Introduction

In October 1995 the U.S. Geological Survey (USGS), in cooperation with the Nevada Department of Conservation and Natural Resources (NDCNR) and the U.S. Bureau of Land Management, began an assessment of the regional water resources of the Humboldt River Basin. This assessment was undertaken in response to concerns over increasing demand for the limited water resources of the basin and potential effects of mine dewatering during the past 10 years. The assessment has focused on 14 hydrographic areas in the middle Humboldt River Basin (fig. 1). This part of the basin includes large areas of irrigated agriculture as well as most of the large gold mining operations in northern Nevada. This progress report is the sixth in a series that have been published since 1996. The purpose of each report has been to discuss assessment activities and progress made during previous years.  This report discusses activities and progress during the period from March 2002 through September 2004. Phase one of the assessment began in October 1995 and was completed in September 1998. Phase two began in October 1998 and was scheduled to be completed in September 2003. However, the project timeframe has been extended, and it is now scheduled to be completed in 2005.

Phase-Two Activities
March 2002-September 2004

Computer Models of Streamflow and Ground-Water Flow

The objective of this activity is to develop a computer model that will simulate the effects of different ground-water withdrawals and climate variability on ground-water levels and streamflow in the middle Humboldt River Basin. This model, referred to as a linked ground-water/surface-water model, will be constructed from a streamflow routing model, rainfall/runoff models of individual watersheds, and a ground-water flow model.

Streamflow Routing Model

A streamflow-routing model of a 153-mile reach of the Humboldt River between the Carlin stream-gaging station and the State Route 789 bridge at Preble was completed in 2002. The model is based on surveyed cross sections of the Humboldt River channel, flow measurements of the river, its tributaries, and diversions, and statistical analysis of historic streamflow records. Model results were published in 2002.

Watershed Models

A watershed model has been developed for the middle Humboldt River Basin. This model will provide the recharge input to the final linked model.

Ground-Water Flow Model

The ground-water flow model is being constructed in two steps. The first step was to construct a model of pre-development or steady-state conditions that were present in the middle Humboldt River Basin before large scale mining and before much of the irrigation development.  This model was completed in 2003.

The second step will be to construct a transient flow model in which the effects of ground-water withdrawals and climate variations are imposed on the steady-state model. Construction of this model is nearly complete and transient simulations should begin in November 2004.

Reports

Five reports have been released as part of the assessment:

Berger, D.L., 2000, Water Budgets for Pine Valley, Carico Lake Valley, and Upper Reese River Valley Hydrographic Areas, Middle Humboldt River Basin, North-Central Nevada—Methods for Estimation and Results:  U.S. Geological Survey Water-Resources Investigations Report 99-4272, 40 p., (See fig. 1 for valley locations).

Berger, D.L., 2000, Water-Budget Estimates for the 14 Hydrographic Areas in the Middle Humboldt River Basin, North-Central Nevada: U.S. Geological Survey Water-Resources Investigations Report 00-4168, 55 p.

Hess, G.W., 2002, Simulation of streamflow, middle Humboldt River Basin, north-central Nevada: U.S. Geological Survey Water-Resources Investigations Report 01-4231, 35 p.

Plume, R.W. and Ponce, D.A., 1999, Hydrogeologic Framework and Ground-Water Levels, 1982 and 1996, Middle Humboldt River Basin, North-Central Nevada:  U.S. Geological Survey Water-Resources Investigations Report 98-4209, 2 map sheets.

Plume, R.W., 2003, Ground-water use, locations of production wells, and areas irrigated using ground water in 1998, middle Humboldt River Basin, north-central Nevada: U.S. Geological Survey Water-Resources Investigations Report 03-4227, 16 p.

Two reports presently (October 2004) are under preparation and should be completed in calendar year 2005. The titles are:

Prudic, D.E., Niswonger, R.G., and Plume, R.W., in press, Trends in streamflow on the Humboldt River between Elko and Imlay, Nevada, 1950-99: U.S. Geological Survey Scientific-Investigations Report 05-xxxx.

Prudic, D.E., Halford, K.J., and Plume, R.W., in press, Evaluation of ground-water pumping on flow in the Humboldt River, middle Humboldt River Basin, north-central Nevada: U.S. Geological Survey Scientific-Investigations Report 05-xxxx.

An additional report was completed in 2004. Although not part of the project, completion of this report was necessary for the modeling effort.

Prudic, D.E., Konikow, L.F., and Banta, E.R., A new streamflow-routing (SFR1) package to simulate stream-aquifer interaction with MODFLOW-2000: U.S. Geological Survey Open-File Report 2004-1042, 95 p.

Funding

Phase two funding for the Humboldt River Basin Assessment has come from USGS, Nevada Division of Water Resources, the Nevada State Legislature, and three mining companies—Barrick Goldstrike Mines, Newmont Mining Corporation, and Glamis Gold Limited. The total six-year budget for phase two is about $2,360,000.