Hydrological monitoring and modeling of an alpine catchment

Since 2008 we have been monitoring a watershed in the alps to assess the impact of the spatial heterogeneity of meteorological variables over a complex terrain and identify the mechanisms generating streamflow. The study area is located in the Swiss Alps along the southernmost ridge that borders Italy. The total surface area is 20.4 km2 with altitude ranges from 1775 m at the outlet to 3206 m at the border with Italy. Its climate is characterized by a long winter where permanent snow cover becomes significant in December and lasts until mid-summer. Spring period runoff is typically snowmelt dominated and summer is generally mild with occasional thunderstorms and typically low-base flows. Heavy rains, and occasional snowfalls, become more regular and important in autumn. The area is characterized by steep and complex terrain leading to local cooling and heating airflow patterns. The watershed is heavily monitored with wireless meteorological stations, measuring precipitation, solar radiation, air temperature and humidity, skin temperature, wind speed and direction, soil temperature and humidity, and soil matrix potential. Discharge measurements using the salt dilution method are carried out on a weekly basis from late April until late-October since 2008. The stage-discharge relation has been established combining the discharge measurement along with continuous monitoring of the water level. During the 2011 field campaign, the discharge of two sub-basins has been monitored in order to compare the results with a semi-distributed model. Moreover, water from different rivers of the basin has been sampled automatically, along with water samples from precipitation, in order to proceed to a two-component hydrograph separation with stable isotopes analysis. We discuss the relative importance of snowmelt, precipitation and local geomorphology, based on the results of different models in combination with the data collected in the past years.