Integration of the system of environmental economic accounting-ecosystem accounting (SEEA-EA) framework with a semi-distributed hydrological and water quality simulation model

This research is aimed to map the ecosystem accounting according to the System of Environmental-Economic Accounting-Ecosystem Accounting (SEEA-EA) framework in river-basin scale, while examining the potential of the Soil and Water Assessment Tool (SWAT) in drawing the ecosystem accounting. The focus of the accounting is on the physical ecosystem extent (EEA), condition (ECA), and services (ESA) in the Karaj River-basin, Iran. To analyze the EEA, we attributed the ecosystems based on the Global Ecosystem Typology developed by the International Union for Conservation of Nature (IUCN). Then, the attribute tables of each sub-basin were processed in ArcMap environment to quantify the changes between 2005 and 2010. SWAT model of the study area was calibrated and validated based on hydrological and water quality data to evaluate the ECA and ESA. Furthermore, we assessed the water supply for different purposes among the ecosystem services by employing the SWAT model. This research determined the contribution of water provision by the ecosystem to various uses and beneficiaries, and evaluated the trends and attribution of the changes.

Concerning terrestrial accounts in EEA, the T6.4 (Grassland) ecosystem reduction was the most significant change observed. Also, unmanaged expansions emerged as the predominant factor contributing to changes across various ecosystems. Reviewing the ECA revealed that the T3.2 (Shrubland), T6.4, and T5.1 (Bareland) ecosystems have experienced area reductions of 19.2%, 18.2%, and 8%, respectively, while the T7.3 (Orchard) and F1.1 (Freshwater) ecosystems exhibited approximately 9% and 6% increases in condition. The analysis of the ECA indicated that the decrease in precipitation, particularly snowfall, is the main contributing factor to the deteriorating condition of the terrestrial ecosystems. The examination on the EEA demonstrated a decline in the water supplied by the ecosystems. The findings indicate that incorporating the SWAT model within an ecosystem accounting framework, offers valuable insights to facilitate informed decision-making.