Calibration and Assessment of a Distributed Hydrologic Model Applied to a Glacierized Basin in the Cordillera Blanca, Peru

Glacier retreat has been well documented in the Cordillera Blanca of the Peruvian Andes. It is becoming clearer that changes in glacier area and volume will negatively affect water resources in this region, particularly during the dry season (May to September). Previous studies focusing on this issue in the Cordillera Blanca have had success modeling runoff but did so using somewhat over-simplified hydrologic models. The question driving this study is: How well does the Distributed Hydrology Soil and Vegetation Model (DHSVM) coupled with a new dynamic glacier sub-model replicate runoff in a test basin of the Cordillera Blanca, namely Llanganuco. During the 2011 dry season we collected data on stream discharge, meteorological conditions, soil, and vegetation in the basin. We installed two stage height recorders in the middle reaches of the watershed to complement a third which delineates the basin outlet. Flow data collected at these points will be used for model calibration and/or validation. For geochemical validation we collected spring and meltwater samples for use in a two component isotopic mixing model. We also mapped dominant soil and vegetation types for model input. We use satellite imagery (ASTER and Landsat) to map the change in glacier extent over approximately the last 30 years as this will be another model input. Coupled together, all of these data will be used to run, validate, and refine a model which will also be implemented in other regions of the world where glacier melt is crucial at certain times of the year.