DYNAMICS OF NITRATE, PHOSPHORUS, AND SUSPENDED SEDIMENT TRANSPORT IN TWO AGRICULTURAL STREAMS IN CENTRAL ILLINOIS

Nutrients such as nitrate and phosphorus are necessary for life, but excessive amounts can be detrimental. Large amounts of nutrients entering bodies of water can lead to hypoxic zones such as the one in the Gulf of Mexico. Nutrients are also problematic in drinking water reservoirs, as high concentrations of nitrate in drinking water can cause health conditions such as blue baby syndrome and high phosphorus concentrations can lead to algal blooms. High nutrient concentrations are a recurring problem in the drinking water reservoirs for the City of Bloomington, Illinois where water is drawn from two reservoirs – Evergreen Lake and Lake Bloomington. The primary source for these nutrients is from agriculture, which dominates the land use in the area. To better understand the dynamics of nitrate, phosphorus, and suspended sediment being transported into these reservoirs, water samples are collected at the major tributary for each reservoir - Six Mile Creek for Evergreen Lake and Money Creek for Lake Bloomington. SedEvent, an autosampler system which uses a turbidity threshold sampling method to determine when a rain event is occurring, is used to collect water samples at both tributaries. Water samples are analyzed for nitrate and total phosphorus concentrations using flow injection analysis (FIA). Suspended sediment concentrations are also being examined, as it can be an indicator of pollutants and a means of nutrient transport. There are high nutrient and suspended sediment concentrations and loads in both creeks during or just after rain events, when discharge is high. Nitrate concentrations range from 4.55 to 13.3 ppm, total phosphorus concentrations range from 11.9 to 460 ppb, and total suspended sediment concentrations range from 8 to 4000 ppm. This study will provide the City of Bloomington with information about how much, and when the most nu­trients are entering their drinking water reservoirs and allow them to take the appropriate steps to improve their water management.