Base flow is measured at Sites 1, 2, and 4a. We used to take a spring and fall base flow survey, but as of 2013, we will be doing only a fall base flow survey. The spring survey was done between May 15 and June 15 and the fall survey was done between August 15 and September 15. Base flow condition will be determined by three to four days of flat line flow at the USGS Flow Monitoring Site at County Road F.
Base flow information is included in the annual technical and summary reports.
Base Flow Determination
Base flow is determined by measuring the flow at specific points (for example at 3-meter intervals) along a cross section of the stream that has been measured for water depth. This data is then entered into the computer and flow is computed.
Base flow is important because impervious surfaces created by development will inhibit water from infiltrating into the ground as it did prior to development. Over time, this will draw down the groundwater elevation, which in turn affects spring activity that feeds the river.
In short, the river's base flow will decrease over time if springs aren't replenished by infiltration; which is why base flow is a key indicator to monitor.