Assesing the Water Quality Trading Ratio in the North Bosque Watershed as an Alternative of Maintaining Water Quality

Water quality standard is defined by the level of environment absorptive capacity of pollutants. Total Maximum Daily Load (TMDL) is a program to maintain the water quality in the impaired river segments. Using the Soil Water Assessment Tool (SWAT). The study objective is to assess the possibilities of water quality trading, within the North Bosque Watershed, in term of trading ratios. The model simulation result was not very satisfying, where the calibration of the PO4 has a very high error. For the soluble phosphorus trading, the model cannot be used as the only tool in defining the trading ratio.Keywords: Water Quality, Total Maximum Daily Load (Tmdl), Trading Ratio IntroductionThe North Bosque Watershed (NBW) consists of segment 1226, the North Bosque River, and segment 1255, the Upper North Bosque River. The segments are enlisted in the Texas Clean Water Act (CWA) Section 303(d) List as being impaired, which identifies the insufficient achievement of water quality standard. It implies that water quality standard is defined by the level of environment absorptive capacity of pollutants. One of the concerning pollutant parameters is nutrient as it is being contributed enormously by a Waste Water Treatment Plant (WWTP) discharges as Point Source (PS) and dairies/croplands areas run off as Non Point Source (NPS).The nutrients, phosphorous and nitrogen, of PS can be managed on-site at each plant by controlling the pollutant's level allowed to be discharged also known as Permit Compliance System (PCS). Meanwhile managing the impact of NPS where the pollutant distributed within the watershed is somehow difficult. The amount of nutrient in the streams, which affects the water quality, however is both from PS and NPS. The state of Texas, under the Texas Commission on Environmental Quality (TCEQ) and the Texas State Soil and Water Conservation Board (TSSWCB), maintains the water quality in the impaired river segments by implementing the Total Maximum Daily Load (TMDL) Program