 Ponds are normally not used as stand-alone WSUD measure but are often combined with sediment basins or constructed wetlands as pretreatments.In many cases however, lakes and ponds have been designed as aesthetic features but suffer from poor health which can be caused by lack of appropriate inflows sustaining lake water levels, poor water quality of inflows and high organic carbon loads, infrequent flushing of the lake (too long residence time), and/or inappropriate mixing (stratification) leading to low levels of dissolved oxygen.Bluegreen algae caused by poor water quality and high nutrient levels can be a major threat to the health of lakes.