Technical Appendix 2 Hydrologic Modeling Analysis TABLE OF CONTENTS INTRODUCTION ..................................................................2-1 MODELING APPROACH ...........................................................2-1 RiverWare ..................................................................2-1 RiverWare Model of the San Juan River ..........................................2-2 Configuration for Project Analysis ...............................................2-6 Configuration for Refined Alternative 4 ...........................................2-7 Configuration for Refined Alternative 6 ..........................................2-15 IMPACT ANALYSIS RESULTS .....................................................2-19 Future without Project Analysis ................................................2-19 Refined Alternative 4 Impact Analysis ...........................................2-19 Animas River Impacts from Refined Alternative 4 ...........................2-19 La Plata River Impacts from Refined Alternative 4 ..........................2-21 Mancos River Impacts from Refined Alternative 4 ...........................2-26 San Juan River Impacts for Refined Alternative 4 ...........................2-26 Ridges Basin Reservoir Water Level Impacts from Operation of Refined Alternative 4 ..................................................2-30 Navajo Reservoir Water Level Impact from Operation of the Refined Alternative 4 .................................................2-32 Impacts of the Non-Structural Components of Refined Alternative 4 ............2-32 Refined Alternative 6 Impact Analysis ...........................................2-32 Pine River Impacts from Refined Alternative 6 .............................2-32 Florida River Impacts from Refined Alternative 6 ...........................2-33 Animas River Impacts from Refined Alternative 6 ...........................2-33 La Plata River Impacts from Refined Alternative 6 ..........................2-37 San Juan River Impacts from Refined Alternative 6 ..........................2-38 Mancos River Impacts from Refined Alternative 6 ...........................2-39 Navajo Reservoir Impacts from Refined Alternative 6 ........................2-39 Dolores River Impacts from Refined Alternative 6 ...........................2-39 McElmo Creek Impacts from Refined Alternative 6 ..........................2-39 Impacts due to the Non-Structural Component of Refined Alternative 6 Necessary to Provide an Additional 13,000 afy of Depletion to the Ute Tribes ....................................................2-40 SUMMARY ......................................................................2-40 References .......................................................................2-43 MODEL OUTPUT .................................................................2-44 2-i LIST OF TABLES Table 2-1 Estimated Current Depletions in the San Juan Basin ..........................2-8 Table 2-2 Summary of Future Without Project (Baseline) Depletions in the San Juan River Basin .........................................................2-10 Table 2-3 Modeled Diversion and Depletion Summary for Refined Alternative 4 with All M&I Use at 50% Efficiency .........................................2-12 Table 2-4 Modeled Diversion and Depletion Summary for Refined Alternative 6 with M&I Use at 50% Efficiency ............................................2-17 Table 2-5 Mean, Minimum and Maximum Monthly Average Flow of the Animas River at Three Locations for Future Conditions with and without the Project ...........2-20 Table 2-6 Mean, Minimum, and Maximum Monthly Average Flow of the La Plata River at Two Locations With and Without Refined Alternative 4 ......................2-24 Table 2-7 Mean Monthly Flows for the San Juan River at Four Corners, New Mexico (USGS Gage) with Refined Alternative 4 and without (Baseline Condition) Project for the Modeled Period 1929-1993 .................................2-27 Table 2-8 Summary of Flow Statistics for San Juan River at Four Corners, NM for Pre- and Post-dam Historic Flows, Current Development Level, ALP Baseline Conditions and with Refined Alternative 4 for Period 1929-1993 ............................2-28 Table 2-9 Mean monthly average, maximum and minimum flow (cfs) in the Pine River for Refined Alternative 6 compared to the Future without Project, 1929-1993 ...............2-35 Table 2-10 Mean, Minimum and Maximum Monthly Average Flow of the Animas River at Two Locations for Refined Alternative 6 compared to No Project ...................2-36 Table 2-11 Mean, Minimum and Maximum Monthly Average Flow of the La Plata River at Farmington for Refined Alternative 6 compared to no Project ..................2-37 Table 2-12 Mean, Minimum and Maximum Monthly Average Flow of the San Juan River at Four Corners, NM for Refined Alternative 6 compared to Future without Project Conditions ..........................................................2-38 Table 2-13 Summary of changes in hydrology to rivers in the San Juan Basin from historic conditions due to future non-project development, and the additional depletions for implementation of Refined Alternative 4 and Refined Alternative 6 .............2-41 2-ii LIST OF FIGURES Figure 2-1. Schematic of the San Juan River Basin as Modeled ..........................2-13 Figure 2-2. Detail of components of Refined Alternative 4 in the San Juan Model ...........2-14 Figure 2-3. Schematic of Modeled Components of Refined Alternative 6 ..................2-16 Figure 2-4. Typical Average Year (1945) Hydrograph for the Animas River below the Durango Pumping Plant for Refined Alternative 4 compared to the Future without Project ..2-22 Figure 2-5. Typical Wet Year (1942) Hydrograph for the Animas River below the Durango Pumping Plant for Conditions with and without the Project ....................2-22 Figure 2-6. Typical Dry Year (1951) Hydrograph for the Animas River below the Durango Pumping Plant for Conditions with and without the Project ....................2-23 Figure 2-7. Typical Average Year (1945) Hydrograph for the La Plata River at Farmington for Refined Alternative 4 Compared to the Future without Project .................2-25 Figure 2-8. Typical Wet Year (1942) Hydrograph for the La Plata River at Farmington for Refined Alternative 4 Compared to the Future without Project ........................2-25 Figure 2-9. Typical Dry Year (1951) Hydrograph for the La Plata River at Farmington for Refined Alternative 4 Compared to the Future without Project ........................2-26 Figure 2-10. Typical Average Year (1935) Hydrograph for the San Juan River at Four Corners, New Mexico for Refined Alternative 4 compared to the Future without Project ........2-29 Figure 2-11. Typical Wet Year (1949) Hydrograph for the San Juan River at Four Corners, New Mexico for Refined Alternative 4 compared to the Future without Project ........2-29 Figure 2-12. Typical Dry Year (1951) Hydrograph for the San Juan River at Four Corners, New Mexico for Refined Alternative 4 compared to the Future without Project ........2-30 Figure 2-13. Frequency Distribution of Ridges Basin End-of-month Reservoir Content for the Period 1929-1993 for Standard Operation with Refined Alternative 4 .................2-31 Figure 2-14. Ridges Basin End-of-month Reservoir Content for the Period 1929-1993 for Standard Operation with Refined Alternative 4 .....................................2-31 Figure 2-15. Frequency Distribution of Navajo Reservoir Content for the Period 1929-1993 under Baseline and Standard O peration with Refined Alternative 4 ..................2-34 Figure 2-16. Navajo Reservoir End-of-month Content for the Period 1929-1993 under Baseline Operating Conditions with Refined Alternative 4 ............................2-34 Figure 2-17. Navajo Reservoir End-of-month Content for the Period 1929-1993 under Standard Project Operating Conditions with Refined Alternative 4 ......................2-35 2-iii Appendix 2 Hydrologic Modeling Analysis INTRODUCTION This appendix details the analysis process for determining the water supply available for the Animas La Plata Project (ALP Project) and for examining impacts to hydrology from operation of Refined Alternative 4 and Refined Alternative 6. The results of this modeling effort are also presented. Understanding the impact of the project alternatives on the water resources of the San Juan River basin requires modeling the complex relationships associated with multiple diversion and return flow points associated with the project. A number of basin-scale models exist that take hydrologic input data and simulate the behavior of various processes under different sets of water allocation and infrastructure management. A distinguishing feature of these simulation models is their ability to assess water resource system responses over the long term. There are several best-science river basin simulation models available, any one of which would be appropriate for developing and analyzing San Juan River flow recommendations. RiverWare was selected primarily because of its flexibility and capability to simulate all key features within the San Juan River Basin. RiverWare has been implemented in the San Juan Basin since 1998 in support of assessing the relationship between flow recommendations for endangered fish in the San Juan River and water development. This implementation has been completed by the U.S. Bureau of Reclamation (Reclamation) and Keller-Bliesner Engineering as a consultant for the U.S. Bureau of Indian Affairs (BIA). The