The Humboldt River Basin Assessment
Progress Report
October 1997

Executive Summary

The Humboldt River Basin Assessment was designed to evaluate the regional water resources of the Humboldt River Basin. The assessment consists of three phases, each of which would focus on specific parts of the basin and on differing hydrologic issues. Phase one began on October 1, 1995, and is scheduled to be completed by September 30, 1998. Phase one activities focus on the middle Humboldt River Basin and consist of:

Obtaining hydrologic data and making it available through data bases maintained by the U.S. Geological Survey,
Defining the hydrogeologic framework,
Defining ground-water conditions, and
Refining and developing methods for determining hydrologic budgets at regional scales.

Purpose and Scope

The purpose of this report is to describe progress made as of October 1997 in phase one of the Humboldt River Basin Assessment. A previous report was published describing the progress made as of October 1996. Each of the four activities listed above began in fiscal year 1996 and are nearing completion. Objectives of each of the activities and accomplishments made in 1997 are discussed in this report.

Background

The Humboldt River Basin covers an area of nearly 17,000 square miles in north-central Nevada, and is the only major river basin that is entirely in the State (figure 1). The headwaters of the Humboldt River are in the mountainous regions of northeastern Nevada. In most years, the river terminates at the Humboldt Sink downstream of Lovelock in western Nevada. Water from the Humboldt Sink spills out of the basin into the Carson Sink only in years when winter or spring floods require large releases from Rye Patch Reservoir.

Streamflow of the Humboldt River and its tributaries and ground water are used by diverse, and sometimes competing interests in the basin. Streamflow historically has been used for agricultural purposes--mainly irrigation of crops and meadows and for watering livestock. Agricultural irrigation from surface-water sources accounted for about 75 percent of the estimated 1,000,000 acre-feet of applied irrigation water in 1990 (a drought year; Crompton, 1995). In addition, wetlands along the river and its tributaries provide valuable wildlife habitat, and infiltration of streamflow through stream channels is an important source of ground-water recharge in the basin.

Until about 1980, most ground water in the Humboldt River Basin was pumped for irrigation of crops, for municipal and domestic uses, and for industrial purposes at a few mines scattered throughout the basin. In recent years, increased mining activities have placed new and different demands on the water resources of the basin. As a result of the development of large open-pit mines (figure 1) and the associated increase in population, ground-water use has increased during the last 10-15 years. Currently (1996), there are 23 permitted mining water rights within the Humboldt River Basin (Tim Wilson, Nevada Division of Water Resources, written commun., 1997). Open pits of several gold mines have extended below local ground-water levels. In order to recover ore in these gold mines, it is necessary to dewater the pits. Dewatering rates at individual mines ranged from about 200 to more than 40,000 acre-feet in 1996. Nearly 75 percent or 104,000 acre-feet of the total ground-water withdrawn by mines in 1996 was for dewatering purposes The remaining 39,000 acre-feet was consumed by mining and milling operations.

Excess water from most mine-dewatering operations is reinjected into aquifers nearby or infiltrates to underlying aquifers from storage reservoirs. However, dewatering rates at three of the mines are such that water also must be discharged into the Humboldt River or one of its tributaries. Pumpage of large volumes of ground water for mining use and dewatering has resulted in:

Water-level declines of tens to hundreds of feet in areas of dewatering;
Water-level rises in areas of reinjection or infiltration from reservoirs;
Increases in consumptive use by evapotranspiration;
Use at a nearby power plant; and
Increases in flow of the Humboldt River and its tributaries.

Agencies of Federal, State, and local government and other groups are interested in the long-term viability of the water resources of the Humboldt River Basin because of their regulatory responsibilities and the many varied water uses in the basin. In response to recent increases in mining use and the effects associated with mine dewatering, the U.S. Geological Survey (USGS), in cooperation with the Nevada Department of Conservation and Natural Resources and the U.S. Bureau of Land Management (BLM), has undertaken the Humboldt River Basin Assessment to evaluate the regional water resources of the basin. This assessment is based on an agreement made among the Department of the Interior, Barrick Goldstrike Mines Inc., and Santa Fe Pacific Gold Corporation. Support for the program is being provided, in part, by Barrick Goldstrike Mines Inc. and Santa Fe Pacific Gold Corporation.

The overall objectives of the Humboldt River Basin Assessment are to:

Provide a scientific appraisal of the ground-water and surface-water resources of hydrographic areas in the Humboldt River Basin;
Quantify the contribution of each hydrographic area to the quantity and timing of flows in the main stem Humboldt River; and
Asses the effects of all major water uses in the basin, including mine-related activities, on the quantity, quality, and beneficial uses of those water resources.

A long-term plan for the Humboldt River Basin Assessment was developed by the USGS, with input from the Nevada Department of Conservation and Natural Resources, BLM, Barrick Goldstrike Mines Inc., and Santa Fe Pacific Gold Corporation. Planning also included a series of public meetings in Elko, Winnemucca, Battle Mountain, Carson City, and Reno at the University of Nevada. These meetings were held in 1996 to inform the general public of the Humboldt River Basin Assessment and to use public input to identify water-related issues in the basin. More than 100 people attended the five meetings.

The Humboldt River Basin Assessment will consist of three phases that would extend past the year 2000. Each phase will consist of a series of related and interdependent activities. Present funding is sufficient to carry the assessment only through phase one, which is discussed in this report. The USGS, BLM, and Nevada Department of Conservation and Natural Resources are actively seeking additional funding sources, including mining companies, and other water users, agencies of local, State, and Federal government, and Congressional appropriations. Without continued funding, the assessment can not continue past 1998 when phase one will be completed.

The focus of phase one activities is on the middle Humboldt River Basin which has the greatest current and proposed changes in traditional water uses. The middle Humboldt River Basin consists of 13 hydrographic areas that cover 6,430 square miles (figure 1 and table 1). The 13 areas are tributary to the reach of the Humboldt River that extends from just below Pine Creek on the east to just above Golconda on the west. The principal tributaries to this reach of the river are Rock Creek, and the Reese River. Within the middle part of the basin are large areas of irrigated agriculture, a large power plant, and 16 of the 23 mines with permitted water rights in the Humboldt River Basin.

**Table 1**. Hydrographic areas in the middle Humboldt River Basin
(see figure 1 for locations).
Hydrographic Area
Number	Name	Area (square mi.)
53 54 55 56 57	Pine Valley Crescent Valley Carico Lake Valley Upper Reese River Valley Antelope Valley	1,010 750 380 1,140 450
58 59 60 61 62	Middle Reese River Valley Lower Reese River Valley Whirlwind Valley Boulder Flat Rock Creek Valley	320 590 90 540 440
63 64 65 66	Willow Creek Valley Clovers Area Pumpernickel Valley Kelly Creek Area	410 720 300 300
	Total	7,440

Phase One Objectives and Progress as of October 1997

Hydrologic and Climatic Data

Hydrologic and climatic data have been, and currently are, collected throughout the Humboldt River Basin. Some of these data are collected by private industry to satisfy State or Federal monitoring requirements and are reported to the Nevada Division of Water Resources, Nevada Division of Environmental Protection, or BLM. Other data are collected by State and Federal agencies in support of other studies. Much of these data are stored in different locations and in various formats, including paper files, making data access difficult. The only data that are widely accessible are those collected by the USGS and U.S. National Weather Service. There is a need to assemble hydrologic and climatic data for the Humboldt River Basin together in one data base so that the data are easily accessible. The objective of this part of phase one is to obtain hydrologic and climatic data collected in and around the Humboldt River Basin, and to provide access to this data by way of the internet.

The Humboldt Hydrology web site (http://nevada.usgs.gov/humb) was developed and made operational during fiscal year 1997. The web site facilitates accessing available hydrologic data for the Humboldt River Basin. Currently, only data from the USGS data bases are available through the web site. Documentation describing the proposed long-term plan developed by the USGS and progress reports for each fiscal year published by BLM also can be found on the web site. The Humboldt Hydrology web site also provides access, through internet links, to other web sites including BLM, several mining companies, Nevada Bureau of Mines and Geology and Nevada Mining Association.

Real-time streamflow data, including the most current flow and stage, are available for selected gaging stations within the Humboldt River Basin. Internet accessible hydrologic data bases, available on the Humboldt web site, allows the user to select a geographic area of interest and retrieve several types of hydrologic data within the selected area. These data types include, historical streamflow, well construction and water-level information, and water-quality data.

Although, the weather and climate data bases are not yet available through the web site, the data have been stored on the USGS computer system in Carson City and are currently used in these activities. Climatic data for the Humboldt River Basin also are available through the Natural Resources Conservation Service, the Western Regional Climate Center, and the Nevada State Climatologist. The Natural Resources Conservation Service publishes monthly and annual summaries of data collected at a network of weather stations. These include snowpack data collected at a number of high-altitude sites in the State. BLM operates a network of weather stations in Nevada that is used for predicting fire conditions during the summer. This network of stations is referred to as RAWS (Remote Area Weather Stations) and the data are available through the Western Regional Climate Center.

Also included on the Humboldt Hydrology web site is a reference page that lists citations of both USGS publications and outside journal articles that present information on at least some part of the Humboldt River Basin. These citations can be retrieved either by date of publication (since 1885) or by hydrographic area.

During the period between May and October of 1997 there were over 100 users accessing the Humboldt Hydrology web site. The majority of the users accessed the web site for data searches, however; a fair amount of users used the web site for data retrieval. The web site was found by most users through the Nevada District Projects page and through user specified hotlinks and bookmarks.

Hydrogeologic Framework and Ground-Water Conditions

The geologic environment is a major controlling factor in the hydrologic system within the Humboldt River Basin. An important first step in a hydrologic study is defining the hydrogeologic framework of the study area. Along with the hydrogeologic framework, defining ground-water conditions of the study area also is a critical first step. As an outcome of these considerations, the results of these two activities will be combined and presented together in a single map-style report.

The hydrogeologic framework provides the foundation upon which subsequent parts of the study can be based. The main objectives of this activity are to define the hydrogeologic framework of the middle Humboldt River Basin in terms of those parts of the framework that store and transmit ground water and those parts that impede ground-water movement. Of particular importance are the hydraulic properties, thickness, and lateral extent of basin-fill deposits, because they constitute some of the principal aquifers in the basin. To meet these objectives, USGS personal from the Water Resources Division and Geologic Division collaborated to develop the hydrogeologic framework of the middle Humboldt River Basin. As part of a separate mineral-resources program in the Humboldt River basin, Geologic Division personal used interpretations of gravity data to develop maps showing thickness of Cenozoic basin fill and volcanic rocks. The thickness data is presented as part of the hydrogeologic framework of each hydrographic area, along with information about hydraulic properties of units that makeup the framework in the middle Humboldt River Basin.

Defining ground-water conditions in the middle Humboldt River Basin will form the basis for development of ground-water models in a later phase of the assessment. The purpose of this activity is to describe ground-water conditions, in terms of water levels, in the middle Humboldt River Basin in spring 1982 and spring 1996 with emphasis on conditions of shallow ground water. In spring 1982, the USGS measured water levels at wells throughout the Humboldt River Basin. Measurements were made at 162 wells in the 13 hydrographic areas in the middle part of the basin. In addition, the Nevada Division of Water Resources measured water levels at 65 wells in two of those hydrographic areas. These water levels predate most of the mining activities, including major dewatering, presently underway in the basin, and have been used to develop a map of spring 1982 ground-water levels. However, the water levels do not represent pre-development conditions in the basin because large areas of agriculture were being irrigated by ground water in 1982.

In the spring of 1996, the USGS measured water levels at 211 wells in the middle Humboldt River Basin. In addition, water levels were measured at 115 wells by the Nevada Division of Water Resources, at 21 wells by Sierra Pacific Power Company east of the Valmy Power Plant, and at 184 wells by mining companies at three mines, for a total of 531 wells. These water levels have been used to develop a map of ground-water level as of spring 1996. Changes in ground-water conditions have been documented by comparison of levels in spring 1982 with levels in spring 1996 and with hydrographs for selected wells with long periods of water-level record. The draft report that combines the hydrogeologic framework with ground-water conditions for the two time periods for the middle Humboldt River Basin is completed and going through internal review. The final report is planned to be released by summer 1998.

Hydrologic Budget

Hydrologic budgets were developed for only a few selected hydrographic areas in the middle Humboldt River Basin as part of a series of reconnaissance-level studies made by the USGS in the 1960s. These budgets were based on an empirically derived approach and sparse hydrologic and climatic data and need to be refined. The purpose of this part of phase one activities is to refine and develop methods that can be used to estimate hydrologic budgets at a regional scale by incorporating new data and advanced remote-sensing and geographic information system (GIS) techniques.

The general approach of this activity is to subdivide a hydrographic area into three principal physiographic units or landforms; mountain block, piedmont slope, and valley lowlands, similar to the approach taken by Eakin and others, (1965) and Eakin and Lamke (1966). The budget components within each landform are identified, and the contribution of each is measured or estimated using methods developed as part of this activity. Some budget components are obtained by direct determinations; however, other components were obtained by differences. Three hydrographic areas were selected to test and refine the methods. The estimated budget components are believed to represent average natural conditions. They do not account for streamflow diversions, ground-water withdrawals, and land-use changes, which induce stresses to a hydrologic system and alter the natural conditions. Hydrologic budgets developed for natural conditions provide a foundation upon which the effects of these stresses can be determined by subsequent studies. The final report will document the methods developed so that the same methods can be applied to other basins in the Humboldt River Basin and in the Great Basin generally.

As of October 1997, a conceptualization of a hydrologic budget has been developed and individual budget components within each landform have been identified. A preliminary hydrologic budget for each test basin also have been developed. The report is planned to be released by September 1998.

References Cited

Crompton, E.J., 1995, Potential hydrologic effects of mining in the Humboldt River, northern Nevada: U.S. Geological Survey Water-Resources Investigations Report 94-4233, 2 sheets.

Eakin, T.E., Moore, D.O., and Everett, D.E., 1965, Water resources appraisal of the Upper Reese River Valley, Lander and Nye Counties, Nevada: Nevada Department of Conservation and Natural Resources, Ground-Water Resources - Reconnaissance Report 31, 47 p.

Eakin, T.E. and Lamke, R.D., 1966, Hydrologic reconnaissance of the Humboldt River Basin, Nevada, with a section on Quality of water, by D.E. Everett: Nevada Department of Conservation and Natural Resources, Water Resources Bulletin No. 32, 107 p.

The Humboldt River Basin Assessment Progress Report October 1997