Fryingpan River E-Flows

The Fryingpan River, located west of Basalt, Colorado, is widely known for its Gold-Medal trout fishery and stunning scenic beauty. Ruedi Reservoir impounds the Fryingpan River 15 miles upstream of Basalt. Water releases out of Ruedi Reservoir support a renowned trout fishery, hydropower generation for the City of Aspen, and water supply for downstream municipalities and agricultural water users. Constraints on water availability and the timing of inflows to the reservoir make it difficult to manage releases to optimally support each downstream use at all times of the year. This is particularly true in dry years. In times of water scarcity, water stored in Ruedi Reservoir is primarily used to deliver water for irrigated agriculture and habitat requirements for Threatened & Endangered fish species on the Colorado River near Grand Junction. In these years, modification of the Fryingpan River’s hydrological regime can be significant.

Reservoir operations in the summer of 2018 highlighted the need for a more strategic approach to managing releases from Ruedi Reservoir. Recent dialog between Roaring Fork Conservancy (RFC), the Ruedi Water and Power Authority (RWAPA), City of Aspen (Aspen), Colorado Water Conservation Board (CWCB), Colorado River Water Conservation District (River District), and the Bureau of Reclamation (USBR) resulted in a commitment from all parties to participate in ongoing cooperative dialog about optimization of water releases to support multiple uses. RFC requires assistance characterizing optimal water management approaches for supporting aquatic life across seasons and different hydrological year types.

Riverine ecosystems are adapted to long-term characteristics of hydrologic behavior and other bio-geophysical factors. Broad patterns of precipitation and topography largely determine a river’s flow regime. In turn, fluvial ecologists generally treat flow regime as the “master variable” exerting an outsized influence on riverine ecosystem form and function. Operation of reservoirs alters the hydrological behavior of downstream streams and rivers.

The interrelationships between physical attributes of the river system affected by reservoirs—including hydrological regime behavior, sediment transport, thermal regimes, and water chemistry—and river health indicators of interest to RFC like trout recruitment, presence and diversity of aquatic macroinvertebrate communities, blooms of didymo (a.k.a. snot rock), and formation of anchor ice is complex. Studies conducted over the previous 80 years explore various aspects of this complexity. 

The body of research and studies generated on the Fryingpan River between the 1940s and the present supports the development of a conceptual model of ecosystem responses to hydrological regime behavior and streamflow management activities. This conceptual model should encourage conversations about system behavior and collective understanding among stakeholders regarding connections between specific hydrological regime characteristics affected by management of Ruedi Reservoir and the ecological or biological variables important to local communities. For the sake of simplicity, the model includes mostly unidirectional relationships—feedback loops are exploded to reveal intermediate connections between variables. This approach increases the number of variables represented in the system, perhaps increasing its complexity at first glance. However, the primary benefit to the end user is that the model becomes more readable and explicit in its representation of system behavior. 

Questions about the ecological ramifications of hydrological modification on the Fryingpan River resulted in numerous studies that attempted to identify “optimal” flow management targets for notable or emblematic species living in and along the river course. While the conceptual model presented above cannot provide instruction or targets for management activities, the historical assessments completed on the Fryingpan River do provide some recommendations for streamflow management for the benefit of the ecosystem.  Flow thresholds provided below reflect recommendations made in those studies. Future work on the Fryingpan River may lead to revision or disqualification of any of these recommended environmental flow thresholds.

RFC requires tools to help guide management activities on the Fryingpan River that will benefit the aquatic and riparian ecosystem. Two such tools are presented here. The first tool predicts ecologically-relevant hydrological regime characteristics using streamflow and climate forecasting data for the Colorado River Basin. The second tool predicts the probability of an exceedance of water temperature water quality standards on the Roaring Fork River in Glenwood as a function of air temperature, streamflows on the Roaring Fork, and the flow contributions from Ruedi Reservoir. Both tools were developed as Bayesian network models and intend to provide decision makers and stakeholders with a means for characterizing events of interest in probabilistic terms, exploring the effects of forecast uncertainty on predictions for the future.

The decision support tools developed and presented here aim to encourage dialog between RFC, RWAPA, Aspen, CWCB, the River District, and USBR in a way to produce a more informed water management decision-making process on the Fryingpan River across year types and into an uncertain future where climate change-induced alteration of regional hydrology may necessitate new operational strategies and release schedules for Ruedi Reservoir. 

The concepts, information, and tools presented here will be most useful to RFC and other local stakeholders where they are incorporated into an adaptive management framework. Adaptive management is simply a management approach that responds to new data and information over time as it relates to success or failure at meeting some stated set of goals or objectives. Annual data collection and analysis efforts will yield information about changing conditions, which can be addressed with on-the-ground action or expanded monitoring and analysis to better understand a given issue. Some suggestions for structuring an adaptive management process on the Fryingpan River are provided below. 

Any functional adaptive management process is built on functional personal and professional relationships. RFC will continue to work with Ruedi Water and Power Authority, City of Aspen, Colorado Water Conservation Board, Colorado River Water Conservation District, and the Bureau of Reclamation to formalize schedules and timelines for dialog, data review, and water management decision-making on the Fryingpan River in the months and years to come.

1. Anderson, R. M. Nehring, R. Barry, and Winters, D., “Stream Fisheries Investigations: Federal Aid Study F-51,” Colorado Division of Wildlife, Jul. 1984.
2. Baessler, J. “Request for Administration of Instream Flow Rights on the Fryingpan River, 02-Sep-2009. 
3. BRW, Dames and Moore, and Colorado State University. 1999. Roaring Fork and Fryingpan Rivers Multi-Objective Planning Project. Prepared for Colorado Water Conservancy Board.
4. Benyahya, L., Caissie, D., St-Hilaire, A., Ouarda, T.B.M.J. and Bobée, B. (2007) A Review of Statistical Water Temperature Models, Canadian Water Resources Journal, 32:3, 179-192, DOI: 10.4296/cwrj3203179
5. Caissie, D. (2006). The thermal regime of rivers: a review. Freshwater biology, 51(8), 1389-1406.
6. Clarke, S. Fuller M., and Sullivan R. A., “Roaring Fork Watershed Plan,” 2012.
7. Colorado Mountain College Natural Resources Management Program, “Didymo Survey, Lower Fryingpan River, Basalt, Colorado, Second Annual Report,” 2015.
8. Colorado Mountain College, Natural Resource Management Program, “Didymo Survey, Lower Fryingpan River, Basalt, Colorado,” 2014.
9. Cubley, Erin S., et al. "Using vegetation guilds to predict bird habitat characteristics in riparian areas." Wetlands (2020): 1-20.
10. Crandall, K. “Fryingpan Valley Economic Study,” Jun. 2002.
11. Gordon, Eric, and Ross K. Meentemeyer. "Effects of dam operation and land use on stream channel morphology and riparian vegetation." Geomorphology 82.3-4 (2006): 412-429.
12. Malone D. G., MSES, “Survey of American Dipper (Cinclus mexicanus) Distribution, Abundance and Reproductive Success as a Baseline Indicator of Stream and Riparian Health on the Fryingpan River, Basalt, Colorado.,” Jun. 2014.
13. England Jr., J. F., Cohn, T. A., Faber, B. A., Stedinger, J. R., Thomas Jr., W. O., Veilleux, A. G., Mason, Jr., R. R. 2019. Guidelines for determining flood flow frequency—Bulletin 17C (USGS Numbered Series No. 4-B5; p. 168). Retrieved from U.S. Geological Survey website:  http://pubs.er.usgs.gov/publication/tm4B5 
14. Espegren, G. D.  Miller, D. D.  and Nehring, R. B.  “Modeling the Effects of Various Angling Regulations on Trout Populations in Colorado Streams,” Colorado Division of Wildlife, Dec. 1990.
15. Finnell, L. M. “Fryingpan-Arkansas Fish Research Investigations: Project Report No. 1,” Colorado Division of Wildlife, Jun. 1972.
16. Finnell, L.M., “Fryingpan-Arkansas Fish Research Investigations: Final Report,” Colorado Division of Wildlife, Oct. 1977.
17. Finnell, L.M. and Bennet, G.L., “Fryingpan-Arkansas Fish Research Investigations: Project Report No. 2,” Colorado Division of Wildlife, Jun. 1973.
18. Finnell, L.M. and Bennet, G.L., “Fryingpan-Arkansas Fish Research Investigations: Project Report No. 3,” Colorado Division of Wildlife, Jun. 1974.
19. Grand River Consulting, “Hydrology Memo: Alternatives that Involved Ruedi Reservoir – 10825 Steering Committee Files,” 01-Jan-2008.
20. Hoppe, R. A. and Finnell, Larry M., “Aquatic Studies on Fryingpan River, Colorado 1969-70,” 1970.
21. Hunter G. N., and O. A. Parson. 1943. A Stream Census of the Fryingpan River, 19421943. Colorado Game and Fish Department. 
22. Leonard, C., Legleiter, C., & Overstreet, B. 2017. Effects of lateral confinement in natural and leveed reaches of a gravel-bed river: Snake River, Wyoming, USA. Earth Surface Processes and Landforms, 42(13), 2119–2138. https://doi.org/10.1002/esp.4157
23. Mahoney, J.M., Rood, S.B. 1998. Streamflow requirements for cottonwood seedling recruitment—An integrative model. Wetlands 18, 634–645. https://doi.org/10.1007/BF03161678
24. Malone and Emeric. 2007. Roaring Fork Stream Health Initiative: Frying Pan River. Prepared for the Roaring Fork Conservancy.
25. Malone, Delia G. 2014. Survey of American Dipper (Cinclus mexicanus) Distribution, Abundance and Reproductive Success as a Baseline Indicator of Stream and Riparian Health on the Fryingpan River, Basalt, Colorado. Prepared for the Roaring Fork Conservancy.
26. Miller Ecological Consultants, Inc., “Fryingpan-Roaring Fork Literature Review,” Feb. 2002.
27. Miller Ecological Consultants, Inc., “A Study of Macroinvertebrate Community Responses to Winter Flows on the Fryingpan River,” Sep. 2006.
28. Miller, W. J. “Roaring Fork Conservancy Basalt, Colorado,” Mar. 2008.
29. Miller, W. J. “Lower Fryingpan River Benthic Macroinvertebrate Study,” Aug. 2014.
30. Nehring, R. B. “Stream Fisheries Investigations: Federal Aid Project F-51-R ‘1988b,’” Colorado Division of Wildlife, Jul. 1988.
31. Nehring, R. B. and Anderson, R. “Stream Fisheries Investigations: Federal Aid Study F-51-R,” Colorado Division of Wildlife, Jul. 1983.
32. Nehring, R. B., “Stream Fishery Investigations: Project F-51-R,” Colorado Division of Wildlife, Jul. 1980.
33. Nehring, R. B., “Stream Fisheries Investigations: Federal Aid Project F-51-R,” Colorado Division of Wildlife, Jul. 1986. 
34. Nehring, R. B., “Stream Fisheries Investigations: Federal Aid Project F-51-R ‘1988a,’” ColoradoDivision of Wildlife, Jul. 1988.
35. Nehring, R. B., “Stream Fisheries Investigations: Federal Aid Project F-51-R,” Colorado Division of Wildlife, May 1990.
36. Nehring, R. B., “Stream Fisheries Investigations: Federal Aid Project F-51,” Colorado Division of Wildlife, May 1991.
37. Nehring, R. B., “Stream Fisheries Investigations: Federal Aid Project F-237-R5,” Colorado Division of Wildlife, Sep. 1998.
38. Nehring, R. B., “Stream Fisheries Investigations: Federal Aid Project F-237-R6,” Colorado Division of Wildlife, Sep. 1999.
39. Nehring, R. B. and Anderson, R. “Stream Fisheries Investigations: Job Progress Report Project F-51-R-6,” Colorado Division of Wildlife, Jun. 1981.
40. Nehring, R. B. and Anderson, R. “Stream Fisheries Investigations: Job Progress Report Project F-51-R-7,” Colorado Division of Wildlife, Jun. 1982.
41. Nehring, R. B. and Thompson, K. G. “Stream Fisheries Investigations: Federal Aid Project F-237R-2 (Formerly Project F-51),” Colorado Division of Wildlife, Aug. 1995.
42. Nehring, R. B. and Thompson, K. G. “Stream Fisheries Investigations: Federal Aid Project F-51,” Colorado Division of Wildlife, Aug. 1994.
43. Nehring, R. B. and Thompson, K. G. “Stream Fisheries Investigations: Federal Aid Project F-237R-3,” Colorado Division of Wildlife, Aug. 1996.
44. Nehring, R. B. and Thompson, K. G. “Stream Fisheries Investigations: Federal Aid Project F-237R-4,” Colorado Division of Wildlife, Aug. 1997.
45. Nehring, R. B. and Anderson, R. M., “Stream Fisheries Investigations: Federal Aid Study F-51,” Colorado Division of Wildlife, Jul. 1985.
46. Nehring, R. Barry, K. Thompson, J. Padia, and B. Neuschwanger, “Whirling Disease Investigations: Federal Aid Project F-237-R7,” Colorado Division of Wildlife, Aug. 2000.
47. Parker, G., & Klingeman, P. C. 1982. On why gravel bed streams are paved. Water Resources Research, 18(5), 1409–1423. https://doi.org/10.1029/WR018i005p01409
48. Ptacek, J. A. Rees, D. E. and Miller, W. J.  “A Study of the Ecological Processes on the Fryingpan and Roaring Fork Rivers Related to Operation of Ruedi Reservoir,” Jun. 2003.
49. Rees, D. E. Ptacek, and Miller, W. J. “A Study of Macroinvertebrate Community Responses to Winter Flows on the Fryingpan River,” Aug. 2004.
50. Rees, D. E. Ptacek, J. A. ., and Miller, W. J., “Supplemental Report: A Study of the Ecological Processes on the Fryingpan and Roaring Fork Rivers Related to Operation of Ruedi Reservoir,” Sep. 2003.
51. Rickenmann, D., & Recking, A. 2011. Evaluation of flow resistance in gravel‐bed rivers through a large field data set. Water Resources Research, 47(7).  https://doi.org/10.1029/2010WR009793 
52. Roaring Fork Conservancy, “Comprehensive Lower Fryingpan River Assessment 2013-2015,” 2014.
53. Roaring Fork Conservancy and Timberline Aquatics, “A Review of Aquatic Life and Stream Health in the Roaring Fork Watershed,” Jul. 2012.
54. Schmidt, L. J., & Potyondy, J. P. 2004. Quantifying Channel Maintenance Instream Flows: An Approach for Gravel-Bed Streams in the Western United States. Gen. Tech. Rep. RMRS-GTR-128. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station. 33 P., 128. https://doi.org/10.2737/RMRS-GTR-128
55. Simons, Li and Associates Inc. 1983. Fryingpan-Arkansas Project, Ruedi Resevoir, Colorado, Round 2 Water Sale, Environmental Assessment. Prepared for Bureau of Reclamation. Denver, Colorado.
56. Tonolla, Diego, Martin Geilhausen, and Michael Doering. "Seven decades of hydrogeomorphological changes in a near‐natural (Sense River) and a hydropower‐regulated (Sarine River) pre‐Alpine river floodplain in Western Switzerland." Earth Surface Processes and Landforms (2020).
57. U.S. Bureau of Reclamation, “Finding of No Significant Impact: Ruedi Reservoir Agreements to Offset HUP Shortages at Green Mountain Reservoir,” Aug. 2002.
58. U.S. Bureau of Reclamation, “Finding of No Significant Impact: Ruedi Reservoir 2012 Agreement,” May 2003.
59. U.S. Department of Interior, Bureau of Reclamation, Simons, Li and Associates Inc., Environmental Research and Technology, Inc. 1989. “Ruedi Reservoir, Colorado, Round II Water Marketing Program, Final Supplement to the Environmental Statement, Fryingpan Arkansas Project. Denver, Colorado. 
60. U.S. Department of Interior, Bureau of Reclamation. 1990. Ruedi Reservoir, Fryingpan-Arkansas Project, Final Supplement to the Environmental Statement, Round II Water Marketing Program, Record of Decision. Denver, Colorado.
61. Venarsky, Michael P., et al. "Shifting stream planform state decreases stream productivity yet increases riparian animal production." Oecologia 187.1 (2018): 167-180.
62. Wesche, T. A. 1991. Flushing flow requirements of mountain stream channels. Report submitted to Wyoming Water Research Center, Laramie, and Wyoming Water Development Commission, Cheyenne.