1. Lake Chesdin VWP Permit 2012
Proposed permit operational rules and analysis of cumulative impacts to beneficial uses.

2. Elements of Analysis Projected Demands Impact on Beneficial Uses
Safe Yield / days of storage remaining
Impact on Beneficial Uses
Water Supply
Downstream aquatic life (IFIM)
On-lake aquatic life
On-lake recreation
Downstream water quality
Downstream water supply

3. Water Budget: Permitting Period Demands
Historical Maximum monthly withdrawal rate of 47 MGD in 2010
JPA Requests maximum monthly withdrawal of 62 MGD in 2030
15 MGD = 0.23 inches/day or 7.5 inches per month
Summer-time use ~ 52 MGD projected in 2030
Figure 2: Withdrawal trends in Lake Chesdin from

4. Water Budget: Gage Inflow Statistics
40 MGD use ~ 0.6 in / day
Summer evap. rate ~ 0.15 in/day
Monthly Patterns:
July is when the biggest drop in inflows occurs
August is when the lowest single day flows occur
September is when the lowest average monthly flows occur
Recent inflows ( ) are much lower than historical values (Table 1)
Figure 9: Approximate water level loss, summer evap. & 40 MGD withdrawal.
Inflow Value
Occurrence
Occurrence
190 cfs / 1.8 in
1 out of 5 summers
1 out of 2 summers
155 cfs / 1.5 in
1 out of 7 summers
1 out of 3 summers
120 cfs / 1.2 in
1 out of 10 summers
1 out of 4 summers
90 cfs / 0.9 in
1 out of 20 summers
43 cfs / 0.4 in
1 out of 50 summers
Table 1: Comparison of inflows between period and

5. Climatic Trends: Wet & Dry Periods
Simulations were run for “dry” ( ) & “normal” ( )
Recent meteorological patterns suggest a pattern of more signif- icant droughts
It is not clear if this is simply a short-term trend or “the new normal”
Dry periods result in more frequent draw-downs, drought restrictions and reduced in-stream flows.
Figure 4: Linear regression showing trends in minimum annual inflow to Lake Chesdin since 1947.

6. Beneficial Use Analysis
Predictive modeling of reservoir release rules.
IFIM study of downstream aquatic habitat (for Juv. Shad, E. Complenata , Smallmouth Bass and the Deep-Fast, Deep-Slow, Shallow-Fast, and Shallow-Slow guilds)
Modeling of lake-levels:
impacts to public water supply,
on-lake recreation, and freedom of movement for migratory species.
Monitoring of resident species populations and an analysis of the impact of lake-level fluctuations on them.
Consult with DEQ staff re: the James River Chlorophyll A TMDL & water quality in Appomattox near tidal-fresh James River.
Consulted with DEQ Piedmont Regional Office regarding the South Central Wastewater Treatment plant discharge.

7. Goals for Reservoir Management
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).

8. IFIM Overview
Analysis of downstream habitat based on flows and field surveys
Regulated flows from cfs
>10% habitat loss shown to result in negative impacts
Figure 3: Size and Catch Per Unit Effort of largemouth bass as a function of previous year drawdown in Lake Chesdin.

9. On-Lake: DGIF On-Lake Biota and 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).
Figure 4: Size and Catch Per Unit Effort of largemouth bass as a function of previous year drawdown in Lake Chesdin.

10. Proposed Permit Rules Basic Permit Rules Maximum Release (Qmax*)
Inflow
Release
0-60 cfs
100% of Inflow
cfs
90% of Inflow
cfs
Lesser of 80% of Inflow or Qmax*
200+ cfs
Lesser of 75% of Inflow or Qmax*
Maximum Release (Qmax*)
Condition
Qmax
Normal
250 cfs
Drought Watch or R25 < 0.25
190 cfs
Drought Warning or 0.25 < R25 < 0.40
140 cfs

11. Likelihood of Summertime Drought Flows - R25
Probability of < 25% flow based on winter recharge
Used to reduce max release,
< drawdown
> storm capture
2002 = 54%
2003 = 24%
2012 = 48%
Figure 5: Probability of a summertime flow less than the 25% “non-exceedence” level based on flow November-February.

12. Permit Effects: Downstream Shad
Median habitat
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 6: Median Juvenile shad habitat for pre-dam, current permit & draft permit rules.

13. Permit Effects: Downstream Deep Fast Guild
Current Permit shows 15% loss in June, October, <5% loss in other months (including some slight gains)
Proposed 13-20% in June-November
Figure 7: Median Juvenile shad habitat for pre-dam, current permit & draft permit rules.

14. Permit Effects: Downstream Shallow Fast Guild
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. 
Figure 8: Median Shallow-Fast habitat for pre-dam, current permit & draft permit rules.

15. On-Lake Recreational Area
Boating Area available considered to be water > 3 feet deep.
Dock Access:
“Based on feedback from Chesterfield County and Dinwiddie County … a lake level of 3 to 4 feet below normal pool is … where dock access is significantly impaired. “ (IFIM, 2012)
Certain areas of lake have impaired dock access at ~18” drawdown (Chesdin Landing).
Feet Below Full
(Acres)
# Acres > 3 ft Deep
Cumulative % Decrease
Pool
2,006 0% 1
foot
1,776
11% 2
feet
1,620
19% 3
1,455
27% 4
1,343
33% 5
1,253
38%
Table 2: Estimated amount of lake area with water > 3 feet deep at various levels of drawdown.

16. Permit Effects: On-Lake Recreational Area
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 10: Number of years with draw-downs > 2 ft by month for June-September.

17. Permit Effects: On-Lake Recreational Area
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
Figure 11: Number of years with draw-downs > 1 ft by month for June-September.

18. Impacts of Dam Raising
Minimal effects on relative draw-down (i.e. -1 ft)
Substantial effects on absolute draw-down (i.e. feet above sea level)
Increases total recreational area
Decreases incidence of dry-docks
Increase “safe-yield” of reservoir for water supply
1.5’ rise increases safe yield to ~ 63 MGD (+10 MGD)
Inundation study, necessary
Wetlands impacts
Flood impacts
Guide Curve approach to management useful
Sedimentation may reduce gains made by dam raising over a years period.

19. Additional Permit Info
These are Proposed Permit Rules
A storage management plan is required for this permit issuance.
Sedimentation plan
There will be a provision to monitor & report on procurement of future storage/source acquisition
Demand increases over time
Loss of storage due to sedimentation
Plans for meeting future need.
Potential for provisions that address operations under increased dam level in this permit

20. Next Steps Provide draft permit to ARWA.
Address any comments they have.
Initiate public notice.
Depending on comments:
Issue permit, or
Public hearing -> State Water Control Board

21. Common Statistical Measures of Impact
Median – the value which marks the 50% line. For example, if we say:
Median July release is 120 cfs = 50% of release flows are less than 120 cfs during July
Median July drawdown is 1.5 feet = lake is drawn down more than 1.5 feet half of the time
10th %ile – the lowest 10% of occurrences. For example:
10th %ile August Inflow is 120 cfs = 90% of the time, inflows during August are greater than 120 cfs
10th %ile flow is considered drought warning status in Virginia state plan
Median may be thought of as “chronic”, whereas 10th %ile may be thought of as “acute”