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Hydrology of the Eastern Plateau Planning Area - Surface Water Hydrology

Click to view Figure 2.0-6

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 hydrologic area (Seaber et al., 1987).  A 6-unit code corresponds to accounting units, which are used by the USGS for designing and managing the National Water Data Network.  There are portions of five watersheds in the planning area at the accounting level: the Little Colorado River, the Lower San Juan River, the Upper Colorado River-Lake Powell Area, the Upper San Juan River and a very small portion of the Lower Colorado River-Lees Ferry to Lake Mead (see Figure 2.0-6). The two largest watersheds, the Little Colorado River and the Lower San Juan River are discussed briefly below.

The Little Colorado River is the main drainage for the planning area, flowing from the White Mountains area and leaving the basin at Cameron.  The northeastern part of the planning area drains northward toward the San Juan River as part of the Colorado River Watershed.  In this area, Chinle Creek collects the majority of the surface water runoff. The southern two-thirds of the basin are within the Little Colorado River watershed. Streams and runoff in this area generally flow toward the Little Colorado River.

Little Colorado River

The Little Colorado River Watershed covers most of the planning area and extends west into the Coconino Plateau Basin where it drains to the Colorado River. The eastern part of the watershed extends into New Mexico. The watershed area is approximately 27,051 square miles and covers about 19% of the state (Parra and others, 2006). The Little Colorado River is the major surface drainage in the watershed, originating in the White Mountains and flowing northwest to the Colorado River. The river was formerly perennial throughout its length but it now flows perennially only from its headwaters to Lyman Lake, north of Springerville (Tellman and others, 1997), below its confluence with Silver Creek and below Blue Springs near its confluence with the Colorado River in the Western Plateau Planning Area. Elsewhere it is intermittent due primarily to impoundments, diversions and falling groundwater levels (Tellman and others, 1997). A number of perennial and intermittent streams occur at higher elevations in the watershed, including Silver Creek and Chevelon Creek (see Figure 2.1-6). Ninety-six percent of the streams in the watershed are ephemeral or intermittent (Parra and others, 2006).

There are currently 21 active streamgage stations in the watershed. The maximum recorded annual flow in the watershed was 587,869 acre-feet at a discontinued gage on the Little Colorado River at Grand Falls located downstream of Leupp. The median flow at this station was 162,171 acre-feet. (see Table 2.1-2)

Most of the 70 major springs in the planning area are located in the Little Colorado River Watershed. Approximately a quarter of the major springs have discharge rates of 100 gpm or more. Discharges from most springs were measured during or prior to 1990 and may not be indicative of current conditions. There are clusters of major springs near Tuba City, in the vicinity of Pinetop-Lakeside and in the Saint Johns-Concho area.  The largest spring, with a measured discharge of over 3,600 gpm is Silver Springs (Table 2.1-5).  Silver Springs discharges water from the volcanic portion of the Pinetop-Lakeside aquifer and maintains perennial flow in Silver Creek.  Historically, Silver Springs provided the majority of the surface water supply for the Silver Creek Irrigation District. White Mountain Lake is the major water storage reservoir for the District (ADWR, 1990b).  There are 94 large reservoirs in the planning area. Information on their storage capacity or surface area, type of use and owner/operator are listed in Table 2.1-4.

Silver Creek

Silver Creek near Snowflake    

Within the watershed, reaches of the Little Colorado River and Nutrioso Creek have impaired water quality due to levels of turbidity, lead, copper and silver in excess of use standards. In addition, eight lakes are impaired due primarily to concentrations of mercury exceeding use standards (see Table 2.1-7)

Lower San Juan River

The Lower San Juan River Watershed drains most of the northeastern portion of the planning area. Chinle Creek is the major drainage, collecting most of the surface water runoff in the area that originates primarily in the Chuska Mountains and the Defiance Plateau (Grahame and Sisk, 2002).  The watershed drains northward toward Utah and the San Juan River which in turn is tributary to the Colorado River. Chinle Creek is perennial for approximately six miles near the Utah border (ADWR, 1994a).

Only one of the four streamgages shown on Figure 2.1-5 is currently active; a real-time gage at Chinle Creek near Mexican Water close to the Utah border. The others were discontinued during 2005-2006. The maximum recorded flow in the watershed was measured at this remaining active gage with a flow of almost 67,700 acre-feet in 1982. Median flow at this gage is about 15,500 AFA (see Table 2.1-2).

There are seven major springs identified in the watershed.  The largest is an unnamed spring west of Kayenta with a discharge rate of 30 gpm. There are seven large reservoirs in the watershed including the fourth largest in the planning area, Many Farms Lake.  The dam was constructed in 1937 for irrigation purposes at the community of Many Farms north of Chinle.


For more information on surface water in the Eastern Plateau Planning Area see Section 2.1.4 - Surface Water Conditions and Section 2.1.5 - Perennial/Intermittent Streams and Springs

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