SENSITIVITY TO SECONDARY SOIL SALINISATION : AN ASSESSMENT USING REMOTE SENSING AND GIS V.K. Verma, P.K. Litoria, Anil Sood, P.K. Sharma and Charanjit Singh Punjab Remote Sensing Centre PAU Campus, Ludhiana-141004 Phone : 2478484 Fax : 2478483 E-Mail : vip_verma@rediffmail.com litoria_pk@rediffmail.com ABSTRACT Secondary salinisation is the most harmful and extended phenomenon among the unfavourable effects of irrigation on the soils and environment. In order to predict the long term effect of ground water use on the soils, the soils and ground water quality maps of Muktsar district, Punjab were prepared, digitsed and integrated using ArcInfo GIS to generate an integrated map showing varying degrees of relative sensitivity to secondary soil salinisation. The map depicts eight mapping units indicating fine textured soils as highly sensitive(14% of TGA), medium textured soils as moderately sensitive (38%), coarse textured soils as less/low sensitive(10%) and the soils with good ground water as non- sensitive(37%) to secondary salinisation. The study indicates that 62% area is prone to secondary salinisation if ground water alone is used for irrigation, unabatedly. The causes of secondary soil salinisation have also been discussed. INTRODUCTION In recent years, there has been a great deal of emphasis on irrigation in arid areas and in consequence, the scope of exploitation of ground water resources has been very much enlarged. In an arid environment the accumulation of salts in the soil is faster under irrigation than under non-irrigated conditions. Therefore, by far the largest proportion of saline soils have developed under the influence of irrigation(USSR-UNEP Project, 1982; Shainberg and Shalhevet, 1984). Until now, the influence of the geochemical and hydrogeochemical processes have been under- estimated in many places. Although reports of studies on quality parameters for irrigation water is available, the effect of ground water on soil salinity is often left out of consideration. Neither do we have upto date information on the extent of potential salt affected soils. Potential salt affected soils are those which are non-saline or non- alkaline at the moment but may be salinised by irrigation. Survey of potential salt affected soils has been conducted in some European countries but such type of studies are lacking in India. Unfortunately, no such studies are available on the prediction of sensitivity to secondary soil salinisation resulting from the use of brackish ground waters for irrigation. The Muktsar district in the arid tract of Punjab experience problems of water logging, changing hydrological regime, soil salinity, declining yield of crops etc. In order to address the problem of water logging, changing hydrological regime, soil salinity, an attempt was made to predict the relative sensitivity of soil salinisation as a consequence of application of ground water for irrigation.