Eutrophication model driven by light and nutrients condition change in sluice-controlled river reaches

Abstract

River eutrophication has become a challenging environmental problem worldwide because of the strong interference of anthropogenic activities and hydraulic structures. The driving mechanism of algae growth in sluice-controlled river reaches (SCRRs) is more complicated than that of natural rivers, because the operation mode of the sluices is an important influencing factor which changes the light and nutrient conditions of the water body. The main purpose of this study was to assess algal growth in SCRRs under external conditions and sluice regulation. In this study, a eutrophication model for SCRRs was developed based on the mechanism of river hydrodynamics and algae growth kinetics, considering the variation in underwater light intensity and nutrient condition. By choosing the light intensity, phosphorus concentration and sluice gate opening size as the influencing factors, 16 different combination conditions were proposed by orthogonal experimental design, and eutrophication of water bodies in the SCRRs was simulated using a eutrophication model. In the scenario design, four gate opening sizes were set, and the light intensity and nutrients were enlarged or reduced based on the original monitoring data. The results showed that both light intensity and nutrient concentration can promote the algal growth within a suitable range, and increasing the gate opening size can inhibit algal growth.

Keywords: Eutrophication; Light intensity; Nutrients; Scenario analysis; Sluice-controlled river reaches.