Effects of forest on stream water quality in southeast China

Seasonal effects of forest stream and rainfall on the nutrients-pH, the biochemical oxygen demand (BOD), chemical oxygen demand (COD) and dissolved oxygen (DO), total nitrogen (TN), total phosphorus (TP) and ammonia nitrogen (NH3-N) in Huangongwan forest park was monitored monthly during January to December 2009. Lower concentrations of BOD, COD, TP and NH3-N were found in forest stream compared to that of rainfall. The concentration of TN was higher in the forest stream across different months than that in rainfall. The annual average values of DO, BOD, COD, NH3-N, TP, TN and pH were 8.10 mg/l, 1.60 mg/l, 1.77 mg/l, 0.13 mg/l, 0.01 mg/l, 7.68 mg/l and 4.79 respectively. These results showed that the water quality of rainfall was improved significantly after purifying through forests ecosystem. Except for TN and pH values, other water quality indicators in forest stream were superior to Grade I national water quality standard.