Site suitability of sub-surface dam for environmental sustainability in mountainous watershed using MCDM approach.

Mountainous watershed faces significant challenges, such as water scarcity during the summer and land degradation in the monsoon season. In these watersheds, water harvesting and conservation are essential for promoting ecological harmony and achieving sustainable development goals. Moreover, the absence of a canal system and the depletion of tube wells exacerbate the situation in hot summers. To address these issues, sub-surface dams offer an effective solution by conserving underground water with minimal evaporation loss, low maintenance costs, easy construction, reduced contamination risks, and no threat to human life. This paper compared multi-criteria decision-making approaches (analytical hierarchy process and fuzzy logic) for proposing sites for constructing the sub-surface dam through surface parameters in the Morni watershed, India. For the selection of parameters, maturity assessment has been performed. The parameters including slope, fault, geology, and land use/land cover were considered as constraints used for site identification, and then comparison was made based on conditional parameters such as climate (annual rainfall), geology (distance from fault, geomorphology), hydrogeology (slope, stream order), and socio-economic (distance from road, distance from agricultural land, distance from village) parameters. Three decision-making techniques were employed: Boolean Algorithm, Analytical hierarchy process, and Fuzzy logic. In the initial step, 1430 sites were identified as suitable for construction using Boolean approach. The overlayed analytical hierarchy process and Boolean Algorithm approach found 68 sites, whereas the overlayed Fuzzy and Boolean algorithm approach found 28 sites appropriate for the construction of sub-surface dam in the research area. The best sites proposed based on their presence on stream order greater than or equal to 3, which becomes 15 sites by the analytical hierarchy process and 12 sites in the Fuzzy approach. The field and online Google map survey were used to validate the proposed sites based on distance from the existing sub-surface dams. From comparing the distance, the Fuzzy approach was found to be more appropriate than the analytical hierarchy process approach for the selection of sub-surface dam construction sites in mountainous watersheds.