Using the EFDC model to evaluate the risks of eutrophication in an urban constructed pond from different water supply strategies

Managers of urban lakes are faced with the challenge of finding a balance between saving water resources and preventing eutrophication. One way to address both of these issues is to use the unconventional water source s such as stormwater and reclaimed water to maintain the water supply in urban constructed ponds. We validated and calibrated the Environmental Fluid Dynamics Code and then evaluated the risks of eutrophication from various water supply scenarios, such as different proportions of stormwater (SW), reclaimed water (RW), and tap water (TW). We found that the different types of water influenced the nutrient or Chla levels in the constructed ponds, but that there was little difference between different hydrological years. The range of the trophic state index in the study pond increased from 5.55% to 68.17% in the urban ponds as the proportion of RW increased from 0% to 100%. Stormwater collection strategies had a clear effect on the trophic state of TW-fed ponds but not of RW-fed ponds. Using an index that integrated the eutrophication risks, eutrophication state, and economic costs, we found that the optimal water supply strategy was to collect treated SW and use TW to replenish the water supply.