Special Publication SJ97-SP8 Water Management Alternatives: Effects on Lake Levels and Wetlands in the Orange Creek Basin

Transcription

1 St. Johns St. Johns River River Water Management District District Special Publication SJ97-SP8 Water Management Alternatives: Effects on Lake Levels and Wetlands in the Orange Creek Basin G. B. Sonny Hall, Ph.D. Bureau of Resource Evaluation and Modeling

2 The Problem Man-made alterations within Orange Creek Basin (OCB) changed natural hydrology (flows and water levels) Resulted in ecological degradation: Stabilization of water levels through construction of weirs Excessive growth of nuisance aquatic plants Water quality degradation Increased accumulation of sediments Declines in recreational fishing 2

3 The Study In response to these issues, as part of an interagency working group, SJRWMD completed a mid-1990s study to evaluate ecological value of alternative surface water management strategies Study objectives: Develop alternative water management strategies Assess environmental consequences of alternative strategies Identify which strategies require more specialized study (e.g., geologic, ecologic, or economic studies) 3

4 Management Scenarios Twenty alternative surface water management strategies were evaluated for Orange and Lochloosa lakes 4 alternatives include removal of the Orange Lake weir 11 alternatives include active sinkhole management The assessment compared hydrologic and ecological changes between Existing Conditions and the water management alternative 4

5 Management Alternatives 5

6 Management Alternatives 6

7 Summary of Results Changes between Existing Conditions and Water Management Alternatives for Orange and Lochloosa Lakes Water Management Alternative Change in Wetland Area (acres) Change in Water Level Fluctuation Range (ft) Change in Boater Access at 56 ft Advantages Environmental Impacts Plug Orange Lake weir +204 (+2%) 0 (2%) Increases average lake levels Decreases base flow to Orange Creek Remove Orange Lake weir Manage sinkholes Manage sinkholes and remove Orange Lake weir -597 (-7%) -399 to (-4 to -23%) to (-15 to 32%) 0 to -0.3 ft) (-11%) (0 to -3.9 ft) (1 to 18%) -1.6 to -4.0 ft (-9 to +8%) Increases potential for flushing of organics and nutrients Increases average lake levels Increases potential for flushing of organics and nutrients Decreases average water levels Decreases emergent wetland area Causes potential hydrogeological impacts Decreases average water levels Decreases emergent wetland area Causes potential hydrogeological impacts

8 Management Scenarios

9 Management Scenarios

10 Management Scenarios

11 Management Scenarios 11

12 Management Scenarios 12

13 Management Scenarios 13

14 Management Scenarios

15 Management Scenarios

16 Management Scenarios

17 Management Scenarios

18 Ecological Evaluation Summary of wetland and hydrologic effects of surface water management alternatives for Orange and Lochloosa lakes 18

19 Ecological Evaluation Wetland and hydrologic effects of surface water management alternatives for Orange and Lochloosa lakes

20 Ecological Evaluation Wetland and hydrologic effects of surface water management alternatives for Orange and Lochloosa lakes

21 Ecological Evaluation Summary of wetland and hydrologic effects of surface water management alternatives for Orange and Lochloosa lakes

22 Questions 22