Changes in Snow Cover Dynamics over the Indus Basin: Evidences from 2008 to 2018 MODIS NDSI Trends Analysis

Sikandar Ali,Muhammad Mohsin Waqas,Usman Khalid Awan,Muhammad Waseem,Muhammad Jehanzeb Masud Cheema,Tasneem Khaliq

doi:10.3390/rs12172782

Abstract

The frozen water reserves on the Earth are not only very dynamic in their nature, but also have significant effects on hydrological response of complex and dynamic river basins. The Indus basin is one of the most complex river basins in the world and receives most of its share from the Asian Water Tower (Himalayas). In such a huge river basin with high-altitude mountains, the regular quantification of snow cover is a great challenge to researchers for the management of downstream ecosystems. In this study, Moderate Resolution Imaging Spectroradiometer (MODIS) daily (MOD09GA) and 8-day (MOD09A1) products were used for the spatiotemporal quantification of snow cover over the Indus basin and the western rivers’ catchments from 2008 to 2018. The high-resolution Landsat Enhanced Thematic Mapper Plus (ETM+) was used as a standard product with a minimum Normalized Difference Snow Index (NDSI) threshold (0.4) to delineate the snow cover for 120 scenes over the Indus basin on different days. All types of errors of commission/omission were masked out using water, sand, cloud, and forest masks at different spatiotemporal resolutions. The snow cover comparison of MODIS products with Landsat ETM+, in situ snow data and Google Earth imagery indicated that the minimum NDSI threshold of 0.34 fits well compared to the globally accepted threshold of 0.4 due to the coarser resolution of MODIS products. The intercomparison of the time series snow cover area of MODIS products indicated R2 values of 0.96, 0.95, 0.97, 0.96 and 0.98, for the Chenab, Jhelum, Indus and eastern rivers’ catchments and Indus basin, respectively. A linear least squares regression analysis of the snow cover area of the Indus basin indicated a declining trend of about 3358 and 2459 km2 per year for MOD09A1 and MOD09GA products, respectively. The results also revealed a decrease in snow cover area over all the parts of the Indus basin and its sub-catchments. Our results suggest that MODIS time series NDSI analysis is a useful technique to estimate snow cover over the mountainous areas of complex river basins.

Highlights

Snow is a crucial component of the available freshwater resources in the world
The comparison indicates that the overall pattern of both the lakes is good, while there are some disturbances on the borders of lakes, owing to the coarser resolution of the Moderate Resolution Imaging Spectroradiometer (MODIS) products
The Normalized Difference Vegetation Index (NDVI) (≈0.1) and Normalized Difference Snow Index (NDSI) (

Summary

Introduction

Snow is a crucial component of the available freshwater resources in the world. It does hold significant hydrological importance in mid- to high-latitude mountainous areas [1], and dominates the climate over mountainous ranges across the globe [2]. The Indus basin is a complex river basin fed by the Asian Water Tower, which holds several mid- to high-latitude mountainous glaciers and has significant effects on downstream hydrometeorological conditions [9]. The agriculture-based economy of Pakistan is dependent on the waters of the Indus basin and 90% of its flow originates from mountainous ranges of the Karakoram, Hindu Kush and western Himalayas [10]

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