Preliminary Estimation of Snow Covers Extents of Astore River Basin in Northern Areas, Pakistan

An assessment of snow accumulation and depletion is necessary for the management of water resources in the region, where a great portion of annual precipitation falls in form of snow. This study was done to estimate the snow covered area of Northern Areas (Astore) in snow accumulation and snow ablation period with the aid of remote sensing (RS) techniques. Satellite image of Moderate Resolution Imaging Spectroradiometer (MODIS) was used to evaluate snow cover and classify the behavior of different image pixels in snow covered, partially covered and snow free pixels respectively. In order to nullify the obstruction offered by clouds only one cloud free image per week was selected for the years of 2008-2009 and data was analyzed using different ArcGIS and ERDAS Imagine tools. Watershed area of Astore river basin was calculated by using Digital Elevation Model. Normalized Differential Snow Index (NDSI) was used to draw snow cover map. Snow covered area was calculated in square kilometer and curves of snow cover extents were made for both years separately. Furthermore correlation curves were made for snow cover fluctuation with varying precipitation, minimum temperature and maximum temperature for years of 2008-2009. The observed correlation coefficient between snow cover, maximum temperature, minimum temperature and precipitation was found to be -0.784 (0.003), -0.767(0.004), 0.561(0.058) respectively for both the years. Moreover multiple linear regression equation was generated for future snow cover prediction under different climatic scenarios. January and February was found to be snow accumulation period and for May, July, June it was snow ablation period for both years.