1. RiverWare User’s Group Meeting Pecos River Adjudication Settlement: Application of an Integrated Surface and Ground Water Modeling System June 18, 2003

2. Presentation Outline Overview of Pecos River Institutions / Operational Policies Adjudication Settlement: Problems and Solutions The Pecos River DSS Evaluating the Settlement Terms Conclusions

3. Institutions and Operations Pecos River Compact and Amended Decree (New Mexico / Texas) Water Rights - Prior Appropriation Doctrine; adjudication and administration ESA operations for Pecos Bluntnose Shiner 2 NEPA EIS programs Carlsbad Project (reservoir operations, GW diversions) Other diverters (FSID, river pumpers, M&I, etc) PVACD groundwater diversions

4. Major Irrigators, Physical Features, and Critical Resource Locations in the Pecos Basin Carlsbad Irrigation District Fort Sumner Irrigation District Santa Rosa Reservoir Brantley Reservoir NM - TX State Line / Pecos River Compact Pecos Valley Artesian Conservancy District USGS gage PR @ Acme Sumner Reservoir

5. Pecos Adjudication Settlement Parties: PVACD, CID, NM ISC, United States Purpose : –Ensure long-term compliance with the Pecos River Compact and Amended Decree –Avoid need for priority administration of water rights –Maintain or enhance water supplies / aquifer storage levels Proposal: –NM ISC purchases water rights / land from PVACD and CID –CID water delivered to state line for Compact deliveries –PVACD lands retired, water provides augmentation supply when needed

6. Pecos Adjudication Settlement - Evaluation of the Proposal Use existing modeling tools to evaluate and refine Settlement terms. Pecos River DSS integrates RiverWare, two MODFLOW models, an accounting model, and numerous I/O tools. “Rules” simulate baseline conditions and proposed actions. Various resource indicators used to quantify “value” of actions by comparing baseline and Settlement model results.

7. Approximate Spatial Domain of Pecos Decision Support System Models Pecos River RiverWare Model Roswell Artesian Basin Groundwater Model Carlsbad Area Groundwater Model Red Bluff Accounting Model Santa Rosa Reservoir Brantley Reservoir NM / TX State Line

8. Pecos River RiverWare Model Rule-based simulation of Pecos River hydrology and reservoir operations from Santa Rosa Reservoir to Avalon Dam USBR, Tetra Tech, Hydrosphere, Pecos HWG

9. Roswell Artesian Basin Groundwater Model Calibrated MODFLOW model of groundwater flow in Roswell Artesian Basin, in both the deep artesian and shallow alluvial aquifers Simulates areal and stream recharge, pumping stress, Pecos River - groundwater interaction Predicts base inflows to the Pecos River Amy Lewis, NM SEO (Eric Keyes), SSPA, Hydrosphere

10. Carlsbad Area Groundwater Model MODFLOW model that simulates groundwater flow in the Capitan Reef and overlying alluvial aquifer in the Pecos River Basin from Lake Avalon to the Malaga Bend Simulates surface-water irrigation, groundwater diversions, losses, and return flows Predicts base inflows to the Pecos River Amy Lewis, NM SEO (Peggy Barroll), Intera/Hydrosphere

11. Red Bluff Accounting Model Computes Monthly and Annual Flows at Red Bluff –Historical (Calibration) –Current Conditions (Alternative Evaluation) Red Bluff Flow = Resource Indicator –Evaluation of Policy Alternatives –Interstate Compact Implications Calculation of Calibration Targets for CAGW

12. Data Processing Tool (DPT) Input/Output for Models Data Archiving/ Metadata Alternative Evaluation and Archiving RiverWare Data Processing Tool RBAMCAGWRABGW

13. Settlement Modeling Challenges CID Allotment based on surface water supply (RiverWare) Augmentation pumping in Roswell Basin conditioned on CID water supply: pumping occurs when CID supplies short of 90Kaf; up to 35Kaf/year, 100 Kaf per 5-year accounting period (Feedback from RiverWare to RABGW model) Compact credit thresholds computed by Red Bluff model drive RiverWare rules for water deliveries (Feedback from RBAM, via CAGW, to RiverWare): –Carlsbad Irrigation District allotment and distribution –Delivery of water to Texas

14. RiverWare Res Ops Water Delivery Data Processing Tool (DPT) Red Bluff Acct Model Pecos Compact CAGW Surface water diversions Supplemental GW pumping RABGW Land Retirement Aug. Pumping Pecos Decision Support System: Model Linkages Feedback Loops: Compact deliveries drive reservoir ops CID Supply drives Roswell augmentation pumping

15. Settlement Model Implementation Baseline model w/ Settlement Rules Iterate between RiverWare and RABGW to determine total augmentation pumping Sensitivity analysis in Carlsbad GW model; results used by RiverWare to estimate compact credit Simulate basin operations to state line and verify estimates used in RiverWare

16. Evaluation of Settlement Terms Avoid priority administration (50,000 AF Supply on March 1) Meet Compact delivery requirements (Stateline flows and Compact accounting) Maintain or enhance CID water supply Maintain or enhance Roswell basin aquifer storage levels

17. Resource Indicator: Roswell Basin Aquifer Storage Derived from RABGW Model

18. Resource Indicator: CID Supply and Sources - March 1 Supply - Settlement Scenario

19. Resource Indicator: Compact Obligations and Departures: Cumulative Departure

20. Settlement Gains to Stateline Flows

21. What’s Next? Settlement parties signed agreement in spring 2003 Ongoing applications of PRDSS: –Identification/evaluation of candidate lands for retirement (PVACD and CID) –FWS B.O. on Pecos Bluntnose Shiner –Identification, evaluation, and refinement of alternatives for ongoing Carlsbad Project EIS –Annual Carlsbad Project water accounting (Reclamation)

23. Settlement Model Assumptions (example) Distribution of water from 6,000 acres of CID land purchased by ISC conditioned on cumulative Compact credit and current water supply (ISC water “yield” = 1.176 x allotment): –If CID supply < 50Kaf on March 1, ISC water realloted to CID –If credit < 50Kaf, deliver ISC water to stateline 5x annually –if 50Kaf 90Kaf, ISC gets all water > 90 Kaf, up to 24,696 af (3.5x1.176x6000). Beyond 114,696 af, water is alloted to all 25,055 acres equally. –if 50Kaf < credit < 115 Kaf, AND current supply < 90Kaf, ISC shall make its CID water available for re-distribution to CID irrigators up to 3.5 af/acre (90Kaf) –if credit > 115 Kaf, ISC shall make its CID water available for re- distribution to CID irrigators up to decreed limit (3.697 af/acre); IF CID irrigators have full allotment, excess water to be held over in storage

24. RiverWare Rulebased Simulation Operational policy is simulated using RiverWare rules Management alternatives can be readily evaluated

25. RiverWare - Implementation USBR began work in 1991 following FWS B.O. –Data collection program –Daily timestep model of river/reservoir operations –Need to evaluate operational alternatives HWG review / enhancement process started 1999 –Evaluation of data and methods (side inflows, routing, gain/loss, evaporation, bank storage, etc.) –Development of “Ruleset” representing current reservoir operations policy Relevance to Settlement: –Impact of reservoir operations and physical processes on Texas deliveries and CID allotments –Long-term water supply implications

26. Roswell Artesian Basin Groundwater Model - Implementation RABGW “roots”: Lewis model (1991-1995); Keyes and SSPA enhancements Calibrated based on 1967-2000 heads, 1967-2000 pumping data, and 67-2000 Pecos River base inflows Relevance to NEPA process: –Interrelationships between surface water deliveries, well pumping, and climatic drivers –Direct impact on Pecos River flows from Acme to Artesia

27. Carlsbad Area Groundwater Model - Implementation CAGW “roots”: Lewis model (1991); Bjorklund and Motts survey (1959) Updated and enhanced by NM OSE and Intera Relevance to Settlement: –Interrelationships between surface water deliveries, supplemental well pumping, and return flows –Direct impact on Pecos River flows below Avalon (and thus stateline deliveries)

28. RBAM - Implementation Mass-balance calculation of Red Bluff flows –Input includes RiverWare and CAGW outputs via DPT Monthly and annual surface-water budget for the Avalon to state-line reach Relevance to Settlement: –Pecos Compact obligations and departures –Impacts of potential changes in reservoir operation and CID irrigation supply sources on stateline deliveries

29. DPT - Implementation Coupling of RiverWare, CAGW, and RBAM RiverWare post-processing –CID diversion, Avalon seepage and Avalon releases –Time-step conversion CAGW pre- and post-processing –Determination of CID supplemental well pumping entitlements –Computation of Pecos River gains below Avalon Archiving –Data –Policy alternatives