MONITORING OF STRUCTURAL COMPONENTS AND WATER BALANCE AS AN AID TO WETLAND MANAGEMENT USING GEOSPATIAL TECHNIQUES – A CASE STUDY FOR NALSAROVAR LAKE, GUJARAT

摘要

The hydrologic variability greatly influences the structural components of wetlands that have a great bearing on habitats for avifauna, aquatic fauna including fish etc. This paper highlights the results of a study ca rried out to derive changes in open-water and vegetation, and also water balance for Nalsarovar Lake, Gujarat. MODIS 8-day composite data for three consecutive years viz 2002/03, 2003/04 and 2004/05 were used to study the seasonal and inter annual dynamics of water regime in the lake. Digital elevation model derived using Shuttle Radar Topographic Mission data with interpolated bottom topography was used to generate elevation contours and compute water volume from water spread data. The reference data of 2002 (drought year) shows the maximum extent of wetland to be 8.06 km~2 with emergent vegetation of recorded as 2.36 km~2 and open-water as 5.70 km~2. The rainfall has an impact on the preferred habitat availability for various species of avifauna and it is noted that emergent vege tation present in the lake completely dried up by summer 2002, a rainfall deficit year but revived again in the preceding year i.e. 2003 which was a good rainfall year with 46.68 km~2 under emergent vegetation and 61.96 km~2 under open-water. The 2002 being a drought year has shown very low reference storage (0.256 MCM), which has shown a gradual decrease in the storage to 0.00019 MCM in March 2003. The reference storage also registered a steep increase to 18.165 MCM in October 2003 and decreased 1.264 MCM in March 2004. From this study it is evident that water level of about 9 m elevation at the end of the rainy season is found to be optimal for maintaining various habitats that in turn support the avifauna for the rest of the lean period.