Hydrogeology and Hydrologic Landscape Regions of Nevada
Scientific Investigations Report 2004–5131
Prepared in cooperation with the NEVADA DEPARTMENT OF CONSERVATION AND NATURAL RESOURCES, NEVADA DIVISION OF ENVIRONMENTAL PROTECTION
U.S. Department of the Interior U.S. Geological Survey (Back of Cover) Hydrogeology and Hydrologic Landscape Regions of Nevada
By Douglas K. Maurer, Thomas J. Lopes, Rose L. Medina, and J. LaRue Smith
U.S. GEOLOGICAL SURVEY Scientific Investigations Report 2004–5131
Prepared in cooperation with the NEVADA DEPARTMENT OF CONSERVATION AND NATURAL RESOURCES, NEVADA DIVISION OF ENVIRONMENTAL PROTECTION
Carson City, Nevada 2004 U.S. DEPARTMENT OF THE INTERIOR GALE A. NORTON, Secretary
U.S. GEOLOGICAL SURVEY CHARLES G. GROAT, Director
Any use of trade, product, or firm names in this publication is for descriptive purposes only and does not imply endorsement by the U.S. Government
For additional information Copies of this report can be contact: purchased from:
District Chief U.S. Geological Survey U.S. Geological Survey Information Services 333 West Nye Lane, Room 203 Building 810 Carson City, NV 89706–0866 Box 25286, Federal Center Denver, CO 80225–0286 email: [email protected] http://nevada.usgs.gov iii
CONTENTS
Abstract...... 1 Introduction ...... 2 Purpose and Scope ...... 2 Acknowledgments...... 2 Previous Studies ...... 3 Hydrogeologic Units...... 4 Consolidated-Rock Hydrogeologic Units ...... 4 Unconsolidated-Sedimentary Hydrogeologic Units ...... 7 Soil Permeability...... 10 Faulting and Ground-Water Flow ...... 11 Hydrologic Landscape Regions...... 13 Delineation of Hydrologic Landscape Regions...... 13 Use of Hydrologic Landscape Regions ...... 15 Summary...... 19 References Cited ...... 20 Appendix: Detailed summary of hydraulic conductivity estimates ...... 25 Supplemental Geospatial Digital Data: Hydrologic landscape regions of Nevada, by J. LaRue Smith
FIGURES
1. Diagram showing ground-water flow characteristics for different types of hydrographic areas in Nevada ...... 3 2. Graph showing range in horizontal hydraulic conductivity for hydrogeologic units...... 7 3. Diagram showing typical ground-water flow patterns perpendicular to the long axis of valleys in Nevada for mountain blocks with different permeability and annual precipitation...... 9 4. Diagram showing potential effects of faults on ground-water flow for different types of aquifer and fault permeability...... 12 5. Graph showing ranges in mean annual precipitation, soil permeability, slope, and aspect for hydrologic landscape regions with low and high horizontal hydraulic conductivity ...... 15 6. Map showing hydrologic landscape regions 9, 10, 14, and 15 in the most urbanized areas of Nevada ...... 17
PLATES
1. Map showing distribution of consolidated rocks and unconsolidated sediments, historic to Quaternary-age faults, and springs in Nevada 2. Map showing distribution of hydrogeologic units in Nevada 3. Map showing areas of similar soil permeability and hardpan in Nevada 4. Map showing hydrologic landscape regions of Nevada iv
TABLES 1. Correlation of hydrogeologic units with geologic-map units of Stewart and Carlson (1978a) ...... 5 2. Range in horizontal hydraulic conductivity for hydrogeologic units ...... 6 3. Range in soil permeability for descriptive categories of unconsolidated sediments and corresponding geomorphic features...... 10 4. Characteristics, distribution, area, and population of hydrologic landscape regions ...... 16 5. Example of a sampling strategy using hydrologic landscape regions...... 19
CONVERSION FACTORS
Multiply By To obtain foot (ft) 0.3048 meter foot per day (ft/d) 0.3048 meter per day gallon per minute (gal/min) 0.06309 liter per second inch (in.) 25.4 millimeter mile (mi) 1.609 kilometer square mile (mi2) 2.590 square kilometer Hydrogeology and Hydrologic Landscape Regions of Nevada
By Douglas K. Maurer, Thomas J. Lopes, Rose L. Medina, and J. LaRue Smith
Abstract Soil permeability was grouped into five descriptive categories ranging from very high to very low, which generally correspond to mapped geomorphic features such as playas and In 1999, the U.S. Environmental Protection Agency initi- alluvial slopes. In general, soil permeability is low to moderate ated a rule to protect ground water in areas other than source- in northern, northeastern, and eastern Nevada and high to very water protection areas. These other sensitive ground water areas high in western, southwestern, and southern Nevada. Within a (OSGWAs) are aquifers that are not currently but could eventu- particular basin, soil permeability decreases downslope from ally be used as a source of drinking water. The OSGWA pro- the bedrock contact. The type of parent rock, climate, and gram specifically addresses existing wells that are used for streamflow velocities are factors that likely cause these spatial underground injection of motor vehicle waste. If the injection patterns. well is in a ground-water protection area or an OSGWA, well Faults in unconsolidated sediments usually are barriers owners must either close the well or apply for a permit. The to ground-water flow. In consolidated rocks, permeability and Nevada Division of Environmental Protection will evaluate ground-water flow is reduced in directions normal to the fault site-specific information and determine if the aquifer associated zone and increased in directions parallel to the fault zone. With with a permit application is susceptible to contamination. A time, mineral precipitation may seal fractures in consolidated basic part of evaluating OSGWAs is characterizing the hydro- rocks, reducing the permeability. However, continued move- geology of aquifer systems including the lithology, hydrologic ment along the fault may form new fractures, resulting in a properties, soil permeability, and faulting, which partly control fault alternating from a zone of preferred flow to a flow barrier the susceptibility of ground water to contamination. Detailed during geologic time. The effect of faults on ground-water flow studies that evaluate ground-water susceptibility are not practi- at a particular location is difficult to determine without a site- cal in a largely unpopulated State like Nevada. However, exist- specific investigation. ing and new information could be extrapolated to other areas of Hydrologic landscape regions were delineated by over- the State if there is an objective framework to transfer the infor- laying a grid of 100-foot (30-meter) cells over the State, mation. The concept of hydrologic landscape regions, which estimating the value of five variables for each cell, and conduct- identify areas with similar hydrologic characteristics, provides ing cluster analysis to assign each cell to a region such that each this framework. This report describes the hydrogeology and region is fairly homogeneous and distinct from other regions. hydrologic landscape regions of Nevada. The five variables include mean annual precipitation, soil per- Consolidated rocks that form mountain ranges and uncon- meability, slope, aspect, and hydrogeologic unit. The number of solidated sediments that fill the basins between the ranges are clusters was increased until each region had only one category grouped into hydrogeologic units having similar lithology and of hydrogeologic unit, which resulted in 16 regions. Most of assumed to have similar hydrologic properties. Consolidated Nevada has moderate (8 to 16 inches) precipitation (58 percent), rocks and unconsolidated sediments are the two major hydro- low (less than 5 feet per day) soil permeability (50.1 percent), geologic units and comprise 51 and 49 percent of the State, moderate (3 to 25 percent) slope (58.1 percent), non-northerly respectively. Consolidated rocks are subdivided into 8 hydro- aspect (88.7 percent), and hydrogeologic units with high geologic units. In approximate order of decreasing horizontal (greater than 40 feet per day) horizontal hydraulic conductivity hydraulic conductivity, consolidated-rock hydrogeologic units (59.8 percent). consist of: (1) carbonate rocks, Quaternary to Tertiary age; Regions with moderate to high precipitation (equal to or (2) basaltic, (3) rhyolitic, and (4) andesitic volcanic flows; greater than 8 inches per year), moderate to high soil permeabil- (5) volcanic breccias, tuffs, and volcanic rocks older than ity (greater than 5 feet per day), low to moderate slope (equal to Tertiary age; (6) intrusive and metamorphic rocks; (7) consoli- or less than 25 percent), and high hydraulic conductivity could dated and semi-consolidated tuffaceous rocks and sediments; have greater recharge rates and be more susceptible to contam- and (8) clastic rocks consisting of sandstone and siltstone. ination than other regions. These characteristics describe hydro- Unconsolidated sediments are subdivided into four hydrogeo- logic landscape regions 9, 14 and 15, which comprises 27.1 per- logic units on the basis of flow regime, topographic slope, and cent of Nevada. These hydrologic landscape regions represent mapped stream channels. The four units are (1) alluvial slopes, valley floors and alluvial slopes of most basins in eastern and (2) valley floors, (3) fluvial deposits, and (4) playas. central Nevada. In the most populated areas of Nevada, hydro- 2 Hydrogeology and Hydrologic Landscape Regions of Nevada
logic landscape regions 9, 10, 14 and 15 comprise a large por- through an aquifer (Focazio and others, 2002). Susceptibility tion of Las Vegas, Reno, Carson City, Minden, Gardnerville, depends on characteristics of the unsaturated zone, aquifer, and and Spanish Springs. These areas could be most vulnerable due hydrologic conditions, and is independent of the chemical char- to their hydrologic characteristics and contaminants associated acteristics and sources of contaminants. Vulnerability depends with urban land-use practices. on the sources and environmental behavior of contaminants in addition to the factors that affect recharge and ground-water flow. An area can have a low susceptibility to contamination, such as in Nevada where recharge rates are low. However, the Introduction same area can have a high vulnerability if contaminants are quickly flushed to the water table when water is applied by var- Protecting sources of drinking water from anthropogenic ious land-use practices. DRASTIC (Aller and others, 1987) is contamination is a priority for State and Federal Agencies. commonly referred to as a method of evaluating aquifer vulner- Programs to protect underground sources of drinking water, ability. DRASTIC stands for depth to water table (D), recharge such as well-head and source-water protection programs, have (R), aquifer lithology (A), soil type (S), topographic slope (T), been in place since the 1980s. The goal of these programs is to unsaturated zone lithology (I), and hydraulic conductivity of the protect the quality of aquifers that are currently being used for aquifer (C). As defined in this report, DRASTIC is a method public water supply. However, source-water protection areas of evaluating aquifer susceptibility because it only considers comprise a small percentage of the aquifers in Nevada. It also is natural factors affecting recharge and ground-water flow. important to protect the quality of aquifers that are not currently The hydrogeology of an area depends on many factors in but could eventually be used as a source of drinking water. In addition to the hydrologic properties of the hydrogeologic units. 1999, a new rule was initiated to protect ground water in areas An extreme perspective is that the hydrogeology of any area is other than source-water protection areas (U.S. Environmental unique because it will have a unique combination of factors that Protection Agency, 2000). These other sensitive ground water control the movement of water and contaminants through an areas (OSGWAs) could eventually be used as a source of drink- aquifer. Another perspective is that some areas have similar ing water. The rule gave regulatory agencies the option to hydrogeology because they have similar values for certain designate specific sites, areas, or the entire state as an OSGWA. hydrologic variables, such as precipitation and soil permeabil- The Nevada Division of Environmental Protection (NDEP) ity. Therefore, information from detailed studies in one area elected to designate specific sites because of the unique geolog- could be extrapolated to other areas of the state if there is an ical condition that exists in the state. objective framework to transfer the information. The concept The OSGWA program specifically addresses existing of hydrologic landscapes (Winter, 2001), which have similar wells that are used for underground injection of motor vehicle values for selected hydrologic variables, provides this frame- waste; new injection wells are banned. If the injection well is work. in a ground-water protection area or an OSGWA, well owners must either close the well or apply for a permit. A permit is Purpose and Scope granted only if the injectate fluids meet drinking-water standards. Nevada is a large, rural, and hydrologically complex The purpose of this report is to describe the hydrogeology state. Except for populated areas, scant data makes it difficult to and hydrologic landscape regions of Nevada. The description of determine which aquifers could be vulnerable to contamination. the hydrogeology includes the lithology, horizontal hydraulic Rather than designate all or specific areas of Nevada as an conductivity, soil permeability, and recent faulting of hydro- OSGWA, NDEP will evaluate site-specific information associ- geologic units that comprise bedrock and alluvial aquifer ated with a permit application to determine if the aquifer at that systems, and how these features may affect the flow of ground site is susceptible (Nevada Division of Environmental Protec- water and movement of anthropogenic contaminants. Hydro- tion, 2003). A basic part of evaluating OSGWAs is characteriz- logic landscape regions delineate areas of Nevada with similar ing the lithology, hydrologic properties, soil permeability, and mean annual precipitation, soil permeability, slope, aspect, and faulting of hydrogeologic units, which partly control the horizontal hydraulic conductivity. susceptibility of ground water to contamination. Susceptibility and vulnerability are similar terms that have Acknowledgments been used differently by different authors. This report uses the definition of Tesoriero and Voss (1997) who defined aquifer The authors wish to acknowledge Michael Leigh of susceptibility as the "relative ease with which a contaminant NDEP, Bureau of Mining Regulation and Reclamation, Russell applied on or near a land surface can migrate to the aquifer", and Land and Arthur Ledger of NDEP, Bureau of Water Pollution vulnerability as the "relative ease with which a contaminant Control, for providing access to State files that were used to applied at or near the land surface can migrate to an aquifer of compile estimates of horizontal hydraulic conductivity, and interest, for a given set of land-use practices." The distinction is Michael Machette of the USGS, Geologic Hazards Team, that susceptibility, also called sensitivity, considers only natural Golden, Colorado, for providing a preliminary electronic factors that affect how easily water recharges and moves copy of Quaternary and Tertiary faults in Nevada. Introduction 3
Previous Studies properties, and age. Two basin-fill units include younger basin- fill deposits of Holocene to Pliocene age and older basin-fill The first hydrologic classification of the Great Basin phys- deposits of Pliocene to Miocene age. Consolidated-rock units iographic province was made by Synder (1962) who devised include a volcanic-rock unit of lava flows and tuffs of Quater- a scheme based on topography and degree of ground-water nary to Tertiary age, an intrusive-rock unit from Miocene to Late drainage. Most of Nevada lies within the Great Basin, except Triassic age, a marine-sedimentary unit and volcanic-rock unit for small areas along the northern, western, and southern of Early Miocene to Middle Triassic age, and a basement-rock boundaries of the State. In the late 1960's, Cardinalli and others unit of Precambrian age. In eastern Nevada, consolidated-rock (1968) and Rush (1968), delineated hydrographic areas (HAs) units include two clastic-rock units, one younger (Late for Nevada, based generally on topographic and drainage-area Permian to Late Devonian age) and one older (Early Cambrian divides. HAs are different than hydrologic units (National Atlas to Late Precambrian age) than three carbonate-rock units which of the United States, 1998) and are used for scientific and range in age from Late Triassic to Middle Cambrian. administrative purposes. Later, Plume (1996) simplified these 12 units into 6 hydro- An HA can be either topographically closed or open. Open geologic units with an emphasis on delineating basin-fill and HAs have surface-water inflow or outflow, whereas closed HAs carbonate-rock regional aquifer systems (Plume, 1996, p. B3, have no surface-water flow across their boundaries. The amount B11). In western Nevada, the simplified hydrogeologic units of ground-water drainage depends on the rock types underlying include younger basin-fill deposits, older basin-fill deposits, and and bounding the HAs (fig. 1). HAs underlain and bounded by a sedimentary- and igneous-rock unit. The sedimentary- and impermeable bedrock generally are undrained with no subsur- igneous-rock unit of western Nevada was considered a face inflow or outflow, the water table beneath the valley floor barrier to ground-water flow through the basin-fill aquifer is near land surface, and ground water is discharged by springs system. In eastern Nevada, the simplified hydrogeologic and evapotranspiration from phreatophytes and bare soil. units include another sedimentary- and igneous-rock unit, a Ground water can drain into and/or out of HAs underlain and carbonate- and clastic-rock unit, and a metamorphic-, igneous-, bounded by permeable bedrock. In a completely drained HA, and sedimentary-rock unit (Plume, 1996, plate 2). The the water table beneath the valley floor may be so deep that carbonate- and clastic-rock unit forms the carbonate-rock all ground-water discharge is by subsurface outflow (Eakin aquifer system of eastern Nevada. The metamorphic-, igneous-, and others, 1976, p. G3). All combinations of open, closed, and sedimentary-rock unit forms a barrier to ground-water flow undrained, partly drained, and completely drained HAs are through the carbonate-rock aquifer system. found in Nevada. The hydrogeology of southern Nevada also has been Plume and Carlton (1988) grouped geologic formations described in greater detail than the Great Basin. Winograd and and rock units into hydrogeologic units for the Great Basin Thordarson (1975, p. C14) delineated 10 hydrogeologic units using the geologic map of Nevada (Stewart and Carlson, 1978a). near the Nevada Test Site including two clastic-rock confining Plume and Carlton (1988) delineated 12 hydrogeologic units units, two carbonate-rock aquifer units, five volcanic-rock based on lithology, areal extent, estimated hydrologic units, and a basin-fill aquifer. These hydrogeologic units have
Alluvial fans Dry playa phreatophytes
Water Alluvial table deposits
"Impermeable" "Impermeable" bedrock Permeable bedrock bedrock
Undrained closed Partly drained closed Partly drained Drained closed basin Sink basin basin tributary area Single basin system Regional system
Figure 1. Ground-water flow characteristics for different types of hydrographic areas in Nevada. Modified from Eakin and others (1976, p. G10). 4 Hydrogeology and Hydrologic Landscape Regions of Nevada
been used in more recent studies to delineate similar or determines the volume of fluid that may be stored in the open additional hydrogeologic units in southern Nevada (Belcher pores of rocks and sediments. In general, the porosity of uncon- and others, 2001, p. 6). D'Agnese and others (1997, p. 17) solidated sediments is greater than that of consolidated rocks delineated 10 hydrogeologic units and D'Agnese and others because pore spaces between sediment grains may be more (2002, p. 17) delineated 28 hydrogeologic units in the Death numerous and more interconnected than pores in consolidated Valley region near southern Nevada. Other studies of the Death rock. However, consolidated rocks that typically have very low Valley ground-water flow system have delineated as many as primary porosity may develop secondary porosity from open 19 hydrogeologic units in the Death Valley flow system. The spaces along fractures and joints, or from dissolution of rocks 19 hydrogeologic units were simplified into 11 units by Belcher along fractures and joints. and others (2001, table 1). Consolidated rocks and unconsolidated sediments The concept of hydrologic landscapes was first proposed comprise the two major hydrogeologic units because their by Winter (2001). Hydrologic landscapes identify areas with hydrologic properties are quite different. Plate 1 shows the similar hydrologic characteristics and form the basis for a con- distribution of consolidated rocks and unconsolidated sedi- ceptual framework to describe hydrologic processes. Wolock ments in Nevada. Consolidated rocks and unconsolidated (2003) describes one approach of constructing hydrologic- sediments cover approximately equal areas in Nevada. landscape maps and how 20 hydrologic landscape regions were Consolidated rocks are exposed over 56,108 mi2 (51 percent) delineated for the United States. Lopes and Price (1997) used of Nevada and unconsolidated sediments are exposed over a similar approach to group metropolitan areas of the United 54,250 mi2 (49 percent) of the state (table 1). These two major States that have similar climate. hydrogeologic units are further subdivided into more detailed hydrogeologic units based on lithology, horizontal hydraulic conductivity, slope, soil permeability, and mapped stream- Hydrogeologic Units channels. The hydrogeologic dataset is available at
Table 1. Correlation of hydrogeologic units with geologic-map units of Stewart and Carlson (1978a)
Area, Geologic-map unit of in square miles Hydrogeologic unit Stewart and Carlson (1978a) (percent of total area)
Consolidated rock
Quaternary to Tertiary-age volcanic flows–—Total 15,584 (14) Basalt Qtb, Tba, Tb, Tbg 6,823 (6) Rhyolite Qtr, Tr3, Tr2, Tr1 4,749 (4) Andesite Qta, Ta3, Ta2, Ta1 4,012 (4)
Volcanic breccias, tuffs, and volcanic rocks older Tbr, Tob, Tt3, Tt2, Tt1, Trt, Tts, TRk, TRPvs, 13,656 (12) than Tertiary age Msv, Jv
Carbonate rocks Ml, PlPa, PlPcd, lPcd, Pc, PMc, Psc, PlPc, 10,085 (9) lPc, Mc, St, Dc, DCc, Sc, Soc, TRc, MDmc, MDs, Dt, Ot, OCc, OCt, Oc, Cc
Tertiary tuffacious rocks and sediments QTs, Ts3, Ths, Tksu, Ts2, Ts1 6,493 (6)
Clastic rocks TKs, Ks, Jd, Jgb, JTRa, TRmt, TRPd, Css, 5,630 (5) JTRs, TRch, JPu, TRPs, PMh, DCsv, Dsl, Ds, Se, Ss, Osv, Os, Ch, Csc, Ct, CZs, Zw, CZq, Zqs
Intrusive and metamorphic rocks JTRsv, Tri, Tmi, Ti, TJgr, Tgr, MZgr, Kgr, 4,660 (4) KJd, Jgr, TRgr, KJim, TRlgr, PZsp, Ygr, Xm
Consolidated rock—Total 56,108 (51)
Unconsolidated sediments
Alluvial slope -- 33,733 (31)
Valley floor -- 13,976 (13)
Playas Qp 5,002 (4)
Fluvial deposits -- 1,539 (1)
Unconsolidated sediments—Total Qa, Qp, Qls, Qm, Qtoa 54,250 (49)
solidification of the flows (Davis and DeWiest, 1966, p. 337). northern Nevada, generally north of the Humboldt River, along Basaltic rocks often have a high porosity from open vesicles the western boundary of the State, and at scattered locations formed by gasses entrained in the molten lava, but also may throughout the remainder of the State (plate 2). Volcanic flows be quite dense with low porosity. Basaltic rocks may form aqui- in the northwestern corner of Nevada are part of the Modoc fers with close to the greatest horizontal hydraulic conductivity Plateau that extends into northeastern California (Macdonald, known (Davis and DeWiest, 1966, p. 333; Plume, 1996, 1966, p. 65). Volcanic flows along the northern boundary of the p. B20). Of the Tertiary volcanic flows, rhyolitic flows are state are part of the Owyhee Upland that bounds the southern somewhat less permeable than basaltic flows and andesitic Snake River Plain (Stewart, 1980, p. 7). flows are least permeable (table 2). Ground-water flow between Volcanic breccias, tuffs, and older volcanic rocks consist several basins in Nevada has been found to occur through vol- of Tertiary-age breccias and welded to non-welded tuffs, and canic flows of Tertiary age (Handman and others, 1990, p. 53; older volcanic rocks ranging from Jurassic to Triassic in age Maurer, 1993, p. 21; Maurer, Plume, Thomas, and Johnson, (138 to 240 Ma). These rocks are assumed to have low to mod- 1996, p. 34; Harrill and Preissler, 1994, p. 11). All three types erate horizontal hydraulic conductivity. Welded tuffs locally of volcanic flows are found in association with each other in form aquifers near the Nevada Test Site and may have a great 6 Hydrogeology and Hydrologic Landscape Regions of Nevada
Table 2. Range in horizontal hydraulic conductivity for hydro- (plate 2). Tertiary-age volcanic tuffs associated and interbedded with Tertiary-age volcanic flows also are exposed along the geologic units. See Appendix 1 for detailed information on northern part of Nevada (Stewart, 1980, p. 92, 98, 102). hydraulic conductivity Carbonate rocks consisting of limestone, dolomite, and Range in horizontal units mapped as mixtures of limestone and clastic rocks by hydraulic Stewart and Carlson (1978a) range in age from Permian to Hydrogeologic unit conductivity Cambrian (240 to 570 Ma). These rocks generally have great (feet per day) horizontal hydraulic conductivity caused by fractures and joints that have been widened by dissolution, forming open channels Consolidated Rock ranging in width from inches to tens of feet (Plume, 1996, Carbonate rocks 3x10-5 to 3,300 p. B11). Drill logs of deep petroleum exploration wells indicate that fractured zones of high horizontal hydraulic conductivity Quaternary to Tertiary-age volcanic flows and porosity in carbonate rocks range in thickness from a few Basalt 2x10-4 to 1,300 Rhyolite 2x10-5 to 260 tens of feet to usually not more than 100 ft, separated by unfrac- Andesite 2x10-4 to 60 tured rocks of low horizontal hydraulic conductivity and poros- ity hundreds to thousands of feet thick (Plume, 1966, p. B12). Volcanic breccias, tuffs, and volcanic 3x10-7 to 600 Carbonate rocks form a regional aquifer system in the eastern rocks older than Tertiary-age and southern part of the State, where ground water flows for Intrusive and metamorphic rocks 7x10-8 to 30 hundreds of miles beneath many basins (Harrill and Prudic, 1998, p. 28–35). Tertiary tuffaceous rocks and sediments 2x10-4to 20 Tertiary tuffaceous rocks and sediments range from consolidated to semi-consolidated and are mostly fine-grained Clastic rocks with low horizontal hydraulic conductivity. They consist of Sandstone 7x10-4 to18 Siltstone 2x10-9 to 16 sediments deposited in lacustrine, fluvial, and aeolian settings that have variable degrees of consolidation. Tuffaceous rocks Unconsolidated Sediment and sediments are of Tertiary age (6 to 43 Ma; Stewart, 1980, p. 87–93). At various locations they also contain lenses of Fluvial deposits 4 to 2,200 gravel, conglomerate, sandstone, siltstone, lava flows, ash-flow Basin-fill undifferentiated 1x10-3 to 590 tuffs, and limestone (Stewart, 1980, p. 87–89). The sediments were deposited in down-faulted basins that were the precursors, Alluvial slope but not necessarily the same configuration, of present-day Upper 0.5 to 140 basins in Nevada (Stewart, 1980, p. 92). They comprise a large Lower 0.02 to 140 Undifferentiated 2x10-4 to over 150 part of the basin-fill sediments in the northeastern part of Nevada (plate 2), and include sequences of volcanic tuffs in the Valley floor 2 to 90 northwestern part of the State (Stewart, 1980, p. 92; Stewart and Carlson (1978a). Plume (1996, p. B15) notes that they probably Playa 3x10-5 to 2 underlie younger, unconsolidated basin-fill sediments in most valleys. Clastic rocks consist of sandstone, siltstone, and shale horizontal hydraulic conductivity (Harrill and Prudic, 1998, from Cretaceous to Precambrian age (63 to more than 570 Ma). p. A19; D'Agnese and others, 1997, p. 19). However, rock units These rocks are assumed to have low to moderate horizontal mapped as welded tuffs by Stewart and Carlson (1978a) also hydraulic conductivity and porosity, although they are consid- include non-welded tuffs, and the horizontal hydraulic conduc- ered barriers to ground-water flow where they are interbedded tivity of the mapped units as a whole is probably low to moder- or in contact with rocks of greater permeability (Harrill and ate. Older volcanic rocks are assumed to have low to moderate Prudic, 1998, p. A19; Davis and DeWiest, 1966, p. 347; horizontal hydraulic conductivity caused by weathering and D'Agnese and others, 1997, p. 20). Table 2 shows that sand- filling of pores with secondary minerals (Davis and DeWiest, stone is somewhat more permeable than siltstone. The perme- 1966, p. 337). This assumption is substantiated by Stewart and ability of sandstone is one to three orders of magnitude less than Carlson (1978a) who describe many of the older volcanic rocks that of unconsolidated sediments of similar grain size due to as altered and Plume (1996, p. 20) who notes that older volcanic cementation by clay minerals, calcite, or silica (Davis and rocks that have been extensively tested near the east-central part DeWiest, 1966, p. 350–351). The porosity of sandstone has of the State have a low horizontal hydraulic conductivity. This been shown to decrease with depth (Freeze and Cherry, 1979, hydrogeologic unit forms a northwest/southeast trending band p. 152). Because of the low solubility of most clastic rocks, from north of Las Vegas to near the center of Churchill County secondary porosity from solution is not developed, and Hydrogeologic Units 7
Fluvial deposits Undifferentiated basin fill Lower alluvial fan Undifferentiated alluvial fan
SEDIMENTS Valley floor Upper alluvial fan Mean of range UNCONSOLIDATED Playa Carbonate Basalt Rhyolite Andesite Breccia/Tuff Intrusive/Metamorphic Sandstone Siltstone CONSOLIDATED ROCK Tertiary sedimentary rocks
10-9 10-8 10-7 10-6 10-5 10-4 10-3 10-2 10-1 100 101 102 103 104 HORIZONTAL HYDRAULIC CONDUCTIVITY, IN FEET PER DAY Figure 2. Range in horizontal hydraulic conductivity for hydrogeologic units. fractures may become sealed by plastic deformation of sand- Unconsolidated-Sedimentary Hydrogeologic Units stone and interbedded siltstone (D'Agnese and others, 1997, p. 20). Clastic rocks are exposed in a northwest/southeast Unconsolidated sediments that fill the basins between the trending band from north-central Nye County to central mountain blocks comprise the most used aquifers in Nevada Humboldt County, in Esmeralda County, and in association and range in age from Pliocene (6 Ma) to recent. The majority with carbonate rocks in the eastern and southern parts of the of sediments are of Quaternary age (<2 Ma; plate 1; Stewart, state (plate 2). Clastic rocks generally are siltstone and shale in 1980, p. 93). Unconsolidated sediments mapped by Stewart and northern Nevada. Sandstone is exposed mainly in Clark and Carlson (1978a) were subdivided into four hydrogeologic units southern Lincoln Counties (Stewart, 1980, p. 23, 27, 31, 34, on the basis of ground-water flow regime, topographic slope, 43, 48, 62, 74). and mapped stream channels to provide more detailed hydro- Intrusive and metamorphic rocks range in age from logic information on basin-fill sediments. The four unconsoli- Jurassic to Precambrian. Igneous intrusive rocks cooled dated-sedimentary hydrogeologic units are alluvial slopes, underground and generally are less fractured than volcanic valley floors, fluvial deposits, and playas. Available estimates flows. Igneous intrusive rocks mainly are granodiorite and of horizontal hydraulic conductivity for these geomorphic quartz monzonite, similar in composition to the Sierra Nevada features are summarized in figure 2 and table 2 with detailed batholith (Stewart, 1980, p. 73–76). Metamorphic rocks are of estimates listed in appendix 1. sedimentary or volcanic origin and have been subjected to high After water and contaminants move past the soil horizon, temperatures, pressures, or both. Igneous and metamorphic their movement is controlled by the permeability of sediments rocks have low horizontal hydraulic conductivity and low underlying alluvial slopes and the valley floors. In general, porosity, except where fractured or faulted. Freeze and Cherry sediments forming alluvial slopes are coarse-grained and poorly (1979, p. 159–160) note that the horizontal hydraulic conduc- sorted with relatively few interbedded clay layers (Plume, 1996, tivity of intrusive rocks greatly decreases at more than 100 to p. B16–B17; Bedsun, 1980; Mifflin, 1988, p. 71; Anderson and 200 ft below land surface as overburden pressures cause frac- others, 1983, p. 1059). The grain size of basin-fill sediments tures to close. Prudic and others (1995, p. 11) note that these decreases towards the center of the valley (Plume, 1996, p. B15; rocks generally act as barriers to regional ground-water flow Davis, 1988, p. 286), and the lower parts of alluvial slopes are through carbonate rocks. Intrusive and metamorphic rocks likely to interfinger with layers of well sorted sand, silt, and clay are exposed mainly in the western half of Nevada with widely deposited on the valley floor (Plume, 1996, p. B15; Bedsun, scattered exposures in the eastern half. 1980). Basin-fill sediments on the valley floor may contain 8 Hydrogeology and Hydrologic Landscape Regions of Nevada
individual layers with high horizontal and vertical hydraulic merge with the valley floor in the Basin and Range province. conductivity, but the overall vertical hydraulic conductivity is The lower parts of alluvial slopes are most likely to interfinger relatively low because of the interbedded clay layers. Johnson with finer-grained sediments of the valley floor (Plume, 1996, and others (1968, table 5) report vertical hydraulic conductivi- p. B15; Bedsun, 1980). Thus, a slope somewhat greater than the ties of valley-floor sediments in central California that range lower values reported for alluvial slopes is probably reasonable from 9 x 10-6 ft/d for clay layers to 90 ft/d for sand layers. to delineate alluvial slopes from valley floors. The average of Harrill and Prudic (1998, p. 55) report vertical hydraulic con- the 5 values for lower alluvial slopes is 2.2 percent. For this ductivities that range from one to three orders of magnitude less study, areas with a slope greater than 3 percent (1.7 degrees) than horizontal hydraulic conductivities used for modeling five were designated as alluvial slope, and areas with a slope of less alluvial basins in and near Nevada. Thus, the potential for than 3 percent were designated as valley floor. vertical flow of fluids through unconsolidated sediments is The 3-percent slope break was determined using the likely greater on alluvial slopes than on the valley floor. National Elevation Dataset, which is a 100-ft (30-m) resolution Most ground-water recharge occurs on alluvial slopes digital-raster elevation dataset based primarily on USGS 7.5 from infiltration of precipitation and streamflow from moun- minute digital elevation models. Using a geographic informa- tain-blocks, resulting in generally downward ground-water tion system, 100-ft (30-m) cells with slopes less than 3 percent flow (Mifflin, 1988, p. 76). On the valley floor, little ground- were distinguished as a first approximation of the valley floor. water recharge occurs and ground-water flow generally is par- A line was then digitized around the first approximation to allel to land surface or upward where it discharges by evapo- refine the alluvial slope/valley floor contact. The digitized transpiration from plants and bare soil (Mifflin, 1988, p. 76; line was overlain on Landsat Thematic Mapper satellite images Freeze and Cherry, 1979, p. 145 and 193–194). In addition, at a scale of 1:100,000 to check the position of the alluvial water-table gradients that drive lateral ground-water flow gen- slope/valley floor contact. For most of Nevada, the contact erally are greater beneath alluvial slopes, ranging from 0.02 to provides a reasonable delineation of alluvial slopes and valley 0.005, whereas beneath the valley floor they range from floors (plate 2). 0.002 to 6 x 10-7 (Handman and Kilroy, 1997, p. 61; Harrill and Alluvial slopes are almost 2.5 times the area of valley Preissler, 1994, p. 10; Maurer, 1986, p. 17; Prudic and Herman, floors in Nevada. Visual inspection of plate 2 and calculated 1996, p. 16; Thomas and others, 1989, pl. 2). These generalized percentages of consolidated rock, alluvial slope, and valley descriptions of ground-water flow may vary somewhat depend- floor for each HA shows that valley floors comprises the largest ing on the permeability of consolidated rocks forming the percentage of the HAs in central and western Nevada, and allu- mountain block and the amount of annual precipitation, but vial slopes comprise the largest percentage of HAs in southern are applicable to all valleys in Nevada (fig. 3). Nevada. The high percentage of alluvial slopes in southern These distinctions in flow regime have direct implications Nevada could be due to a combination of diminished tectonic for aquifer susceptibility. Contaminants released on alluvial activity in southern Nevada with erosion as a dominant geologic slopes compared to valley floors are more likely to spread process (Best and Hamblin, 1978; p. 331) and the small basin quickly through large areas and reach deep aquifers because size, resulting in alluvial slopes from surrounding mountains ground-water flow is downward and vertical hydraulic conduc- that coalesce in the center of the basin. Consolidated rocks tivity, recharge, and water-table gradients are relatively high. comprise the largest percentage of HAs in northwestern and Contaminants released on valley floors compared to alluvial northern Nevada, which corresponds to Tertiary-age volcanic slopes are more likely to spread slowly through small areas of flows of the Modoc Plateau and the Owyhee Upland. shallow aquifers because ground-water flow is either parallel to Playas, mapped by Stewart and Carlson (1978a; plate 2), land surface or upward and the recharge rate, vertical hydraulic form at the lowest altitudes of many basins in Nevada. Playas conductivity, and water-table gradient are relatively low. Typi- typically are devoid of vegetation and often consist of fine- cally, deep aquifers are used for municipal supply and shallow grained sediments that were deposited in lakes that occupied aquifers are used for domestic supply. many valleys of Nevada during the Pleistocene epoch Because of the different flow regimes, topographic slope (10 thousand years [Ka]) to 1.6 Ma; Stewart, 1980, p. 97). was used to divide unconsolidated sediments into two major However, Motts and others (1970, p. 14) describe a few coarse- groups—alluvial slope and valley floor. Alluvial slopes are grained playas that consist of sand and silt-sized sediments. reported to have a wide range of topographic slope. Motts Examples are the playas in the Rhodes and Columbus Salt and others (1970, p. 10) report average alluvial slopes of 3.5 to Marsh Valleys and Clayton Valley playas in southwestern 5 percent (2 to 3 degrees); the reported slopes of ten alluvial Nevada, which have moderate to great soil permeability (5 to slopes in Nevada range from 1.6 to 7.1 percent (1 to 4 degrees; 20 ft/d; plate 3; HAs 118, 119, and 143). The water table French, 1987, p. 200); the lower parts of alluvial slopes in Death beneath coarse-grained playas generally is coincident with the Valley range from 1.3 to 6.2 percent (0.7 to 3.5 degrees; Denny, playa surface, and ground-water discharge commonly produces 1965, p. 42–49); Abrahams and Parsons (1994, p. 329) cite a evaporites (Motts and others, 1970, p. 14). range of 3.5 to 7 percent (2 to 4 degrees) for alluvial slopes in Because of their hydrologic significance, active stream the southwestern United States; and Peterson (1981, p. 8) cites channels were mapped and superimposed on all hydrogeologic about 1 percent (0.6 degrees) as the point where alluvial slopes units. As reported by Plume (1996, p. B18) and Bredehoeft Hydrogeologic Units 9
A MOUNTAIN BLOCK ALLUVIAL SLOPE VALLEY FLOOR
Zone of Zone of Zone of Arid-zone precipitation recharge lateral flow discharge
Infiltration Meager runoff e tabl ter WaterWa table ZoneZ o n of weather e o f Evapotranspiration w e a t h e r iingn g r e t a e w - d
i PermeableP e r m e a b l e d v i n CConsolidatedo n s o l i d a t e d divide d divide BasinB a s i n u o
r rrocko c k fillf i l l Ground-water G
B MOUNTAIN BLOCK ALLUVIAL SLOPE VALLEY FLOOR Zone of Zone of Zone of recharge Arid-zone precipitation lateral flow discharge
le Infiltration ab r t ate WaterW table ZoneZ o n of weathering e o Streamflow f w e a t h e r i n g Evapotranspiration r e t a e w - d i d v
i PoorlyP o o r l y PermeableP e r m e a b l e n divide d divide u CConsolidatedo n s o l i d a t e d o r rrocko c k BasinB a s i n G Ground-water Ground-water fillf i l l
C MOUNTAIN BLOCK ALLUVIAL SLOPE VALLEY FLOOR Zone of recharge Semi-arid-zone precipitation Zone of discharge In le filtr ab atio r t n a Zone of te nd e a vapo lateral flow WaterW table ZoneZ o of weatheringtransp Streamflow n e iration o f w e a t h e r i n g Infiltration Evapotranspiration r e t a e w - d i
d PPoorlyo o r l y PPermeablee r m e a b l e v i n divide divide d u CConsolidatedo n s o l i d a t e d o r rrocko c k G Ground-water Ground-water BasinB a s i n fillf i l l
Modified from Berger (2000, p.7) Figure 3. Typical ground-water flow patterns perpendicular to the long axis of valleys in Nevada for mountain blocks with different permeability and annual precipitation. Modified from Berger (2000, p. 7). A, arid precipitation on permeable consolidated rock. B, Arid precipitation on poorly permeable consolidated rock. C, semi-arid precipitation on poorly permeable consolidated rock. 10 Hydrogeology and Hydrologic Landscape Regions of Nevada
(1963, p. 28) and shown in table 3, sediments deposited by in Nevada ranges from about 0.02 to 30 ft/d. Average soil per- streams, commonly called fluvial deposits, may have signifi- meability was grouped into five descriptive categories ranging cantly greater permeability than those of alluvial-slope or from very high to very low (table 3; plate 3). The limits of soil valley-floor deposits because of their high degree of sorting and permeability for descriptive categories are arbitrary, but were coarse texture. Fluvial deposits represent zones of potentially selected so that they provide a reasonable match to geomorphic high horizontal hydraulic conductivity and preferred pathways features in unconsolidated-sedimentary units such as playas, for contaminants. Fluvial deposits are easily recognized by alluvial slopes, flood plains, and stream channels mapped by braided-stream patterns on aerial photographs (Bredehoeft, various investigators (Stewart and Carlson, 1978a; Stewart and 1963, p. 28). McKee, 1977; Cohen, 1963; Bredehoeft, 1963; Johnson, 1977; For this study, Landsat Thematic Mapper images taken Tschanz and Pampeyan, 1970). from April to June 2000 were used to determine the location and approximate width of recently active stream channels. Active stream channels were recognized as roughly linear or braided Table 3. Range in soil permeability for descriptive categories of unconsolidated sediments and corresponding geomorphic features lacking vegetation as observed at a scale of 1:100,000. features The 1:100,000-scale hydrography digital line graph data (U.S. Geological Survey, various dates) was overlain on Land- Soil Corresponding Descriptive sat images, and stream segments corresponding to active stream permeability geomorphic category channels were assigned the measured width. Stream-channel (feet per day) feature widths measured from the Landsat images were checked by field verification and found to be reasonably accurate. During Very high 20 to 30 Alluvial slope/dune sand field verification, it was found that a large part of the channel High 10 to 20 Alluvial slope/stream channel that appeared active from the Landsat images was actually covered by fine-grained sediments. The fine-grained sediments Moderate 5 to 10 Valley-floor alluvium likely were deposited after recession of sediment-laden high flows in the stream channels, and their lateral extent marks Low 1 to 5 Flood plain/lake deposits the stream's active flood plain. Despite the presence of fine- Very low 0.02 to 1 Playa grained sediments near land surface, the mapped fluvial deposits (plate 2) likely represent areas where well-sorted fluvial sediments are present at depth. Over geologic time as the basins filled with sediments, stream channels have migrated In general, soil permeability is low to moderate in north- laterally across the valley floor or lower alluvial slope (Plume, ern, northeastern, and eastern Nevada and high to very high in 1996, p. B15; Bedsun, 1980, p. 51), and old stream-channel western, southwestern, and southern Nevada (plate 3). The type deposits may be present in areas not shown as active channels of parent rock and climate are factors that likely cause these in plate 2. For this reason, the mapped fluvial deposits should be spatial patterns. Granitic rocks and tuffaceous volcanic rocks of considered only as generalized areas having potential for rapid western and southwestern Nevada (plate 2) are more likely to ground-water flow parallel to the direction of the channel. produce sandy, permeable soils than other types of parent rock (Candland, 1984, p. 271; Buol and others, 1973, p. 111–113). Granitic and tuffaceous rocks have a high percentage of quartz, Soil Permeability which does not weather into clay minerals. In contrast, weath- ering of basaltic and andesitic volcanic rocks, siltstones, and shales in northern and northeastern Nevada generally produce The movement of water and contaminants into the subsur- clayey soils with low permeability (Buol and others, 1973, face is first controlled by the permeability of soils that develop p. 110–112). Ascribing likely soil types formed from carbonate in the upper several feet of unconsolidated sediments and con- solidated rocks. Soil permeability was estimated from a compi- rocks is difficult in Nevada because carbonate rocks of differing lation of soil properties by Schwarz and Alexander (1995). The ages and lithology are exposed near each other. Stewart (1980) compilation used values for individual soil layers to calculate describes carbonate rocks of Ordovician, Devonian, and weighted averages of permeability and other properties of Pennsylvanian/Permian age that are relatively sandy (Stewart, mapped soils for the entire thickness or to a depth of 60 inches, 1980, p. 25, 32, and 46). Carbonate rocks of Cambrian, Silurian, whichever was less. In Nevada, soil thickness from Schwarz and Mississippian age are siltier and interbedded with shale and Alexander (1995) and slope from the National Elevation (Stewart, 1980, p. 17, 29, and 41). Stewart (1980 p. 17–22) Dataset is significantly and inversely correlated with slope (cor- describes a limestone and shale province along the western edge relation coefficient -0.75). Soil thickness decreases from about of the carbonates where deposition likely occurred in deeper 60 inches, the maximum thickness measured, on flat slopes to water, producing rocks with a greater silt content. Sandy car- about 30 inches on 40-percent slopes. Average soil permeability bonate rocks are likely to form sandy soils and silty carbonate Faulting and Ground-Water Flow 11 rocks are likely to form clayey soils (Buol and others, 1973, In low-porosity consolidated rocks, the fault plane typi- p. 110). Buol and others (1973, p. 126) also note that greater cally is surrounded by a wide zone of fractures. Within the fault rainfall produces more clayey soils, which would accelerate the plane, gouge can develop and reduce the horizontal hydraulic weathering process in relatively wet northern Nevada. conductivity relative to the parent material and fracture zone. In addition to parent rock-type and climate, eolian deposi- In the fracture zone, horizontal hydraulic conductivity is high tion of sediments from quartz-rich parent rocks has produced relative to the parent material (Goodwin and others, 1999, highly permeable sand-dune complexes covering large areas of p. 1–2; Caine and Forster, 1999, p. 102). Thus, in consolidated many valleys in the western and southwestern parts of the state. rocks, ground-water flow is reduced in directions normal to the Notable examples are southern Desert and Silver State Valleys fault zone and increased in directions parallel to the fault zone (plate 3, HAs 31 and 32), Pyramid and Winnemucca Lake (Caine and Forster, 1999, p. 124; McKee and others, 1998, p. 8). Valleys (HAs 80 and 81), the Carson Desert (HA 101), Fish With time, carbonate and silica minerals can precipitate in the Lake Valley (HA 117), and Amargosa Valley (HA 230). fractures and can reduce ground-water flow (Antonellini and In most valleys, soil permeability is greatest near the others, 1999, p. 24). However, continued faulting may form margins of the valley and decreases toward the valley floor new fractures so that a fault may cycle between a zone of pre- (plate 3). This is likely due to sorting of sediments as stream ferred flow and a flow barrier (Nelson and others, 1999, p. 69). velocity decreases from the alluvial slopes toward the center of Faunt (1997, p. 30) states that faults in areas of extentional the valleys (Plume, 1996, p. B15; Davis, 1988, p. 286; Rust and stress fields are likely to be open to ground-water flow, whereas Koster, 1984, p. 55). Coarse, sandy sediments are deposited those in compressional stress fields are likely to be closed to on the alluvial slopes as streams emerge from mountainous ground-water flow. A detailed analysis of stress fields, faults, canyons and fine, clayey sediments are transported further and ground-water flow in southern Nevada was compiled by down valley (Plume, 1996, p. B15; Davis, 1988, p. 286), which Faunt (1997). However, such an analysis for the entire State is could result in the decrease in soil permeability. Notable excep- beyond the scope of this study. Figure 4 shows the potential tions to this general trend are several valleys about 40 miles effects of faults for various combinations of permeability of north of Las Vegas. Soils near the center of these valleys have faulted aquifer materials and fault zones. very high permeability (plate 3, HAs 161, 168, 169B, 211, Large-scale faulting occurred in east-central Nevada dur- and 216). ing the Antler orogeny (360–365 Ma), in central Nevada during Another important soil characteristic in controlling verti- the Sonoma orogeny (200–215 Ma), and at various times and cal flow is the presence of a hardpan within the soil profile. locations during the Mesozoic era (66–240 Ma; Stewart, 1980, Areas in unconsolidated sediments where soils have developed p. 36, 55, and 76–87). Many of the large-scale faults were thrust a continuous hardpan greater than 3-in. thick or where hardpan faults, which moved large blocks of rock up to 90 miles over is more than 18-in. thick and discontinuous or fractured are underlying rocks (Stewart, 1980, p. 36, 57, 77, 79, 84). Other shown on plate 3. In general, hardpan forms near exposures of types of faults include strike-slip faults that laterally offset carbonate rocks in the eastern part of the State (plate 2). Vertical aquifer materials and normal faults that offset aquifer materials flow may be restricted by hardpan in these areas. in a vertical direction. Many of these faults are inactive. How- ever, the juxtaposition of different rock types may greatly affect ground-water flow, especially in carbonate-rock aquifers (Plume, 1996, p. B24; McKee and others, 1998, p. 1). Faulting and Ground-Water Flow Faulting that produced the present-day Basin-and-Range topography began about 17 Ma (Stewart, 1980, p. 110). The Another geologic factor that may affect ground-water flow faults generally are steeply dipping normal faults that uplifted is the offset of aquifer materials along faults. In unconsolidated mountain blocks (horsts) and down-dropped the valley floors sediments, a fault zone can have a horizontal hydraulic conduc- (grabens) (Stewart, 1980, p. 110). The faults were produced by tivity that is three orders of magnitude less than the parent extension of the earth's crust beneath the Basin and Range phys- material (Goodwin and others, 1999, p. 2). Movement along the iographic province and have vertical offsets as great as 6,000 to fault can juxtapose sand and clay layers and create gouge, 15,000 ft (Stewart, 1980, p. 110). Along southwestern Nevada which is a zone of finely ground or mixed sediments along the from Las Vegas to north of Reno, right-lateral strike-slip fault- fault plane (Heynekamp and others, 1999, p.27). In addition, ing occurs in a wide zone known as the Walker Lane. Lateral Heynekamp and others (1999, p. 41) note that cementation offsets as much as 20 mi have been suggested along the Walker often occurs on the basin-ward side of faults in coarse-grained Lane (Stewart, 1980, p. 115). Recent and historic movement sediments, further reducing the permeability of the fault zone. along both normal and strike-slip faults show that the region is Thus, faults in unconsolidated sediments usually are barriers to still tectonicly active (Stewart, 1980, p. 117). ground-water flow, which could force contaminated ground Faults that were determined to have movement in the Qua- water to land surface in spring discharge. However, Sigda and ternary period (<2MA) are shown on plate 1, as compiled by the others (1999, p. 67) note that fine-grained fault gouge may act U.S. Geological Survey (2003). Many long faults are coincident as a capillary conduit through the unsaturated zone to the water with or near the contact between consolidated rocks and uncon- table. solidated sediments. In comparison, faults in unconsolidated 12 Hydrogeology and Hydrologic Landscape Regions of Nevada
OPEN FAULT—Springs along fault or flow changes direction along fault; depending on permeability contrast, there may be a large drop in head CLOSED FAULT—Springs or diffuse discharge upstream from fault
OPEN FAULT—Large drop in head across fault or, depending on permeability contrast, flow may change along fault CLOSED FAULT—If fault is less permeable than unit, there may be some springs or diffuse discharge upstream from fault; large drop in head across fault
OPEN FAULT—Flow along fault or springs along fault line, possibly a large drop in head at and/or across fault CLOSED FAULT—Springs or diffuse discharge upstream from fault
OPEN FAULT—If fault is more permeable than unit, possible flow along fault and/or springs along fault line; possible negligible effect CLOSED FAULT—If fault is less permeable than unit, there may be some springs or diffuse discharge upstream from fault; large drop in head across fault
EXPLANATION
RELATIVELY LOW PERMEABILITY RELATIVELY HIGH PERMEABILITY
DIRECTION OF GROUND-WATER FLOW Figure 4. Potential effects of faults on ground-water flow for different types of aquifer and fault permeability. Modified from Faunt (1997, p. 32). sediments are relatively short and occur as clusters of faults. effect of faulting on ground-water flow (plate 1). Springs shown Another pattern is that most faults in southern Nevada have on plate 1 have flow of 200 to more than 1,000 gal/min (Harrill relatively low slip rates and are generally older compared to and others, 1988, plate 2). Most of the springs are in eastern- faults along western Nevada and scattered locations in the central Nevada in carbonate rocks, in unconsolidated sediments north. Best and Hamblin (1978, p. 331) suggest that tectonic surrounded by carbonate rocks, or near the contact between activity has moved progressively northward across the state and consolidated rock/unconsolidated sediment where faults are that fault activity in the southern part of the state (south of common. Springs at this contact could be due to restricted latitude 37ºN) has slowed since about 10 Ma. ground-water flow caused by fault gouge or the juxtaposition The effect of faults on ground-water flow is difficult to of rocks with different hydraulic conductivity. Some springs in determine without site-specific investigation. Faults may unconsolidated sediments occur along faults (White River restrict ground-water flow in unconsolidated sediments and Valley, HA 207; Amargosa Desert, HA 230), which is a good either restrict or enhance flow in consolidated rocks. The indication that these faults restrict ground-water flow. How- co-occurrence of faults and springs is one indication of the ever, most faults that are distant from the contact between Hydrologic Landscape Regions 13 consolidated rock/unconsolidated sediment do not have springs, wide maps exist and they were assumed to be related to aquifer indicating ground-water flow is not sufficiently restricted to susceptibility and contaminant transport. Hydrologic processes cause spring discharge. are controlled by many variables in addition to these five. The length of Quaternary-age faults within each hydrogeo- Considering more variables would make HLRs too complex. logic unit was divided by the area of the hydrogeologic unit Processing of the datasets was done using a geographic infor- (table 1) to evaluate relative amounts of faulting. Alluvial mation system and the datasets are available at URL slopes and andesitic volcanic flows are the most faulted hydro-
five categories of soil permeability resulted in regions with a Partitioning-around-medoids (PAM) and agglomerative- large variance in soil permeability. Therefore, the simplified hierarchical (AH) cluster analysis on the standardized values version using three categories was chosen to better distinguish were solved using S-Plus 6.1 (Mathsoft, 2001). The number of regions for the final iteration. clusters was increased until each region had only one category Topographic slope and aspect are important variables in of hydrogeologic unit. This criterion for the minimum number snow accumulation, sublimation, and soil infiltration. Slope of clusters was used because it has a physical basis as opposed was divided into three categories: low (<3 percent), moderate to statistical criteria that can be used to estimate the optimal (3 to 25 percent), and high (>25 percent). The 3-percent slope number of clusters. PAM using numerical values for categories break distinguishes valley floor from alluvial slopes and the resulted in a minimum of 16 regions. Values of other variables 25 percent slope break is a critical condition for snow stability in each region have little variance and, except for 2 regions, (Gray and Male, 1981, p. 501). Slopes greater than 25 percent have symmetrical distributions (fig 5). PAM using truly categor- are less likely to have significant snow accumulation due to ical values and AH using both categorical types resulted in 21 or avalanches. Aspect is the average compass direction that a cell more regions, and other variables had large variances. There- faces and was divided into two categories based on the relative fore, PAM using numerical values was chosen for the final amount of solar radiation. Easterly, westerly and flat aspects cluster analysis because this technique was most efficient at receive similar solar radiation, and southerly aspects receive the producing the fewest regions that are homogeneous and distinct most radiation. Northerly aspects receive considerably less from each other. The resulting map was nominally filtered—a radiation than non-northerly aspects (Gray and Male, 1981, raster- processing technique that removed clusters of fewer than p. 365). As a result, snow is more likely to infiltrate and less 40 cells that are of a different HLR than their surroundings likely to sublimate and runoff from northerly slopes compared (plate 4; table 3). to non-northerly slopes. The range in northerly aspect that is Differences in all five variables distinguish the HLRs. hydrologically significant is unknown, so a wide range was Most of Nevada has moderate precipitation (58 percent), low used. Northerly slopes are greater than 3 percent and have an soil permeability (50.1 percent), moderate slope (58.1 percent), aspect of 300 to 60 degrees; non-northerly slopes are less than non-northerly aspect (88.7 percent), and high horizontal 3-percent or greater than 3-percent slope and have an aspect of hydraulic conductivity (59.8 percent; table 4). Without consid- 299 to 61 degrees. ering combinations of these variables, these characteristics There are few data on vertical hydraulic conductivity, indicate that most of Nevada could have a high susceptibility to which can be orders of magnitude less than the horizontal contamination. For example, if recharge occurs where precipi- hydraulic conductivity. Therefore, horizontal hydraulic con- tation is more than 8 inches (Maxey and Eakin, 1949; Nichols, ductivity was used to categorize hydrogeologic units because 2000), then most of Nevada is susceptible regardless of other it affects the transport rate after a contaminant has entered the variables. However, susceptibility is a function of many aquifer. A large or small area of an aquifer could be susceptible variables. Even if variables indicate a low susceptibility, to contamination depending on horizontal hydraulic conductiv- aquifers could be vulnerable due to rapid development in ity, attenuation, and other factors. A mean of the range of less Nevada. Irrigation, urban runoff, septic tanks, and other land- than or greater than 40 ft/d for horizontal hydraulic conductivity use practices could flush contaminants into ground water. was used to categorize hydrogeologic units. This value divides Regions with moderate to high precipitation, soil perme- hydrogeologic units into categories of low or high horizontal ability, and horizontal hydraulic conductivity and low to mod- hydraulic conductivity fairly well. No other meaningful break erate slope could be more susceptible to contamination than in horizontal hydraulic conductivity is apparent (fig. 2). Car- other regions. These characteristics describe HLRs 9, 14, and bonates, basalt, and unconsolidated sediments except for playas 15, which comprise 27.1 percent of Nevada. HLRs 9, 14, and comprise hydrogeologic units with high horizontal hydraulic 15 represent alluvial slopes and valley floors and occur in most conductivity. Playas, rhyolite, andesite, breccia/tuff, intrusives/ basins of eastern and central Nevada (plate 4). Aspect could metamorphics, sandstone, siltstone, and tertiary sedimentary be an important variable affecting susceptibility in HLR 14 rocks comprise hydrogeologic units with low horizontal because Indian Springs Valley (HA 161) and Three Lakes hydraulic conductivity. Rhyolite and volcanic breccias, tuffs Valley (HA 211) have a large amount of slopes with a northerly and volcanic rocks older than Tertiary age seem to have high aspect. Aspect may not be an important variable for other HLRs horizontal hydraulic conductivity (table 2). However, this is due because of the scattered distribution of northerly slopes. to a few anomalous hydraulic conductivity values reported for Almost 90 percent of Nevada's population lives on hydro- these units (appendix 1). These hydrogeologic units generally geologic units with high horizontal hydraulic conductivity. are not productive aquifers and most reported values are less HLR 9 could be more susceptible to contamination than other than 40 ft/d. regions and has 38 percent of Nevada's population, indicating it Cluster analysis was done using two techniques on truly also is vulnerable. Except for its low precipitation, HLR 10 has categorical values, such as high and low, and on numerical similar characteristics to HLR 9 and 25.9 percent of the values, such as 1 and 2, assigned to each category. Numerical Nevada's population, suggesting it also could be vulnerable. values for the categories were not significantly correlated, HLR 9 represents the alluvial slopes and valley floors of west- so autocorrelation among variables was not a problem. ern Las Vegas and Spanish Springs, alluvial slopes and fluvial Hydrologic Landscape Regions 15
>16
8-16 PRECIPITATION,
INCHES PER YEAR <8
>10
5-10 FEET PER DAY <5 SOIL PERMEABILITY.
NORTHERLY ASPECT
NON-NORTHERLY
>25
3-25
SLOPE, PERCENT <3
12345678910111213141516 HLRs 1-8 WITH HYDRAULIC CONDUCTIVITY HLRs 9-16 WITH HYDRAULIC CONDUCTIVITY LESS THAN 40 FEET PER DAY GREATER THAN 40 FEET PER DAY
Figure 5. Ranges in mean annual precipitation, soil permeability, slope, and aspect for hydrologic landscape regions with low and high horizontal hydraulic conductivity.
deposits of western Reno, and valley floors where virtually This approach of using the HLRs as a framework to all the population is located in Carson City, Minden, and represent various hydrologic settings in Nevada is being used Gardnerville (Fig. 6a). HLR 10 represents alluvial slopes and as part of a statewide evaluation of ground-water susceptibility valley floors of southern Las Vegas (Fig. 6b). These areas could and vulnerability. Previous studies (Eckhardt and Stackelberg, be most vulnerable due to their hydrologic characteristics and 1995; Squillace and others, 1999) found that population density urban land-use practices that use water and chemicals. Develop- is correlated with the occurrence of anthropogenic contami- ment on alluvial slopes could be of particular concern because nants. This correlation and the HLRs were used to design a contaminants could reach the deep aquifer that is used for public stratified sampling strategy that represents both natural and supply by most cities. anthropogenic factors affecting ground water quality. Within each HLR, samples are being collected in low to high popula- Use of Hydrologic Landscape Regions tion-density areas. Samples are being analyzed for dissolved Hydrologic information representing much of the State can solids and nutrients including nitrate, which is one of the most be obtained by conducting studies in strategic locations so that commonly occurring anthropogenic contaminants. Samples the results would have high transfer value. For example, 5 of the also are being dated using chlorofluorocarbons to determine 16 HLRs comprise more than 60 percent of the State. A limited where ground water has recharged during the past 50 years number of detailed studies in these HLRs could greatly improve (Plummer and Friedman, 1999). The occurrence of young the understanding of hydrologic processes throughout much of ground water indicates that the aquifer is susceptible to Nevada. contamination. 16 Hydrogeology and Hydrologic Landscape Regions of Nevada 7,863 (0.4) 7,863 (0.4) 8,116 (0.2) 3,419 60,616 (3.0) 60,616 (1.5) 30,006 (0.8) 16,185 (1.5) 29,984 (0.8) 15,271 (2.6) 51,234 (0.8) 15,481 (2.9) 58,555 (0.5) 10,010 (1.2) 24,251 759,691 (38.0) 759,691 (25.9) 517,549 (19.5) 388,411 2000 population (percent of total)(percent 8,110 (7.4) 8,110 (6.1) 6,750 (5.2) 5,700 (2.6) 2,840 (2.4) 2,660 (2.3) 2,570 (1.0) 1,100 (6.1) 6,750 (3.8) 4,200 (2.9) 3,210 (2.0) 2,160 (1.3) 1,440 14,390 (13.1) 14,390 (22.2) 24,390 (12.1) 13,330 (9.3) 10,260 (percent of total)(percent Area, square miles most ranges throughout Nevada throughout most ranges idated rock throughout Nevada Nevada rock throughout idated in western to southern Nevada western to southern in olidated rock throughout Nevada rock throughout olidated (HA 28) and Smoke Creek Desert (HA 28) and Smoke 31) and central eastern 31) and central eastern Nevada ern to southern Nevada nd southwestern Nevada southeastern Nevada ern and southern Nevada and southern ern nductivity (<40 feet/day) nductivity areas in consolidated rock throughout throughout areas in consolidated rock Predominant distribution l eastern and western Nevada western and eastern l Owyhee Upland, Modoc Plateau, Owyhee Upland, Playas in Black Rock Desert (HA 21), Carson Sink, a Ranges in central and (HA Playas in Desert Valley in consol Small, scattered areas in cons Small, scattered areas Playas and consolidated rock Nevada ranges in northwestern and 227B) (HA Canyon Fortymile Nevada central north and central floors in east Valley Alluvial slopes from west Ranges in centra Nevada Alluvial slopes in southwestern and southern Ranges in eastern and southern Nevada 211), (HA Valley (HA Three Lakes 161), Valley Springs Indian scattered and small, Nevada Alluvial slopes in east and rock in eastern in consolidated areas scattered Small, southern Nevada Low horizontal co Low hydraulic High horizontal hydraulic conductivity (>40 feet/day) (>40 conductivity hydraulic High horizontal Aspect Non-northerly Non-northerly Non-northerly Non-northerly Northerly Northerly Non-northerly Non-northerly Non-northerly Non-northerly Non-northerly Non-northerly Non-northerly Northerly Non-northerly Northerly square miles and percent is rounded to one decimal place.] <3 <3 >25 >25 >25 >25 Slope, 3 to 25 3 to 25 3 to 25 3 to 25 3 to 25 3 to 25 3 to 25 3 to 25 3 to 25 3 to 25 percent <5 <5 <5 <5 bution, area, and population of hydrologic landscape regions area, and population(HLR) hydrologic bution, of >10 >10 >10 >10 Soil 5 to 10 5 to 10 5 to 10 5 to 10 5 to 10 5 to 10 5 to 10 5 to 10 feet/day permeability, <8 <8 <8 <8 >16 >16 >16 >16 8 to 16 8 to 16 8 to 16 8 to 16 8 to 16 8 to 16 8 to 16 8 to 16 inches/year Precipitation,
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 HLR Table 4. Characteristics, 4. distri Table HA,[Abbreviation: hydrographic area. Area is rounded to 10 Hydrologic Landscape Regions 17
A
120°00' 119°45' 119°30'
100A 94 81 99 93 39°45' 84
82
100 92A 85 92B SSpanishpanish SSpringsprings
100A 86 RenoReno - SSparksparks EXPLANATION
76 91 83 Hydrographic-area boundary and 39°30' number—See plate 1 for names 87 Urban Area Boundary— Population density of at least 500 people per square mile, 91 Bureau of the Census, 2000
Hydrologic landscape regions 9 88 14 15
89 39°15' 103
MAP NEVADA AREA
CCarsonarson 104 CCityity 90 102
39°00'
105 NEVADAN CALIFORNIAC E MMindeninden A V L A IF D O A 107 R N GardnervilleGardnerville IA
106
Base from Nevada Department of Transportation digital data, 2002. 0 5 10 MILES 1:750,000 Hydrographic areas from U.S. Geological Survey digital data (unpublished). Urban areas from U.S. Department of Commerce, Bureau of the Census, Geography Division, Cartographic Boundary Files, 2000 census. 0 5 10 KILOMETERS Universal Transverse Mercator Projection, Zone 11, North American Datum 1927. Figure 6. Hydrologic landscape regions 9, 10, 14, and 15 in the most urbanized areas of Nevada. A, Reno-Sparks, Carson City, Minden and Gardnerville areas. B, Las Vegas, Boulder City, and Pahrump, Nevada. 18 Hydrogeology and Hydrologic Landscape Regions of Nevada
B 116°00' 115°30' 115°00'
219219 221010 222525
211211 217217 223030 36°30'
218218 116161 216216
212212
LasLas VVegasegas
PahrumpPahrump
116262
215215
36°00' NEVADA BBoulderoulder CCityity
MAP AREA 116363
165165 166166
1164A64A 167167 EXPLANATION
213213 230 Hydrographic-area boundary and number—See plate 1 for names
Urban Area Boundary— Population density of at least 500 people per square mile, Bureau of the Census, 2000 1164B64B 35°30' Hydrologic landscape regions 9 14
10 15 CALIFORNIANEVAD 214214
Base from Nevada Department of Transportation digital data, 2002. A 1:750,000 Hydrographic areas from U.S. Geological Survey digital 0 10 20 MILES data (unpublished). Urban areas from U.S. Department of Commerce, Bureau of the Census, Geography Division, Cartographic Boundary Files, 2000 census. 0 10 20 KILOMETERS Universal Transverse Mercator Projection, Zone 11, North American Datum 1927. Figure 6. -- Continued. Summary 19
An example of a sampling design using HLRs is shown in Hydrogeologic units are geologic formations with similar table 5. A certain number of samples are collected in each HLR lithology and assumed to have similar hydrologic properties. that represents a range in population density. The number of The geologic map of Nevada is the primary source of lithology samples may not be equal among HLRs for various reasons. For used to delineate hydrogeologic units. Because the hydrologic example, more samples may be collected in the most densely properties of consolidated rocks and unconsolidated sediments populated areas of an HLR, more samples may be collected in are quite different, they comprise the two major hydrogeologic HLRs with the largest total population, and no samples may be units. Consolidated rocks are exposed over 56,000 mi2 (51 per- collected in HLRs that are a small percentage of the total area cent) of Nevada and unconsolidated sediments are exposed over and population. 54,000 mi2 (49 percent) of the State. These two major hydro- geologic units were further subdivided into more detailed hydrogeologic units based on lithology, horizontal hydraulic Table 5. Example of a sampling strategy using hydrologic conductivity, slope, and mapped stream channels. landscape regions Consolidated rocks were subdivided into eight hydro- [Abbreviation: HLR, hydrologic landscape region.] geologic units. In order of decreasing area covering Nevada, the eight consolidated-rock hydrogeologic units consist of Range in population density Quaternary to Tertiary age volcanic flows of (1) basaltic, HLR (2) rhyolitic, and (3) andesitic composition; (4) volcanic 1st 2nd 3rd 4th breccias, tuffs, and volcanic rocks older than Tertiary age; quartile quartile quartile quartile (5) carbonate rocks; (6) Tertiary-age consolidated and semi- 1 2 3 4 5 consolidated tuffaceous rocks and sediments, (7) clastic rocks 2 2 3 4 5 consisting of sandstone and siltstone; and (8) intrusive and 3 2 2 2 2 metamorphic rocks. 4 2 2 3 3 Unconsolidated sediments were subdivided into four 5 2 2 2 2 hydrogeologic units. Alluvial slopes were defined as uncon- solidated sediments with a topographic slope greater than 6 2 2 2 2 7 2 2 2 2 3 percent. Alluvial slopes typically are recharge areas with 8 0 0 0 0 downward ground-water flow and high gradients. Valley 9 4 5 5 6 floor deposits have a topographic slope of less than 3 percent. 10 3 4 4 5 Ground-water flow beneath valley floors generally is parallel to land surface or upward, vertical flow is restricted by layering, 11 3 4 4 5 and gradients are low. Fluvial deposits could be areas of prefer- 12 3 3 3 3 ential flow and were mapped as a separate unit using Landsat 13 2 2 2 2 imagery. Playas have low hydraulic conductivities and were 14 2 2 2 2 15 0 0 0 0 mapped by Stewart and Carlson (1978a). 16 0 0 0 0 Soil permeability was grouped into five descriptive cate- gories ranging from very high to very low, which generally Summary correspond to mapped geomorphic features such as playas, alluvial slopes, flood plains, and stream channels. In general, soil permeability is low to moderate in northern, northeastern, In 1999, the U.S. Environmental Protection Agency initi- and eastern Nevada and high to very high in western, south- ated a rule to protect ground water in areas other than source- western, and southern Nevada. Within a particular basin, soil water protection areas. These OSGWAs are aquifers that are not permeability decreases down slope from the bedrock contact. currently but could eventually be used as a source of drinking The type of parent rock, climate, and streamflow velocities are water. NDEP will evaluate site-specific information and deter- factors that likely cause these spatial patterns. Soil thickness is mine if an aquifer associated with a permit application is sus- significantly correlated with slope and decreases from about ceptible to contamination. A basic part of evaluating OSGWAs 60 in. on flat slopes to about 30 in. on 40-percent slopes. is characterizing the hydrogeology of aquifer systems including Faults in unconsolidated sediments usually are barriers the lithology, hydrologic properties, soil permeability, and to ground-water flow. However, in the unsaturated zone, fine- faulting, which partly control the susceptibility of ground water grained fault gouge may act as a capillary conduit to the water to contamination. Detailed studies that evaluate ground-water table. In consolidated rocks, permeability and ground-water susceptibility are not practical in a largely unpopulated State flow is reduced in directions normal to the fault zone and like Nevada. However, existing and new information could be increased in directions parallel to the fault zone. During extrapolated to other areas of the State if there is an objective geologic time, fractures in consolidated rocks may become framework to transfer the information. The concept of hydro- cemented and sealed due to precipitation of carbonate minerals, logic landscape regions, which identify areas with similar reducing the permeability. However, continued movement hydrologic characteristics, provides this framework. along the fault may form new fractures so that a fault may cycle 20 Hydrogeology and Hydrologic Landscape Regions of Nevada
between a zone of preferred flow and a flow barrier. The effect Anderson, R.E., Zoback, M.L., and Thompson, G.A., 1983, of faults on ground-water flow is difficult to determine without Implications of selected subsurface data on the structural site-specific investigation. form and evolution of some basins in the northern Basin and Range province, Nevada and Utah: Geological Society of HLRs were delineated by gridding the State into 100-ft America Bulletin, v. 94, p. 1055–1072. (30-m) cells, estimating the value of five variables for each cell, Antonellini, Marco, Aydin, Atilla, and Orr, Lynn, 1999, and conducting cluster analysis to assign each cell to a region Outcrop-aided characterization of a faulted hydrocarbon such that each region is fairly homogeneous and distinct from reservoir: Arroyo Grande Oil Field, California, USA, in other regions. The five variables include mean annual precipi- Haneberg, W.C., Mozley, P.S., Moore, J.C., and Goodwin, tation, soil permeability, slope, aspect, and hydrogeologic unit. L.B., eds., Faults and subsurface fluid flow in the shallow The number of clusters was increased until each region had crust, Geophysical Monograph 113, American Geophysical only one category of hydrogeologic unit, which resulted in Union, Washington, D.C., 222 p. 16 regions. Five of the16 HLRs comprise more than 60 percent Aquifer Science Inc., 2001, Wellhead protection program for of the State. A limited number of detailed studies in these HLRs Cottonwood Mobile Home Park water system: Aquifer could greatly improve the understanding of hydrologic pro- Science Inc, Salt Lake City, Utah, 8 numbered sections, cesses throughout much of Nevada. 1 glossary. Most (59.8 percent) of Nevada is comprised of HLRs with Bedinger, M.S., Langer, W.H., and Reed, J.E., 1986, Synthesis high horizontal hydraulic conductivity. Regions with moderate of hydraulic properties of rocks with reference to the Basin to high precipitation, moderate to high soil permeability, low to and Range Province, southwestern United States, in Selected moderate slope, and high hydraulic conductivity could have papers in the hydrologic sciences, U.S. Geological Survey greater recharge rates and be more susceptible to contamination Water-Supply Paper 2310, p. 35–41. relative to other regions. These characteristics describe HLRs 9, Bedsun, D.A., 1980, Geological and hydrological profiles in 14 and 15, which comprises 27.1 percent of Nevada and repre- Missile-X valleys: Defense Nuclear Agency, Air Force sent alluvial slopes and valley floors in most basins of eastern Weapons Laboratory, Kirtland Air Force Base, New Mexico, and central Nevada. Aspect could be an important variable 69 p. affecting susceptibility in Indian Springs Valley (HA 161) and Belcher, W.R., Elliot, P.E., and Geldon, A.L., 2001, Hydraulic- Three Lakes Valley (HA 211) because they have a large amount property estimates for use with a transient ground-water flow of slopes with a northerly aspect. Aspect may not be an impor- model of the Death Valley regional ground-water flow tant variable for other HLRs because of the scattered distribu- system, Nevada and California: U.S. Geological Survey tion of northerly slopes. Water-Resources Investigations Report 01–4210, 25 p. Almost 90 percent of Nevada's population lives on hydro- Berger, D.L., 1995, Ground-water conditions and effects of geologic units with high horizontal hydraulic conductivity. mine dewatering in Desert Valley, Humboldt and Pershing HLR 9 could be more susceptible than other regions and Counties, northwestern Nevada, 1962–91: U.S. Geological has 38 percent of Nevada's population, indicating it also is Survey Water-Resources Investigations Report 95–4119, vulnerable to contamination. HLR 9 represents the alluvial 79 p. slope and valley floor of western Las Vegas and Spanish Berger, D.L., Ross, W.C., Thodal, C.E., and Robledo, A.R., Springs, alluvial slope and fluvial deposits of western Reno, 1997, Hydrogeology and simulated effects of urban develop- and valley floor of Carson City, Minden, and Gardnerville ment on water resources of Spanish Springs Valley, Washoe where virtually all the population is located. 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Canyons, Carson City, Nevada, estimated from Darcy's Law Hydrologic Consultants, Inc., 2000, 1999 update of numerical and the chloride-balance method: U.S. Geological Survey ground-water flow modeling for Newmont Mining Corpora- Water-Resources Investigations Report 96–4088, 74 p. tion's Lone Tree Mine Humboldt County, Nevada: prepared Maurer, D.K., Plume, R.W., Thomas, J.M., and Johnson, A.K., for Newmont Mining Corporation, HCI–834, Lakewood, 1996, Water Resources and effects of changes in ground- Colorado, 39 p. water use along the Carlin Trend, North-Central Nevada: JBR Consultants Group, 1989, Technical report in support of an U.S. Geological Survey Water-Resources Investigations application for a Class V injection well Cyanco Winnemucca Report 96–4134, 146 p. plant: prepared for Cyanco, Salt Lake City, Utah, 33 p. Maurer, D.K., and Welch, A.H., 2001, Hydrogeology and Johnson, A.I., Moston, R.P., and Morris, D.A., 1968, Physical geochemistry of the Fallon basalt and adjacent aquifers, and and hydrologic properties of water-bearing deposits in sub- potential sources of basalt recharge, in Churchill County, siding areas in central California: U.S. Geological Survey Nevada: U.S. Geological Survey Water-Resources Professional Paper 497–A, 71 p. Investigations Report 01–4130, 72 p. References Cited 23
Maxey, G.B., and Eakin, T.E., 1949, Ground water in White Porter Geotechnical, 1997, Remediation status report: prepared River Valley, White, Nye, and Lincoln Counties, Nevada: for Sierra Machinery, Inc, Sparks, Nevada, 9 p. Nevada State Engineer, Water Resources Bulletin 8, 59 p. Prudic, D.E., Harrill, J.R., and Burbey, T.J., 1995, Conceptual McDonald and Morrissey Associates, Inc., 1998, Regional evaluation of regional ground-water flow in the carbonate- hydrologic model, Barrick Goldstrike Mines Inc., Elko and rock province of the Great Basin, Nevada, Utah, and adjacent Eureka Counties, Nevada: prepared for Barrick Goldstrike states: U.S. Geological Survey Professional Paper 1409–D, Mines, Inc., McDonald and Morrissey Associates, Inc., 102 p. Reston, Virginia, 54 p. Prudic, D.E., and Herman, M.E., 1996, Ground-water flow and McKee, E.H., Wickham, T.A., and Wheeler, K.L., 1998, Eval- simulated effects of development in Paradise Valley, a basin uation of faults and their effect on ground-water flow south- tributary to the Humboldt River in Humboldt County, west of Frenchman Flat, Nye and Clark Counties, Nevada: Nevada: U.S. Geological Survey Professional Paper 1409–F, U.S. Geological Survey Open-File Report 98–580, 14 p. 92 p. Mifflin, M.D., 1988, Region 5, Great Basin, in Back, W., Rosenshein, J.S., and Seaber, P.R., eds., Hydrogeology, PTI Environmental Services, Inc., 1994, The hydrogeochem- v. O–2, Geology of North America, 524 p. istry of the Robinson Mining District, White Pine County, Nevada, prepared for Magma Mining Company, Tucson, Morgan, D.S., and Dettinger, M.D., 1996, Ground-water Arizona, 8 numbered sections, 1 appendix. conditions in Las Vegas Valley, Clark County, Nevada, part 2, hydrogeology and simulation of ground-water flow: PTI Environmental Services, Inc., 1997, Effects of pumping the U.S. Geological Survey Water-Supply Paper 2320–B, 124 p. proposed Olinghouse Mine supply well on Dodge Flat and Motts, W.S., Carpenter, David, Groat, C.G., Matz, David, and the Truckee River, Washoe County, Nevada: prepared for Walker, R.F., 1970, Geology and hydrology of selected Bureau of Land Management, Carson City Field Office, playas in western United States, Ward S. Mott, ed.: Final PTI Contract CV1T, 02–01, PTI Environmental Services, Scientific Report (Part II), Contract No. AFL 19(628)–2486, Boulder, Colorado, 19 p. Air Force Cambridge Research Laboratories, Bedford, Rush, F.E., 1968, Index of hydrographic areas: Nevada Massachusetts, 286 p. Division of Water Resources Information Report 6, 38 p. National Atlas of the United States, 1998, Hydrologic Units: Rust, B.R., and Koster, E.H., 1984, Coarse alluvial deposits, compiled by the U.S. Geological Survey, 1:3,500,000 scale in Walker, R.G., ed., Facies Models, (2nd ed.): Geoscience map: accessed October 15, 2003 at URL Canada, Reprint Series 1, Geological Association of Canada
Star City and Nevada Rural Water Association, 2002, Star City U.S. Geological Survey, 2003, Quaternary fault and fold data- wellhead protection program: Star City Property Owners base of the United States: U.S. Geological Survey Open-File Association, Winnemucca, Nevada; and Nevada Rural Report 03–417: accessed April 20, 2004 at URL Water Association, Minden, Nevada, 8 numbered sections,
APPENDIX—Detailed summary of hydraulic conductivity estimates 26 Hydrogeology and Hydrologic Landscape Regions of Nevada -2 to 50 to 2700 to 3300 nr nr -4 to 7x10 -5 -3 (ft/d) -3 Range 3 to 370 25 to 94 10 to 300 10 to 300 1.1 to 15 0.7 to 700 to 0.7 900 to 0.1 a 130 to 530 3x10 0.03 to 2700 to 0.03 3x10 2x10 2x10 a nr nr nr nr nr nr nr nr nr 20 (ft) 1,500 tested Thickness 30 to 1,700 to 30 1,700 to 30 1,700 to 30 17 nr nr nr nr b 0.01 (ft/d) 6 - A 2 - G 6 - M 6 - M 9 - 10 -G b Mean 80 - A 80 - 0.3 - G -A 400 -A 300 200 - G 350 - A 200 - A 0.01 - G - 0.01 median - M arithmetic - A geometric - G - geometric 1 1 4 9 1 4 of 10 nr nr nr nr 19 18 51 Number samples Test type/ Test data source Literature search Literature search Literature test Pumping test Pumping test Pumping search Literature test Pumping test Pumping test Pumping test Pumping test Pumping test Pumping test Pumping test Pumping Location Basin and Range Basin and Range Basin and Southern Nevada Southern Nevada Southern Nevada Range Basin and Near Carlin, Nevada Near McGill, Nevada Crescent Valley, Nevada Crescent Valley, Nevada Near Ruth, Nevada Near Ruth, Nevada Site Near Test Eastern Nevada
rs, 1986, table 1 rs, 1986, table 1 hers, 1997, p. 17 hers, Reference Bedinger and othe Bedinger and othe Belcher and others, 2 2001, table Belcher and others, 2 2001, table Belcher and others, 2 2001, table ot D’Agnese and McDonald and Morrissey Inc, table Associates, 1998, 2 Inc., 1997, table 5-1 Geomega 24-26 p. Inc, 1998a, Geomega 24-26 p. Inc, 1998a, Geomega p. 3-3 Inc, 1998b, Geomega p. 3-3 Inc, 1998b, Geomega p. B13 Plume, 1996, p. B13 Plume, 1996,
unit Hydrogeologic Hydrogeologic
Carbonate rocks, dense Carbonate rocks, fractured, Carbonate rocks, karstic unfaulted Carbonate rocks, and Carbonate rocks, faulted karstic Carbonate rocks Carbonate rocks Carbonate rocks Carbonate rocks Carbonate rocks Carbonate rocks Carbonate rocks, metamorphosed Carbonate rocks, unmetamorphosed Carbonate rocks Carbonate rocks [Abbreviations: ft, feet; ft/d, feet per day; nr, not reported.] nr, per day; ft/d, feet ft, feet; [Abbreviations: Appendix—Detailed summary of hydraulic conductivitysummary estimates of hydraulic Appendix—Detailed Appendix–Detailed summary conductivity estimates—Continued of hydraulic APPENDIX—Detailed summary of hydraulic conductivity estimates 27 to 0.1 to 3 to 0.01 -4 -4 -4 nr (ft/d) >100 Range 3 to 500 1.1 to 26 0.03 to 2 0.07 to 30 90 to 340 0.07 to 13 0.07 260 to 850 a 2x10 130 to 1,300 5 x 10 2 x 10 a nr nr nr nr nr nr nr nr nr nr (ft) tested 4 to 30 26 to 100 200 to 260 Thickness - G - b -3 2 nr nr nr nr nr nr nr nr 1 (ft/d) Mean 0.1 - A 0.3 - G 0.001 - M - 0.001 median - M 1 x 10 1 x arithmetic - A geometric - G - geometric 8 2 2 3 2 nr nr nr nr nr nr nr nr of Number samples
Test type/ Test data source Drill-Stem test Drill-Stem test, Pumping literature search search Literature search Literature and Pumping slug test search Literature test Pumping value Modeled Slug test test/ Pumping slug test test Pumping test Pumping test Pumping Eastern Great Basin Near Ruth, Nevada Range Basin and Range Basin and Southern Nevada Range Basin and Valley, Lake Honey and Nevada California Nevada Near Valmy, Eagle Valley, Nevada Desert, Carson Nevada Great Basin Near Fernley, Nevada Near Winnemucca, Nevada
rs, 1986, table 1 rs, 1986, table 1 hers, 1997, p. 17 hers, Reference Location Plume, 1996, p. B13 Plume, 1996, Inc., Services, PTI Environmental 6-6 table 1994, Bedinger and othe Bedinger and othe Belcher and others, 2 2001, table ot D’Agnese and Handman and others, 1990, p. 15 Inc., 2000, Hydrologic Consultants, table 6 p. 11 1997, and Berger, Maurer p. 25 2001, Welch, and Maurer p. B20 Plume, 1996, Miller Consultants, 1997, Shepherd p. 3-5 Engineers, Consulting Wateresource p. 13 2000, Basalt, dense Basalt, unit Hydrogeologic Hydrogeologic Carbonate rocks Carbonate rocks to Tertiary-age Quaternary volcanic flows: to Tertiary-age Quaternary Basalt, flows: volcanic and cavernous fractured to Tertiary-age Quaternary Basalt flows: volcanic to Tertiary-age Quaternary Basalt flows: volcanic to Tertiary-age Quaternary Basalt flows: volcanic to Tertiary-age Quaternary Basalt flows: volcanic to Tertiary-age Quaternary Basalt flows: volcanic to Tertiary-age Quaternary Basalt flows: volcanic to Tertiary-age Quaternary Basalt flows: volcanic to Tertiary-age Quaternary Basalt flows: volcanic to Tertiary-age Quaternary Basalt flows: volcanic Appendix–Detailed summary conductivity estimates—Continued of hydraulic 28 Hydrogeology and Hydrologic Landscape Regions of Nevada to 3 to 3 to .01 to .01 to 13 to 0.02 -4 -4 -4 -5 -4 (ft/d) Range 1 to 16 1 to 260 40 to 60 0.03 to 2 0.07 to 30 a 2x10 2x10 0.01 to 0.06 2x10 2x10 a 1x10 nr nr nr nr nr nr nr nr (ft) 220 tested 40-640 23 to 5000 Thickness - G - G -3 -3 2 nr nr nr nr nr (ft/d) 3 - G Mean 0.3 - G 0.6 - A 0.3 - G 1x10 1x10 median - M arithmetic - A geometric - G - geometric 6 1 nr nr nr nr nr nr nr nr of 25 Number samples Test type/ Test data source Literature search Literature search Literature test Pumping search Literature test Pumping test Pumping test Pumping search Literature test Pumping search Literature search Literature Basin and Range Basin and Range Basin and Southern Nevada Range Basin and Near Carlin, Nevada Near Ruth, Nevada Nevada Near Tracy, Range Basin and Near Fernley, Nevada Range Basin and Range Basin and
rs, 1997, table 1 rs, 1986, table 1 rs, 1986, table 1 rs, 1986, table 1 rs, 1986, table 1 hers, 1997, p. 17 hers, Reference Location Bedinger and othe Bedinger and othe Belcher and others, 2 2001, table othe D’Agnese and McDonald and Morrissey Inc., 1998, table 2 Associates, Inc., Services, PTI Environmental 6-6 table 1994, Consulting Services Associates, Inc, K. Halford, interpreted by 1997, Survey, U.S. Geological 2001 written commun., ot D’Agnese and Miller Inc, 1997, Shepherd p. 3-5 Bedinger and othe Bedinger and othe unit Hydrogeologic Hydrogeologic Quaternary to Tertiary-age to Tertiary-age Quaternary Rhyolite, flows: volcanic dense to Tertiary-age Quaternary Rhyolite, flows: volcanic fractured to Tertiary-age Quaternary Rhyolite flows: volcanic to Tertiary-age Quaternary Rhyolite flows: volcanic to Tertiary-age Quaternary Rhyolite flows: volcanic to Tertiary-age Quaternary Rhyolite flows: volcanic to Tertiary-age Quaternary Andesite flows: volcanic to Tertiary-age Quaternary Andesite flows: volcanic to Tertiary-age Quaternary Andesite flows: volcanic and volcanic Breccias, Tuffs, rocks older than Tertiary-age: welded and fractured Tuff, and volcanic Breccias, Tuffs, rocks older than Tertiary-age: welded and moderately Tuff, to dense fractured Appendix–Detailed summary conductivity estimates—Continued of hydraulic APPENDIX—Detailed summary of hydraulic conductivity estimates 29 to 3 to 50 to 16 to 0.3 to 600 to to 0.02 -5 nr -3 -4 -6 -5 -5 (ft/d) Range 0.1 to 40 1.5 to 17 3x10 3x10 2x10 1x10 3x10-7 to 0.2 7x10 7x10 nr nr nr nr nr nr (ft) 200 tested 30 to 5000 30 to 5000 30 to 5000 Thickness to to - G - A - M - -6 -4 -2 -4 45 nr nr b (ft/d) 1 - G Mean 16 - A 16 - A 13 - 0.3 - G 0.2 - A 0.4 - G 0.01 - G - 0.01 A - 0.02 8x10 6x10 1x10 4x10 median - M arithmetic - A geometric - G - geometric 1 nr nr nr of 11 46 27 54 109 128 Number samples Test type/ Test data source Literature search Literature test Pumping test Pumping test Pumping search Literature test Pumping and Pumping slug test test Pumping tests Drill-stem test Lab Basin and Range Basin and Southern Nevada Southern Nevada Southern Nevada Range Basin and Valley, Desert Nevada Springs Warm Valley, Nevada Site Test Nevada and White Railroad Valleys, River Nevada Site Test Nevada
y & Associates, rs, 1997, table 1 rs, 1986, table 1 Reference Location Bedinger and othe Belcher and others, 2 2001, table Belcher and others, 2 2001, table Belcher and others, 2 2001, table othe D’Agnese and Errol L. Montgomer p. 21 Inc., 1988, Resources Groundwater Inc., p. 20 Consultants, 1994, Plume 1996, p. B20 Plume 1996, p. B20 p. 51-52 1982, Wolff, unit Hydrogeologic Hydrogeologic Breccias, Tuffs, and volcanic Breccias, Tuffs, rocks older than Tertiary-age: non-welded Tuff, and volcanic Breccias, Tuffs, rocks older than Tertiary-age: ash-flow Tuff, and volcanic Breccias, Tuffs, rocks older than Tertiary-age: breccia Tuff and volcanic Breccias, Tuffs, rocks older than Tertiary-age: rocks older volcanic and volcanic Breccias, Tuffs, rocks older than Tertiary-age: ash-flow Tuff, and volcanic Breccias, Tuffs, rocks older than Tertiary-age: Tuff and volcanic Breccias, Tuffs, rocks older than Tertiary-age: Tuff and volcanic Breccias, Tuffs, rocks older than Tertiary-age: Tuff and volcanic Breccias, Tuffs, rocks older than Tertiary-age: rocks older volcanic and volcanic Breccias, Tuffs, rocks older than Tertiary-age: Tuff Appendix–Detailed summary conductivity estimates—Continued of hydraulic 30 Hydrogeology and Hydrologic Landscape Regions of Nevada
-5 -5 to 1 to .07 to 3 to 1 to 0.2 to 0.6 -3 -2 -4 -5 nr nr nr to 2x10 to 3x10 -8 -3 (ft/d) -8 -7 2 to 4 Range 0.05 to 4 0.02 to 1 0.02 to 1 0.01 to 30 0.01 7x10 2x10 7x10 2x10 a 7x10 9x10 a 7x10 1x10 a a nr nr nr nr nr nr nr nr nr nr nr 10 (ft) 1200 tested 20 to 30 10 to 100 30 to 1400 Thickness - G - G - G - G 3 -3 -6 -3 -6 18 nr nr nr nr nr nr b 0.01 b (ft/d) 1 - A b Mean 0.1 - G 0.1 - G 0.01 - G - 0.01 A - 0.02 2x10 1x10 7x10 2x10 median - M arithmetic - A geometric - G - geometric 7 9 4 1 1 nr nr nr nr nr nr nr nr nr of 11 16 Number samples Test type/ Test data source Literature search Literature search Literature search Literature test Pumping search Literature test Pumping value Modeled Slug test Slug test test Pumping search Literature test Pumping search Literature test Pumping test Lab search Literature Basin and Range Basin and Range Basin and Range Basin and Southern Nevada Range Basin and Lake, Near Topaz Nevada Nevada Near Valmy, Near Eagle Valley, Nevada Near Eagle Valley, Nevada Near Carlin, Nevada Range Basin and Southern Nevada Range Basin and Near Ruth, Nevada Site Test Nevada Range Basin and
nts, Inc., 2000, rs, 1997, table 1 rs, 1997, table 1 rs, 1986, table 1 rs, 1986, table 1 rs, 1986, table 1 rs, 1986, table 1 rs, 1986, table 1 Reference Location 21
Bedinger and othe Bedinger and othe Bedinger and othe Belcher and others, 2 2001, table othe D’Agnese and 1998, Inc., GTE California, C appendix Hydrologic Consulta table 6 and Prudic, 1996, Berger, Maurer, p. p. 11 1997, and Berger, Maurer McDonald and Morrissey Inc., 1998, table 2 Associates, Bedinger and othe Belcher and others, 2 2001, table othe D’Agnese and Inc., Services, PTI Environmental 6-6 table 1994, p. 41 1982, Wolff, Bedinger and othe
unit Hydrogeologic Hydrogeologic Intrusive and metamorphic Intrusive rocks, weathered and metamorphic Intrusive rocks, less than 1,000 ft deep and metamorphic Intrusive than rocks, more 1,000-ft deep and metamorphic Intrusive rocks and metamorphic Intrusive rocks and metamorphic Intrusive rocks and metamorphic Intrusive rocks and metamorphic Intrusive rocks and metamorphic Intrusive rocks and metamorphic Intrusive rocks rocks: Sandstone Clastic rocks: Sandstone Clastic rocks: Sandstone Clastic rocks: Sandstone Clastic rocks: Sandstone Clastic rocks: Siltstone Clastic Appendix–Detailed summary conductivity estimates—Continued of hydraulic APPENDIX—Detailed summary of hydraulic conductivity estimates 31 4 -5 to 16 to 20 to 0.2 to 0.02 to 1x10 nr -7 -3 -8 140 -4 (ft/d) -9 Range 9 to 16 6 to 140 0.08 to 4 0.04 to 3 0.05 to 3 20 to 1000 1x10 1x10 less than 0.3 less than 7x10 2x10 less than 2x10- less than 2x10 nr nr nr nr nr nr nr nr 50 (ft) tested 15 to 60 30 to 230 40 to 300 Thickness 50 to 4,200 to 50 200 to 1000 200 to 1,000
- G -4 nr nr nr nr nr nr nr nr nr nr nr 0.9 b (ft/d) 5 - A Mean 0.7 - A 0.2 - G 135 - A 1x10 median - M arithmetic - A geometric - G - geometric 6 5 5 1 nr nr nr nr nr nr of 30 26 15 22 35 Number samples Test type/ Test data source Pumping test Pumping search Literature value Modeled test Pumping test Pumping test Pumping test Lab test Pumping search Literature Specific capacity test Pumping test Pumping Specific capacity Specific capacity test Pumping Southern Nevada Range Basin and Nevada Near Valmy Near Carlin, Nevada Near Ruth, Nevada Near Ruth, Nevada Site Test Nevada Southern Nevada Range Basin and Valley, Carson Nevada Near Carlin, Nevada Southern Nevada Humboldt Lower Basin River Valley, Desert Nevada Near Sparks, Nevada
rs, 1997, table 1 rs, 1997, table 1 Reference Location Belcher and Belcher and others, 2 2001, table othe D’Agnese and Inc., 2000, Hydrologic Consultants, table 6 McDonald and Morrissey Inc., 1998, table 2 Associates, Inc., Services, PTI Environmental 6-6 table 1994, Inc., Services, PTI Environmental 6-6 table 1994, p. 41 1982, Wolff, Belcher and others, 2 2001, table othe D’Agnese and p. 29 1986, Maurer, McDonald and Morrissey Inc., 1998, table 2 Associates, others, 2001, and Belcher Appendix A 1963, p. 46 Bredehoeft, p. 22 1995, Berger, Inc., 1996, Camp Dresser & McKee, table 2 unit Hydrogeologic Hydrogeologic Clastic rocks: rocks: Siltstone Clastic rocks: Siltstone Clastic rocks: Siltstone Clastic rocks: Siltstone Clastic rocks: Siltstone Clastic rocks: Shale Clastic rocks: Siltstone Clastic rocks and tuffaceous Tertiary sediment rocks and tuffaceous Tertiary sediment rocks and tuffaceous Tertiary sediment rocks and tuffaceous Tertiary sediment sediments: Unconsolidated Fluvial deposits sediments: Unconsolidated Fluvial deposits sediments: Unconsolidated Fluvial deposits sediments: Unconsolidated Fluvial deposits Appendix–Detailed summary conductivity estimates—Continued of hydraulic 32 Hydrogeology and Hydrologic Landscape Regions of Nevada -3 -3 to 130 to to 7x10 -3 (ft/d) -5 Range 4 to 65 4 to 12 6 to 11 3 to 230 5 to 320 0.5 to 12 a 40 to 100 Fine - 0.1 4 to 2,200 to 12 0.03 10 to 1,200 Coarse - 15 Medium - 1 1x10 3x10 a 5 to more than 80 than5 to more nr nr nr nr nr nr 40 (ft) 350 180 330 tested 11 to 56 20 to 60 20 to 500 100 to 250 Thickness - G -4 nr nr nr nr nr nr nr nr 110 (ft/d) 2 - G Mean 30 - G 30 - A 11 - A 65 - 113 - G 7x10 median - M arithmetic - A geometric - G - geometric 5 2 9 4 nr nr of 10 19 25 43 19 17 several several Number samples
Test type/ Test data source Pumping test Pumping test Pumping test Pumping test Pumping search Literature search Literature test Pumping test Pumping Specific capacity test Pumping Grain-size analysis test Pumping test Pumping Slug test Near Ruth, Nevada Near Fernley, Nevada Near Hidden Valley, Nevada Valley, Las Vegas Nevada Range Basin and Range Basin and Eagle Valley, Nevada Southern Nevada Valley, Desert Nevada Spanish Springs Valley, Nevada Valley, Dixie Nevada Springs Warm Valley, Nevada Valley, Las Vegas Nevada Nevada Fallon,
c., 2001, p. 3-8 c., 2001, rs, 1986, table 1 rs, 1986, table 1 Reference Location Geomega, Inc., 1998a, p. 22 Geomega, Inc., Services, PTI Environmental p. 8 1997, Inc., 1996, p. 25 Engineering, Vector p. B56 1996, Dettinger, and Morgan Bedinger and othe Bedinger and othe Aquifer Science, In Belcher and others, 2 2001, table p. 21 1995, Berger, 1997, p. 21 and others, Berger p. 11 Campana, 1987, Consultants, and CDM Engineers Inc, 1997, table 5 data, 1996 unpub. D.J. Donovan, Corporation, Earth Technology p. 3-2 1993, unit Hydrogeologic Hydrogeologic Unconsolidated sediments: Unconsolidated Fluvial deposits sediments: Unconsolidated Fluvial deposits sediments: Unconsolidated Fluvial deposits sediments: Unconsolidated medium, - coarse, Basin-fill grained and fine sediments: Unconsolidated coarse-grained Basin-fill, sediments: Unconsolidated Basin-fill, fine-grained sediments: Unconsolidated undifferentiated Basin-fill sediments: Unconsolidated undifferentiated Basin-fill sediments: Unconsolidated undifferentiated Basin-fill sediments: Unconsolidated undifferentiated Basin-fill sediments: Unconsolidated undifferentiated Basin-fill sediments: Unconsolidated undifferentiated Basin-fill sediments: Unconsolidated undifferentiated Basin-fill sediments: Unconsolidated undifferentiated Basin-fill Appendix–Detailed summary conductivity estimates—Continued of hydraulic APPENDIX—Detailed summary of hydraulic conductivity estimates 33 to 400 to nr nr nr nr -3 (ft/d) 20-70 Range 3 to 60 75-100 0.1 to 1 0.1 to 5 2 to 100 15 to 160 0.2 to 590 to 0.2 0.02 to 400 1x10 nr nr nr nr nr nr nr nr nr 23 (ft) 270 210 542 tested 100 to 500 Thickness
3 16 nr nr nr nr nr nr nr nr b 130 b b (ft/d) 8 - M 8 - Mean 0.33 - G - 0.33 4 to 20 - G - 4 to 20 median - M arithmetic - A geometric - G - geometric 2 1 1 1 5 2 nr nr nr nr of 27 36 12 11 Number samples
Test type/ Test data source Pumping test Pumping slug Aquifer and test Specific capacity values Modeled values Modeled test Pumping test Pumping test Pumping test Pumping and test Pumping specific capacity Specific capacity/ test Pumping Slug test/ test Pumping test Pumping test Pumping
Northern White White Northern Valley, River Nevada Springs Warm Valley, Nevada Valley, Lake Honey Nevada Great Basin Nevada Near Valmy, Near Winnemucca, Nevada Nevada Near Elko, Nevada Near Wells, Near Austin, Nevada Near Carlin, Nevada Nevada Near Fallon, Near Sparks, Nevada Near Ruth, Nevada Near Fernley, Nevada
Reference Location Geomega, Inc., 1997, table 5-1 Inc., Geomega, Resources Groundwater Inc., p. 17 Consultants, 1994, Handman and others, 1990, p. 15 1998, p. A55 Prudic, and Harrill Inc., 2000, Hydrologic Consultants, table 6 1989, p. 13 JBR Consultants Group. Co., 2002a, Piesold and Knight 1 appendix p. 7 Co., 2002b, Piesold and Knight Rural Nevada and Lander County Association, 2001 Water McDonald and Morrissey Inc., 1998, table 2 Associates, p. 25 2001, Welch, and Maurer p. Porter Geotechnical, 1997, 4 Inc., Services, PTI Environmental 6-6 table 1994, Inc., Services, PTI Environmental p. 8 1997, unit Hydrogeologic Hydrogeologic Unconsolidated sediments: Unconsolidated undifferentiated Basin-fill sediments: Unconsolidated undifferentiated Basin-fill sediments: Unconsolidated undifferentiated Basin-fill sediments: Unconsolidated undifferentiated Basin-fill sediments: Unconsolidated undifferentiated Basin-fill sediments: Unconsolidated undifferentiated Basin-fill sediments: Unconsolidated undifferentiated Basin-fill sediments: Unconsolidated undifferentiated Basin-fill sediments: Unconsolidated undifferentiated Basin-fill sediments: Unconsolidated undifferentiated Basin-fill sediments: Unconsolidated undifferentiated Basin-fill sediments: Unconsolidated undifferentiated Basin-fill sediments: Unconsolidated undifferentiated Basin-fill sediments: Unconsolidated undifferentiated Basin-fill Appendix–Detailed summary conductivity estimates—Continued of hydraulic 34 Hydrogeology and Hydrologic Landscape Regions of Nevada to 140 nr nr -4 (ft/d) Range 2 to 50 8 to 14 5 to 45 7 to 180 10 to 20 0.5 to 80 80 to 140 14 to 100 0.02 to 140 2x10 0.1 to over 150 0.1 to over nr nr nr nr nr nr nr (ft) 160 350 tested 20 to 370 20 to 530 100 to 700 100 to 230 Thickness 5 nr nr nr nr nr nr nr nr nr b 130 b (ft/d) Mean 63 - A 63 - 67 - M 90 - M 103 - A median - M arithmetic - A geometric - G - geometric 1 7 5 7 6 3 nr nr nr of 17 26 27 several Number samples Test type/ Test data source Pumping test Pumping test Pumping test Pumping test Pumping Specific capacity test Pumping test Pumping values Modeled test Pumping value Modeled test Pumping test Pumping search Literature Near Winnemucca, Near Winnemucca, Nevada Eagle Valley, Nevada Southern Nevada Great Basin Big Northern Valley, Smoky Nevada Southern Nevada Great Basin Big Northern Valley, Smoky Nevada Southern Nevada Nevada Near Valmy, Near Beowawe, Nevada Near Beowawe, Nevada Near Pahrump, Nevada
ulting Engineers, ulting Reference Location Star City and Nevada RuralStar City Water and Nevada 2002, 12 p. Association, Cons Wateresource A appendix Inc., 1993, others, 2001, and Belcher A appendix p. B17 Plume, 1996, 1997, p. 48 Kilroy, and Handman others, 2001, and Belcher A appendix p. B17 Plume, 1996, 1997, p. 48 Kilroy, and Handman others, 2001, and Belcher A appendix Inc., 2000, Hydrologic Consultants, table 6 Inc., 1998a, p. 22 Geomega, Inc., 1998a, p. 22 Geomega, 1986, Harrill, p. 10 unit Hydrogeologic Hydrogeologic Unconsolidated sediments: Unconsolidated undifferentiated Basin-fill sediments: Unconsolidated undifferentiated Basin-fill sediments: Unconsolidated lower Alluvial fan, sediments: Unconsolidated lower Alluvial fan, sediments: Unconsolidated lower Alluvial fan, sediments: Unconsolidated upper Alluvial fan, sediments: Unconsolidated upper Alluvial fan, sediments: Unconsolidated upper Alluvial fan, sediments: Unconsolidated undifferentiated Alluvial fan, sediments: Unconsolidated undifferentiated Alluvial fan, sediments: Unconsolidated undifferentiated Alluvial fan, sediments: Unconsolidated undifferentiated Alluvial fan, sediments: Unconsolidated undifferentiated Alluvial fan, Appendix–Detailed summary conductivity estimates—Continued of hydraulic APPENDIX—Detailed summary of hydraulic conductivity estimates 35 -3 -3 to 30 to 1.6 nr to 7x10 -3 -3 (ft/d) -5 2 to 8 Range 4 to 20 5 to 17 9 to 90 3 to 60 1.5 to 13 less than2 0.01 to 100 0.01 9x10 c 1x10 3x10 a nr nr nr nr nr nr nr nr nr 20 (ft) tested 22 to 36 1 to 770 Thickness - G -4 nr nr nr nr nr nr nr nr nr 0.1 b (ft/d) Mean 10 - G 10 - A 36 - 7x10 median - M arithmetic - A geometric - G - geometric 5 7 2 nr nr nr nr nr of 12 11 13 150 Number samples
Test type/ Test data source Slug test Slug test test Pumping test Pumping values Modeled Specific capacity Specific capacity/ test Pumping search Literature test Pumping values Modeled search Literature values Modeled Near Carson City, Near Carson City, Nevada Near Carson City, Nevada South Truckee Meadows Southern Truckee Nevada Meadows, Big Northern Valley, Smoky Nevada Valley, Carson Nevada Nevada Near Fallon, Range Basin and Southern Nevada Big Northern Valley, Smoky Nevada Near Pahrump, Nevada Nevada Near Valmy,
rs, 1986, table 1 Reference Location 21 16
Maurer, Berger, and Prudic, 1996, Berger, Maurer, p. p. 11 1997, and Berger, Maurer 1998, Hoozer, and Van Widmer p. CH2MHill, 1986, p. 16 1997, p. 48 Kilroy, and Handman p. 29 1986, Maurer, p. 25 2001, Welch, and Maurer Bedinger and othe Belcher and others, 2 2001, table 1997, p. 48 Kilroy, and Handman 1986, Harrill, p. 10 Inc., 2000, Hydrologic Consultants, table 6 esent clayey playa deposits. d 83.5percentiles. unit Hydrogeologic Hydrogeologic Mean is single reported value. Range is for 16.5 an 16.5 for is Range High range value may not repr a b c Unconsolidated sediments: Unconsolidated undifferentiated Alluvial fan, sediments: Unconsolidated undifferentiated Alluvial fan, sediments: Unconsolidated undifferentiated Alluvial fan, sediments: Unconsolidated floor Valley sediments: Unconsolidated floor Valley sediments: Unconsolidated floor Valley sediments: Unconsolidated floor Valley sediments: Unconsolidated Playa sediments: Unconsolidated Playa sediments: Unconsolidated Playa sediments: Unconsolidated Playa sediments: Unconsolidated Playa Appendix–Detailed summary conductivity estimates—Continued of hydraulic