Modeling the groundwater fluctuation in Sphagnum mire in northern Hokkaido, Japan

摘要

This research aims to investigate the role of wetland parameters in controlling the response of groundwater level (GWL) towards hydrologic condition and climate condition in Sphagnum mire of Sarobetsu Mire, northern Hokkaido, Japan. Hourly data of GWL, rainfall, and climate of summer for year 1993, 1994, 1997, 2003, 2008, and 2009 are used for modeling GWL fluctuation at point E on the observed area. The GWL modeling in this research adopts the philosophy of Sugawara's tank model, which involved c1 as a function of soil porosity, c2 as a function of rainfall rate, and c3 as a function of soil hydraulic conductivity and slope. Parameter optimization of the model is undertaken by adjusting c1, c2, and c3. The model is quite successful in imitating the behavior of GWL on observed area indicated by average NS value of about 70%. The best-fit model of each year of simulation shows that the value of c1 and c3 is 1.3 and 0.0, respectively. The value of 0.0 for c3 indicates that there is no discharge coming out from the system. The value of c2 varied and depended on the rate of rainfall and evapotranspiration. The research also found that basically c2 is the ratio between rainfall and evapotranspiration. The model also indicates very small or almost no effect of lateral water balance such as lateral inflow from or to other sources on surrounding the observed area.