Laserfiche WebLink
<br />1'1 ~l': l. 64 <br />...,v_~ <br /> <br />. <br /> <br />supply is dependent upon State of Colorado water rights administration and may not be a firm <br />supply if those rights are abandoned or otherwise unused. A managed pool goal of at least <br />36,500 acre-feet for downstream fisheries has been suggested to better protect them. <br /> <br />McElmo Creek is much smaller than the Dolores River and is a tributary to the San Juan River. <br />It has been heavily developed for irrigation purposes and presently discharges approximately 35- <br />45,000 acre-feet into the San Juan River, mostly return flow from irrigation water diverted from <br />the Dolores River basin and from tributaries to the San Juan River. Irrigation return flows in the <br />Montezuma Valley area also enter the San Juan River via Navajo Wash, and Montezuma Creek <br />carries return flows to the San Juan from some of the Dove Creek lands. <br /> <br />As indicated above, the 6,000-8,000 acre-feet of water involved in the Carriage eontract <br />discussed in this EA is considered non-project water that MVIe historically diverted from the <br />Dolores River and used and reused in the San Juan River drainage for irrigation. Return flow <br />from that irrigation historically entered the San Juan River. As the efficiency of the MVIC <br />system increased as a result of the salinity features and the assistance from the Natural Resources <br />Conservation Service, and as other factors such as the subdivision development which has <br />occurred in the last 5-10 years, this water became surplus to MVIC irrigators' needs. <br /> <br />When the OWeD acquires the 6,000-8,000 acre-feet, they will supply the water to the Dove <br />Creek area to irrigate new lands. The total annual MVIC diversion for irrigation, including both <br />Dolores Project and non-project water (including the 6,000-8,000 acre-feet being discussed) <br />would continue to be limited by contract to 150,400 acre-feet. The return flows from the new <br />lands would enter the San Juan River via intermittent tributaries that flow into McElmo Creek. It <br />is not possible to ascertain what would occur under the No Action alternative; however, DWCD <br />has indicated they would continue to pursue acquiring the water and using it in the area without <br />using Federal canals. <br /> <br />In terms of salinity, the 6,000-8,000 acre-feet originally was used for irrigation in an area of soils <br />that are known as "gray soils" formed from the Mancos Shale and Mesaverde Formation. Gray <br />soils can present problems for irrigation because of high salinity and poor drainage. The new <br />irrigation lands are on "red soils" with lower salt content. These red soils are eolian soils formed <br />from windblown silt and sand that were reworked by water. These are underlain by sandstone <br />and shale of the Dakota Sandstone Formation (U.S.G.S. et ai, 1997). Thus, any long-term water <br />quality problems associated with deep percolation of irrigation water and resulting return flows <br />should be reduced as compared to using the water on gray soils. <br /> <br />It has long been recognized that irrigation, reservoir evaporation, and municipal and industrial <br />use of water in the Colorado River Basin increases the salinity of the Colorado River. The <br />objective of the Colorado River Basin Salinity Control Program, under which irrigation <br /> <br />2See Response No. 18 in the Consultation and eoordination Section for a discussion of <br />non-project water. <br /> <br />9 <br />