RELATIONSHIP BETWEEN RAINFALL RATES AND LAG TIMES OF PEAK DISCHARGE AND TURBIDITY

During rain events, water accumulates into river systems over a period of time affecting the discharge and turbidity of these systems. Because of the addition of water into rivers, discharge and turbidity are increased, potentially leading to flooding and reducing water quality. Understanding the relationship between the lag time of the rainfall event and peak discharge and turbidity could improve water quality management. In this study, we explored how different rates of rainfall in rain events would affect the variance in lag time of peak discharge and turbidity in an agricultural watershed in central Illinois. Six Mile Creek flows into a drinking water resevoir that is used by the city of Bloomington. A stream monitoring station collected rainfall, discharge, and turbidity data at every 15 minutes intervals. We calculated the rate of rainfall for different rain events as well as the lag time between the peaks for each of the variables. We found a general trend in rainfall rate and lag time being negatively correlated variables. The weak relationship with rainfall and high variations in lag times of discharge and turbidity may be related to agricultural land use practices.