[Effect of Check Dam on Phosphorus Transport and Retention in the Qingshui River, in Zhangjiakou City].

Abstract

The transport and retention of phosphorus is a key process in nutrient cycling in river ecosystems and one of the main indicators used to evaluate river health. To explore the effect of check dams on the transport and retention of phosphorus, water samples were collected from four representative monitoring sections of a check-dammed reach of the Qingshui River in Zhangjiakou City. Various forms of phosphorus and runoff process were monitored, and local real-time rainfall data were also collected. The results showed that:① The average concentration ratios of total phosphorus (TP), total dissolved phosphorus (TDP), total particulate phosphorus (TPP), and total suspended solids (TSS) downstream to upstream of the dam were 50%, 79%, 47%, and 58%, respectively, indicating that the check dam has a retention effect on phosphorus and sediment. ② During non-rainfall periods, TP, TDP, and TPP were retained in the check dam reach, while these forms of phosphorus were both retained and transported in the check dam reach during period of rainfall; the ratio of TP, TDP, and TPP retaining rainfall events to total rainfall events was 63.6%, 9%, and 81.8%, respectively, indicating that the transport-retention process was affected by the time interval, duration, and intensity of rainfall events. ③ When a single rainfall event or continuous event exceeded 56 mm, the retention effect of the check dam notably decreased.