Karl Flessa

Professor of Geosciences

University of Arizona

Karl Flessa

Contact Information

Phone: (520) 621-7336
Email: kflessa@email.arizona.edu

Research Interests & Background

Karl Flessa and his students have been conducting research on the Colorado River delta since 1992.  They have documented the effects of upstream water diversions on the fauna of the river’s estuary and estimated flows necessary for their restoration.  Flessa directed the NSF-supported Research Coordination Network: Colorado River Delta, the environmental monitoring program for the Ciénega de Santa Clara during the test run of the Yuma Desalting Plant and is currently the Chief Scientist for the Minute 323 Monitoring Program for the Colorado River Delta.  He was a Distinguished Visiting Scientist at Australia’s CSIRO, where he studied river management in the Murray-Darling Basin.  He received his undergraduate degree at Lafayette College and his Ph.D. from Brown University.

Selected Colorado River Publications & Presentations


Flessa, K., 2022.  A proposed Arizona Water Authority is not enough tot save us.  Arizona republic, April 8, 2022.  https://www.azcentral.com/story/opinion/op-ed/2022/04/08/arizona-water-authority-alone-wont-solve-shortage/9485583002/

Zamora, H.A., Eastoe, C.J., McIntosh, J.C. and Flessa, K.W., 2021.  Groundwater origin and dynamics on the eastern flank of the Colorado River Delta, Mexico. Hydrology 2021, 8, 80. https://doi.org/10.3390/hydrology8020080

Gómez‐Sapiens, M.M., Jarchow, C.J., Flessa, K.W., Shafroth, P.B., Glenn. E.P., and Nagler, P.L., 2020.Effect of an environmental flow on vegetation growth and health using ground and remote sensing metrics.  Hydrological Processes.  34: 1682-1696. https://doi.org/10.1002/hyp.13689

Nelson, S.M., Kendy, E., Flessa, K.W., Rodríguez‐Burgueño, J.E., Ramírez‐Hernández, J., Rivas‐Salcedo, T.E.. 2020. Channel incision by headcut migration: Reconnection of the Colorado River to its estuary and the Gulf of California during the floods of 1979–1988. Hydrological Processes. 34: 4156– 4174. https://doi.org/10.1002/hyp.13858

Wilder, M.O., Varady, R.G., Gerlak, A.K., Mumme, S.P., Flessa, K.W., Zuniga-Teran, A.A., Scott, C.A., Pineda Pablos, N. and Sharon B. Megdal, S.B., 2020. Hydrodiplomacy and adaptive governance at the U.S.-Mexico border: 75 years of tradition and innovation in transboundary water management. Environmental Science & Policy, 112: 89-202. https://doi.org/10.1016/j.envsci.2020.05.013

Glenn, E., Flessa, K.W., Kendy, E., Shafroth, P.B., Ramirez-Hernandez, Gomez-Sapiens, M., and Nagler, P.L., eds.  Environmental flows for the Colorado River Delta: Results of an experimental pulse release from the US to Mexico.  Ecological Engineering 106, Part B., 629-808. https://www.sciencedirect.com/journal/ecological-engineering/vol/106/part/PB

Bark, R.H., Robinson, C.J. and Flessa, K.W., 2016.  “Tracking cultural ecosystem services: water chasing the Colorado River restoration pulse flow.”  Ecological Economics 127:165-172. http://www.sciencedirect.com/science/article/pii/S0921800915304067

Flessa, K.W., E.P. Glenn, O. Hinojosa-Huerta, C.A. de la Parra-Renteria, J. Ramirez-Hernandez, J.C. Schmidt, and F. Zamora-Arroyo.  2013.  Flooding the Colorado River Delta: A landscape-scale experiment.  EOS 94: 485-486.  http://onlinelibrary.wiley.com/doi/10.1002/2013EO500001/pdf


Arizona Public Media, 2020 The Delta.  https://tv.azpm.org/p/season5/2019/4/29/150657-the-delta/

Flessa, K.W.  2021.  Video lecture (46 minutes): Conservation paleobiology of the Colorado River Delta. https://conservationpaleorcn.org/webinar-1-content-page/  Research Coordination Network for Conservation Paleobiology

“Possible Delta Solutions” at the Colorado River Conversations: Integrating Science and Identifying Solutions conference. Tucson, AZ; October 29, 2019. https://ccass.arizona.edu/sites/default/files/CRCC_FinalAgenda_0.pdf

"Minute 319 and Minute 323 of the US-Mexico Water Treaty: When science matters and when it doesn’t” at the Sustainable Development for the Americas conference. Tucson, AZ; October 24, 2019.  https://shepdiplomacy.arizona.edu/2019-conference/conference-agenda

“Establishing a Baseline With Science” at the Desert Waters International Symposium.  Tucson, AZ; April 2, 2019.

“Looking back/looking forward: Minute 319/Minute 323” at the Lessons Learned Workshop.  Mexicali, Mexico; October 24, 2018.

“Minute 319 and the Colorado River delta” at the Binational Water Relations at 75 Years: Retrospectives, Resilience, and U.S.-Mexico Border Water Resources Governance.  Tucson, AZ; October 15, 2018. http://aquasec.org/events/workshops/binational-workshop-at-75-years/

“The Sum of the Parts: A Blueprint for Lower Basin Sustainability?” at the conference “Fighting Back on the Colorado River: Carving Out Progress on Multiple Fronts.”  Getches-Wilkinson Center for Natural Resources, Energy and the Environment, University of Colorado; Boulder, CO; June 8, 2017. https://www.getches-wilkinsoncenter.cu.law/2017/06/11/martz-summer-conference-2017/

“Transboundary environmental flows to the Colorado River Delta: When the past matters and when it doesn't” at the International Conference on Ecological Sciences. Marseille, France; October 26, 2016.  https://sfecologie2016.sciencesconf.org/106008

“Two years after the flow: Hydrologic and ecological effects of the 2014 environmental flow to the Colorado River delta” at the Geological Society of America Annual Meeting. Denver, CO; Sept 26, 2016. https://gsa.confex.com/gsa/2016AM/webprogram/Paper278839.html

Presenter at the Conservation Biology Program, University of Minnesota, Twin Cities: “A brief meeting of the waters: Science and policy of the first environmental flow to the Colorado River Delta” to the Conservation Biology Program, University of Minnesota, Twin Cities; February, 2016.