Land Degradation Modeling in Dal lake Catchment

Soil erosion is a complex dynamic process by which productive surface soils are detached, transported and accumulated in a distant place resulting in exposure of subsurface soil and sedimentation downstream. Soil erosion in catchment areas and its subsequent deposition in rivers, lakes and reservoirs are of great concern to humanity. The soil erosion upstream results in the loss of reservoir capacity as well as degradation of water quality downstream. Picturesque fresh water lakes in Jammu & Kashmir, particularly the well known Dal Lake in Srinagar, is facing eutrophication problem due to soil erosion in the catchment area. The Dal Lake is of great tourist and economic importance for the people of the Kashmir valley. The Dal Lake which has shrunk in dimensions, from 25 sq. km in past century to less than 11 sq. km now is fighting a loosing battle against rampant pollution and sedimentation. As a pilot study, the Dal Lake watershed spread over an area of 337 sq. km was taken up for soil erosion study using remotely sensed data, GIS and simulation modeling. The study utilized different types of data including Survey of India topographic maps for generating DEM of 40 meter resolution, soil map, Landsat TM & ETM satellite data and the field observations. Two date Landsat image, 1992 and 2001, were used for generating the land use/land cover map of the study area and to detect the changes between these two time periods. The various land use and land cover classes identified include agriculture, orchards, plantation, mixed forest, evergreen forest, degraded forest, Built up, meadows, lake vegetation, pasture, river boulders, clouds, shadow, bare rock, fallow, barren and open water. The classes dominating in Landsat 1992 are mixed forest (20.26 % area), degraded forest (11.75 % area), plantation (10.52 % area) and pasture (9.01 % area). Agriculture and built up covers 5.93 % area and 1.68 % area respectively. In Landsat 2001 the dominating classes are mixed forest (20.42 % area), pasture (10.18 % area), degraded forest (10.12 % area) and plantation (9.54 % area). Built up and agriculture covers 6.21 % area and 3.53 % area. The Kinematic Runoff and Erosion model KINEROS2, was used for evaluating the effect of land use/cover change on runoff and erosion. Surface runoff, peak sediment discharge and total sediment yield were simulated using the KINEROS2. The results show; 0.3 (mm) 0.27 (mm) min. increase in runoff, 400 (kg) – 5000 (kg) average increase in peak sediment yield, 2500 (t/ha) – 3000 (t/ha) average increase in sediment yield in Planes & Channels respectively from 1992-2001. The results have identified areas where runoff and erosion are increasing as well as areas where the production of these processes have decreased (though marginally). It is hoped that these results would facilitate the prioritization of the micro-watershed in the catchment so that corrective and mitigation measures are taken to arrest the land degradation in the watershed.