WSP10413

• File Number: 7630.175
• Description: Wild and Scenic-Dolores River
• State: CO
• Basin: San Juan/Dolores
• Water Division: 7
• Date: 1/1/3000
• Title: Dolores Study-Wild and Scenic-Corresp Reports tech etc 1968-81-Water Quality
• Water Supply Pro - Doc Type: Report/Study

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of the salt load of the Colorado River at cisco. The U. S.

Environmental Protection Agency estimates that 72 percent of

dissolved constitutents originate from springs and seeps. Less

than 20 percent results from the activities of man including

agricultural and industrial activities in the basin. Runoff from

non-point souces such as intermittent flows from arid shale lands

contribute 8 percent._1

Sedimentary rocks of ~retaceous age underly the Dolores

River basin. Upstream from the town of Dolores, the rocks are

highly resistant and yield large volumes of good quality water.

The weighted concentration of dissolved solids at Dolores averages

137 mg/l which is equivalent to a salt discharge of 250 tons per

day. At Bedrock the dissolved constitutents have reached a

moderately high concentration of 319 mg/l (456 tons per day).

Between Bedrock and the confluence with the San Miguel River

(about 12 miles) the water quality is severely degraded because

of the intrusion of brine from the Paradox Valley salt anticline.

Approximately 688 tons per day of dissolved solids are added to

the river in this valley which represents 50 percent of the

Dolores River salt load to the Colorado River. The Bureau of

Reclamation is investigating the feasibility of reducing the

saline inflow along this reach of the river as a major part

of its overall program aimed at reducing the salinity of the

Colorado River. _I The reach of the Dolores from Bedrock to the

confluence with the San Miguel River is specifical1y excluded

from study under P.L. 93-621 because of this program and its

expected benefits to the Colorado River system.

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