Estimation of surface water quality in a Yazoo River tributary using the duration curve and recurrence interval approach
Pollution of surface water with harmful chemicals and eutrophication of rivers and lakes with excess nutrients are serious environmental concerns. This study estimated surface water quality in a stream within the Yazoo River Basin (YRB), Mississippi, USA, using the duration curve and recurrence interval analysis techniques. Data from the US Geological Survey (USGS) surface water monitoring station located in Deer Creek east of Leland from the YRB were selected for the analysis. Results showed that the water quality constituents, namely water temperature, specific conductivity (SC) and dissolved oxygen (DO), in this stream were found not to be the major concerns as the percentages of the time when these constituents did not meet their criteria were very low. Our results further revealed that the water temperature and SC increased as time elapsed, indicating the potential global warming and contamination impacts in this stream. In contrast, the DO and pH decreased as time elapsed, postulating a potential increase in biochemical oxygen demand and an acidic trend in this stream. Over the last decade, the average recurrence intervals when the water temperature, SC, and DO did not meet their criteria or minimum conditions were around 1 year. Using a target DO value of 429 kg d-1 proposed by the Mississippi Department of Environmental Quality, results from this study showed that there was about 25% of the time when the DO load did not meet the target value. This study suggests that the duration curve and recurrence interval analysis techniques are useful statistical tools for water quality trend estimation.