The District has identified seasonal low, medium and high flow periods for the Upper Hillsborough River. Short-term minimum flow compliance standards were developed for each of these periods using a "building block" approach. The Minimum Low Flow for the low flow period (Block 1, April 20 through June 24) is the natural flow minus 10% at the USGS Morris Bridge gage. For the Minimum High Flow for the high flow period (Block 3, June 25 through October 27), is a stepped flow reduction of 13% and 8% of the historic flows, with the step occurring at the 15% exceedance flow (470 cfs) at the USGS Morris Bridge gage. To protect high flows regardless of their seasonality, the high flow step of an 8% reduction for flows above 470 cfs is maintained throughout the year. For the medium flow period (October 28 to April 19) it was determined that changes in habitat availability for fish and macroinvertebrates determined the Minimum Medium Flow. The Minimum Medium Flow is established as the flow less 11% at the USGS Morris Bridge. Five and ten year means and medians are proposed as long-term compliance standards. A minimum flow for the Crystal Springs complex is established as 46 cfs based on a 5-year running mean and median.