Assessing watershed sustainability using the watershed sustainability index (Case study: Bujin watershed in Hamadan province)

Introduction In many regions, ecosystem sustainability and environmental security have become more fragile. Because watersheds are dynamic systems, their hydrological function and health are constantly changing under the influence of land use, climate change, and human interventions. Since the destruction of the ecosystems of a watershed has harmful economic and social consequences, in recent decades there has been a general tendency to evaluate the relative conditions or health of watersheds on a national and local scale. Ecologists have paid special attention to the study of how natural resource ecosystems respond to different types of stress caused by human activities. The watershed sustainability index (WSI) can be considered as an effective tool in watershed management including priorities monitoring changes and influencing factors on ecosystem management. In recent years, various studies and plans have been conducted to preserve natural resources and achieve sustainable development. The sustainability of watersheds includes four important goals of regulating the water flow regime, maintaining and improving water quality, maintaining the ecological quality of plants and animals, and energy resources. In this context, the pressure-state-response (PSR) model has been introduced and used for a comprehensive assessment of the health of an ecosystem. The conceptual model of PSR was developed using a set of criteria expressing environmental performance. This study aimed to evaluate the sustainability level of the Bujin watershed. Materials and methods One of the methods for evaluating watershed sustainability is the use of the conceptual pressure-state-response model (PSR). Applying the causal-effect PSR model using theWSI criteria in the form of four sub-criteria of hydrology (qualitative and quantitative), environment, life, and policy-making, one can evaluate the sustainability of the watershed numerically. In this method, considering the available data and information to investigate each sub-criteria, the parameter values are determined in three modes of pressure, state, and response, and in the scoring range from zero to one, five categories are converted to quantitative mode. Therefore, the PSR framework has three types of criteria: pressure criteria that evaluate environmental pressure resulting from human activities (waste, sewage), and state criteria that express environmental conditions (water quality). and the response criteria that evaluate the