1. Effects of Annual Snowmelt on the New York City Water Supply Adam Czekanski 29 November 2005

2. Agenda The NYC Water Supply System Geographic Setting Delaware / Catskill Watershed Watershed Delineation Snowmelt Collection / Distribution / Total Rainfall Data / Totals Conclusion

3. The NYC Water Supply System Three systems: Delaware/Catskills (90%), Croton (10%) 1.4 billion gallons of water per day to 9 million people ~ 550 billion gallons of storage capacity (19 reservoirs) Watershed covers 4,000+ square kilometers

4. The NYC Water Supply System Courtesy of the City of New York Department of Environmental Protection

5. Geographic Setting

6. Delaware / Catskill Watershed Six HUC span ~ 460 billion gallon capacity Six reservoirs

7. Delaware / Catskill Watershed

8. Watershed Delineation 21 USGS stream gages used initially CONSISTENT ERRORS / MUCH FRUSTRATION

9. Watershed Delineation Reservoir outlets ultimately used (SUCCESS!!) Watershed area = 4,071 km 2

10. Watershed Delineation

12. Snowmelt Data Collection National Operational Hydrologic Remote Sensing Center (NOHRSC) interactive web page 25 observation stations selected Monthly snowmelt data taken from each Data availability begins January 2004

13. Snowmelt Distribution Raw snowmelt data made into x/y event and interpolated to raster Data range is January – April of specified year

14. Snowmelt Total Snowmelt raster overlaid with delineated watersheds Zonal statistics used to sum snowmelt (mm) Multiply by cell size for total snowmelt volume (m 3 )

15. Snowmelt Totals Winter 2004: 3,207,770 m 3 (850 million gallons) Winter 2005: 5,617,850 m 3 (1.5 billion gallons)

16. Rainfall Totals May and June selected as sample months PRISM data used for monthly precipitation averages / converted to raster Total precipitation in the watershed (using zonal statistics): –May: 453,762,618 m 3 (119.9 billion gallons) –June: 429,721,518 m 3 (113.5 billion gallons)

17. Conclusion The affect of snowmelt on reservoir levels is not nearly as significant as the affect of rainfall

18. Lesson Reinforced WORK SMARTER NOT HARDER

19. Final Conclusion GIS is Satan’s spawn!!!