Application of TOPMODELs for Assessment of Ecosystem Services: Regulating Service in Agricultural and Forest Watershed

Abstract

According to Millennium Ecosystem Assessment, ecosystem services are divided into four services. Among them, regulating services include water regulation and natural hazard regulation which regulate water-discharge to rivers and mitigate flood risk by forest ecosystem. This research investigated characteristics of river flow changes at the time of rainfall runoff in two different land-use types, i.e.,1) watershed forest in Soebethu river watershed in Hokkaido and 2) intermixed watershed forest and pastureland in Igarashi river watershed in Hokkaido. A semi-distributed hydrological model, TOPMODEL was applied to simulate the amount of water discharge to the rivers. The conventional TOPMODEL was applied to the watershed forest, and the developed version of TOPMODEL to the intermixed watershed and pastureland. Monte Carlo simulation was used to identify unknown parameters required for the simulation. By comparing the identified parameters in the two different watersheds, flood control effect was evaluated in both land-use watersheds and each watershed and pastureland separately in the intermixed land-use. As the results of comparing the unknown parameters between the different land-use in the intermixed watershed and pastureland, the model showed that watershed forest has higher regulating service than pastureland. In addition, the research found that the difference of the type of surface soil influenced the amount of water discharge, that is, flood control effect. As the consequence, TOPMODEL was applicable for quantitative assessment of water regulation: the regulating service of the forest ecosystems.