Note: I asked Elaine to write a brief article for an issue of Water Resources IMPACT and this is what she produced. I met Elaine in the late 1970s when she was running a program on the geothermal resources of Dixie Valley, NV. It was my first exposure to geothermal energy. I left Nevada in the late 1980s but renewed our friendship about 15 years ago. She is one of the smartest people I know. I feature her bulletin boards each Monday (tomorrow).
Forgive the formatting; the problems are mine, not hers.
Later!
Nevada Changed How We Viewed Surface Water and Groundwater
Elaine J. Hanford
Nevada has been a fertile environment for new paradigms on water—first surface water and then groundwater. That may seem counterintuitive since Nevada is recognized as the driest state in the United States, with a state-wide average of only 10.2 inches of annual precipitation over the past century.
A bit of history and the evolution of perspectives in Nevada provide context for the use and assessment of groundwater in Golden Valley as a sub-basin of the Lemmon Valley Hydrographic Basin in Western Nevada (Figure 1). This distillation is drawn from “Hydrogeology of Golden Valley, Nevada - A Case Study.”
A Brief Synopsis of History
Gold lured thousands to California, but to get there the 49ers had to cross the Great Basin. That landscape was dominated by fault-block mountains and intervening valleys where surface waters were generally scarce and in “bad years” the rivers ran dry. Where pluvial lakes, such as Bonneville and Lahontan, had once stood hundreds of feet deep, true climate change left only ephemeral playas to fleetingly hold water.
In June 1859, the first major discovery of silver ore in the United States occurred near Virginia City, Nevada, drawing fortune seekers and miners from the goldfields of California and the East to the Comstock Lode. The resulting growth in population, mining, and agriculture provided the impetus for the creation of the Nevada Territory in 1861 and statehood in 1864.
As many settlers turned to agriculture in the 1860s, they needed a stable water supply. A haphazard system of diversion canals was dug to irrigate land grabs adjacent to existing surface waters. The 1888–1890 Powell Irrigation Survey sought to locate, map, and monitor available water supplies. On June 17, 1902, Congress passed the Newlands Reclamation Act (which ultimately produced what is now the U.S. Bureau of Reclamation), authorizing the federal government to commission water diversion, retention, and transmission projects in the American West, with the first major project in Western Nevada. For the next 50 years, surface water would support population and economic growth in Nevada.
Evolving Perspectives in Nevada
The perspectives on water in Nevada illustrate the evolution of thought on use and value of surface water and groundwater resources. Use of water in the State has evolved through several stages:
- Take what surface waters you can get.
- Use of groundwater based on perennial yield.
- Use of groundwater based on safe yield.
- Use based on sustainable yield where surface and ground waters are viewed as an interconnected entity—this concept is currently evolving.
Figure 1. Golden Valley Sub-basin of the Lemmon Valley Hydrologic
Basin. Source: Complied by author
Nearly complete utilization of surface waters and streams for agriculture and mining led to the first U.S. Geological Survey groundwater investigation in 1915, to identify alternate sources of water in Nevada. During the next several decades, systematic investigations resulted in publications on groundwater. George Burke Maxey and Thomas “Tom” Emery Eakin developed techniques for estimating natural groundwater recharge in the White River Valley in east-central Nevada. Their approach used predicted perennial yield and recognized that artificial recharge could be feasible, leading to the development of groundwater in Nevada in the 1950s.
Estimates, however, can often have a high degree of uncertainty. Perennial yield was assumed to be equal to natural recharge and was the amount of groundwater that could be extracted over the long term without depleting the groundwater reservoir. However, perennial yield did not consider the natural discharge of groundwater to streams, springs, or wetlands. Perennial yield gave way to safe yield.
Safe yield requires assessing pumping stresses over time in conjunction with monitoring and basin management to determine the amount of water that can be withdrawn from an aquifer without producing adverse impacts on water quantity and/or water quality. More recent understanding of changing climatic conditions emphasizes sustainability defined by the potential of the resource and the ability of resource managers to continue to meet the demand for water resources for human use and critical habitats. This view recognizes the interconnected character of surface and ground waters.
Sustainability also facilitates understanding the effects of pumping on timing, rates, and location of depletions. This approach still involves the concepts of a water budget with respect to the broader issues of ecology, water quality, and welfare. (See Addendum) It recognizes that recharge is not necessarily the factor that limits sustainable pumping rates. This is of particular importance with respect to confined aquifers, where the placement of wells significantly affects the dynamic response of the aquifer and the rate and amount of natural recharge that can be captured.
Aquifers Defined
An aquifer is a geologic formation, group of formations, or part of a formation that contains permeable material that will yield significant quantities of water to wells, streams, and/or springs. A principal aquifer is defined as a regionally extensive aquifer or aquifer system that has the potential to be used as a source of potable water (Figure 2).
Aquifers can be grouped into five types based on lithology and location:
- Unconsolidated and semi-consolidated sand and gravel aquifers (including alluvial and glacial deposits)
- Sandstone aquifers
- Carbonate rock aquifers
- Aquifers in interbedded sandstone and carbonate rocks
- Aquifers in igneous and metamorphic rocks (crystalline rock and volcanic rock)
Groundwater models based on flow through porous media can effectively be applied to the first four types. Crystalline rock formations, however, pose numerous unique challenges.
In the western Great Basin, hydrogeologic units include igneous rocks primarily of Mesozoic age that may locally be overlain by younger volcanic flows, as well as older (Miocene and Pliocene) and younger (Pliocene to Holocene) basin-fill deposits. These internally drained basins have limited recharge derived from precipitation under arid to semi-arid climatic conditions. Basin fill typically consists of coarse-grained sediments with interbedded layers and lenses of clays (pluvial lake deposits or playa sediments).
Crystalline rocks are geologically complex, with very low porosity and very low permeability. Effective movement of groundwater through these rocks is restricted to fracture flow that generally moves from highland recharge areas to discharge areas. These geologic properties limit the application of porous-medium groundwater models to crystalline rock formations.
Population Growth Leads to Increasing Production of Groundwater
As the population of Western Nevada increased beginning in the 1960s, municipal wells were drilled in southern Lemmon Valley to meet the demand for potable water. While no municipal wells were drilled in Golden Valley, municipal wells were drilled (and deepened) west of the Golden Valley watershed to supply two trailer parks. Production from the fractured andesitic bedrock intercepted by these wells produced significant drawdown. As production increased from around 40 to roughly 120 acre-feet per year, cones of depression deepened to 115 feet or more.
Municipal well LVP3 was drilled approximately 2000 feet downgradient from the Golden Valley outlet boundary. This well was drilled by the Lemmon Valley Water Company with water rights later transferred to Washoe County and the Truckee Meadows Water Authority. A maximum of 142 acre-feet was extracted in 1973, with average annual production of approximately 77 acre-feet/year in the 1980s through 2002. Static water level in this well declined from 60 feet in 1963 to more than 100 feet in 1982, and to a maximum depth of 205 feet in 2002.
The first platted subdivision in Golden Valley was established in 1962, with additional subdivisions platted during the 1970s and 1980s. Domestic wells were drilled to support residential development generally on 1-acre parcels across most of Golden Valley. By 1980, 362 wells had been drilled, with 104 wells added in the 1980s, 33 wells in the 1990s, and 15 wells added by 2015.
Recognition of declining groundwater levels over multiple years beginning in the 1980s threatened the water supply in Golden Valley for multiple residential users. Conditions necessitated deepening a number of domestic wells across the northern and eastern portions of the valley.
With funding from the U.S. Bureau of Reclamation, the Golden Valley Artificial Groundwater Recharge Program was initiated as a pilot program in the 1980s to assess the feasibility of stabilizing groundwater levels. In the 1990s, potable water from the Truckee River was injected through sequenced injection wells on the eastern margin of the valley.
With little understanding of why groundwater levels were declining, residents asked Washoe County to continue artificial recharge beginning in 2002. Injection continued until 2016 when rising groundwater levels led to suspension of the injection program.
Modeling—the Good, the Bad, and Reality
Several groundwater flow models have been developed for Lemmon Valley/Golden Valley over the last two decades. These models incorporated hydrostratigraphic layers, water budgets for the interval 1991 through 2001, and applied finite difference grids within graphical user interface software programs and MODFLOW-2005. These models predicted trends that are generally consistent with time-sequence analysis of hydrographic data based on historically measured water levels. Predicted water levels may differ by several tens of feet higher or lower than measured values, which can be significant depending on well depth.
However, no model can capture all the complexities and intricacies of real-world conditions (e.g., lithologic variations in valley fill, structural geology, short-term weather, and long-term climate). Movement of water within a crystalline fracture system depends on various factors, including fracture orientation, length, density, spacing and infilling, connectivity of the fractures, and surface roughness of the fracture planes.
Subsurface conditions are interpreted from drillers well logs. Colloquial terms like “shail” and “sponge rock” must be translated to conventional geologic terms. Most logs contain limited information on the fractures and the occurrence of groundwater.
These models, therefore, provide only a first approximation of actual subsurface conditions. Golden Valley is typical of a Basin and Range fault-bounded valley, with recharge derived from areas of higher elevation, fracture flow to depth and toward the valley center, and percolation of surface water downward through the valley-fill inhibited by clay lenses and layers (Figure 3). Faults may facilitate or inhibit the movement of groundwater—the most important of these being Estates Fault.
Fate of Groundwater in Golden Valley
Synoptic analysis of all available hydrologic and geologic data recognizes the existence of both piezometric and limited phreatic groundwater conditions within Golden Valley (Figure 4). By 1991, static water levels in wells drilled into the underlying granitic bedrock fracture system showed significant loss of piezometric pressure compared to 1971. In the northern and eastern portions of Golden Valley (i.e., north and east of Estates Fault), piezometric water levels dropped by 40 feet or more, necessitating the deepening of a number of domestic wells. West of Estates Fault, phreatic water levels dropped by 10 to 20 feet.
Beginning in the early 2000s, with importation of water from the Truckee River, the mobile home park municipal wells were abandoned, coinciding with the end of pumping LVP3. Both piezometric and phreatic groundwater levels began rising. Even after the Golden Valley Artificial Recharge Program was paused in 2016, piezometric groundwater levels continued to rise, confirming the impact of municipal well LVP3 on the granitic bedrock fracture system across Golden Valley (Figure 5).
Beginning in the early 2000s, with importation of water from the Truckee River, the mobile home park municipal wells were abandoned, coinciding with the end of pumping LVP3. Both piezometric and phreatic groundwater levels began rising. Even after the Golden Valley Artificial Recharge Program was paused in 2016, piezometric groundwater levels continued to rise, confirming the impact of municipal well LVP3 on the granitic bedrock fracture system across Golden Valley (Figure 5).
Looking to the Future
Reviewing the hydrogeology of Golden Valley (a sub-basin of the Lemmon Valley Hydrographic Basin) in Western Nevada reveals the importance of the volume of groundwater within the granitic fracture flow system. It also shows the importance of hydrostatic pressure within the aquifer. Protecting the waters and hydrostatic pressure within the bedrock fracture system of Golden Valley is consistent with the current sustainability perspective on water resources in Nevada.
By the latest revision to the County Ordinance, injection in the Golden Valley Artificial Recharge Program has been suspended for the next decade, but water levels and water quality will be routinely monitored. Present and future use of groundwater as a resource within Lemmon Valley (and the Golden Valley sub-basin) should prioritize sustainability not only in terms of groundwater quality and quantity but also hydrostatic pressure within the confined bedrock aquifer. This approach will ensure long-term availability of groundwater for domestic use by the more than 550 families living in Golden Valley.
The future remains unknown. There may come a time when demand once again exceeds supply as residential and commercial/industrial growth are promoted in Lemmon Valley. Municipal wells (including LVP3) and existing municipal water rights are being maintained in Lemmon Valley and could potentially be pressed into production. Residents are aware that natural events (e.g., major earthquake, significant wildfire, and/or drought) or programmatic/political events may trigger conditions under which resumption of groundwater recharge may be advisable.
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- E. J. Hanford ([email protected]) is a retired professional geologist, registered since 1979 and formally retired since 2012. She has more than 45 years of experience as a geologist and environmental scientist consulting for the public and private sectors, as well as university teaching and research. Her work has been honored for more than four decades at professional conferences and published in peer-reviewed national and international journals. She compiles weekly Geoscience, Environmental Science, and Coastal Zone Management Bulletin Boards. Many thanks to William J. Elliott, consulting engineering geologist, for his “red pen” and helpful critique.
Links:
Hydrogeology of Golden Valley, Nevada - A Case Study
Principle Aquifers of the US:
https://www.usgs.gov/media/images/aquifers-map-principal-aquifers-united-states
AWRA IMPACT v. 24 no. 2 p. 13-16 - “Pluvial Lakes of the Great Basin”
AWRA IMPACT v. 24 no. 5 p. 34-36 – “The Newlands Project”
https://www.researchgate.net/publication/376610822_Newlands_Project_-_AWRA_IMPACT_May-June_2022
Addendum – evidence of evolving Nevada perspective on groundwater:
Nevada Supreme Court unanimously ruled that State can restrict new groundwater pumping
SULLIVAN v. LINCOLN COUNTY WATER DISTRICT LLC LLC NV LLC (2024)
https://caselaw.findlaw.com/court/nv-supreme-court/115758424.html
"When the well's dry, we know the worth of water.” – Benjamin Franklin.
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