Hydrosphere
SAC carries out studies related to land hydrological modeling and applications. It involves retrieval of hydro-meteorological parameters from satellite and modeling of Hydrological Processes from field to National scale. Timely and reliable assessment of available water resources through satellites and models provide important input to devise strategies and water management in the country. Some of the studies of national importance are described below:



Surface Runoff modelling: A National scale surface runoff modeling was done using the modified curve number model. Rainfall, soil texture, land cover types, slope etc. were processed at grid cell size of 5x5 km. It was estimated that on average 33.8% of the rainfall got converted to the surface runoff considering the 35 years period (1971-2005). Changes in runoff provide valuable information for understanding the region's sensitivity to climatic variability.

Radar Altimetry for Inland water bodies: SAC utilises Saral-Altika satellite data regularly in near real time to monitor water levels in different rivers (Ganga, Godavari, Brahmaputra, Gandak, Kosi, Yamuna, Son, Ghaghara etc.) as well selected major reservoirs/Lakes (Ukai, Ranapratap, Bandhsagar, Gandhisagar, sambhar Lake etc.). Also, retrieved river water levels are being used for river flow modeling and other applications.

Flood and Hydrological Drought: Incessant rainfall in the hilly regions of North Gujarat and Rajasthan borders created flood situation during 25-29 July, 2015. Inundation simulations were done using the hybrid technique (coupling CN and 2D-overland flow models) and integrating remote sensing derived products such as rainfall, Land cover and DEM. Flood wave was detected in Brahmaputra river on 9 June 2015 using SARAL-Altika data. A detailed study on Ukai reservoir using SARAL-Altika data revealed lowest water levels in April 2016 as compared to previous years during same period.

Water Quality: Information contained in remote sensing imagery is used to accurately quantify water quality constituents. Water quality refers to water property in terms of physical, chemical and biological characteristics. Pollutants in water surface changes the spectral signature of surface water. Field campaign was carried out in Feb. 2016 to establish the spectral signature of water in Ganga river, near Buxar, Bihar under AVIRIS-NG Program. Water simulator model is being developed to simulate the reflectance spectra at different water quality conditions.

Effects of Depleting Ground Water: Over exploitation of ground water in Punjab and Haryana region has been reported by several studies using the satellite based gravity anomaly from GRACE mission and also using observed data. This decline in groundwater has enforced change in the irrigation practices which have been captured using the multi-year passive microwave (AMSR-E) soil wetness analysis. Study showed an overall 18-20 days delay (152 Julian day to 172 Julian day) in irrigation practices (in absence of rainfall) in the region during 2002 to 2011.