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 remainingSafe Yield / days of storage remaining  Impact on Beneficial Uses Water SupplyWater Supply Downstream aquatic life (IFIM)Downstream aquatic life (IFIM) On-lake aquatic lifeOn-lake aquatic life On-lake recreationOn-lake recreation Downstream water qualityDownstream water quality Downstream water supplyDownstream water supply

Water Budget: Permitting Period Demands  Historical Maximum monthly withdrawal rate of 47 MGD in 2010  JPA Requests maximum monthly withdrawal of 62 MGD in MGD = 0.23 inches/day or 7.5 inches per month15 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

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 occursJuly is when the biggest drop in inflows occurs August is when the lowest single day flows occurAugust is when the lowest single day flows occur September is when the lowest average monthly flows occurSeptember is when the lowest average monthly flows occur  Recent inflows ( ) are much lower than historical values (Table 1) Inflow ValueOccurrence Occurrence cfs / 1.8 in1 out of 5 summers1 out of 2 summers 155 cfs / 1.5 in1 out of 7 summers1 out of 3 summers 120 cfs / 1.2 in1 out of 10 summers1 out of 4 summers 90 cfs / 0.9 in1 out of 20 summers1 out of 5 summers 43 cfs / 0.4 in1 out of 50 summers1 out of 10 summers Table 1: Comparison of inflows between period and Figure 9: Approximate water level loss, summer evap. & 40 MGD withdrawal.

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”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.

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,impacts to public water supply, on-lake recreation, and freedom of movement for migratory species.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.

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).

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.

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.

Proposed Permit Rules InflowRelease 0-60 cfs100% of Inflow cfs 90% of Inflow cfsLesser of 80% of Inflow or Qmax* 200+ cfsLesser of 75% of Inflow or Qmax* ConditionQmax Normal250 cfs Drought Watch or R 25 < cfs Drought Warning or 0.25 < R 25 < cfs Maximum Release (Qmax*) Basic Permit Rules

Likelihood of Summertime Drought Flows - R 25  Probability of < 25% flow based on winter recharge  Used to reduce max release, < drawdown< drawdown > storm capture> 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.

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.

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

Permit Effects: Downstream Shallow Fast Guild  Current Permit shows 15% loss in June, October, <5% loss in other months  Proposed % in Jun- Aug, and Oct. & 17-18% in Sep. and Nov.  Proposed % 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.

On-Lake Recreational Area Feet Below Full # Acres > 3 ft Deep Cumulative % Decrease 02,0060% 11,77611% 21,62019% 31,45527% 41,34333% 51,25338% Table 2: Estimated amount of lake area with water > 3 feet deep at various levels of drawdown.  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)“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).Certain areas of lake have impaired dock access at ~18” drawdown (Chesdin Landing).

Permit Effects: On-Lake Recreational Area  Summer months (June-September) with at least 1 day drawn down > 2 ft ( 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.

Permit Effects: On-Lake Recreational Area  Summer months (June-September) with at least 1 day drawn down > 1 ft ( 1 ft (<11% loss of rec area)  Dry period > 25% decrease Jun&Aug, 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.

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 areaIncreases total recreational area Decreases incidence of dry-docksDecreases incidence of dry-docks  Increase “safe-yield” of reservoir for water supply 1.5’ rise increases safe yield to ~ 63 MGD (+10 MGD)1.5’ rise increases safe yield to ~ 63 MGD (+10 MGD)  Inundation study, necessary Wetlands impactsWetlands impacts Flood impactsFlood impacts  Guide Curve approach to management useful  Sedimentation may reduce gains made by dam raising over a years period.

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

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

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 JulyMedian 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 timeMedian July drawdown is 1.5 feet = lake is drawn down more than 1.5 feet half of the time  10 th %ile – the lowest 10% of occurrences. For example: 10 th %ile August Inflow is 120 cfs = 90% of the time, inflows during August are greater than 120 cfs10 th %ile August Inflow is 120 cfs = 90% of the time, inflows during August are greater than 120 cfs  10 th %ile flow is considered drought warning status in Virginia state plan  Median may be thought of as “chronic”, whereas 10 th %ile may be thought of as “acute”