Effect of in-stream impoundment on water quality of a suburban stream

This study aims to confirm the effect of a small stream impoundment on phosphorus and nitrogen dynamics in a suburban watershed. The results show that the phosphate concentration in the water body was significantly higher than that in the inflowing water under ordinary flow conditions. The phosphorus promotes algal growth that causes significant diurnal dissolved oxygen variation because of photosynthesis and respiration. The phosphate exchange between the sediment and overlying water was mainly controlled by diffusion flux rather than by advective flux seepage because of large amounts of phosphorus accumulated on the surface of the sediment. When a flood occurs, the phosphorus-enriched water is flushed downstream by rain-swollen currents. In summary, an impoundment affects in-stream phosphorus concentration through organic matter degradation and the release of phosphate in the sediment.