Dry Season Runoff and Natural Water Storage Capacity in the High Andean Catchment of the River Ronquillo in the Northern Sierra of Peru

In the northern Sierra of Peru, water scarcity issues arise owing to the seasonal rainfall distribution and the lack of appropriate natural water storage capacity of river basins. The present study assesses the base flow and water storage volume of the Ronquillo watershed, an important rivulet for water abstraction for the city of Cajamarca. Mean base flow is 184 ls(-1), thus representing 44 percent of total stream flow. Flow recession curve analysis yields a mean catchment water storage volume of 3.57 x 10(6) m(3), which corresponds to a runoff depth of 85 mm. The dischargeable water storage volume of Andosols, a soil type known to be a very important water reservoir in the Andes, corresponds to a runoff depth of 33 mm. Moreover, the study shows that the geological environment is of major relevance. Springs (18 mm) and an effluent flow regime (20 mm) contribute significantly to dry seasonal runoff. The findings imply that water conservation in the Ronquillo watershed should place emphasis not only on the preservation of soils, but also on subsurface water flow paths, as water availability is affected by processes operating beyond topographically derived catchment boundaries.