The effects of damming on the materials flux in the Colorado River delta |
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Authors: | José D Carriquiry Julio A Villaescusa Víctor Camacho-Ibar L Walter Daesslé Pedro G Castro-Castro |
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Institution: | 1.Environmental Geosciences Research Group, Instituto de Investigaciones Oceanológicas,Universidad Autónoma de Baja California,Ensenada,Mexico |
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Abstract: | During the last century, the Colorado River delta (CRD) has been dramatically altered by the diversion of river water for
use in human activities. This alteration has eliminated the delivery of fresh water to the Gulf of California radically transforming
the former estuary into an inverse-estuary. Under the new conditions, the new materials budget was estimated at the mouth
of the Colorado River in terms of salts, total suspended sediments, organic suspended matter and nutrients. The results of
this study show that, because of the asymmetry of the tidal wave, the variability of seston concentration follows a sedimentation
pattern of three successive stages: re-suspension (erosion at ebb flow) > dilution (during flood flow) > sedimentation (at
the end of the flood stage). The tidal asymmetry during neap tides was characterized by longer ebb (at least, 30 min longer)
than flood and more intense ebb currents (as much as 43% higher), hence characterizing an ebb-dominated system. The CRD is
characterized by high nutrients concentrations. Maximal levels are: nitrates (41 μM), phosphates (2.6 μM) and silicates (68 μM),
nitrite (15 μM). The mass balance indicates that the system acts as a net exporter of suspended sediment with rates as high
as 7 tons per tidal cycle. This behavior indicates that the CRD is in a destructive stage as a result of the lack of freshwater
inflow and supply of sediment into the system. |
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