Ambient Groundwater Quality of the Sacramento Valley Basin: An ADEQ 1999 Baseline Study

Chloride I, Introduction

The Sacramento Valley Groundwater Basin (SVGB). located in northwestern (Figure 1), is an arid region with striking natural landscapes and a small, but rapidly growing population. The popularity of the area is influenced by its proximity to tourist destinations Sacramento Valley such as the and Groun(Jwater Laughlin, , and by an abundance Basin of relatively inexpensive, undeveloped private land. Groundwater is the primary water source for municipal, domestic, industrial, mining, livestock, and irrigation in the basin. Population growth and the associated economic development in the SVGB will likely increase demand on groundwater and, over time, may influence water quality.

These groundwater quality concerns prompted the Arizona Department of Environmental Quality (ADEQ) to conduct a regional groundwater quality study in 1999 to determine groundwater suitability for drinking purposes, appraise current baseline conditions, and examine spatial groundwater quality patterns. This factsheet is a summary of the more extensive hydrology report available from ADEQ (1). ^

8 8 16 Miles

Figure 1. Infrared satellite image (6/1993) of the Sacramento Valley groundwater basin (SVGB). Mountain forests appear crimson, upland areas are dark blue, and valley areas are beige/white. Inset map shows the location of the SVGB within Arizona. Inset photo shows a mural on an abandoned Route 66 gas station located in Yucca that reflects the intense desert conditions found in the basin.

II. Background elevation, averaging 4 inches annually in the valley, 10 inches near the city of The SVGB encompasses more than Kingman, and more than 20 inches at 1,500 square miles in Mohave County, Hualapai Peak (2). Natural vegetation Arizona. It is bounded by the Cerbat, varies with topography and water Hualapai, and McCracken Mountains to availability. Creosote bush, cactus, the east, the Castaneda Hills and Mohave yucca, and Joshua trees grow in the Mountains to the south, the Colorado valleys, whereas juniper, pinyon pine, River and the Black Mountains to the and scrub oak are found at intermediate west, and an unnamed bajada to the elevations, and ponderosa pine forests north (Figure 1). Basin elevations range are abundant above 6,500 feet (2). from a high of 8,417 feet at Hualapai Peak to a low of 500 feet near the Colorado River and averages 2,500 feet. ^'Despite frequent water quality standard exceedances, sampled Surface topography consists of sloping sites in much of the SVGB met alluvial fans which extend from the drinking water standards." Figure 2. Twin windmills pump to a water surrounding rugged mountains to the tank in the southern Hualapai Mountains. valley floor. Precipitation increases with Basin communities include the historic No perennial streams exist within the mining town of Chloride, Golden Valley, SVGB. though a few watercourses flow the city of Kingman, Yucca, and the almost continuously in their upper Colorado River resort community of reaches (2). The main surface water Topock (Figure 1). Most land within drainage is the ephemeral Sacramento the SVGB. particularly rugged upland Wash, which originates north of Golden areas, are managed by the Bureau of Valley, tlows south, then west, and Land Management while private and eventually discharges an average of 500 State lands are common in valley areas. acre-feet per year into the Colorado River near Topock. III. Hydrogeology IV. Methods of Investigation The alluvium that underlies the valley floor and occurs within mountain This study was conducted by the ADEQ canyons is the most important aquifer in Groundwater Monitoring Program which the SVGB. These deposits are separated is authorized by the legislative into older, intermediate, and younger requirement in Arizona Re\ised Statute alluvium, based on their lithologic and VJ49-225 to monitor the quality of the hydrologic properties. The older allu\ial state's groundwater. To characterize aquifer yields and stores the greatest regional groundwater quality. 48 sites quantity of water in the basin. The (Figure 4) were sampled for inorganic intermediate and younger alluvium are constituents (field parameters, general less important hydrologically since these mineral characteristics, major ions, units lie predominantly above the water nutrients, and trace elements), volatile table (2). organic compounds (VOCs), perchlorate (a man-made inorganic salt), and The mountains that form the basin isotopes of hydrogen, oxygen, and ^ Primary MCL + Q % consist predominantly of granitic, nitrogen. At 40 sites, samples were also Secondary MCL volcanic, and metamorphic rocks with collected for radiochemistry analyses. limited outcrops of sedimentary rocks. O Secondary MCL While all rock types produce limited Of the 48 sampled sites. 40 were random • None amounts of water, especially where sites and 8 were targeted sites. Sampling Granitic Rock extensively fractured, volcanic rocks are protocol followed the ADEQ Quality the most important source in mountain Assurance Project Plan. Interpretation areas supplying large quantities of water of quality control data indicated that the Figure 4. Water quality exceedances most for use in Kingman (2). sampling equipment and laboratory commonly occur near the town of Chloride, in procedures had no significant effects on granitic areas of the Hualapai Mountains, and in downgradient areas of the basin near Topock. For this study, the older, intermediate, the analytical results. and younger alluvium are considered the alluvial aquifer. Granitic, volcanic, V. Water Quality Sampling Results sampled. 28 exceeded Secondary MCLs metamorphic, and sedimentary rock are including total dissolved solids or TDS Groundwater sample results were considered the hardrock aquifer. (24 sites), fluoride (16 sites), sulfate (7 compared to federal Safe Drinking sites), chloride (7 sites), manganese (3 Water (SDW) quality standards. sites), and iron (2 sites) (Figure 4). Primary Maximum Contaminant Levels (MCLs) are enforceable, health-based, VOCs were not detected at any sample water quality standards that public water site. Perchlorate, an inorganic salt used systems must meet when supplying in the manufacmre of solid fuel water to customers (3). Primary MCLs propellants and explosives, was are based on a lifetime consumption of detected in the northwest part of the two liters of water per day (3). Of the 48 sites sampled. 22 had constituents basin at four sites. All perchlorate that exceeded a Primary MCL (Figure detections were at concentrations below 4). Constituents with Primary MCL the Arizona provisional Drinking Water exceedances included gross alpha (18 Health-Based Guidance Level of sites), nitrate (6 sites), fluoride (4 sites), 31 micrograms per liter (A/g/1). radium-226+228 (4 sites), and antimony (2 sites). ^'Sample sites exceeding Secondary MCLs are unenforceable, water quality standards aesthetics-based, water quality generally occurred in three areas: guidelines for public water systems (3). (1) near the town of Chloride, Water with Secondary MCL (2) in the central and southern exceedances may be unpleasant to drink Hualapai Mountains, and and/or create unwanted cosmetic or laundry effects but is not considered to (3) near the town of Topock." Figure 3. A domestic well house and water tank arc situated in the shadow of Thimble Mountain, be a health concern (3). Of the 48 sites a famous Route 66 landmark west of Kingman. VI. Groundwater Composition concentrations of various constituents. Depending on the dominant cation, there In general, groundwater in the SVGB is were two general patterns. With slightly alkaline (pH > 7 standard units), calcium, correlations occurred among fresh (TDS < 1000 milligrams per liter or magnesium, bicarbonate, sulfate, mg/1), and ranges from moderately hard hardness (all positive), and pH to very hard. Groundwater chemistry is (negative). With sodium, positive frequently of a calcium-bicarbonate correlations occurred with boron type, however, calcium-sulfate and (Figure 5) as well as with chloride, sodium-bicarbonate sites were also sulfate, and fluoride (Pearson identified. The only sodium-sulfate Correlation Coefficient test. p< 0.05). samples were collected at the two most downgradient sites near Topock. Nitrate These test findings support the observed (as nitrogen) concentrations were greater flowpath evolution in the SVGB. Along than 3 milligrams per liter (mg/1) at 42 the groundwater flowpath, that parallels percent of sites, which may indicate the course of Sacramento Wash (2), impacts from human acti\ities. Most calcium, magnesium, bicarbonate, and trace elements such as aluminum, hardness concentrations generally antimony, barium, beryllium, cadmium, decreased downgradient. In contrast, iron, lead, manganese, mercury, silver, sodium, chloride, fluoride, and boron and thallium were rarely detected. concentrations initially decreased, and Arsenic, boron, chromium, copper, then increased dramatically in fluoride, selenium, and zinc were the downgradient areas. These flowpath only trace elements detected at more than changes appear to indicate that the 10 percent of the sites. SVGB is largely a chemically closed basin, or one in which the aqueous VII. Groundwater Spatial Patterns chemistry is determined mainly by the reactions of recharge waters with the Bicarbonate, calcium, gross beta, various in situ minerals and gases as the hardness, magnesium, specific groundwater moves downgradient (4). conductivity (SC), total alkalinity, TDS, and total Kjeldahl nitrogen (TKN) were Figure 6. ADEQ staff sample a windmill on higher in the hardrock aquifer than in the western tlank of the Hualapai Mountains. the alluvial aquifer. The opposite The windmill pumps water for stock use; the pattern was apparent for pH and Black Mountains are in the background. temperamre (Kruskal-Wallis test, p< 0.05). This hardrock-alluvial aquifer concentrations remain generally constituent pattern has been noted in constant at groundwater depths greater other Arizona groundwater basins (1). than the critical level and are highly variable at more shallow depths. To further examine groundwater quality Approximate critical levels for other patterns within the basin, geologic constituents significantly correlated categories (granitic, volcanic, with groundwater depth ranged from 50 metamorphic, sedimentary, and alluvial feet bis for cross alpha to 200 feet bis fill) were compared. Generally, for TDS. groundwater associated with granitic rock had significantly greater constituent concentrations than groundwater 100 200 300 400 associated with alluvial fill, Sodium (mg/1) metamorphic rock, and volcanic rock (Kruskal-Wallis and Tukey test, p< Figure 5. Boron concentrations generally 0.05). Thus, many of the hardrock- increase with increasing sodium concentrations alluvial aquifer patterns are related to (Pearson Correlation Coefficient test, p<0.01) differences between groundwater associated with granite and other rock VIII. Groundwater Depth Patterns classifications. Bicarbonate, calcium, gross alpha, gross Boron, fluoride, gross alpha, pH, beta, hardness, SC, total alkalinity, and sodium, sulfate, temperature, and zinc TDS decreased with increasing were higher in the southern, groundwater depth below land surface downgradient areas than the northern (bis). In contrast, pH and temperature upgradient areas of the basin (Kruskal- increased with increasing groundwater 900 Wallis test, p< 0.05). The opposite trend depth bis (regression analysis, p< 0.05). 200 400 600 800 1000 1200 Hardness as CaC03 (mg/1) occurred with magnesium. Many of these constituents show a similar pattern to hardness (Figure 7) Similar patterns were found by assessing which attains a critical level at Figure 7. Hardness generally decreases the strength of association among with increasing groundwater depth bis approximately 150 feet bis. Hardness (regression analysis, p < 0.01). IX. Groundwater Changes

A time-trend analysis was conducted based on data collected from 14 wells by the U.S. Geological Survey in 1979. the Arizona Department of Water Resources in 1990, and ADEQ in 1999. Si.xteen (16) constiments were compared over three time periods. Temperature and pH were the only parameters that varied significantly between 1990 and 1999 (Wilcoxon ranked-sum test. p< 0.05).

X. Groundwater Conclusions

Although groundwater in much of the SVGB met water quality standards, approximately one-half of sample sites in the basin did not meet water quality standards. Thus, ADEQ suggests that well owners periodically have their groundwater analyzed by certified laboratories. The majority of sample Figure 8. Alkali Spring emerges in the arid Black Mountains and ponds in this depression, sites that exceeded water quality providing both valuable riparian habitat and a perennial water source for livestock and wildlife. standards occurred in three areas: constituents in most areas of the basin Near the town of Chloride appear to be controlled by natural In the central and southern Hualapai geochemical reactions and would References Cited Mountains probably not vary significantly in the Near the town of Topock short term. Sites exceeding water quality standards in the Hualapai Mountains and 1. Towne, D.C. and M.C. Freark, 2001. Although only limited time-trend near Topock appear to be the result of Ambient Groundwater Quality of the Sacramento Vallev Bosin: A 1999 analyses were conducted for this smdy. natural conditions. Previous smdies Baseline Study. ADEQ Open File have noted that groundwater found in Report 01-04, Phoenix, Arizona, 79 p. and near the mountains is generally more 2. Gillespie, J.B. andC.B. Bentley, 1971. mineralized than groundwater in the Groundwater Dating Method Geohydrology of Hualapai and center of the valley (2). Elevated Sacramento Valleys, Mohave County, fluoride, TDS. and chloride levels near Arizona. U.S. Geological Survey Stable isotopes of oxygen (oxygen-18) Topock may be due to dissolution Water-supply Paper 1899-H, 37 p. and hydrogen (deuterium) were reactions that increase constiment 3. U.S. Environmental Protection Agency, analyzed to examine the origin and age concentrations as groundwater migrates 1993. The Safe Drinking Water Act - A of groundwater in the basin. Isotopic downgradient within the basin (4). Pocket Guide to the Requirements for data was compared to the Global the Operators of Small Water Systems. Meteoric Water Line (GMWL), the USEPA Region 9, San Francisco, In contrast, some water quality standard reference water based upon , 47 p. exceedances in the Chloride area appear world-wide precipitation data which 4. Robertson, F.N., 1991. GeochemisUy of to be influenced by anthropomorphic has not been exposed to evaporation Ground Water in Alluvial Basins of activities. Elevated radiochemistry (4). The SVGB data lie below and to Arizona and Adjacent Parts of Nevada, concentrations appear to be related to New Mexico, and Calij'ornia. the right of the GWML, which is granitic rock that occurs in much of the U.S.Geological Survey Professional characteristic of waters exposed to Hualapai and Cerbat Mountains, but are Paper1406-C,90 p. evaporation (4). This pattern suggests likely exacerbated by nearby, mostly that SVGB groundwater is probably inactive mines. Nitrate levels, which derived from local recharge, the sometimes exceed water quality majority of which occurred in the standards at sites in Chloride, appear to distant past. be related to the high-density of older For More Information Contact septic systems used for domestic and Nitrogen isotopes (nitrogen-15) were commercial wastewater treatment. These Douglas C. Towne - ADEQ also collected to assist in determining systems are often simated in soils that 3033 North Central Ave. #360 sources of nitrate in groundwater. are classified as marginally suitable for Phoenix, AZ 85012 However, interpretation of the results septic use. Other indicators of septic suggest that pinpointing the nitrate system impacts, TDS and chloride, are 1-800-234-5677 or (602)207-4412 source was not possible using this also frequently elevated over Secondary [email protected] method without techniques to MCLs at sites in the Chloride area. determine basin-specific groundwater www.adeq.state.az.us/environ/water/ signatures of various nitrate sources —Douglas Towne and Maureen Freark assess/ambient.html found in the area. Maps by Larry W. Stephenson ADEQ Fact Sheet 01-10 September 2001