WSP12647 ‎(2)‎

• File Number: 8282.400
• Description: Colorado River Operations and Accounting - Deliveries to Mexico
• State: CO
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 6/1/1999
• Author: Environmental Defense Fund
• Title: A Delta Once More - Restoring Riparian and Wetland Habitat in the Colorado River Delta - Environmental Defense Fund - 06-01-99
• Water Supply Pro - Doc Type: Report/Study

0033?3

Colorado River Delta Riparian
Corridor and Wetland (Zone 4)

. Identify measures to restore a perennial source of
water to riparian corridor and wetlands to support
cottonwood-willow habitat and its high biodiversity
value. IBWC CNA, BOR,SEMARNAP-INe

. Evaluate the possibility of routing treated waste-
water from Mexicali to wetlands downstream of the
Rio Colorado/Rio Hardy confluence. The Mexicali II
wastewater treatment plant is currently in the
advanced planning stage. Unanswered questions
include the quantity and quality of wastewater avail-
able, the cost of pumping wastewater to the Rio
Hardy basin (if the plant is located outside the
basin), the environmental consequences of using the
wastewater, and the potential for sharing the waste-
water with agricultural users in the Mexicali Valley.
IBWC CNA, EPA, SEMARNAP-INE

. Identify the potential for delta wetlands to serve as a
component of the Mexicali wastewater treatment pro-
cess. This alternative could save treatment costs and
provide a perennial source of water for some portion
of delta wetlands. Unanswered questions include the
cost of the system, the environmental impact, and the
value of this water to wetland habitat and species.
SEMARNAP-lNE EPA, CNA

Rio Hardy Wetlands (Zones 4 8- 5)

. Monitor levels of selenium, boron, arsenic, and
salinity to determine if water is safe for activities such
as water skiing, swimming, fishing, agriculture, and
aquaculture. Pay particular attention to levels at
Campo Mosqueda, Cucapa EI Mayor, Cucapa
Complex, the Colorado River riparian corridor, the
Pescaderos River, Campo Sonora, and EI Mayor.
SEMARNAP-INe EPA, CNA, PRONATURA

. Use monitoring to identify ways to improve water
quality, particularly in areas frequented by people.
SEMARNAP-INe lTESM, PRONATURA

ENvmONMENTAl0EHNSE FUND

. Restore stream capacity of the Colorado River, just
below its confluence with Rio Hardy (in the Cucapa
EI Mayor-Cucapa Complex), for storing water in
wetlands used by the Cucapa for fishing. CNA

. Identify opportunities to use floodwater or pulse
flows released into the levee system along the Hardy
and Colorado rivers at Campo Sonora and EI Mayor
to reestablish flows and flush selenium. CNA,
FRONA TURA, research institution..,

. Erect signs to warn of water quality problems.
SEMARNAP-INePRONATURA

La Ch!nega de Santa Clara/EI Doctor /
Ellndio (Zone 7)

. Maintain the water supply to la Cienega de Santa
Clara by ensuring that the Yuma Desalting Plant does
not begin to divert wastewater from the MODE
canal. The Bureau of Reclamation is considering
proposals to allow the plant to be used to treat
agricultural wastewater from California's Imperial Ir-
rigation District. This plan can be supported if it
would not effect water supplies to la Cienega de Santa
Clara. BO~ SEMARNAP-INe CNA, IBWC

. In the event that agricultural drainage is diverted to
the Yuma treatment plant, ensure it is replaced with
another source of water. Substitute sources might
include groundwater pumped at the border, water
now delivered to the Southern International
Boundary (if Mexico negotiates delivery of its full
treaty amount at the Northern International
Boundary), or agricultural return flows collected and
treated (if necessary) in Mexico. BOR, CNA, IBWC

. Begin monitoring for selenium in water flowing into
la Cienega de Santa Clara. Also monitor levels in
sediments, plants, and vertebrates and track changes
in selenium concentrations that might indicate toxic
hazards to fish and wildlife. Conduct a study to model
the mass balance of selenium throughout the
ecosystem. SEMARNAP-INe USEPA

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