Assessment of water quality conditions in the St. Louis Bay watershed

Abstract

The water quality data from 14 sampling stations in the St. Louis Bay watershed were analyzed to evaluate the water quality conditions. The differences in water quality parameters between base and storm flow events were compared to identify the pollutant sources. The results indicated that fecal coliform was the primary cause for water quality impairment of the study area. The overall water quality conditions were good in terms of dissolved oxygen, eutrophication, and total suspended solid (TSS). The dominant sources of bio-chemical oxygen demand (BOD) could be from the failing septic system; the majority of the water samples exceeding Mississippi Department of Environmental Quality (MDEQ) target levels were from base flow events. Different from BOD, the majority of the water samples exceeding the water quality criteria and MDEQ target levels were from the storm events for fecal coliform, chemical oxygen demand, total organic carbon, TKN, NO₃, NH₃, chlorophyll a, and TSS. Based on cluster analysis, the sampling stations were classified into two major categories: upstream and near-coast stations. The major differences between upstream and near-coast stations are elevation, soil texture, and impacts of human activity. The results from this research would provide useful information for total maximum daily load calculation, development of a computational watershed model, and development of best management practices for the St. Louis Bay watershed and similar study area.

Keywords:

• Water quality assessment
• spatial variation
• base flow events
• storm flow events

Acknowledgments

This work was supported by the Mississippi Department of Environmental Quality (MDEQ), and Office of Pollution Control, Environmental Protection Agency Gulf of Mexico Program Office (GMPO).

Notes

* MPN is Most Probable Number.