Seasonal variations and trend prediction of upstream water quality of Dahuofang Reservoir in Hunhe River

摘要

Dahuofang Reservoir is one of the most important water conservation projects supplying water to the cities of Shenyang and Fushun. Water quality security is the key to protecting the safety of water supply. To determine the current state of the water quality conditions in Hunhe River upstream of Dahuofang Reservoir, a seasonal analysis was conducted on the basis of the water quality monitoring data collected from three storage sections (Beizamu, Gulou, and Taigou) upstream of Dahuofang Reservoir from 2004 to 2012. The Kendall testing method for analysis of possible trends in pollutant concentration variation in the upstream portion of Dahuofang Reservoir was utilized. The results showed that (1) in all seasons and sections, the minimum total nitrogen concentration was 2.1 mg/L, a little greater than grade V water quality standard value 2 mg/L and is gradually increasing over recent years. Therefore, the primary source in need of pollution control is total nitrogen in Hunhe River upstream of Dahuofang Reservoir. (2) Concentrations of ammonia nitrogen and permanganate were 0.694 and 4.2 mg/L in Beizamu section during dry season, which exceeded 38.8% and 5% of grade II standard of National Surface Water Quality (NSWQ), respectively, well above that noted during wet and normal seasons and higher than that found in any other section. Therefore, the predominant pollution control sources are ammonia nitrogen and permanganate index at Beizamu section in dry season. (3) Five-day biochemical oxygen demand (BOD5) in Gulou section during wet season was 3.3 mg/L, which is more than 10% of grade II standard of NSWQ and greater than that of any other section and any other period. Thus, the predominant pollution originates from BOD5 in Gulou section during wet season. (4) All pollution indices of Taigou section were found to be above grade II standard of NSWQ.