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

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

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

Schoharie Reservoir Turbidity

GCM - Emission Scenario Current Conditions Scenario 65 Year into Future Scenario 100 Year into Future Scenario ECHAM-A1B ECHAM-A2“““ ECHAM-B1“““ GISS-A1B 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

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

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 Scenarios

Results - Schoharie Input Turbidity Fraction of Time over 100 NTU Baseline Scenario Scenarios Scenarios

Results - Schoharie Segment 7 In-Lake Turbidity Fraction of Time over 100 NTU Baseline Scenario Scenarios Scenarios

Results - Schoharie Segment 7 In-Lake Turbidity Fraction of Time over 15 NTU Baseline Scenario Scenarios Scenarios

Cannonsville Reservoir Eutrophication

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-A1B ECHAM-A2“““ ECHAM-B1“““ GISS-A1B GISS-A2“““ GISS-B1“““ CGCM3-A1B CGCM3-A2“““ “““

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

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

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

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

Results - Cannonsville Epilimnion Chl-a Concentration Epilimnion Water Temperature Water Temperature (C) Frequency Frequency Chl-a Concentration (mg/m 3 ) Current Climate Scenarios Daily Histograms Chl-a Conc. (mg/m 3 ) Month Water Temperature (C) Month Average Monthly Values Current Climate Scenarios

Results - Cannonsville Thermal Stratification Density Difference (Epilimnion – Hypolimnion) Density Difference (kg/m 3 ) Current Climate

0 Growing Season Averages Chl-aTotal P Frequency Chl a (mg/m 3 )Total P (mg/m 3 ) Pre-MOA Current Climate - Post-MOA Future Climate: Future Climate: Frequency

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

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

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

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