Abstract
A distributed water quality tank model was developed to evaluate nitrogen load reduction by artificial wetlands in the A10 area, located in the Lake Kasumigaura watershed in Japan. In order to collect data for model calibration and verification, a year-long field investigation was conducted. The study area was divided into a 50 m × 50 m grid, and attributes and the model are added to each cell. The model simulates the runoff and the total nitrogen (TN) concentration with average relative errors of 10% and 2%, respectively, except for no-rain periods. Scenario analyses were conducted considering artificial wetlands at different locations. The three scenarios are as follows: no artificial wetland, cell located at the head of the valley and cell located on a flow path through animal waste cell. Compared with case 1, the annual TN concentration was lower by 4% and 11% in cases 2 and 3, respectively. The results suggest that artificial wetlands on water flow paths with a large nitrogen load effectively reduce these loads and that the model quantitatively evaluates the difference in the nitrogen concentration across locations.
