1. Potential Impacts of Climate Change on Water Quality in the New York City Water Supply System Watershed Science and Technical Conference West Point, New York September 14-15, 2009 Mark S. Zion, Elliot M. Schneiderman and Donald C. Pierson Bureau of Water Supply, New York City Department of Environmental Protection Hampus Markensten, Emmet Owens, Rakesh Gelda, Steve Effler Upstate Freshwater Institute Adao H. Matonse, Aavudai Anandhi and Allan Frei Institute for Sustainable Cities, City University of New York New York City Department of Environmental Protection Bureau of Water Supply Water Quality

2. NYC DEP Climate Change Integrated Modeling Project Water Quality – Phase I  Purpose: To evaluate the potential effects of future climate change on the water quality of New York City Water Supply Turbidity in Schoharie Reservoir Eutrophication in Cannonsville Reservoir  Integrated Modeling Strategy Use of an integrated suite of already developed models Preliminary development of tools and measures future water quality  Phase I result highlights Preliminary model applications to obtain initial estimates of climate effects

3. Climate Change Phase I Study Areas Location Map NY State NY City Turbidity – Focus on Schoharie Reservoir Eutrophication – Focus on Cannonsville Reservoir

4. Schoharie Reservoir Turbidity

5. GCM - Emission Scenario Current Conditions Scenario 65 Year into Future Scenario 100 Year into Future Scenario ECHAM-A1B1981-20002046-20652081-2100 ECHAM-A2“““ ECHAM-B1“““ GISS-A1B1981-20002046-20652081-2100 GISS-A2“““ GISS-B1“““ NCAR-A2“““ GCM/Emission Scenario data obtained from IPCC AR4 (2007) For each GCM/Emission Scenario, precipitation and air temperature are compared in control vs. future periods to derive monthly delta change factors. Climate Change Scenarios Phase I – Schoharie Turbidity Delta Change Method Applied for 7 GCM/Emission Scenarios

6. Phase I - Schoharie Turbidity Modeling System Delta Change, GWLF, OASIS and W2 Models Historical Meteorology Precip Air Temp Stream Flow Inflows Turbidity Loads Stream Temp Tunnel Ops Reservoir Water Quality Pre- Processor  Calculate turbidity inputs using sediment rating curve  Estimate inflow water temperature  Reformat data for W2 model CEQUAL-W2 Reservoir Model Simulate reservoir volume, temperature and constituents in 2 dimensions (vertical, longitudinal) Air Temp GWLF Watershed Model Simulate streamflow and evaporation Tunnel Flows OASIS System Model Simulate tunnel operations Delta Change Calculate future climate scenarios PET Streamflows

7. Results - Schoharie Input Flow Input Turbidity In-Lake Turbidity (Segment 7) Reservoir Inflow (cms) Input Turbidity (NTU) Segment 7 Turbidity (NTU) Average Monthly Values Current Climate 2080-2100 Scenarios

8. Results - Schoharie Input Turbidity Fraction of Time over 100 NTU Baseline Scenario 2046-2065 Scenarios 2081-2100 Scenarios

9. Results - Schoharie Segment 7 In-Lake Turbidity Fraction of Time over 100 NTU Baseline Scenario 2046-2065 Scenarios 2081-2100 Scenarios

10. Results - Schoharie Segment 7 In-Lake Turbidity Fraction of Time over 15 NTU Baseline Scenario 2046-2065 Scenarios 2081-2100 Scenarios

11. Cannonsville Reservoir Eutrophication

12. GCM/Emission Scenario data obtained from IPCC AR4 (2007) For each GCM/Emission Scenario, precipitation and air temperature are compared in control vs. future periods to derive monthly delta change factors. Climate Change Scenarios Phase I – Cannonsville Eutrophication Delta Change Method Applied for 9 GCM/Emission Scenarios GCM - Emission Scenario Current Conditions Scenario 65 Year into Future Scenario 100 Year into Future Scenario ECHAM-A1B1981-20002046-20652081-2100 ECHAM-A2“““ ECHAM-B1“““ GISS-A1B1981-20002046-20652081-2100 GISS-A2“““ GISS-B1“““ CGCM3-A1B1980-19992046-20652081-2100 CGCM3-A2“““ “““

13. Phase I - Schoharie Turbidity Modeling System Delta Change, GWLF, UFI-1D/PROTECH Models Historical Meteorology Precip Air Temp Inflows Meteorology Nutrient Loads Stream Temp Reservoir Ops Reservoir Water Quality Pre- Processor  Adjust reservoir water balance based on future inputs  Estimate inflow water temperature  Estimate dew point temperature  Reformat data for W2 model UFI-1D / PROTECH Reservoir Model Simulate reservoir volume, temperature, nutrients and phytoplankton functional groups in vertical dimension Air Temp Wind Speed PAR GWLF Watershed Model Simulate streamflow, evaporation, nutrient and sediment loads PET Streamflows Nutrient Loads Delta Change Calculate future climate scenarios Historical Operations

14. Example: Strategy to Evaluate Watershed Management Streamflow Dissolved P Particulate P Baseline Loads Reservoir Model (calibrated) Streamflow Dissolved P Particulate P Scenario Loads Baseline Reservoir Chl a Baseline Chl a Frequency Distribution ? Reservoir Model (calibrated) Scenario Reservoir Chl a Scenario Chl a Frequency Distribution freq mg/m 3

15. Example: Changes in Mean Annual Chlorophyll Concentration Epilimnion Cannonsville Reservoir Due to MOA Programs Frequency Pre - MOA Current Climate Post - MOA Input DP Load 51015202530 51015202530 0.00 0.25 0.00 0.25 Chlorophyll (mg m -3 ) Pre - MOA Post - MOA

16. Results - Cannonsville Input DP LoadInput PP Load 2081-2100 Climate Scenarios DP Load (kg/day) PP Load (kg/day) Reservoir Inflow Reservoir Inflow (cms) Average Monthly Values Current Climate 2080-2100 Scenarios

17. Results - Cannonsville Epilimnion Chl-a Concentration Epilimnion Water Temperature Water Temperature (C) Frequency 1020300 0.00 0.25 Frequency Chl-a Concentration (mg/m 3 ) 102030 40 0 0.00 0.50 Current Climate 2080-2100 Scenarios Daily Histograms Chl-a Conc. (mg/m 3 ) 2 4 6 8 10 12 14 Month Water Temperature (C) 5 10 15 20 25 Month Average Monthly Values Current Climate 2080-2100 Scenarios

18. Results - Cannonsville Thermal Stratification Density Difference (Epilimnion – Hypolimnion) Density Difference (kg/m 3 ) Current Climate 2046-2065 2081-2100

19. 0 Growing Season Averages Chl-aTotal P Frequency Chl a (mg/m 3 )Total P (mg/m 3 ) 5 0.00 15202530 20406080 30 Pre-MOA Current Climate - Post-MOA Future Climate: 2046-2065 Future Climate: 2081-2100 5 0.25 0.00 0.25 0.00 0.25 0.00 0.25 0.00 0.30 0.00 0.30 0.00 0.30 0.00 0.30 Frequency

20. Results - Cannonsville Epilimnion Chl-a Concentration Fraction of Time over 15 mg/m 3 Future Climate: 2080-2100 Pre-MOA Post-MOA / Current Climate Boxes/whiskers show range of 2081-2100 climate scenarios

21. Summary of Results  Schoharie Reservoir Turbidity: Increased fall and early winter flows lead to increase turbidity loading during these time periods. Reduced spring flows lead to reduction in loading during these periods Turbidity levels in the reservoir at the Shandaken Tunnel gate are increased in fall and early winter, reduced in late winter and unchanged in summer.  Cannonsville Reservoir Eutrophication Slightly longer period of thermal stratification. Enhanced phytoplankton blooms due to slightly increased DP loads and thermal stratification changes Increased phytoplankton much less than magnitude of reductions in algal growth due to watershed management program implementation

22. Future Work – Phase II  Extend turbidity analysis to Ashokan Reservoir  Implement fully connected OASIS/W2 model  Incorporation of improved watershed turbidity loading models  Extend eutrophication analysis to other Delaware System reservoirs  Implement feedback between OASIS and UFI-1D/PROTECH model results  Improved simulation of watershed biogeochemistry to better reflect climate change effects on nutrient loads

23. Potential Impacts of Climate Change on Water Quality in the New York City Water Supply System Watershed Science and Technical Conference West Point, New York September 14-15, 2009 Mark S. Zion, Elliot M. Schneiderman and Donald C. Pierson Bureau of Water Supply, New York City Department of Environmental Protection Hampus Markensten, Emmet Owens, Rakesh Gelda, Steve Effler Upstate Freshwater Institute Adao H. Matonse, Aavudai Anandhi and Allan Frei Institute for Sustainable Cities, City University of New York New York City Department of Environmental Protection Bureau of Water Supply Water Quality