optimizing reservoir operations for water supply and ecological objectives using flow modeling

1. Hernán A. M. Quinodoz, Ph.D.Delaware River Basin CommissionDelaware Estuary Science Conference 2007 optimizing reservoir operations for water supply and ecological objectives using flow modeling

2. preview • DRB basic facts • flow management highlights • drought operating plans • basin reservoirs • DRBC daily flow model • flows versus ecological needs • use of the daily flow model • caveats

3. Delaware River Basin selected facts (1): • the longest undammed river east of the Mississippi – 330 miles • world-class trout fishery • wild and scenic river

4. … facts (2) New York City, which lies outside the basin, gets roughly half its water from three reservoirs located on tributaries to the Delaware – Cannonsville, Pepacton, and Neversink. Water filtration is not necessary Map: NYC DEP Web Site

5. Delaware River Basin (inter-state) flow management timeline • 1931 – Supreme Court Decree • NJ sues NY and New York City • Equitable Apportionment of Water • 1954 – Amended Supreme Court Decree • Case reopened by New York City • 1961 –DRBC created, with authority to adjust the terms of the 1954 Supreme Court Decree, subject to unanimous consent of the five decree parties • 1980’s – DRBC adopts drought management plans and Trenton flow target

6. 1954 Supreme Court Decree • NYC – 800 mgd combined (running average) diversion • Montague Target – 1750 cfs (1130 mgd) • NJ – 100 mgd diversion (D&R Canal) • No provisions for instream flow needs • No conditions on wise use of water

7. DRBC Drought Operating Plans • New York City Delaware Basin reservoirs drive the basin-wide operating plan. • Cannonsville • Pepacton • Neversink • Two Corps of Engineers reservoirs drive lower-basin operating plan • Beltzville • Blue Marsh Montague Trenton

9. Reservoirs for Interstate Flow Management in the Delaware River Basin 140 BG 96 BG 35 BG 15 BG (Emergency) 30 BG (Emergency) 11 BG (Emergency) 13 BG 16 BG 13 BG (Emergency) 6.5 BG 69 BG OF STORAGE FOR FLOW AUGMENTATIONMADE AVAILABLE THROUGH DRBCEMERGENCY ACTIONS 4.0 BG Numbers indicate storage capacities BG = billion gallons

10. Basin-wide Operating Plan Controls • NYC diversions • New Jersey diversions • Montague flow target • Trenton flow target • Salt line location • Conservation releases

11. salinity control – Upper Estuary • DRBC water-quality objective: maximum 30-day average Chloride concentration of 180 mg/L at R.M. 98 • DRBC drought plan established Trenton flow target to provide for minimum freshwater inflows to the Estuary • Trenton flow target adjusts dynamically with the 7-day average location of the “salt line” (250 mg/L Chloride) in the estuary

12. DRBCdaily flow model

13. DRBC daily flow model • 1981 – Daily Flow Model • developed by CDM as a • simulation model • 2002 – OASIS developed by • HydroLogics, Inc., adding • optimization component to • meet conflicting demands • one-dimensional network of nodes at USGS gages (70+) • includes 12 major reservoirs • driven by historical unregulated hydrology (1928-present)

14. extension of daily flow model into the estuary • daily flow model does not include solute transport (e.g., chloride) • when salinity-related metrics are important, the daily flow model is coupled to a one-dimensional estuary hydrodynamics and chloride-transport model, which spans the estuary downstream of Trenton (currently available) • when resolving two- and three-dimensional hydrodynamics and transport is important, the daily flow model will have to be coupled to a higher-dimensional model (future)

15. incorporating ecological needs into models and analyses (1) • flow relationships are the simplest option • require a one-to-one relationship to a given model output variable (e.g., Trenton flow) • example: habitat vs. flow at nearest gage • can easily be built-in, avoiding need to run a post-processing (ecological) model • ecological metrics convert directly into flow model variable metrics

16. incorporating ecological needs into models and analyses (2) • sometimes more complex functions of flow are needed or unavoidable  example: habitat persistence, habitat spatial continuity • cannot easily be built-in, requiring development of a post-processing (ecological) model  example: USGS decision-support system (DSS) for eleven stream reaches in the Upper Delaware (habitat functions) • allows more complex evaluations, with user-controlled analysis (e.g., thresholds)

17. use of the daily flow model • supports DRBC decision making in a planning mode • modified periodically to incorporate changes in reservoir operation plans • utilized extensively to analyze alternative proposals • primary aid in designing new reservoir operation plans • available to interested stakeholders (several copies in use) • provides a common platform to test new ideas and learn about system behavior and performance • flexible tool, can adapt to changing needs • can be easily modified to incorporate new flow relationships and test new objectives

18. wrap up

19. caveats – reservoirs Do reservoirs affect stream conditions downstream? • Yes, with significant effects directly downstream • Yes, with minor effects many miles downstream • Yes, with negligible effects hundreds of miles downstream Percent of drainage area controlled by reservoirs

20. caveats – general • here we focused only on the model as a tool, avoiding policy and management issues and constraints • technical solutions have to go through interstate negotiation process to eventually affect reservoir operations and management • scientific studies are needed to define ecological needs in the estuary and relate them to freshwater inflows (when appropriate) • extensive monitoring and modeling have to inform each other to maximize efficiency

21. science to support change:studies currently underway (UB) • Upper Delaware instream fish habitat assessment (USGS) • Upper Delaware instream temperature modeling (USGS) • Dwarf Wedgemussels in the Upper Delaware – Minimum flows required to sustain this federally endangered species • Dwarf Wedgemussel – Determination of Host Fish • Dwarf Wedgemussel – Habitat study on the Upper Delaware • Flow forecasting improvements for the Upper Delaware • Rate-of-Change in flow recommendations • Flow, temperature and biological monitoring in the Delaware River Tailwaters, 2004-2006 • Fish Inventories of Upper and Middle Delaware River • Tri-State Watershed Management

22. summary • DRB basic facts • flow management highlights • drought operating plans • basin reservoirs • DRBC daily flow model • flows versus ecological needs • use of the daily flow model • caveats

23. www.drbc.net