Middle St. Johns River Minimum Flows and Levels Hydrologic Methods Report. Technical Publication SJ2004-2

摘要

The middle St. Johns River (MSJR) is being considered as a possible alternative water supply source to help meet the projected future increased demand for water in the St. Johns River Water Management District (SJRWMD) (Figure ES1). Although other factors may ultimately be more limiting, minimum flows and levels (MFLs) will provide the initial limits to surface water withdrawals from the MSJR. The basic task in analyzing changes to a hydrologic system is to quantify those changes and assess their acceptability. Often, simple operations are performed on gage records to assess the effects of alterations on a hydrologic system. For example, the amount of surface water withdrawal might be subtracted from daily flows gaged at a site. Frequency analysis on the resulting time series could then be used to assess changes to the system. However, a riverine system as complex as the MSJR requires the use of hydrologic modeling and the concomitant analyses. This is especially true when analyzing hydrologic changes in the context of MFLs. Modeling results will provide the framework needed to analyze and implement MFLs on the MSJR. By analyzing the output from hydrologic models, reasonable management decisions can be made regarding surface water withdrawals from the MSJR.