WATER QUALITY MODELING OF AN AGRICULTURAL WATERSHED WITH BEST MANAGEMENT PRACTICES

Abstract

Simulation of Best Management Practices (BMPs) affecting water quality is necessary while modeling the water quality of agricultural watersheds with BMPs in place to mitigate pollution of river. Previous studies explored methods to represent some of the water quality BMPs. However, there are still gaps in the research to represent some other BMPs such as constructed wetlands, wastewater reuse, residue management and nutrient management. This paper focuses on modeling of BMPs affecting water quality. The study area is a 1692 Km 2 cultivated watershed in South Texas, USA where water quality is impaired for dissolved oxygen (DO). The water quality constituents analyzed for the study are sediment, nitrogen, phosphorus, water temperature and dissolved oxygen. Apart from identification of methodology to simulate BMPs, this study estimated extent of pollution mitigation by each type of BMP. Binomial method of water quality analysis was used to judge the compliance of river reach for meeting DO criterion. This manuscript will discuss modeling of water quality constituents and the BMPs that affect water quality. In addition, the estimation of dissolved oxygen compliance of the watershed is also discussed. The results from the study indicate that the agricultural BMPs implemented in the watershed and establishment of stringer water quality criteria have in fact improved the DO trends in the tidal section of the river, which did not meet the stipulated DO criterion before.