Hydrological Study of Tanks in an Urban Sub-Basin

Abstract

In urban areas, tanks are the major means for harvesting surface water as most of the land surfaces are found to be paved. But these tanks experience significant decrease in their water spread area and storage capacity owing to rapid urbanization. Thus, hydrological study of these tanks would serve as an effective key to monitor, conserve and maintain them effectively. Manimangalam tank along with cluster of tanks located in the upstream catchment of Adyar river basin, Tamil Nadu has been selected for the study. SCS-CN method has been used for estimating the daily run off volume generated. The land use-land cover map (LULC) for the year 2000 and 2015 (before and after the onset of urbanization process) has been prepared using the satellite images and Geographic Information System (GIS) tools. The overlay analysis was carried out with the LULC map and hydrologic soil map and unique hydrologic response units were identified. The weighted curve number was calculated for antecedent moisture conditions I, II and III respectively. The initial abstractions and daily runoff occurring within the individual tank catchments were calculated for the selected years between 1980 and 2016. The impact of urbanization on the rainfall – runoff processes over the years that have taken place within the study area has been assessed.