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Western Plateau Planning Area Hydrology - Surface Water

Click to view Figure 6.0-7

Figure 6.0-7 USGS Watersheds in the Western Plateau Planning Area

The U.S. Geological Survey (USGS) divides and subdivides the United States into successively smaller hydrologic units based on hydrologic features.  These units are classified into four levels. From largest to smallest these are: regions, subregions, accounting units and cataloging units.  A hydrologic unit code (HUC) consisting of two digits for each level in the system is used to identify any hydrologic area (Seaber et al., 1987).  A 6-digit code corresponds to accounting units, which are used by the USGS for designing and managing the National Water Data Network.  There are portions of three watersheds in the planning area at the accounting unit level: Upper Colorado River-Lake Powell; Little Colorado River; and Lower Colorado River, Lees Ferry to Lake Mead (Figure 6.0-7).

Upper Colorado River-Lake Powell Watershed

The boundary of the Upper Colorado River-Lake Powell Watershed in Arizona coincides generally with the Paria Basin boundary.  It includes the Paria River Canyon and a small portion of the Kanab Plateau Basin.  The Paria River originates in south-central Utah, draining an area of about 1,410 square miles before discharging to the Colorado River north of Lees Ferry.  The annual flood series of the Paria River shows a decrease in flood peaks over the period 1909, 1924-2003. There have been no significant changes in basin diversions over this period, suggesting that construction of stockponds may be responsible (Webb and others, 2007).

The Paria River and the Colorado River are the only perennial streams in this portion of the watershed.  The single streamflow gage in the watershed is located on the Paria River at Lees Ferry.  With 79 years of record, the average annual flow is over 20,000 acre-feet and maximum flow was almost 48,000 acre-feet in 1980 (Table 6.3-2).  There are two nearby gages on the west side of the Colorado River in the Eastern Plateau Planning Area; the Colorado River below Glen Canyon Dam and the Colorado River at Lees Ferry.  The gage below Glen Canyon Dam was installed after dam construction and reflects regulatory/managed releases from Lake Powell.  Prior to construction of the dam in 1963, the average flow was about 12.9 maf per year.  The average annual flow at this gage is now 8.4 maf.  Downstream, flow records at the gage on the Colorado River at Lees Ferry show an average annual flow of 20.3 maf.  This gage has been in operation since 1921.

In May 1983, a heavy snowpack in the Upper  Colorado River Basin combined with sudden warming and rainfall caused severe flooding along the Colorado River, forcing use of the Glen Canyon Dam spillways for the first time since dam completion in 1964.  The total discharge peaked at 92,000 cubic feet per second (cfs) and the reservoir level topped out on July 15th, six feet below the crest of the dam (Hannon, 2003).  By contrast, daily releases from Glen Canyon Dam in August 2009 were 13,000 cfs on average and, due to prolonged drought, the reservoir is projected to be at 65.8% capacity by the end of the water year on September 30, 2009 (USBOR, 2009).  From 2000 though 2008, inflow to Lake Powell was below average in all but two years. Further, the average natural flow during this period for the Colorado River at Lees Ferry is the lowest nine-year average in over 100 years of record keeping on the Colorado River (USBOR, 2008).

Lake Powell provides water storage to meet flow obligations at Lees Ferry under the terms of the 1922 Colorado River Compact. (See Volume 1)  The Compact apportioned to the Upper and Lower Basin states the beneficial consumptive use of 7.5 maf of water to each basin annually, measured at the Colorado River at the Compact Point near Lees Ferry.  The reservoir has a total storage capacity of 27 maf, generally equivalent to the average annual flow of the Colorado River over a two-year period, making it the second largest reservoir in the country.  The Glen Canyon Power Plant consists of eight generating units and provides most of the electrical energy generated by the Colorado River Storage Project.  Total generating capacity is 1,296,000 kilowatts (USBOR, 2005).

Glen Canyon Dam

Glen Canyon Dam, Paria Basin.  In May 1983, a heavy snowpack in the Upper Colorado River Basin combined with sudden warming and rainfall caused severe flooding along the Colorado River, forcing use of the Glen Canyon Dam spillways for the first time since dam completion in 1964. 

There are no major springs (>10gpm) in the watershed although springs reportedly have supported domestic and stock watering uses in the Paria Basin (Bush and Lane, 1980).  The Paria River has been identified as an impaired reach for its entire 29-mile length in Arizona, due to a high concentration of suspended sediments (ADEQ, 2005a), see Figures 6.3-10 and 6.4-9.

The Little Colorado River Watershed

The Little Colorado River Watershed extends over a large portion of northeastern Arizona, including most of the Eastern Plateau Planning Area. Within the Western Plateau Planning Area, this watershed covers the eastern portion of the Coconino Plateau Basin from The Gap and Desert View south toward Flagstaff.  The Little Colorado River is the major drainage in the entire Coconino Plateau Basin, flowing east to west to join the Colorado River.  The only perennial flow in this portion of the watershed is a 13-mile stretch of the Little Colorado River below Blue Springs.

Little Colorado River at Cameron

Little Colorado River at Cameron. An active gage on the Little Colorado River at Cameron has been in operation since 1947. Maximum annual flow at this gage was over 603,000 acre-feet in 1993.

An active gage on the Little Colorado River at Cameron has been in operation since 1947.  Flow is highest in the winter at this gage, with a median annual flow of over 138,000 acre-feet.  Maximum annual flow at this gage was over 603,000 acre-feet in 1993 (see Figures 6.1-5 and 6.1-6 and Table 6.1-2).

The springs in the lower reach of the Little Colorado River, about 13 miles upstream of its confluence with the Colorado River, are sometimes collectively referred to as Blue Springs. Other sources refer to the main spring as Blue Spring. Discharge from the Blue Springs area is estimated at over 101,000 gpm, or about 164,000 AFA (Table 6.1-5). These springs emanate from solution channels in the R-aquifer while the discharge is thought to be downward leakage from the C-aquifer (Leake and others, 2005).

 

water drop Click here to continue to Section 6.0.2 Hydrology - Surface Water (Lower Colorado River Lees Ferry to Lake Mead Watershed)

 

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