Long-Term Trends of Water Quality in Upstream of Daling River in China

Abstract

Long-term trends and spatial patterns of water quality at 5 stations in the upstream of the Daling River basin of North China were examined for 5 parameters—pH, suspended sediment (SS), dissolved oxygen (DO), permanganate demand (CODMn) and biochemical oxygen demand (BOD5). Analysis determined the trends of parameters of each station between 1987 and 2007. The variations in permanganate demand and biochemical oxygen demand showed increasing trends and the variations in dissolved oxygen were decrease in 1990s. Multi-year average values of permanganate demand and dissolved oxygen in Chaoyang station and Jianping station were 2.8 mg/L, 37.6 mg/L and 9.6 mg/L, 6.1 mg/L, respectively. The parameter characteristics of water quality in flood and dry season showed significant heterogeneity at main stream and tributary. Correlations between parameters were analyzed using a regression analysis method. The correlations of each parameter determined there were linear negative correlation between dissolved oxygen and permanganate demand, dissolved oxygen and biochemical oxygen demand at Habaqi station, Dachengzi station and Chaoyang station. The permanganate demand and biochemical oxygen demand was significant positive correlation in 3 stations.