Abstract:
The nature, characteristics and the extent of area covered under waterlogging and salt affected soils vary depending upon the climate. topography. surface hydrology, irrigation and cropping practices, geohydrology etc.
Irrigation projects involving inter basin transfer of water without adequate drainage has disrupted the equilibrium between the around water recharge and discharge resulting in accretions to the ground water table. This is the major cause for waterlogging and secondary salinisation in various irrigation commands.
Although Precise estimation on the magnitude of the problem are not known but the available information projects heavy socio-economic losses. Several thousand hectare areas need adequate drainage to Prevent or reclaim degraded saline soils in different
irrigation command areas in India. At least 20 to 30 thousand hectare of irrigated land is lost every year due to waterlogging and salinisation.
The National Commission for Irrieation (1972) and National Commission on Agriculture (1976), Ministry of Agriculture (1985) renorted waterlogged area in India is 4.84,6.00 and 8.53 m.ha respectively. However Ministry of Water Resources (1991) has estimated 2.46 m.ha waterlogged area. NCA (19761 has estimated 7 m.ha salt affected area, out of which 2.5 m.ha is under alkali soil and 4.5 m.ha under saline soil. Ministry of Agriculture
(19851 estimated this area to the extent. of 9.08 m.ha,which include 3.58 m.ha alkaline and 5.50 m.ha under saline soils including coastal areas. The recent estimate (MOWR 1991) indicates 3.06 m.ha and 0.24 m.ha under saline and alkali soil respectively in command areas.
There has been no systematic survey so far in order to firm ur, the total area affected by waterlogging and salinity. Future soil survey in different states, if properly organised may brine. Out more waterlogged and salt affected areas. A rapid and accurate assessment of the extent of affected areas can be made from using remotely sensed data. Results of the studies undertaken in the country so far, clearly demonstrate the usefulness of remote sensing techniques in detecting and monitoring waterlogged and saline/alkaline soils.
