Laserfiche WebLink
DRAFT DRAFT DRAFT <br />Mountains was from south to north toward the Lake Uinta lowlands (Northeast <br />Utah, Northwest Colorado, and Southwest Wyoming), and the anticline did not <br />exist yet. <br />Some 20 to 30 million years ago, renewed uplifts from the La Plata Mountains <br />southward forced the San Juan to relocate further south into New Mexico, but the <br />upper Dolores River which was formerly just a tributary, inherited the entire route. <br />Since then, the anticline has been uplifted, but the Dolores was entrenched and <br />simply dug deeper to form Dolores Canyon. The zigzag path within Dolores <br />Canyon is probably a remnant of another ancestral river (the ancestral Chaco <br />River) that joined the ancestral San Juan before it too was truncated some 20 to <br />30 million years ago." [Bill Butler, Appendix to the Evolution of the Colorado <br />River and its Tributaries (Part 5)] <br />For purposes of this correlation report conditions immediately prior to European <br />settlement will be broadly described. The pre-settlement flow regime in the <br />Dolores River was characterized by high spring runoff flows in April through June <br />which tapered down to the lowest flows in December, January and February. <br />Figure 4 below depicts the monthly percentage of total flows extrapolated from <br />Dolores gage data to include McPhee Reservoir tributaries below the gage (e.g., <br />Plateau Creek). These data will be used in conjunction with annual inflow data <br />for the 76 years from 1928 through 2004 as the best approximation of pre-MVIC <br />flows during dry, wet and average flow years. <br />McPHEE RESERVOIR -PERCENT INFFLOW PER MONTH <br />35.00% <br />32.7% <br />30.00% <br />25.00% <br />20.00% <br />15.00% <br />10.00% <br />5.00% <br />0.00% <br /> <br /> 25.0% <br /> <br />15.0% <br /> <br /> <br />4.2% 7.7% <br />4.8% <br /> <br /> <br />0 <br />° 1.1% 1.1% 1.2% 3.1 <br />2.4% <br />NOV DEC JAN FEB MAR APR MAY JUN JUL AUG SEP OCT <br />Figure 4. Monthly native inflow to McPhee Reservoir, based on gaged data from <br />the Dolores gage data and accounting for tributary inflow below the gage. <br />9/5/06 13 <br />