Lake Chesdin VWP Permit 2012. Proposed permit operational rules and analysis of cumulative impacts to beneficial uses. Elements of Analysis. Projected Demands Safe Yield / days of storage remaining Impact on Beneficial Uses Water Supply Downstream aquatic life (IFIM) On-lake aquatic life
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Lake Chesdin VWP Permit 2012
Proposed permit operational rules and analysis of cumulative impacts to beneficial uses.
Figure 2: Withdrawal trends in Lake Chesdin from 2000-2012.
Figure 9: Approximate water level loss, summer evap. & 40 MGD withdrawal.
Table 1: Comparison of inflows between period 1946-2012 and 2000-2012.
Figure 4: Linear regression showing trends in minimum annual inflow to Lake Chesdin since 1947.
Meet the projected water supply needs of 52.3 MGD during the critical 180 day draw-down period, and 60 days minimum storage during the drought of record.
Minimize loss of downstream habitat (0-20% during normal-high flow conditions and 0-10% during drought).
Minimize long-term (>45 days) closure of fish out-migration, eliminate post October 15th.
Minimize draw-down >2 feet during summer months to preserve on-lake recreation.
Maintain safe-yield (the original 55 MGD).
Figure 3: Size and Catch Per Unit Effort of largemouth bass as a function of previous year drawdown in Lake Chesdin.
Analysis of downstream habitat based on flows and field surveys
Figure 4: Size and Catch Per Unit Effort of largemouth bass as a function of previous year drawdown in Lake Chesdin.
Littoral species inhabit shallow water areas that change with low lake levels.
In Chesdin, these are primarily sunfish species (largemouth bass and bluegill)
DGIF data since 1986, intensively since 2000
Biologists conclude that drawdown has little to no effect on these littoral species (Fig. 5).
Basic Permit Rules
Maximum Release (Qmax*)
Figure 5: Probability of a summertime flow less than the 25% “non-exceedence” level based on flow November-February.
Figure 6: Median Juvenile shad habitat for pre-dam, current permit & draft permit rules.
Current Permit shows 1-5% loss in June, October, ~ 0% loss in other months
Proposed rules limit additional losses to < 8% in all months
Figure 7: Median Juvenile shad habitat for pre-dam, current permit & draft permit rules.
Current Permit shows 15% loss in June, October, <5% loss in other months (including some slight gains)
Proposed 13-20% in June-November
Figure 8: Median Shallow-Fast habitat for pre-dam, current permit & draft permit rules.
Current Permit shows 15% loss in June, October, <5% loss in other months
Proposed 25-35% in Jun-Aug, and Oct. & 17-18% in Sep. and Nov.
Table 2: Estimated amount of lake area with water > 3 feet deep at various levels of drawdown.
Figure 10: Number of years with draw-downs > 2 ft by month for June-September.
Summer months (June-September) with at least 1 day drawn down > 2 ft (<20% loss of rec area)
Dry period > 50% decrease Jun-Jul, 10-20% Aug-Sep
Full period > 60% decrease Jun-Jul, 30-40% Aug-Sep
Figure 11: Number of years with draw-downs > 1 ft by month for June-September.
Summer months (June-September) with at least 1 day drawn down > 1 ft (<11% loss of rec area)
Dry period > 25% decrease Jun&Aug, <10% Jul&Sep
Full period > 40% decrease Jun-Jul, 15-20% Aug-Sep