Snow cover and soil monitoring in Sagarmatha National Park (Nepal): an integrated approach

Since 2012, in the Sagarmatha National Park, a monitoring project (SHARE‒RIVERS) has been carried out with the main purpose of studying the water cycle, with a special focus on the influence of climate change. Project activities include a wide variety of in-situ (water and soil sampling) and remote analyses. Two expeditions have been carried out (2012 and 2013) for a soil and water survey in the area. In particular the measurement of soil temperature (Maxim I-Button) along an altitudinal transect (2660-5320 m asl) was carried out during winter 2012-2013 in order to gather data about patterns of ground surface temperature and the snow cover duration. The soil temperature measurement is still going on (HOBO U23 Pro v2). Moreover, in the last expedition, the occurrence of Pahilin cyclone (65 cm of snowfall at sites higher than 4615 m asl in three days) in the valley allowed the performing of several snow sampling along an altitudinal transect for a chemical characterization. Snow cover duration has been assessed by computing soil daily temperature amplitude and comparing the obtained results with threshold values derived from literature (e.g. 2° C ). These data have been compared with long time series of snow depth data obtained from weather stations located in the Sagarmatha valley and with remote sensing analyses carried out using MODIS satellite scenes. Preliminary results showed an high variability in snow cover duration among the time series and an abrupt change at elevation greater than 5000 m asl. Concerning soil temperature, in the investigated season, a 0.47°C/100 m gradient was computed, a result comparable with air temperature one. At higher elevation the prevalent pattern of ground surface temperature, according to Ishikawa et al. (2003), was “Direct atmospheric cold heat penetration throughout winter”. This pattern didn’t always allow the detection of the snow cover duration, which, for example, during the winter 2011- 2012 ranged between 21 and 329 days. This integrated approach will provide a medium term assessment of snow cover dynamics and soil temperature in the park and a ground work for further analysis on environmental variables influenced by this phenomena e.g. water cycle, nutrient cycling, plant phenology.