Abstract
Abstract. The Himalayan region are home to the world’s youngest and largest mountains, and origins of major rivers systems of South Asia. The present work highlight the importance of remote sensing (RS) data based precipitation and terrain products such as digital elevation models, glacier lakes, drainage morphology along with limited ground data for improving the accuracy of hydrological and hydrodynamic (HD) models in various Himalayan river basins such as Upper Ganga, Beas, Sutlej, Teesta, Koshi etc. The satellite based rainfall have mostly shown under prediction in the study area and few places have are also showing over estimation of rainfall. Hydrological modeling results were most accurate for Beas basin, followed by Upper Ganga basin and were least matching for Sutlej basin. Limited ground truth using GNSS measurements showed that digital elevation model (DEM) for carto version 3.1 is most accurate, followed by ALOS-PALSAR 12.5 DEM as compared to other open source DEMs. Major erosion and deposition was found in Rivers Bhagirathi, Alakhnanda, Gori Ganga and Yamuna in Uttarakhand state and Beas and Sutlej Rivers in Himachal Pradesh using pre and post flood DEM datasets. The terrain data and river cross section data showed that river cross sections and water carrying capacity before and after 2013 floods have changed drastically in many river stretches of upper Ganga and parts of Sutlej river basins. The spatio-temporal variation and evolution of glacier lakes was for lakes along with GLOF modeling few lakes of Upper Chenab, Upper Ganga, Upper Teesta and Koshi river basin was done using time series of RS data from Landsat, Sentinel-1 and Google earth images.
Highlights
IntroductionTraditional methods of measuring precipitation using rain or snow gauges gives accurate and temporal point based estimates of rainfall, but fails to represent spatial variations in precipitation, especially in mountainous regions or river basins such as in Himalayas, where such field instruments are sparse (Bhatt and Nakamura, 2005; Khandelwal et al, 2015; Thakur et al, 2017)
The watershed of basin terrain is stable over longer time periods, whereas, river bed or flood plain is highly dynamic with yearly variations
The satellite based rainfall data is primarily taken from Hydro Estimator Model (HEM), Tropical Rainfall Measuring Mission (TRMM) and Global Precipitation Measurement (GPM) gridded rainfall products
Summary
Traditional methods of measuring precipitation using rain or snow gauges gives accurate and temporal point based estimates of rainfall, but fails to represent spatial variations in precipitation, especially in mountainous regions or river basins such as in Himalayas, where such field instruments are sparse (Bhatt and Nakamura, 2005; Khandelwal et al, 2015; Thakur et al, 2017) In such scenarios, gridded rainfall products from satellites, climate and weather models, re-analysis data and interpolation gauge data have gained significance in the last 20 years and these rainfall products are used extensively in many validation and hydrological studies in Himalayas (Bookhagen and Burbank, 2006, 2010; Shukla et al, 2014b; Thakur et al, 2015; Bharti et al, 2016; Li et al, 2018; Banerjee et al, 2020). Many parts of upper Himalayan river basin have witnessed large scale river bed erosion and deposition during the major flood events of recent past, which have changed their river bed profile in both lateral and longitudinal directions
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