Potential Zones of Peruvanthanam and Valiyathodu Sub-Watersheds of Manimala River Basin

Groundwater is a dynamic and replenishable natural resource. But in hard rock terrains, its availability is of limited extent. In sub-watershed studies, remote sensing and GIS techniques have the advantages of spatial, spectral and temporal data, covering large and inaccessible areas within a short span of time. Thus this technique has become a very handy tool in assessing and monitoring groundwater resources. Multi Criteria Evaluation Technique (MCE) by integration of the thematic maps such as Geomorphology, Geology, Land use/Land cover and Slope prepared from conventional and remote sensing techniques using GIS yield more and near accurate result. The groundwater potential zones are classified in to five zones viz, ‘excellent to very good’, ‘very good to good’, ‘good to moderate’, ‘moderate to poor’ and ‘poor to very poor’. Critical analysis and comparison of ground water potential zones of both sub-watersheds reveals that, 26.10 km² (47.58%) area of Valiyathodu sub-watershed fall under ‘excellent to very good’ category where as in Peruvanthanam sub-watershed it is 7.69 km² (13.64%). In Peruvanthanam sub-watershed, ‘very good to good’ category covers 14.87 km² (26.35%), ‘good to moderate’ covers 17.65 km² (31.28%), ‘moderate to poor’ covers 11.62 km² (20.59%) and ‘poor to very poor’ covers 4.59 km² (8.14%). Where as in Valiyathodu sub-watershed, ‘very good to good’ category covers an area of 18.55 km² (33.82%), ‘good to moderate’ covers 6.65 km² (12.12%) and ‘moderate to poor’ covers 2.43 km² (4.43%) and ‘poor to very poor’ covers 1.12 km² (2.05%). Hence it is explicit that, in general groundwater potential is better in Valiyathodu sub-watershed compared to Peruvanthanam sub-watershed.