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U.S. GEOLOGICAL SURVEY
Scientific Investigations Report 2009–5014

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Introduction

Background

The Humboldt River basin is the largest river basin that is entirely within the State of Nevada. Numerous diversions reduce flow in the river, and the diverted surface water is used almost exclusively for irrigation of crops and meadows, especially in the middle and lower reaches. Even though the upper Humboldt River basin encompasses only about 25 percent of the entire river basin (fig. 1), the upper Humboldt River basin is the source of almost all of the total flow of the river.

Elko County officials and citizens are concerned about growing demand for water within the county and increasing external demands that are occurring statewide. Because flow of the Humboldt River and its tributaries is fully appropriated, any additional water needed to support growth in the upper Humboldt River basin presumably would come from ground water. However, ground water and streamflow can be intimately connected in lowland areas where ground-water discharge to the stream channel sustains flow (baseflow) during low runoff periods. Decisions to further develop the ground-water resources of the upper Humboldt River basin will need to consider the potential effects of such development on streamflow. County and State water-resource managers need information that will enable them to make informed decisions regarding future use of the ground-water resources of the upper Humboldt River basin. To address these needs and concerns, the U.S. Geological Survey (USGS), in cooperation with Elko County, evaluated the water resources of the upper Humboldt River basin in northeastern Nevada during Federal fiscal years 2007–08 (fig. 1).

Purpose and Scope

This report presents the Upper Humboldt River basin phase one results. The objective of this report is to provide hydrologic information that improves the understanding of the water resources of the upper Humboldt River basin; specifically the delineation of the hydrogeologic framework and descriptions of the occurrence and movement of ground water in and between the eight hydrographic areas that make up the basin. The hydrogeologic framework of the study area comprises the extent, both areally and at depth, of rocks and deposits that store and transmit ground water (aquifers) and rocks and deposits that impede the movement of ground water (confining or semiconfining units). Delineation of the hydrogeologic framework of the upper Humboldt River basin is based on geologic and hydrogeologic studies completed during the past 60–70 years. The discussion of the occurrence and movement of ground water is based on water levels that were measured during the spring and summer of 2007 in about 160 wells.

Description of Study Area

The upper Humboldt River basin covers an area of 4,364 mi² in northeastern Nevada, and consists of eight hydrographic areas—Marys River Area, Starr Valley Area, North Fork Area, Lamoille Valley, South Fork Area, Huntington Valley, Dixie Creek–Tenmile Creek Area, and Elko Segment (fig. 1, table 1). These eight areas encompass the headwaters of the Humboldt River, which is the source of nearly all of the total flow of the river in years of average flow. From west to east, gaged tributaries of the upper Humboldt River are South Fork Humboldt River, North Fork Humboldt River, Lamoille Creek, and Marys River. Other tributaries include Secret, Starr, Tabor, and Bishop Creeks. Altitudes of land surface in the study area range from 4,900 to 5,900 ft along the flood plain of the Humboldt River to greater than 11,000 ft in the highest parts of the Ruby Mountains. Each of the hydrographic areas is described briefly below.

The Marys River Area covers 1,073 mi² and is drained by Marys River and its tributaries on the north and west and by Bishop and Tabor Creeks on the east (fig. 1). The area is bounded by the Snake Mountains to the east, the Jarbidge Mountains to the north, the Peko Hills to the west, and by the Humboldt River to the south.

The Starr Valley Area covers 332 mi² and is drained by Starr and Secret Creeks (fig. 1). The area consists of a northwest sloping pediment bounded by the East Humboldt Range to the east and the Humboldt River to the northwest.

The North Fork Area covers 1,110 mi² and consists of an upper and lower basin, both of which are drained by the North Fork Humboldt River and its numerous tributaries (fig. 1). The upper basin is bounded by the Independence Mountains to the west, the south end of the Jarbidge Mountains to the northeast, and the north end of the Adobe Range to the southeast. The lower basin is bounded by the Adobe Range and Peko Hills to the west and east, respectively, the south end of the Jarbidge Mountains to the north, and the Humboldt River to the south.

Lamoille Valley covers an area of 257 mi² and is drained by Lamoille Creek and its tributaries (fig. 1). The area consists of Lamoille Canyon in the Ruby Mountains and a northwest sloping pediment bounded to the southeast by the mountains, to the northwest by the Humboldt River, and by low topographic divides between the Starr Valley Area to the east and the Dixie Creek–Tenmile Creek Area to the west.

The South Fork Area covers 99 mi² and is drained by the South Fork Humboldt River and its numerous tributaries (fig. 1). The area is bounded by topographic divides between the Dixie Creek–Tenmile Creek Area to the north and Huntington Valley to the south. The two divides converge to the northwest and join at the confluence of the South Fork Humboldt River and Huntington Creek. The Ruby Mountains form the high altitude uplands of the area.

Huntington Valley covers 787 mi² and is drained by Huntington Creek and by several tributaries that originate in the northeast part of the area. The area is bounded by the Ruby Mountains to the east, by the Diamond Mountains and Pinon Range to the west, by low topographic divides to the south and north.

The Dixie Creek–Tenmile Creek Area covers 392 mi² and is drained by the South Fork Humboldt River and its two main tributaries in the area—Dixie and Tenmile Creeks (fig. 1). Since December 1987, flow has been regulated by the South Fork Reservoir, which has a maximum altitude of 5,231.4 ft. The Dixie Creek–Tenmile Creek Area is bounded by the South Fork Area and Huntington Valley to the south, Lamoille Valley to the east, the Pinon Range to the west, and by a group of unnamed hills to the north that extend from the Elko Hills to the north end of the Pinon Range.

The Elko Segment covers 314 mi² and consists of the Humboldt River flood plain and adjacent uplands (fig. 1). The area is bounded by the Adobe Range to the north and the Elko Hills and north end of the Pinon Range to the south.

Streamflow is an important component of the water resources of the upper Humboldt River basin. Although a detailed discussion of the streamflow characteristics of the study area is beyond the scope of this report, a short summary, with examples, will help to emphasize the importance of streamflow and its interactions with ground water. See Eakin and Lamke (1966) and Prudic and others (2006) for more details on streamflow characteristics of the Humboldt River.

The streamflow characteristics of the upper Humboldt River and its tributaries are summarized by the flow-duration curves in figure 2, which show the frequency, as percent of time, that a given stream discharge per square mile of drainage area was equaled or exceeded during the period of record for water years 1992–2007. The term “water year” means a 12-month period beginning on October 1 and ending the following September 30. The curves in figure 2 represent streamflow conditions of the Humboldt River at the Elko and Carlin gaging stations and at Marys River, Lamoille Creek, and South Fork Humboldt River above Tenmile Creek (see fig.  1 and table 2 for station locations and descriptions). All curves tend to flatten at their upper ends, indicating that high flows are dominated by snowmelt runoff (Searcy, 1959, p. 22). At their lower ends, the curves for the Elko, Carlin, Lamoille Creek, and South Fork stations also flatten, which indicates that late summer and autumn baseflow of each stream is sustained by ground-water discharge to the stream channel (Searcy, 1959, p. 22). In contrast, the curve for the Marys River station steepens at its lower end indicating the stream at this site has no baseflow and goes dry every summer and autumn.

The curves also indicate that the runoff yield (discharge per square mile of drainage area) of Lamoille Creek is much greater than that of the other four stations. The reason for this is that the entire watershed above the Lamoille Creek station is at high altitude and is underlain by low permeability crystalline rocks. In contrast, the watersheds above the other four stations include large areas of low altitude and they are underlain by rocks of varying permeability.

Curves for the Elko and Carlin stations indicate similar flow characteristics at high to medium flows. At low flows, however, the curves diverge and flow at Carlin is an order of magnitude greater. Two reasons for this are that: (1) regulated flow of the South Fork Humboldt River provides a perennial source of discharge to the mainstem of the river between Elko and Carlin, and (2) flow in the Humboldt River increases downstream of the Elko gaging station due to ground-water discharge.

On October 19, 1992, after several years of below average precipitation, USGS measured the flow of the Humboldt River and its main tributaries and diversions at 35 sites from the Elko to Imlay gaging stations (Emett and others, 1994, p. 475). Three sites were measured that day in the vicinity of Elko—Humboldt River near Elko, Humboldt River near Carlin (sites 4 and 7, fig. 1) and South Fork Humboldt River near Elko at its confluence with the mainstem Humboldt River. The timing of these measurements was such that daily minimum temperatures had been low enough to have minimized the effects of evapotranspiration, but not low enough to cause formation of ice and consequent reduction of streamflow. The three measurements together (Carlin station minus Elko station minus South Fork Station) indicate that the Elko to Carlin reach of the Humboldt River was gaining about 9.1 ft³/s or about 6,600 acre-ft/yr, as ground-water discharge to the river channel. This might be a minimum value of ground-water discharge to the river channel because several years of drought preceded the time of the measurements.

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