Fate of groundwater phosphorus from septic systems near lakes

As lakes become increasingly surrounded by conventional septic systems, it is important to be able to communicate the extent to which these systems will impact a lake’s long-term biological productivity. Previous research suggests a limit to the amount of phosphorus the soil beneath a drainfield can retain, but few studies have shown elevated phosphorus concentrations in lakebed groundwater impacted by septic systems. This project will use novel methods to overcome previous sampling challenges and identify where septic system- impacted groundwater is entering the lakebed. By measuring the phosphorus concentration in that groundwater, we will better understand the impact of septic systems on lake phosphorus loading. Those results will be compared with measurements of phosphorus retention in soils collected near these lakeshores and used to develop an improved methodology for projecting the impact of septic systems on the phosphorus loading to lakes.