Changes in streamflow regime as indicator of upstream urbanization in a humid tropical river basin



Changes in streamflow in the Meenachil river basin, Kerala, are assessed at two upstream gauging stations located at Palai and Cheripad and one downstream gauging station at Peroor to understand changes in flows due to upstream urbanization. An increase of 14% in the population and 46% in the number of housing units have been observed in the entire study area during the last two decades, indicating increase in urbanization. Time series analysis of 29 years data shows an increasing trend at Peroor at 2.8% per year for total flow and 5.2% for peak flow, which indicates the effect of urban land use. There has been a decreasing trend in the flows at 2% at the upstream gauging stations of the river basin. The frequency of occurrence of flows are observed to be increasing at Peroor due to urbanization which brings down vegetation, enhances the impervious area and contributes to fast draining of stormwater. The decrease in both the flow and its frequency of occurrence at the upstream stations are due to the increase in area under plantation crops and also the soil and water conservation works attempted in the area. Copyright © 2011 Royal Meteorological Society