Runoff variation Due to Landuse Change in Small Watersheds of Western Ghats
2022
Abdul hakkim, V.M | Nandakumar, V. | Sajeena, S.
Westerns Ghats form the catchment of all the 44 rivers that sustain the agro-economy of Kerala. A study was conducted to assess the effect of land use on runoff from small watersheds of Western Ghats.. Three small mono-culture watersheds, planted with cashew, coffee, tea and one small watershed with dense forest were selected for the study. Analysis of the rainfall and runoff data indicated that nearly 50% of the total rainfall leaves from the mono-culture watershed as runoff, whereas the runoff from dense forested watershed is only about 30% of the rainfall. The infiltration studies indicated that all these watersheds have high infiltration rates, thereby absorbing even the most intense storms of the study period. The soil analysis indicated that the humus content is high. From the soil profile examination of the study region it was observed taht there exists an impermeable clay layer lying below the laterite with an average thickness of 3.5 m located at 7 to 10.5m below the ground surface. The results lead to the conclusion that the infiltered rain water meets the impermeable layer below and then it flows laterally through the soil. This lateral interflow saturates the valley portion of these watersheds and runoff is generated from these source areas. Thus Hortanian overland flow is a rare phenomenon in the observed watersheds and hence landuse change has no significant effect on the runoff produced by the small watersheds of Western Ghat region.
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