Abstract:
Water resources are affected by development activities and land use change which is undeniable
and most significant. Land use change can alter the hydrology of a watershed. The present study
has been carried out for Rawal and Simly Dams ‘watershed. This study analyzed the historical
land use changes which had taken place in catchment area for the period 1975-2012 (38 years)
for Rawal Dam and for period of 1983-2012 (30 years) for Simly Dam. The main objectives of
this study were to identify the land use change pattern over time, to obtain land use information
from satellite imagery classification using GIS and Remote Sensing and to analyze its effects on
rainfall-runoff and runoff-sediment relationships for the catchment areas of Rawal and Simly
Dam. In this study the catchment area of the Rawal and Simly Dam was delineated on
topographic sheets and using Planimeter the catchment area of Rawal Dam was computed as270
km2 and the catchment area of Simly Dam was computed as150km2. Using digital elevation
model the catchment area of Rawal Dam was computed as 272.8km2 and Catchment area of
Simly Dam as 153.5km2.To check the effect of land use changes on rainfall-runoff and runoffsedimentation
relationship for Rawal and Simly Dam Double Mass Curve analysis was
performed. Double Mass Curves with trend curves of annual rainfall-runoff, Monsoon month’s
rainfall-runoff were drawn for both Rawal and Simly Dam site. It can be concluded that slope of
the trend curve is changing for both Rawal and Simly Dam, which shows that land use changes
have affected the rainfall-runoff and runoff-sedimentation relationship. To quantify land use
change in catchment, the satellite imageries of 1992, 2000 and 2010 were used. The
unsupervised classification was performed and 6 land use classes water body, forest, vegetation
& agriculture, rangeland, built-up area and bare land were made. Land use analysis of 1992-2010
for Rawal catchment has shown 2.4 km2decrease in water bodies’ area, 13.6km2 decrease in
forest area , 37.4km2 decrease in vegetation and agriculture, 28.3km2 increase in range land,
16.6km2 increase in built up area and8.5km2increase in bare land. Similarly land use analysis of
Simly Dam from 1992-2010 has shown 0.6 km2 decrease in water bodies area ,18.7 km2 decrease
in forest, 4.1km2 decrease in vegetation and agriculture,6.8 km2increase in rangeland,6.5km2
increase in built-up area and10.1km2 increase in bare land. It is recommended that more
meteorological stations should be installed in both catchments to monitor meteorological
conditions, sediment data should be collected on yearly basis. GIS and remote sensing with
Double Mass Curve Analysis should be used for watershed management.
