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Use of Remote Sensing in Ground Water Modeling
Rohit Goyal
Reader
A. N. Arora
Research Scholar
Civil Engineering Department
Malaviya National Institute of Technology, Jaipur
Introduction
Water is vital requirement for the successful raising of the crops. Crops must be supplied with water in the required quantities for their optimum growth, particularly at the critical stages of the crop growth. Irrigation provides crops and plants with water needed for their growth. While the gross irrigation potential is estimated to have been increased from 19.5 million hectare at the time of independence to 95 million hectares by the end of year 1999-2000, further development of substantial order is necessary to meet the requirement of country’s estimated 1390 million population by 2025 AD. Production of food grain would need to be raised from present 208 million tonnes to 350 million tonnes by 2025 AD to meet the food grain requirement.
However development of irrigation potential with canals may also have negative environmental impact. Water percolates down into the ground by seepage from the conveyance system and during application of the irrigation water in the fields. This disturbs the pre-existing natural ground water balance, especially at locations where natural drainage is inadequate due to topographic, soil or other reasons. Accumulation of water causes the rise in groundwater. In the absence of sufficient withdrawal, the rise of groundwater table continues. when water table has risen up to the root zone of the crops, it causes waterlogging, rendering the land unsuitable for further agriculture use. Moreover the salts contained in soil & groundwater are transported into the pore spaces of top soil by capillary action and concentration of salts in this manner causes soil salinity.
Waterlogging and salinity are the major land degradation process that restrict the economic and efficient utilization of soil, land and water resources in command areas. Recent revision of as National Water Policy 2002 also places greater emphasis on drainage and reclamation of waterlogged and saline affected lands. According to the policy, drainage system must form an integral part of any irrigation project right from the planning stage. It also sought to intensify research efforts for prevention of waterlogging and soil salinity and reclamation of already waterlogged and saline lands as well as quantifying and reducing negative environmental impacts of water resource projects.
Literature review
Reliable and accurate mapping of areas affected by waterlogging with its location and extent can be extremely useful in chalking out suitable water management strategies to control waterlogging and also to undertake remedial measures to reclaim already waterlogged land. Remote Sensing techniques have shown immense scope for providing a quick inventory of waterlogged area & its monitoring (Sahai et. al. 1982 & Sidhu et. al. 1991). Choubey (1996) stated that a rapid and accurate assessment of the extent of waterlogged areas can be made using remotely sensed data. He determined the waterlogged area in IGNP Stage I from IRS IA LISS II FCC imageries of April 19, 1989 and October 12, 1989. Attempt was also made to correlate the IRS-1A derived waterlogged area with the available water depth and electrical conductivity data to assess the area sensitive to waterlogging.
Sharma (1996) has stated that remote sensing and geographical information system (GIS) can be used separately or in combination with hydrological models. In his study of Arides Mountains, Argentina he has used all the techniques remote sensing, GIS and hydrological modeling successfully. With the aid of these techniques, it is possible to develop better regional model of hydrological processes in a drainage basin.
Arora & Goyal (2002) discussed various causes of waterlogging in IGNP Stage I as high water allowance, excessive seepage from canals, continuous ponding of Ghaggar depressions, lack of use of ground water for irrigation and absence of natural drainage outfall, etc. They concluded that a comprehensive socio-economic survey must be undertaken to visualize negative socio-economic aspects of waterlogging.
Arora & Goyal (2003) highlighted the use of geographical information system (GIS) in development of conceptual groundwater model. Various layers of information such as canal network, recharge zones, subsurface geology and digital terrain model (DTM) of Hanumangarh and Sriganganagar districts were developed in GIS and were then transferred to finite difference grid for developing mathematical groundwater flow model of the area.
Study Area
Indira Gandhi Nahar Pariyojna (IGNP) is one of the largest irrigation and drinking water projects of northwestern Rajasthan. However Hanumangarh and Sriganganagar districts are facing severe waterlogging and salinity conditions since the introduction of the IGNP canal system in that area. Study has been undertaken for this area with the purpose of developing mathematical groundwater model of the area. A greater insight into the reasons of waterlogging and soil salinity in the area and the methodologies to be adopted for its control can be achieved with the help of mathematical model being developed.
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