Ecosystem Health Assessment Using a Fuzzy Spatial Decision Support System in Taleghan Watershed Before and After Dam Construction

Developing new and practical methodologies in order to assess ecosystem health based on physical, ecological and socio-economic indicators is an essential field of environmental studies. Nowadays, because of the considerable importance of the spatiotemporal dynamics of ecosystem variables, scientists utilize technologies such as geospatial information systems and remote sensing to achieve different indicators. In this paper, the Taleghan watershed, in Alborz province in Iran was selected as a study area, which has been exposed to many stresses including the construction of a dam in 2007. First, an indicator system based on Driving force-Pressure-State-Impact (DPSI) model was established. Indicators were quantified before and after construction of the dam. At the end, the assessment was carried out by development of a spatial decision support system based on fuzzy analytical hierarchy process method. This system was made for calculating the weights of indicators, compositing the maps of various indicators, producing and displaying maps of DPSI indicators and regional ecosystem health, and identifying critical areas in terms of ecosystem health. The results show that ecosystem health values in the eastern (especially northeast) parts of the watershed (upstream of the dam) and the areas adjacent to the river have been lower in comparison with other areas before dam construction. However, after the dam construction, critical areas in terms of ecosystem health shifted to the downstream region in the western parts. 29.79% of the region in the first period and 23.37% in the second period had a very low and low level of ecosystem health.