Long-term water balance of a bare soil with slope in Chuncheon, South Korea

Water balance components of a bare soil with slope varying from 5% to 30% in Chuncheon, South Korea, were simulated using the E-DiGOR model, which proposed an interactive way to quantify runoff, drainage, soil water storage, and evaporation. Daily computations were carried out during the period of 1980 to 2009 for the identified soil-topography-climate combination. A strong correlation between measured pan evaporation and calculated potential soil evaporation was observed (R2 = 63.8%, P 0.01) based on the monthly data of the past 30 years (hereafter ‘long-term’). When examining long-term dynamics of simulated soil evaporation, monthly mean potential and actual soil evaporations ranged from 9.1 and 9.0 mm in December to 110.5 and 75.2 mm in June and July, respectively. The ratio of actual to potential soil evaporation (Ea/Ep) had a close linkage with soil water content. The higher the soil water amount, the greater the Ea/Ep ratio was. A nonlinear relationship between rainfall and surface runoff was obtained at a given slope. Excess surface runoff and subsurface flow (percolation + interflow) occurred throughout the rainy months from July to September, with peaks in July. The ratio of direct surface runoff to rainfall increased with the natural logarithm of slope. The long-term mean annual direct surface runoff and subsurface flow at the maximum slope were 408.1 and 437.6 mm, respectively. Furthermore, mean annual surface runoff from the slope of 30% was approximately 2 times higher than that from the slope of 5%.Ağrı İbrahim Çeçen Üniversitesi