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Humboldt River Basin Hydrology A Proposed Program of Study to Evaluate the Regional Water Resources of the Humboldt River Basin, Nevada |
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| Table of Contents Background
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| BACKGROUND The Humboldt River Basin, which covers nearly 17,000 square miles of northern Nevada, is characterized by northwest-trending mountain ranges and intervening valleys. The basin includes more than 30 separate valleys and hydrographic areas. The Humboldt River rises in northeastern Nevada between Wells and Elko and flows west and southwest nearly 1,000 miles until it terminates in the Humboldt Sink near Lovelock. Climate, and climate variability, can have a significant, even profound, impact on the hydrology of the Humboldt River Basin. The largest flood discharge of record occurred in 1984, following record winter snowfall in the upper reaches of the basin. The bridge over the Humboldt River at Winnemucca was destroyed, Rye Patch reservoir overflowed, the Humboldt Sink below Lovelock filled, and discharge from the Humboldt River spilled into Carson Sink. By 1993, following several years of drought, the Carson and Humboldt Sinks were once again dry, dusty playas and Rye Patch reservoir was empty. The effects of development are superimposed on the natural climatic changes in the water resources of the basin. Water users rely heavily on surface-water, and to a lesser extent ground-water, resources. Surface and ground water are diverted or pumped from aquifers in the basin for agricultural, livestock and wildlife, industrial, commercial, municipal, domestic, recreational, and public supply uses. The small annual precipitation on valley floors creates large irrigation requirements for agriculture, the greatest water use in the basin. 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 (Crompton, 1995). Diversion of surface water for irrigation reduces downstream flow. Ground-water pumpage for irrigation water lowers ground-water levels in some areas. Applied irrigation water in other areas may raise ground-water levels. Grazing of livestock may alter the runoff characteristics of some parts of the watershed. Foraging by livestock may alter ephemeral stream channels and banks causing increased sediment discharge during periods of flow. Changes in sediment discharge also may be related to changes in convective storm occurrence and size, mining activities, and urbanization. Population increase leads to demands for more water for municipal and commercial supply and for waste-water treatment. Public supply requirements in 1990 were about 15,000 acre-feet, mostly ground water. In recent years, increased mining activities have placed new and different demands on the water resources of the basin. Currently, 14 large-scale and many smaller open-pit gold mines are active in the basin. Large volumes of ground water are being pumped for pit dewatering at some of the mine sites and for milling and other operating activities. Mining operations pumped about 200,000 acre-feet of water in 1993. Competing, and at times incompatible, demands for and uses of the scarce water resources of the Humboldt River Basin have raised concerns by State and local governments about the effects of these demands and uses on the quantity and timing of streamflow on the main stem of the Humboldt River. Recent uncertainties about the regional and long-term effects of dewatering for open-pit mining operations on the hydrology of the middle Humboldt Basin have raised particular concerns. The mine dewatering operations involve the pumping of relatively large volumes of ground water from small areas. Water-level declines caused by this pumping are on the order of tens to hundreds of feet in the vicinity of the mine and may be feet to tens of feet over tens of square miles. Concurrently, the ground-water discharge from mine dewatering operations must be managed. Options for managing the discharge include injecting the dewatering discharge at a location removed from the dewatered site, discharging it into natural watercourses, applying the discharge to other beneficial uses in satisfaction of existing water rights, or spreading it on land surface. Injecting mine-dewatering discharge may cause rises in ground-water levels of feet to tens of feet over tens of square miles. Discharging it into natural watercourses may change the characteristics of any natural flow in the channel. Spreading of mine-dewatering discharge may cause water logging, the creation of temporary wetlands, and local flooding. These concerns can best be addressed and evaluated through a comprehensive program of studies to appraise the water resources of the Humboldt River Basin. A number of programs operated or managed by agencies such as the State of Nevada Department of Conservation and Natural Resources and the Bureau of Land Management can utilize the data and analyses of this program on a regional, comprehensive basis. The U.S. Geological Survey, State of Nevada, and Bureau of Land Management will seek comments from the public to assist in identifying long-term goals and to assure that studies are not being duplicated by other organizations. The objectives of this program are to scientifically appraise the ground-water and surface-water resources of hydrographic areas within the Humboldt River Basin; their contribution to the quantity and timing of flows in the mainstem Humboldt River; and 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. The proposed approach for achieving the objectives of the program is to met conduct a series of related and interdependent studies designed to develop the data and knowledge needed to understand the regional-scale cause-and-effect relations among the various water uses in the basin. The program has been designed so that each study will address independently a discrete topic relevant to the hydrology of the Humboldt River Basin. Succeeding studies may rely on studies conducted earlier in the program to provide relevant data and information. Table 1 lists each of the studies proposed to be conducted by this program. Each study, described in more detail later in this proposal, would last for 2 or 3 years, at the end of which time a report would be published to describe the results of the study. The studies are grouped into 3- to 4-year long phases, each of which would end with a group of related reports and data products. At the end of each phase of program studies, a report summarizing the findings and conclusions of the studies conducted during that phase will be published. In the last year of the study, a final report will be prepared that summarizes the regional hydrology of the Humboldt River Basin based on the reports and findings of the all the studies conducted as part of this program. For purposes of this program, the Humboldt River Basin is divided into upper, middle, and lower basins (fig. 1), the boundaries of which are similar to those of the earlier hydrologic reconnaissance study by Eakin and Lamke (1966). The focus of the Phase I studies will be on the middle Humboldt River Basin which has the greatest current and proposed changes in traditional water uses. Phase II expands the geographic scope to include the headwater valleys in the upper basin. Phase III studies would integrate the data and results from the preceding phases into an overall quantitative summary analysis of the water resources and major water uses of the entire basin. The proposed program does not include any detailed studies directed specifically at the lower basin because the predominant historical and likely future water use is agricultural, which has been relatively constant in location and over time. However, the program data activities and other studies will address the possible effects of water uses in the middle and upper basins on the timing and magnitude of water supply to the lower basin.
1. Hydrogeologic, Hydrologic, and Climatic data for the Humboldt River Basin Basic hydrogeologic, hydrologic, and climatic data are essential to the successful appraisal of the water resources of the Humboldt River Basin. Some of the individual proposed studies of the program will be expected to collect the basic data needed to execute that study. However, some studies proposed for later years in the program will need specific data collected for several years before that particular study begins in order to complete the study in the 2 or 3 years scheduled. For example, the proposed study of the spatial and temporal variability of spring discharge will require at least 3 or 4 years of data upon which to base any analysis; data collection for this particular study cannot wait until the study begins. Additionally, selected hydrologic data will need to be collected for the life of the program in order to provide continuing data for water-management and resource-appraisal decisions. A data management - data network project operated by a program data manager will ensure the development and maintenance of a computer database designed to meet the data needs and data storage requirements of other projects in the program. Existing data in Geological Survey and other databases, including those maintained by other governmental agencies and industry, will be included in the Humboldt River Basin program database, as appropriate. In some cases, the data included may be a subset of larger existing databases such as the Survey's GWSI (Ground Water Site Inventory) and NWIS (National Water Information System). New data collected by projects will be submitted to the program database with the assistance and guidance of the data program manager. Any data collection networks established for the Humboldt River Basin program will be maintained by the data management - data network project. 2. Hydrogeologic Framework of the Middle Humboldt River Basin. Understanding the hydrogeologic framework of an area is the first step in developing an understanding of the ground-water flow system. Much of the water use in the Humboldt River Basin is in the middle basin as defined for this program (fig. 1). Framework and water resource studies recently have been completed for parts of this area (Fig. 2; Plume, 1995; Maurer and others, in preparation). This project will complete the hydrogeologic framework studies for that part of the middle basin not previously studied. 3. Ground-water budgets and water balance for the middle Humboldt River Basin. Reconnaissance hydrologic budgets for valleys of the middle Humboldt River basin were published by Eakin and Lamke (1966). The methods by which the budgets were estimated are not well documented and some of the budgets show significant imbalance. The objective of this project is to determine reasonable and well documented estimates of ground-water budgets and water balances for the middle Humboldt River Basin. A subsequent study will develop similar estimates for the upper basin. Regional ground-water discharge will be estimated and mapped using recently developed methods that relate phreatophyte vegetation index values derived from Landsat data to ground-water discharge by evapotranspiration. These methods have been applied to areas of central Nevada with good results (W.D. Nichols, U.S. Geological Survey, personal comm., 1995). Estimating ground-water recharge is more problematic. Few new methods have been developed for estimating ground-water recharge in semiarid and arid areas since that proposed by Maxey and Eakin (1949). A deep percolation model method was published by Baurer and Vaccaro (1987), but has not worked well in some areas. Dettinger (1989) evaluated a chloride-balance method in basins in central and eastern Nevada with mixed results. All of these methods, however, require estimates of annual precipitation for the basin or area for which recharge estimates are to be made. The lack of significant advance in defining annual precipitation in Nevada since the work of Hardman (1954), may present an obstacle to making reasonable estimates of ground-water recharge, as well as regional water balances, in the Humboldt River basin. The adequacy of the existing annual precipitation map for Nevada (Hardman, 1954), as well as any more recent maps, will be evaluated. It may be possible to improve on existing data using a model for estimating the spatial distribution of precipitation over mountainous terrain proposed by Daly and others (1994), although this model may not provide the level of resolution needed for the present study. New high-altitude precipitation stations may need to be established. 4. Ground-water levels and water-level trends, middle Humboldt River Basin. Ground-water levels respond to ground-water recharge and discharge. In the absence of pumping or injection of water, ground-water levels rise and fall slowly in response to changes in climate. Ground-water pumping for agricultural and other uses may cause significant declines in ground-water levels, while injection of water into the ground-water system may lead to significant rises in water levels. This project will document changes in water levels and the trend of such changes over time. Ground-water levels were measured throughout the Humboldt River Basin in the spring of 1982. Many of these same wells may be revisited in the spring of 1996; a map then may be prepared showing changes in ground-water levels since 1982. Ground-water level data for the Humboldt River Basin,
particularly the middle basin, will be collected for the
duration of the program as part of the data collection
and management project (Project 1). This will include
water-level data collected by other entities such as the
mining companies and the Nevada State Engineer. Maps of
water-level change will be prepared biennially,
concentrating on those areas where significant changes
have occurred. The maps will be accompanied by a
discussion or graphs of trends in ground-water levels
over the measurement period and the period of record. 5. Flow characteristics of the Humboldt River Basin: The role of channel geometry, bank storage, riparian vegetation, and climate variability. Climate variability has a significant impact on the surface-water resources of the Humboldt River Basin. The table below gives the year of minimum and maximum mean annual water-year discharge at three selected gages on the Humboldt River. The lowest flows are difficult to discuss because two of the gages were not in operation in 1934 when the low flow occurred at the gage at Palisade, the gage with the longest record. All the gages, however, record the highest mean annual flow in 1984, following a winter of greatly-above-normal snowpack in eastern Nevada. In water-year 1992, mean annual minimum discharge was near the minimum of record at some gages. Year of minimum and maximum flow for period of record at selected gages on the Humboldt River
The interrelation of channel geometry,
bank storage, riparian vegetation, and climate on the
flow, especially flood flow, of the Humboldt River has
not been well characterized. Water use and development in
the Humboldt River Basin may alter channel geometry, bank
storage, and riparian vegetation and consequently alter
the flow characteristics. This project will evaluate the
role of these factors and the effect they may have on
flow characteristics of the Humboldt River. This project
may include flow-duration analysis, flood frequency
studies, or trend analysis of flood characteristics. 6. Hydrodynamics of ground-water flow in the middle Humboldt River Basin. A conceptual model of ground-water flow in the middle
Humboldt River Basin will be developed from knowledge
gained by the earlier studies to define the hydrogeologic
framework and ground-water budgets of the area. This
conceptual model will be developed into a preliminary
regional-scale numerical steady-state model of
ground-water flow. The preliminary numerical model will
be constructed in a manner that permits the use of data
from site-specific models developed for individual mine
sites, and will be used to test and evaluate the
conceptual model of the ground-water flow in the basin.
The conceptual and preliminary numerical model will be
revised to provide a more reasonable simulation of the
hydrodynamics of ground-water flow in the basin.
Transient-model simulations will made following the
satisfactory development of a steady-state model. These
simulations may require further modification of the
conceptual and numerical models. A
satisfactorily-calibrated transient-flow model of the
ground-water flow system of the middle Humboldt River
Basin will then allow an analysis of the cause-and-effect
relation among various water uses and changes in
ground-water levels and ground-water discharge. 7. Spatial and temporal variability of spring discharge in the middle Humboldt River Basin. The discharge of many springs in the Humboldt River Basin either has been appropriated or is important to the maintenance of flow in the Humboldt River. The spatial and temporal variability of spring discharge in the middle Humboldt River Basin are related to the hydrogeology, hydroclimatology, and ground-water use in the basin. Changes in spring discharge may be caused by changes in hydroclimatology, geologic effects, changes in the use of ground water in the area, changes in land use, or changes in all of these. To understand the observed variability in spring discharge, the principal control or controls of that discharge and the magnitude of variability will be identified and evaluated. Selected springs will be identified for study early in
the study of the hydrogelogic framework. Discharge
measurements for these springs will be collected as part
of the data program during the second and third years of
the program. Precipitation data collected for the water
balance project together with the spring discharge data
will provide sufficient data to begin an analysis of the
variability of spring discharge in the fourth year of the
program. 8. Ground-water budget and water balance of the upper Humboldt River Basin. This project will develop estimated ground-water
budgets and area-wide water balances for the upper
Humboldt River Basin such as were developed for the
middle Humboldt River Basin as described in project 3.
The upper Humboldt River Basin is the source of
ground-water and surface-water discharge to the Humboldt
River that eventually enters the middle Humboldt River
Basin Any comprehensive analysis of water resources in
the middle Humboldt River Basin requires an understanding
of the contribution from the upper basin. 9. Climatology of the Humboldt River Basin. Watershed-scale analysis of the Humboldt River Basin
(as proposed in project 10 below) will require an
increased level of knowledge of climatological conditions
of the area and may require climatological or
meteorological data beyond that available from standard
Weather Service stations. These data include solar
radiation, humidity, dew-point temperature, and
windspeed. To the extent that these data are available
from other agencies, companies, or organizations, they
will be collected and compiled as part of the project.
This project will be designed to collect any data not
otherwise available, such as solar radiation, and prepare
a synthesis and analysis of data collected. 10. Analysis of multiple uses of the water resources of the Humboldt River Basin. Watershed-type simulations that incorporates both
surface-water and ground-water flow systems will be
developed to evaluate the cause-and-effect relation among
multiple water uses and their impacts on the water
resources of the Humboldt River Basin. Development of
such a simulation requires the knowledge and data derived
from all the preceding projects. Given the understanding
of the hydrology and water resources of the basin
provided by these studies, this project can be designed
to provide resource managers with the kinds of
information needed to make reasonable and rational
management decisions. 11. Effects of increased low flows on flood characteristics and riparian vegetation of the Humboldt River. Any increase in non-natural discharge (e.g. increased
irrigation return flow from ground-water sources,
increased sewage effluent discharge from ground-water
sources, ground-water discharge from mine dewatering
operations) to the Humboldt River may increase low flow
conditions that, in turn, may alter riparian vegetation
and flood-flow characteristics of the river. The
magnitude of change in vegetation and flow
characteristics may depend on the magnitude of discharge
and the increase in low flow. Minor to modest increases
in low flow probably will have little impact, although it
is not certain how small or large a "modest"
increase is. Larger increases in low flow have the
potential for causing greater effects. This project will
be designed to evaluate those effects if it appears there
will be significant increases in low flows as determined
from an analysis of low-flow frequencies. 12. Surface water -- ground water interactions in the middle Humboldt River Basin. Little is known of the dynamics of the interactions
between surface water and ground water in the Humboldt
River Basin. There is significant spring discharge to
some reaches of the river, some reaches are gaining
reaches from slow and diffuse seepage of ground water,
and other reaches lose water to the ground-water system.
This project will study in detail these interactions,
using detailed field measurements and simulation
analysis, in selected areas and along selected reaches of
the Humboldt River and its tributaries to develop a
greater understanding of the dynamics of the
interactions. This knowledge is essential in developing
multiple-use plans for the water resources of the basin. 13. Trends in sediment discharge of the Humboldt River. Increased development and urbanization in the Humboldt
River Basin may lead to changes in sediment discharge by
the Humboldt River. Few data are available to provide a
basis for understanding any changes. This project will be
designed to assemble and analyze sediment discharge data
collected as part of the Humboldt River Basin Program
data network during the earlier years of the program. The
sediment transport analysis should be able to identify
the source or cause of any changes in sediment discharge. 14. Summary report of the regional hydrology of the Humboldt River Basin. In the last year of the program, a final report will be prepared that summarizes the regional hydrology of the Humboldt River Basin based on the reports and findings of the all the studies conducted as part of the program. Water-quality issues are related to a comprehensive analysis of the water resources of the Humboldt River Basin. Two such issues:
may be included in this program, but are outside the
scope of funding indicated on table 2. These studies have
not been included in the proposed funding because other
agencies and parties are, in part, pursuing these issues.
If these studies are undertaken as a part of this
program, other sources of funding will be developed for
them. 15. Effects of ground-water discharge from mine-dewatering operations on ground-water quality and temperature. Infiltration and injection of ground-water discharge
from mine dewatering into the ground-water system can
affect water quality in the aquifers, springs,
newly-formed wetlands, and other receiving waters.
Locally, springflow from mine dewatering discharge
contains concentrations of minor constituents that may
affect water use and biota in streams and wetlands. This
project will evaluate the effect of the water quality of
ground-water discharge from mine-dewatering operations on
water in ground-water systems, including newly-formed
wetlands. 16. Effects of ground-water discharge from mine-dewatering operations on surface-water quality and temperature. Discharge of ground water from mine-dewatering
operations into the Humboldt River and its tributaries
may result in increased loads of minor constituents that
can become concentrated in biota. Constituents such as
selenium that biomagnify up the food chain have the
potential to adversely affect biota in areas of large
evapotranspiration, such as the Humboldt Sink.
Additionally, increased temperature can affect the
biology of receiving waters. This project will assess the
magnitude of any increased loading of minor inorganic
constituents to the surface water system and monitor
streamflow temperatures along the Humboldt River and its
major tributaries. 17. Evolution of open-mine-pit water quality and the regional effects on ground-water and surface-water resources. After the cessation of mining and mine-dewatering activities, some of the major mine pits are expected to fill partially with water as regional ground-water levels recover to pre-mining levels. The primary source of water flowing into the pits will be ground water, because the watershed areas of most pits are commonly relatively small. Ground water in mineralized areas can contain high concentrations of minor constituents, and over time, the chemical quality of the water contained in the pits may adversely affect migratory waterfowl that can be expected to visit the pit lakes. This project will assess the water quality of the pits and the ground water in the vicinity of previously dewatered pits. These data, combined with information on other pit lakes with similar climatic, hydrologic, and geologic settings will be used to provide a preliminary evaluation of water quality in mine-pit lakes in the Humboldt River basin. Each project of the program is designed as a separate activity with its own staff, budget and report requirements. As each project is completed, a report of the findings of that project will be written and published in an appropriate format. Data reports will be published from time to time, and data contained in the program database will be released in electronic form at 3- to 5-year intervals during the life of the program. All data collected by the U.S. Geological Survey will be published in the USGS annual data report. It is proposed that the Humboldt River Basin database will be accessible on the Internet sometime in 1997. Water-level maps and trends will be reported on every 2 years beginning in 1997.
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For further information contact:
Russ Plume USGS, Water Resources Division 333 W. Nye Lane, Room 203 Carson City, NV 89706 Internet: rwplume@usgs.gov Phone: (775) 887-7600 Maintainer: usgsinfo_nv@usgs.gov |
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