| Title |
Application of a Loading Function Model to Estimate Monthly TN and TP Loads in Kyungan Stream Watershed |
| Authors |
유혜진 ( Yu Hye Jin ) ; 박석순 ( Park Seog Sun ) |
| Keywords |
Seasonal load; GWLF model; Kyungan stream; Non-point source; Runoff flow; Nutrients |
| Abstract |
The GWLF (Generalized Watershed Loading Functions) model was applied to the Kyungan stream watershed to estimate monthly nutrient loads. Based on the model structure, the Kyungan stream watershed was divided into 360 grid cells. Each cell had the size of 1,200×1,200 m. The model input parameters were obtained from Digital Elevation Model, Landsat TM imagery, soil map, and published literature on the study area. The model predictions were compared with the field measurements in stream flow as well as in nutrient loads. In most cases, there were reasonable agreements between measurements and predictions, where the coefficients of determination for stream flow, TN, and TP were 0.90, 0.83, and 0 73, respectively. The validated model was used to analyze the seasonal contributions of nutrients according to the types of sources. It was estimated that 7% of TN loads would originate from point sources, 49% from non-point sources and 44% from ground water during rainy season(August), while loads from non-point sources and ground water would be very low during dry season. 46 % of the total annual TN loads was from ground water, 30 % from point sources and 24 % from non-point sources. For land use loads, 14% of total loads were from dry field, 4% from paddy field, 3% from forest and 1% from residential. The contributions of TP loads were more than 90% for non-point sources in August, rainy season, while that of TP loads from non-point sources is very low in dry season. Of the total loads, loads from point sources were 44% and loads from non-point sources were 56% in the annual TP loads. For land use loads, 35% of total loads were from dry field, 11% from paddy field, 7% from forest and 4% from residential. Because nutrients from non-point sources are loaded in rainy season concentrically, appropriate action should be taken for this. In TN loads, contribution of loads from ground water was estimated very high. The results of GWLF model showed reasonable agreement with observed TN, TP loads in Kyungan stream watershed. In summary the GWLF model can be used to quantity non-point source loads effectively. |