Multi Criteria Decision Analysis (MCDA) for Watershed Prioritization

Abstract

River/stream's catchment area, which is the source of endowment for water resource projects, is generally developed without giving much emphasis on protection against soil's erosion from catchment that results into loss of beneficial storage, breach of banks, loss of nutrients and many other environmental problems. The prioritization of sub-watersheds, which are atmost important in developing catchment area treatment (CAT) plan identification of priority sub-watersheds is utmost important in developing any catchment area treatment plan and watershed management activities can help take necessary precautionary measures a-priori. The paper presents the application of Saaty's AHP based Multi criteria decision analysis (MCDA) in prioritizing of vulnerable area of watershed. The analytical hierarchical process based MCDA is a powerful tool that analyzes problems which depend on a number of spatially distributed complex criteria. In the present case, the Saaty's AHP based MCDA tool has been applied to the Kodar reservoir catchment (in Chhattisgarh state in India) using nine erosion hazard parameters (EHPs), which vary spatially and depend on climate, topography, soil, geomorphology, conservation and management practices. For prioritizing the vulnerable areas, the Kodar catchment has been divided into 67 sub-watersheds and analyzed nine EHPs responsible for soil degradation and soil loss in GIS environment using revised universal soil loss equation (RUSLE) model (SL), sediment yield (SY), sediment production rate (SPR), sediment transport index (STI), slope (Slp), drainage density (Dd), channel frequency (Cf), form factor (Rf), circulatory ratio (Rc). To prepare EHPs criteria maps, soil and remote sensing data, topographic information and field knowledge have been used. The normalized values of EHPs and the corresponding weights obtained from Saaty's AHP based MCDA tool have been used to prioritize the sub-watersheds. The results showed, soil loss (SL) occupied the maximum weight of 0.33 and the circulatory ratio had minimum weight of 0.02 at 9.3% consistency ratio (within 10% limit). The priorities of sub-watersheds in the Kodar catchment ranged between 0.12 and 0.74. The normalized priority of 0.74 and 0.12 obtained for SW-44 and SW-41 respectively can be considered as the top and minimum prioritized sub-watersheds for soil conservation measures. The analyzed results could help in developing an implementable CAT plan of the Kodar catchment. The paper also demonstrates a procedure of analyzing EHPs and use of those in MCDA for prioritizing soil erosion vulnerable zones/areas.