1. Climate Change Impact on Water Availability in NYC Water Supply Adao Matonse 1, Allan Frei 1, Donald Pierson 2, Mark Zion 2, Elliot Schneiderman 2, Aavudai Anandhi 1, and Hampus Markensten 3 1 CUNY Institute for Sustainable Cities, Hunter College 2 Bureau of Water Supply, New York City Department of Environmental Protection 3 Upstate Freshwater Institute New York City Department of Environmental Protection Bureau of Water Supply Water Quality

2. Presentation Outline Introduction –What is OASIS ? –The OASIS Model Framework –The NYC Water Supply System –Climate Change Simulations for OASIS Selected Results Summary Preliminary Conclusions Next Steps Discussion 02

3. It has a Graphical User Interface (GUI) - Control data entry into database - Helps manage simulation runs - Helps access to output files - Graphical display of the system (schematic) Routes water from a system of nodes & arcs Introduction What is OASIS with OCL? Reservoir Junction Demand NODES ARCS 03

4. Introduction What is OASIS with OCL? Software by HydroLogics, Inc. Modeling operations of water supply systems Generalized program Data-driven: specify features and rules without altering source code Use Operations Control Language (OCL) to set operating rules Simulates routing by solving a Linear Program (LP) 04

5. The OASIS Modeling Framework Overview - Climate Change Simulations System Descriptors OASIS Watershed Model W Quality Model System Design Default Input Other Measured DemandClimate Change Driving Elements Rules - Constraints - Goals GCM Simulation Integrated System How to do it? LP What to do? OCL 05

6. Introduction The NYC Water Supply System East Of HudsonWest Of Hudson Delaware [1012 sq. mi.] -Cannonsville -Pepacton -Neversink -Rondout Catskill [571 sq. mi.] -Schoharie -East Ashokan -West Ashokan Croton [375 sq. mi.] Present focus on WOH but, OASIS has feedback to what is happening in - Croton and - lower Delaware Croton and Lower Delaware are run with present climate 06 Areas in green

7. Introduction Climate Change Simulations for OASIS GCM Simulations –GCMs: ECHAM, GISS, NCAR –Emission Scenarios: A1B, A2, B1 –Time Slices: Baseline: 1980 – 2000 Future: 2046 – 2065; 2080 – 2100 Monthly delta-change GCM air temperature and precipitation as input in: –GWLF Watershed Model Generate inflow data for OASIS 07

8. Selected Results Identify Relevant System Descriptors West Of Hudson Subsystems –Inflow from GWLF simulations –Drought Conditions –Probability of Subsystem Refill –Storage levels – Inflow – Spills Focus on Delaware Results. Catskill results have similar patterns Results are preliminary 08

9. Results Annual Inflow Baseline Median 09

10. Results Monthly Inflow Baseline Future-4665 Future-8099 10

11. Results Average Number of Days per Year in Drought Condition - Delaware Subsystem 11

12. Results Average Number of Days per Year in Drought Condition 12 Days per Year Baseline Future Scenarios Delaware SubsystemCatskill Subsystem

13. Results Probability of Refill by June 1 st 13 Function of: - Current day’s storage levels - Expected system diversions - Inflow Forecast between today and Jun 1 st

14. Results Inflow – Storage – Spill Baseline Future 14 - Future Inflow more uniform and high in winter months - Future storage and Spill increase during Fall and winter - Future and current storage similar in summer but with less variability for future

15. Summary Climate projections from 3 GCMs, 3 emission scenarios, 1 baseline and 2 future time slices applied in this study Monthly delta-change method for climate projections Projected air temperature and precipitation used in GWLF to generate inflows used in OASIS Simulations for future on WOH watersheds Croton and Lower Delaware run on present climate Rules and Demands were assumed stationary 15

16. Preliminary Conclusions Inflow Most GCMs project increased Winter and reduced early Spring inflows due to earlier snow melt Inflow patterns for all scenarios are similar but GISS and NCAR are of a greater magnitude Inflows for 2046-2064 and 2080-2100 time slices appear similar on annual basis Seasonal changes more pronounced in the 2080 - 2100 simulations 16

17. Preliminary Conclusions System Indicators Reduction in number of days per year system is under Drought Watch, Warning and Emergency with high variability between GCM predictions Increase in Subsystem Probability of Refill by Jun 1 st for future scenarios Increased spills during winter Increased future storage levels during winter months while similar storage levels with less variability in late Spring and Summer 17

18. Next Steps Improve Quality of Input data Apply Climate Change Data to EOH and Lower Delaware Project Future Demands Under Climate Change Optimize OASIS Rules For Each of Above: –Generate Indicators –Evaluate System Performance and Sensitivity –Integrate New Selected Indicators Into OASIS 18

19. Questions?