The Imperial River Basin is located between 37°51’ and 38°56’ latitude south, and its drainage area covers about 12 005 km2 in southern Chile (see Figure 1). The main water course is the Imperial River, which is formed by the confluence of the Cautín and CholChol rivers, with an average annual flow of 260 m3 /s and 230 km from its head in the Andes mountain range to its mouth at the Pacific Ocean (71°25’-73° 30’ longitude west). Within the basin elevations range from 0 m at its mouth to 3 124 m above sea level on its eastern border (Llaima volcano).
For the implementation of the hydrological model two pilot catchments will be selected, one located in the low-elevation valley and the other in the high-elevation areas of the main basin, with a rain- and snow-dominated hydrological regime, respectively. In order to overcome the lack of rainfall and snow-cover measurements in the mountainous part of the basin, this proposal plans to acquire a new meteorological station, able to measure rainfall, snow water equivalent (SWE), snow depth, air temperature, solar radiation, relative humidity and wind speed. Important differences in average precipitation are expected for the raingauges located in the valley with respect to those in the high-elevation area of the basin, which are added to the role of snowmelt processes in short-term water availability predictions.