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:
![](/web/20170618020212im_/http://sac.gov.in/SACSITE/images/H1.gif)
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.