Evaluation of Management Alternatives in the San Acacia Reach Based on High-Resolution Modeling

1. Evaluation of Management Alternatives in theSan Acacia ReachBased on High-Resolution Modeling Robert Bowman and Laura Wilcox, Department of Earth and Environmental Science New Mexico Tech Nabil Shafike New Mexico Interstate Stream Commission

2. Acknowledgements • Collaborators • SS Papadopulos & Associates • Funding Agencies • NM Interstate Stream Commission • US Army Corps of Engineers

3. Motivation for Understanding: Better Balance of Competing Demands • Agriculture • Municipal/Industrial • Environmental • Interstate compacts

4. The San Acacia Reach: Critical for Rio Grande Compact Compliance

5. Relevant Issues • Water consumption by riparian vegetation • Removal of exotic vegetation • Environmental effects of drying of the river • Potential engineering alternatives

6. Demands On Water Resources

7. Elephant Butte Dam Study Area Aerial view of San Acacia Diversion Dam, looking southwest Low Flow Conveyance Channel San Acacia DiversionDam Socorro Main Canal Aerial view of Elephant Butte Reservoir and Dam, looking northeast

8. transpiration precipitation evaporation Well pumping irrigation River flow LFCC gain Groundwater rechargeand discharge Groundwater rechargeand discharge CONCEPTUAL MODEL OF WATER DYNAMICS Rio Grande drain LFCC East West

9. Approach to Determining Surface Water/Groundwater Interactions • Water dynamics • Water chemistry • Hydrologic modeling

10. Water Dynamics • Determine connectivity between surface water bodies • Determine groundwater response to changing river stage • Evaluate temporal changes

11. Monitoring Network • 7 transects over ~50 miles • ~175 monitoring wells • 25 surface-water-level gauges • ~70 transducers taking hourly water level readings

12. Rio Grande Socorro Main Canal LFCC Monitoring Transect Cross Section

13. Groundwater Levels Rise in Winter SRD LFCC Rio Grande Rio Grande Groundwater Wells LFCC

14. Groundwater Levels Rise in Winter LFCC Rio Grande Rio Grande Groundwater Wells LFCC

15. Groundwater Responds to ET

16. Groundwater Responds to Flooding

17. Hydrological Modeling • Integrate current understanding of GW/SW interactions • Evaluate operations of the river and the LFCC • Evaluate impact of groundwater levels on riparian ET • Investigate management alternatives

18. Key Data Collected Geologic Data • Stratigraphy (color, grain size, hydraulic conductivity) Aquifer Data • Hydraulic conductivities (aquifer testing) • Water-elevation time series

19. 400 ft Legend 20 ft Fine to Coarse Sand, Coarse Sand No Sample Clay, Sandy Clay East Rio Grande West Sand and Gravel, Gravel Silt, Silt & Fine Sand 4560 LFCC Clayey Gravel HWY-W06 Fine Sand HWY-E02 HWY-W07 HWY-W04 HWY-E01 Santa Fe Group Bedrock HWY-E03 Fine to Medium Sand, Medium Sand HWY-W02 HWY-W03 Water Surface 4540 Layer 1 Layer 2 4520 Valley alluvium 4500 Layer 3 4480 Santa Fe Formation 4460 Stratigraphy

20. Aquifer Testing

21. Legend Well 0-20 feet Well 40-50 feet Well 80-90 feet Staff gage Extraction well LFCC Rio Grande Low-permeability zone Aquifer Test Instrumentation 0.5 miles north of Highway 380 in San Antonio 10 07 09 Socorro Riverside Drain LFCC Rio Grande

22. Legend Well 0-20 feet Well 40-50 feet Well 80-90 feet LFCC Rio Grande Low-permeability zone Time-drawdown of nested well W07A,B,C r of W07 = 15 feet

23. Telescopic model -smaller domain -refined grid -constant head from regional model Regional model - ISC AREA OF INTEREST FOR HIGH-RESOLUTION MODELING N Magdalena Mountains San Acacia 60 Socorro San Antonio I-25 San Marcial 380 Rio Grande

24. River water losses in this reach are extreme

25. regional model grid is 1000 feet x 1000 feet MODEL CONSTRUCTION - Model Grid Domain is 320 rows x 170 columns = 54400 grid cells OR 6 miles x 3 miles = 18 miles2 Telescopic model grid is 100 feet x 100 feet

26. Layer 1 - sand Layer 3 - sand/gravel 0 feet 0 feet 35 feet 75 feet Three-Layer Model Layer 2 - clay/silt

27. Surface Water System • Designation of grid cells to represent drains, LFCC, and river. • Each cell has values for: • stage • conductance • bottom elevation • bed thickness • vertical hydraulic conductivity

28. Stream –aquifer System Land Surface Water Table Riverbed Conductance = KLW M River Surface Streambed Representation of Stream –aquifer System Impermeable Walls Head in Cell (h) River Stage (HRIV) MODFLOW River Package: - Riv1 (MODFLOW 83) M RBOT W

29. Estimation of River Stage

30. Legend Crop and pasture Riparian Sandbars Other or inactive Riparian Crops Evapotranspiration IKONOS – July 2000

31. Prescribed Head regional model telescopic model Constant head boundary determined from regional model for every stress period

32. Model Calibration Groundwater Budget

33. EVALUATION OF MANAGEMENT ALTERNATIVES • Removal of the Low Flow Conveyance Channel • Relocation of the River Channel • Decrease in Riparian Evapotranspiration

34. Effects of Removing the LFCC • Groundwater levels rise • 8% increase in riparian ET • Seepage from river decreases by ~70% With LFCC Without LFCC

35. Evaluation of Relocation of River Channel Neil Cupp Neil Cupp LFCC LFCC W-91.28-1 W-91.28-1 Present day Rio Grande location Simulated Rio Grande location W-Perini W-Perini N N 0.5 Miles Highway 380 Highway 380

36. Effect of Channel Relocation • Groundwater rises to the east of the river • 2% decrease in riparian ET • Seepage losses from the river decrease by 34% Original channel Relocated channel

37. Effect of Decreased Riparian ET • Groundwater rises to the east of river • 50% decrease in riparian evapotranspiration translates to a 6% decrease in river seepage

38. Conclusions • The Rio Grande and the shallow groundwater system are highly interconnected • Most of the shallow groundwater is of Rio Grande origin • Channel adjustments and control of riparian vegetation can increase river flows

39. Last Updated: November 3, 2002 Project Home • Rio Grande Project • Robert S. Bowman, Professor of Hydrology Study Area Recent Results Calendar Presentations Modeling Efforts Students Associated Organizations Photo Gallery Home | Geology | Geochemistry | Hydrology | Geophysics | Site Map | Contact Welcome to the Rio Grande Project Website! The Rio Grande supports much of New Mexico agriculture and industry. With headwaters in Colorado and a terminus in the Gulf of Mexico, political, trans-state-boundary conflicts have existed for decades. In an effort to distribute water in a fair manner, the Rio Grande Compact was signed by the three US states and Mexico in 1938. The signing of this compact forced New Mexico into a debt/credit system of water delivery to Texas.                                                                                 Maintaining a fair and even balance of water distribution in New Mexico while continuing to deliver the appropriate volume of water downstream is a daunting task. The goal of this project is to study the surface water/groundwater interactions between San Acacia and Elephant Butte Dam. This reach of the Rio Grande shows distinct losses to the shallow aquifer and if a better understanding of the system is achieved, it may be possible to more efficiently deliver water to Elephant Butte Reservoir and ultimately, Texas. This is a joint project funded by the ISC and Army Corps of Engineers, under the authority of Section 729 of the Water Resources Development Act. STUDY AREAWhat area of the river are we studying? Where are the new wells going to be drilled? RECENT RESULTSUpdated November 3, 2002by Laura WilcoxRecent data shows rising water levels with the onset of the monsoon. Latest water quality sampling (June) shows roughly the same trends as February except that the River displays LFCC trends in the south. (click here for graphs and other cool stuff) CALENDARMeetings and conferences? Sampling? Water level measurements? Drilling? Pump tests? See what we are up to now. PRESENTATIONSWant to learn more? Check out our latest abstracts and presentations. MODELING EFFORTSA coupled surface water/groundwater model is currently being finalized and will aid in the creation of a refined model of the region between Luis Lopez and HW 380. STUDENTSCurrently there are three students working on this project, two hydrology masters degree candidates and one undergraduate geophysics student. ASSOCIATIONSWho else is involved with this project? Where does the money come from? For More Information… www.ees.nmt.edu\bowman\research\RioGrandeProject