Just Add Water and the Colorado River Still Reaches the Sea |
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Authors: | Edward P Glenn Karl W Flessa Michael J Cohen Pamela L Nagler Kirsten Rowell Francisco Zamora-Arroyo |
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Institution: | (1) Environmental Research Laboratory, 2601 East Airport Drive, Tucson, Arizona 85706, USA;(2) Department of Geosciences, University of Arizona, Tucson, Arizona 85721, USA;(3) Pacific Institute, Oakland, California 94612, USA;(4) United States Geological Survey, Sonoran Desert Research Station, University of Arizona, Tucson, Arizona 85721, USA;(5) Department of Geosciences, University of Arizona, Tucson, Arizona 85721, USA;(6) Sonoran Institute, Tucson, Arizona 85710, USA |
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Abstract: | A recent article in Environmental Management by All argued that flood flows in North America’s Colorado River do not reach the Gulf of California because they are captured
and evaporated in Laguna Salada, a below sea-level lakebed near the mouth of the river. We refute this hypothesis by showing
that (1) due to its limited area, the Laguna Salada could have evaporated less than 10% of the flood flows that have occurred
since 1989; (2) low flow volumes preferentially flow to the Gulf rather than Laguna Salada; (3) All’s method for detecting
water surface area in the Laguna Salada appears to be flawed because Landsat Thematic Mapper images of the lakebed show it
to be dry when All’s analyses said it was flooded; (4) direct measurements of salinity at the mouth of the river and in the
Upper Gulf of California during flood flows in 1993 and 1998 confirm that flood waters reach the sea; and (5) stable oxygen
isotope signatures in clam shells and fish otoliths recorded the dilution of seawater with fresh water during the 1993 and
1998 flows. Furthermore, All’s conclusion that freshwater flows do not benefit the ecology of the marine zone is incorrect
because the peer-reviewed literature shows that postlarval larval shrimp populations increase during floods, and the subsequent
year’s shrimp harvest increases. Furthermore, freshwater flows increase the nursery area for Gulf corvina (Cynoscion othonopterus), an important commercial fish that requires estuarine habitats with salinities in the range of 26–38‰ during its natal stages.
Although flood flows are now much diminished compared to the pre-dam era, they are still important to the remnant wetland
and riparian habitats of the Colorado River delta and to organisms in the intertidal and marine zone. Only a small fraction
of the flood flows are evaporated in Laguna Salada. |
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Keywords: | Gulf of California Laguna Salada Colorado River estuary Tidal mixing |
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