Can the River Reach the Sea? Re-connecting the Colorado River and the Gulf of California

How often does the Colorado River reach the sea? Can active management increase ecosystem services? River-sea connectivity is essential for restoring ecosystem services by sustaining biodiversity and for providing brackish-water nursery grounds for both commercially important and endangered marine species.  I used 20 years of Landsat 5 TM scenes from the Colorado River Delta and remote sensing software to assess river-sea connectivity and geomorphic processes after 50 years of extensive human manipulation of the Colorado River.  The river’s relict channel is obstructed by an accumulation of sediments deposited during flood tides; ebb flows are not strong enough to keep the channel open.  Tides at the mouth of the river reach 10 m in amplitude and can reach into the former channel.  Satellite images and tide charts show that the river reaches the sea or the sea reaches the river for about 25-30 days per year.  As part of a bi-national effort by U.S. and Mexican research institutions to restore the Colorado River Delta, I seek to understand sedimentation in the Colorado River Delta.  A complementary ²¹⁰Pb geochronology study calibrated with anthropogenic-derived markers will quantify sedimentation rates.  Active management –both dredging and water allocations- is required to reconnect the remaining riparian wetlands in the Colorado River to the Gulf of California. Knowing sedimentation rates in the remnant channel will help determine how often the channel needs to be dredged to maintain this connectivity.