainfall patterns has left many rural communities in the upper Rio Santa basin lacking sufficient fresh water supply to support livestock, irrigation and human consumption. In response to these concerns, a Water Evaluation And Planning (WEAP) model was created by the Stockholm Environmental Institute for simulating glacial melt and flow in the Santa River. Through input parameters of climate, glacial runoff, water use, crop acreage, soil type and groundwater interactions, WEAP has the flexibility to model scenarios for different operation schemes. These schemes allow users to determine the most effective ways to regulate their resources and explore adaptation actions (e.g. altering farming practices and building reservoirs) for future planning. This project improved the existing model by including observed water demand data for irrigation, and evaluating the Climate Forecast System Reanalysis (CFSR) dataset to serve as a potential source for filling gaps in the historic climate record. These improvements added robustness to the model and correlated well with historic stream flow at La Balsa (R² = 0.78 , Nash = 0.68). Two scenarios were explored where (1) a 50% reduction in potato crop was replaced with maize for each sub-basin, and (2) a 10% reduction in precipitation was applied over the upper basin. Results show that the WEAP model is sensitive to changes in crop type and rainfall at the sub-basin scale, an encouraging finding for future exploration. This investigation enables communities to base future decisions on technical evidence and provides a basis for educating citizens on the importance of evaluating their available resources under climate change projections



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