By
Sandra J. Owen-Joyce and C. K. Bell
The upper Verde River area, in contrast to much of Arizona, has several perennial streams: Verde River, Sycamore Creek, Bitter Creek, Oak Creek, Wet Beaver Creek, West Clear Creek, and Fossil Creek (fig. 1). All these streams except Bitter Creek provide water of acceptable quality for irrigation, recreation, warm- and cold-water fisheries and wildlife habitat. Man-made lakes in the area include Upper and Lower Lake Mary, White Horse Lake, and Stehr Lake. Mormon Lake and Stoneman Lake are in natural closed basins. Pecks Lake is a cutoff meander of the Verde River and is fed by a man-made surface diversion from the Verde River (pl. 2). Upper Lake Mary provides a large proportion of the municipal water supply for the city of Flagstaff. The primary uses of most other lakes are associated with recreation, fisheries, wildlife habitat, and livestock watering.
The delineation of the study-area boundary is not coincident with the drainage area boundary of the Verde River. Parts of the upper Verde River area, which total about 160 mi2, are drained by the Little Colorado River (fig. 1). Small drainages, which are along the southeastern boundary of the study area and total about 17 mi2, are drained by the East Verde River, which joins the Verde River downstream from the study area. The uppermost parts of the Sycamore Creek and Oak Creek drainages are outside the study-area boundary, as is the southeast part of the Fossil Creek drainage owing to Fossil Creek being part of the south boundary.
Streamflow is composed of two components-direct runoff and base flow. Direct runoff has little effect on the amount of water available for use in the upper Verde River area. Storm runoff occurs over short periods of time, and snowmelt occurs when there is little need for irrigation water. No major surface-water impoundments are present for the storage of high flows or regulation of the flow of the upper Verde River or its tributaries. Conversely, base flow is an extremely important source of water. In some reaches base flow increases downstream because of ground-water discharge; in other reaches the base flow is depleted by evaporation, transpiration by riparian vegetation, and diversions for irrigation. About 30 irrigation diversions, which draw water directly from the streams by means of low diversion dams and pumps, provide water to 7,781 acres (Northern Arizona Council of Governments, 1979, p. 123) and have a pronounced effect on the low-flow characteristics of some stream reaches. Most primary diversions are operated by groups of landowners. Near Cottonwood and Camp Verde, the irrigation canals often carry more than half the flow of the Verde River, and all the flow in West Clear Creek is often diverted near the mouth. The availability of streamflow, therefore, is limited by natural low flows and upstream usage. Because of its importance, base flow is emphasized more than direct runoff in the following analyses of streamflow.
Base Flow and Ground-Water Seepage
The base-flow characteristics of the Verde River and its major tributaries are a function of precipitation and the properties of the regional aquifer. The capacity of the aquifer to absorb, store, and transmit water has a significant effect on base flow, as does the relative distance of the streams from the aquifer recharge area. Long-term changes in the base flow may indicate changes in the volume of water stored in the aquifer and how discharge from the aquifer is distributed among pumpage, streamflow, and evapotranspiration losses, which are dependent on rainfall and land use.
The ground-water hydrology section of the report describes a large regional aquifer with a recharge area distant from the Verde River. Recharge to the aquifer is large and changes little with time. Base flow of the streams that drain the regional aquifer therefore varies little with precipitation or from year to year.
The base flow in the Verde River and most tributaries varies seasonally in relation to the amount of water used by plants. Base flow is at a maximum in January and February and at a minimum in July and August. The year-to-year variation in base flow that enters the Verde Valley by way of the Verde River and tributaries is small. A comparison of 1976-79 data with 1935-45 data showed variations in the quantity of summer base flow leaving the Verde Valley, which may indicate an increase in use of water along the streams in the valley rather than being a result of pumpage from the regional aquifer. Pumping from the regional aquifer probably would also decrease the winter base flow as well as the summer base flow.
Base flow at each gaging station was determined by visual separation of daily discharge hydrographs into the direct-runoff component and the base-flow component. This method is suitable to the study area because direct runoff from storms generally is of short duration, and streams generally return to base flow within two weeks after a rainfall peak and within two months after a snowmelt peak, but these long periods of melt are infrequent. Neither storm runoff nor snowmelt cause much increase in the base flow.
When base-flow hydrographs for individual years are superimposed, all the hydrographs fall in a narrow band indicated by the upper and lower hydrographs of figures 4 and 5. The spacing between the limiting hydrographs may represent either a true variation in base flow, a variation in computational procedure, or a combination of both. The variations are not chronological and cannot be related to climatic factors of wet or dry years. A hydrograph that follows the center of the band represents the median values and provides the best estimate of base flow for any date. Hydrographs of median values of base flow are shown in figures 4 and 5. Base flow is at a maximum in January and February when plants are dormant and evaporation is low. The high base flow in January represents the average ground-water discharge from the regional aquifer. The seasonal variation in base flow is an indication of evapotranspiration losses in the drainage area upstream from a gaging station, but losses due to riparian vegetation and evaporation from free water surfaces cannot be isolated from other losses if a large quantity of water is diverted.
To determine the areal distribution and magnitude of ground-water inflow to the Verde River between Clarkdale and Fossil Creek, discharge measurements were made at 55 sites during a period of base flow in June 1979. The difference in flow rates between successive measurement sites along the study reach-after adjustment for surface inflow and outflow in tributaries, diversions and returns-can be attributed to gains from or losses to the regional aquifer. In some places the gains occur over a long reach of the stream; however, in other places the gains are localized at springs.
Two previous seepage investigations were run during July 1963 and June 1977. During July 1963, 12 sites were measured on the Verde River from Sullivan Lake (fig. 1) to Chasm Creek (pl. 2), and 38 sites were measured along tributary streams and irrigation diversions but did not include any return flow. During June 1977, 10 sites on the Verde River from Paulden to Chasm Creek and 9 sites along Oak and Beaver Creeks were measured. This investigation did not include any of the other tributaries or the irrigation diversions and returns.
Verde River
Perennial flow in the Verde River begins near Granite Creek 1.2 mi upstream from the study-area boundary (fig. 1). Discharge measurements made in 1977 show that the Verde River gained 20.4 ft3/s between Granite Creek and Stewart Ranch (pl. 3), which is located just inside the study area (U.S. Geological Survey, 1978, p. 507-508). Between Stewart Ranch and the Verde River near Paulden gage, discharge measurements indicated a gain of 6.7 ft3/s. Base flow at the Paulden gage is virtually constant and ranges from 20 to 26 ft3/s (fig. 4A). The seasonal variation in the median base-flow hydrograph is from 22 to 24 ft3/s. Between the gage near Paulden and the gage near Clarkdale, base flow increases. Base flow at Verde River near Clarkdale ranges from 60 to 93 ft3/s, and the seasonal variation in median base flow is from 68 to 83 ft3/s (fig. 4B). Discharge measurements made in 1977 and 1979 (U.S. Geological Survey, 1978; 1980b) show a gain in flow attributed to ground water of about 22 ft3/s at Mormon Pocket, 9 ft3/s from below Mormon Pocket to Sycamore Creek, and 12 ft3/s downstream from Sycamore Creek (pl. 2). No ground water discharges to the Verde River in the 2 mi reach below the Paulden gage but about 2 ft3/s discharges between there and Mormon Pocket. Tributary inflow from Sycamore Creek is 9 ft3/s. The loss in streamflow indicated near French Ranch is probably associated with a small deposit of alluvium and an irrigation diversion.
The gaging station, Verde River near Camp Verde, is located just above Chasm Creek and 9 mi southeast of Camp Verde. Base flow leaving the study area is monitored at this station. Base flow ranges from 180 to 240 ft3/s during January and from 43 to 96 ft3/s during July. The seasonal variation of the median base flow is from 66 to 200 ft3/s. The average winter base flow is 200 ft3/s which does not agree with the value calculated by Twenter and Metzger (1963) of 225 ft3/s; the discrepancy is attributed to the differences in interpretation methods. All the data from the previous period of record from 1935-45 and the current 1976-79 record were used to calculate base-flow hydrographs.
Seasonal variations differ at the three Verde River gaging stations. The large seasonal variation at the Verde River near Camp Verde gage is a result of about 45 ft3/s of evapotranspiration losses along the Verde River and its tributaries between Clarkdale and the gage (Anderson, 1976) and large water use for irrigation. The small seasonal variation at the Paulden and Clarkdale gages is associated with the low water use in this region and low loss of water to evapotranspiration. The water lost to evapotranspiration between Sullivan Lake and Clarkdale is only 8 percent of the loss that occurs between Clarkdale and the East Verde River (Anderson, 1976).
Base flow from the station near Clarkdale to the station near Camp Verde is not accurately quantified because of the variation in river discharge caused by the operation of irrigation-ditch systems (pl. 3). The lateral diversions for water use along the ditches are operated by individuals with surface-water rights and can vary hourly. Return flow to the Verde River can occur at many sites along the ditches where gates are installed or ditches leak. The gates are used to maintain a certain quantity of water in the ditch and therefore the amount of water returning to the river varies with the amount of water used from the ditch.
A seepage investigation made during a period of summer base flow in June 1979 identified the amount of tributary inflow, diversion, irrigation return flow, and ground-water seepage. During the seepage investigation, the amount of discharge in the Verde River at the gage was approximately the same as the median base flow for the period of record (fig. 4C); therefore, the discharge measurements may be indicative of median base-flow conditions. A complete record of all the changes in the diversions and returns during the investigation was nearly impossible to obtain, which prevented use of the data for an accurate determination of streamflow gains and losses. Three significant findings about groundwater inflow, however, resulted from the seepage investigation: (1) the reach between 5th Street at Cottonwood and the OK ditch diversion near Cornville gains inflow, (2) the reach between Beaver Creek and West Clear Creek also gains inflow, and (3) the reach from West Clear Creek to Fossil Creek has no significant seepage gains or losses.
The purpose of the seepage investigation was to assign average gains and losses to the reaches between the measuring sites, but no quantities were assigned because many of the conditions present could not be averaged. Analysis of the data and the prevailing conditions during the investigation indicated that the streamflow fluctuated with time; therefore, the measurements reflect different conditions. Discharge varied owing to irrigation returns and a diurnal change caused by daily fluctuation in evapotranspiration. Additional ditch returns unknown during this investigation were discovered in the southern part of the Verde Valley on subsequent field trips. Prior to the investigation, some of the study area had rain; during the investigation, the Verde River near Camp Verde gaging station showed decreasing daily discharge on a streamflow-peak recession. On June 12, the air temperature rose about 20oF, and because the evapotranspiration rate changes with temperature, the conditions after the temperature rise were not in equilibrium.
Records for the station near Clarkdale from June 1915 to June 1921 indicate that the base flow is virtually identical to the base flow computed for records collected from April 1965 to September 1978. The lack of change suggests that the ground-water system upstream from Clarkdale still represents equilibrium conditions.
The gaging station near Camp Verde was operated from 1935-45 and was reactivated to measure low flows in 1976 (pl. 3). Records from July 1976 to January 1978 are nearly complete, but base-flow data are intermittent after January 1978 owing to sustained high flows during the winter and early spring months. This coincides with a change in the rainfall pattern in which the winters were wetter and the summers dryer. Winter base flow for 1977 and 1978 is close to the minimum hydrograph, which indicates winter base flow is virtually unchanged since 1935 (fig. 4C). The 1976 summer base flow hydrograph is close to the minimum hydrograph, whereas in 1977 and 1978 they are below the minimum hydrograph except for mid-July, which coincides with the lowest part of the minimum hydrograph. During the summer of 1979, the base-flow hydrograph was close to the median hydrograph. During the summers of 1977 and 1978, the river reached base flow on a few isolated days and provided only limited definition for the base-flow hydrograph. These possible changes in summer base flow since 1945 may be an indication that either evapotranspiration or irrigation usage has increased over the years, but no comparative data on irrigation use or amount of riparian vegetation along the Verde River are available to test this assumption. Because winter base flow has remained constant and the summer 1979 base flow returned to the median hydrograph, the assumption can be made that the summer changes in base flow reflect irrigation or vegetation changes and that no changes in base flow occurred because of changes in discharge from the aquifer. Continued monitoring at this site might help to clarify the analysis.
Sycamore Creek
Perennial flow in Sycamore Creek begins near Parsons Spring about 4.2 mi upstream from the mouth (pl. 3). Summers Spring, about 1.8 mi upstream from the mouth, provides about 5 to 7 ft3/s of the flow in Sycamore Creek as indicated by seven measurements made at the spring during 1956-63. On seven occasions from 1956-77, base flow near the mouth of Sycamore Creek was measured; flows ranged from 7.44 ft3/s to 9.42 ft3/s and averaged 8.5 ft3/s. On the basis of the sparse data, ground-water discharge to Sycamore Creek appears to have been rather constant over at least the past 20 years.
Bitter Creek
Bitter Creek drains the area in the Black Hills northeast of Jerome. A number of springs are scattered throughout the drainage area. Mine drainage from the United Verde Mine and adjacent leach dumps drain into a tributary of Bitter Creek and contribute flow to Bitter Creek. Discharge measurements made at the mouth of Bitter Creek from March to November 1980 by the Arizona Department of Water Resources (written commun., 1980) ranged from 1.4 to 4.7 ft3/s, and the median value was 1.6 ft3/s.
Oak Creek
Oak Creek begins at the confluence of Sterling Canyon and Pumphouse Wash, and perennial flow originates at Sterling Springs in Sterling Canyon. Base-flow measurements were made at sites along Oak Creek on January 20, 1975. The base flow of Oak Creek 0.9 mi above Indian Gardens is provided by Sterling Springs and numerous small springs along Oak Creek and West Fork Oak Creek and is 13 ft3/s. Base flow increased to 35 ft3/s 0.75 mi downstream from Indian Gardens owing to discharge from springs in Munds Canyon near its mouth and ground-water seepage into Oak Creek along a cross-canyon fault just downstream from Indian Gardens (pl. 3). Base flow totals 42 ft3/s in the Page Springs area and 59 ft3/s at a site 0.5 mi south of the community of Page Springs. Only 3 ft3/s of the 6 ft3/s discharged by a spring along Spring Creek reaches Oak Creek (Levings, 1980).
The longest period of record for a gaging station in the upper Verde River area is for Oak Creek near Cornville. The median base flow at this station ranges from about 37 ft3/s (fig. 5A) in late January and early February to about 16 ft3/s in early July. This pattern of base flow was constant for the period 1949-72 with the exception of two wet years-1949 and 1965. The gaging station is in a gaining reach; therefore, the record applies only to that specific site. Levings (1980) correlated miscellaneous measurements made downstream from the gage with the station record to compute a winter base flow of 59 ft3/s below the gaining reach in which the gage is located. To calculate a winter base flow at the mouth of Oak Creek, the relation between the gage and the miscellaneous site (Levings, 1980, p. 13) was used to determine whether or not additional ground water inflows between the miscellaneous site and the mouth of the river. Flow at the gage on June 12, 1979, was recorded as 20 ft3/s. Using an average June-July ratio of 0.51, the flow at the miscellaneous site would be 39.2 ft3/s. Accounting for the 3 ft3/s of base flow contributed by Spring Creek, the flow at the mouth of Oak Creek should be 42.2 ft3/s. During a seepage run June 12, 1979, the flow at the mouth of Oak Creek measured 42.3 ft3/s. Therefore, the assumption can be made that little or no additional inflow to the river occurs along this reach and the winter base flow of 62 ft3/s at the mouth is the value at the miscellaneous site plus Spring Creek.
Beaver Creek
Beaver Creek drainage basin is divided into two major subbasins drained by Wet Beaver Creek and Dry Beaver Creek, which merge at McGuireville to form Beaver Creek. As the names suggest, Wet Beaver Creek is perennial and Dry Beaver Creek is intermittent. Six gaging stations have been operated by the U.S. Geological Survey in the Beaver Creek basin. Three stations are at perennial sites-Wet Beaver Creek near Rimrock, Montezuma Well outlet near Rimrock, and Beaver Creek at Camp Verde. Three stations are at intermittent sites-Red Tank Draw near Rimrock, Rattlesnake Canyon near Rimrock, and Dry Beaver Creek near Rimrock (pl. 3).
Dry Beaver Creek has two short perennial reaches- one at Beaverhead Spring about 1 mi downstream from Highway 179 and the other at McGuireville between Interstate Highway 17 and the confluence with Wet Beaver Creek (pl. 3). Both perennial reaches are less than 2 mi long.
Wet Beaver Creek is perennial from its source at springs in sec. 14, T. 15 N., R. 7 E., to the confluence with Dry Beaver Creek, which is a distance of about 20 mi. The accumulated spring discharge at the gaging station, Wet Beaver Creek near Rimrock, averages about ft3/s. Base flow generally ranges from about 6 to 8 ft3/s (fig. 5B). Montezuma Well, a tributary spring to Wet Beaver Creek, yields a fairly constant flow of about 2.5 ft3/s. The flow from Montezuma Well has been diverted at intervals since prehistoric times, and some prehistoric ditches are still being used. The amount of flow from Montezuma Well that actually reaches Wet Beaver Creek is unknown.
Beaver Creek extends about 9 mi from the confluence of Wet Beaver Creek and Dry Beaver Creek to the Verde River. Beaver Creek is perennial from the confluence of Wet and Dry Beaver Creeks to Montezuma Castle National Monument. During summer months, all or part of the flow in Beaver Creek above Montezuma Castle National Monument is diverted for irrigation. In the 1-mile reach above its mouth, the flow in Beaver Creek is interrupted; two observations of no flow were made 0.1 mi upstream from the mouth of Beaver Creek during the summer of 1937. During the seepage investigation of June 12, 1979, measurements of the water in an irrigation ditch 0.8 mi above the mouth of Beaver Creek, Beaver Creek above the ditch, and Beaver Creek at the mouth showed a 6 ft3/s gain owing to ground-water seepage between the ditch and the mouth. This seepage is thought to be subsurface return flow from irrigation.
West Clear Creek
West Clear Creek begins as a perennial stream at the confluence of Clover Creek and Willow Creek in sec. 33, T. 14 N., R. 9 E., and flows westerly for about 37 mi to the Verde River. On December 1, 1966, during a period of base flow, the flow in West Clear Creek 0.3 mi below Willow Creek was 1.88 ft3/s, of which 0.79 ft3/s was contributed by Willow Creek. Several springs along West Clear Creek increased the flow to 19 ft3/s at the gaging station near Camp Verde (pl. 3). Diversions for the irrigation of about 300 acres downstream from Forest Highway 9 often fully deplete the flow of West Clear Creek (pl. 3). Analysis of the streamflow records collected at the gaging station from December 1964 to September 1978 indicate that base flow averages about 16 ft3/s and varies seasonally from about 12 ft3/s in the summer to about 18 ft3/s in the winter (fig. 5C).
Fossil Creek
Fossil Creek is fed by Fossil Springs, (A-12-7)14d (pl. 2), which rise near the head of Fossil Creek Canyon about 3.5 mi northwest of Strawberry (fig. 1). The flow of Fossil Springs is diverted via pipeline to power two hydroelectric power plants at Irving and Childs (pl. 2); downstream from the diversion, Fossil Creek is intermittent (fig. 1). Since 1952, the U.S. Geological Survey has gaged the power plant diversion where the flume spills into Stehr Lake, which is a head-stabilization pond for the Childs power plant. The record represents virtually all the flow of Fossil Springs and indicates that the discharge is fairly constant at about 43 ft3/s (U.S. Geological Survey, 1979, p. 413).
Availability of Streamflow
No surface-water impoundments are along the Verde River and its major tributaries to store or control the streamflow. The primary use of surface water in the upper Verde River area is for irrigation. Important secondary uses include recreation, esthetic enjoyment, and fisheries. All these uses rely mainly on the amount of water present during low flows. The amount of streamflow varies with time and by location throughout the study area as a function of runoff-producing storms and evapotranspiration. In the Verde Valley the streamflow variation is greatest because, in addition to runoff and evapotranspiration, year-round diversion ditches remove water from the streams for irrigation. Gaging stations in the study area can be used as index stations for annual flow characteristics along the streams. Low-flow frequency and flow-duration curves were selected to show the availability of water with time.
Flow Duration
A flow-duration curve is a cumulative frequency curve that shows the percentage of time during the period studied that a specified rate of flow was equaled or exceeded. The curve provides a useful method for analyzing the availability and variability of streamflow without regard to the sequence of the flow events. The distribution of stream-flow with respect to time is a function of many variables including the amounts and type of precipitation, topography, soils, geology, vegetal cover, ground-water movement, and water-use patterns.
Flow-duration curves provide a convenient method for studying the flow characteristics of streams and can be used to determine the relative suitability of different streams for development of a water supply. The slope of the flow-duration curve is a good indication of the capacity of a basin to store water. Storage tends to lower the variability of flow by reducing the peak flows and spreading the same volume of runoff over a longer time period. A steeply sloping duration curve indicates high variability in flow rates and small amounts of natural storage, and a gently sloping curve indicates a low variability, which is characteristic of a consistent component of base flow per unit drainage area.
Flow-duration curves for selected sites in the study area are shown in figure 6. The data on which these curves are based were obtained by computer analysis of the daily streamflow records. At all the sites, the shape of the curves is characterized by a steeply sloping line in the low-exceedence-less than about 15 or 20 percent-or high-flow range indicating that streamflow is in direct response to precipitation. In the upper Verde River area, the flow-duration curves can be divided into two groups as characterized by the low flow end of the curves. The low-flow characteristics depend on location and correlate with irrigation use of surface water. Flow-duration curves for gaging-station sites that have fairly steady base flows are shown in figure 6A. The slope of the curves changes sharply into a mildly sloping line in the high-exceedence or low-flow range, which indicates high storage and low variability in base flow. For the low-flow ranges, the storage is provided by the regional aquifer rather than surface-water impoundments. Flow-duration curves for gaging-station sites (pl. 3) that have a much larger variability (steeper slope) of base flow are shown in figure 6B. All four stations are in or near irrigated areas. Large consumptive use of water upstream from the gaging stations causes the base flow to vary considerably within a year, whereas the discharge from the regional aquifer probably is similar to the base-flow component in figure 6A. Miscellaneous measurements and continuous monitoring of spring discharges show no change in the rate of discharge that occurs from the regional aquifer at these sites.
Flow-duration curves were compared for different time periods between 1916 and 1978 at two sites upstream from the area where water use is greatest and during which base flow had not changed. No significant changes were detected in average inflow or aquifer discharge.
The shape of the flow-duration curves, but not the discharge quantities, can be used to develop curves at ungaged sites. Quantity of flow varies by location along perennial streams in the study area because of increases from ground-water discharge. The curves in figure 6A have similar characteristics in that the sites occur upstream from irrigation use, seasonal differences in evapotranspiration rates are low, and ground water is discharged from Paleozoic rocks. The characteristics of the sites for the curves in figure 6B are similar because ground water is discharged from the Verde Formation and alluvium, the seasonal differences in evapotranspiration rates are high, and numerous irrigation diversions and returns occur along the stream reaches. Any changes caused by the differences in evapotranspiration rates or geology between figures 6A and 6B are masked by the changes caused by irrigation.
Low-Flow Frequency
Low-flow characteristics at a gaging station can also be described by frequency curves. The flow of streams in the upper Verde River area is lowest in summer and early fall when evapotranspiration and the demand for irrigation water are greatest. The frequency with which low flows occur is an important factor in the management of current stream usage and may be an important measure of the effects of future ground-water development. Flow-duration curves are one way of representing low-flow frequency but do not indicate whether the low flows occurred consecutively on many days in each year or on a few days scattered throughout each year. Low-flow frequency curves relate the lowest average discharge in cubic feet per second for various periods of time in days to the frequency of occurrence in years. In these low-flow frequency studies, the daily streamflow records are analyzed by climatic year (April 1 to March 31) in order to confine the low-water season in a 1-year period.
The demand for irrigation water in the Verde Valley is largest in summer. Because no streamflow data are available prior to the installation of irrigation ditches to indicate the amount of water available for irrigation use, an annual analysis is presented at the outflow point of the valley to provide data on the water available to downstream users. Figure 7 shows a family of low-flow frequency curves for the gaging station, Verde River near Camp Verde. The curves show that on an average of about once in 10 years the mean discharges for 7- and 30-day periods are likely to be less than or equal to 51 ft3/s and 62 ft3/s, respectively. The shape of the frequency curves appears typical for perennial streams-smooth curves, concave upward. In streams affected by diversions, the curves deflect downward. In streams where base flow is maintained by a large-capacity ground-water reservoir, a flat frequency curve is produced. The two conditions occur upstream from this site in the Verde Valley, and the curves reflect a condition somewhere between the extremes.
The recurrence interval, stated in years, is the reciprocal of the probability of occurrence for any given year. For example, a low flow for a given period that is assigned a recurrence interval of 10 years has a 0.1 probability or 10-percent chance of occurring in any given year. The recurrence interval must not be thought of as the exact time interval between recurrences but as the average time interval between like events. The possibility exists that the 10-year low flow can occur in several consecutive years if the average recurrence over a long period of time is only once in 10 years. Low-flow frequency data and other flow characteristics for perennial streams are presented in table 6.
Table 6 --Streamflow characteristics at selected sites Period Drainage Annual Winter Discharge equaled or Average 7-day low flow for Average 30-day low flow for exceeded, in cubic indicated recurrence indicated recurrence Station of area at volume base flow,(1) number Station name record, gage, in of base in cubic' feet per second interval interval calendar square flow, in feet per 50 per- 90 per- years miles(2) acre-feet second cent of cent of 2 yrs. 10 yrs. 20 yrs. 2 yrs. 10 yrs. 20 yrs. time time 09503700 Verde River near Paulden 1963-78 2,530 16,000 22 24.0 21.0 20.9 17.6 16.4 21.7 18.7 17.5 09504000 Verde River near 1915-21, Clarkdale 1965-78 3,520 54,000 75 82.0 69.0 67.8 61.5 59.8 70.4 64.3 62.7 09504500 Oak Creek near 1940-45, Cornville(3) 1948-78 357 20,000 37 33.0 19.0 15.5 12.2 11.2 17.3 14.0 13.2 09505200 Wet Beaver Creek near Rimrock 1961-78 111 5,000 7 7.7 6.3 6.4 5.9 5.7 6.6 6.1 5.9 09505800 West Clear Creek near CampVerde 1964-78 241 12,000 17 18.0 14.0 13.0 12.0 11.8 14.0 12.5 12.2 09506000 Verde River near 1934-45 Camp Verde (5)1976-79, 5,024 (4)80,000 200 190 85.0 66.2 51.3 47.5 75.9 62.0 58.9 (1)Winter base-flow conditions occur during January, February, and March. (2)Drainage areas of the Verde River are approximate and include 373 Mi2 in Aubrey Valley Playa, a closed basin located approximately 50 mi northwest of the study area. (3)Low flow affected by several small diversions for irrigation above station. (4)Calculated for the 1977 water year. (5)0perated as a low-flow station only.
Quality of Surface Water
The chemical, physical, and biological quality of water determines the suitability of water for given uses. The following evaluation of surface-water quality is directed toward three major usages-irrigation, swimming, and fisheries. Few if any domestic and industrial water supplies have been developed from surface water in the area, so those uses will not be considered in this section of the report.
Chemical Quality
During low flows, the chemical quality of surface water in the study area is closely related to the quality of ground water that supplies the base flow (pl. 3). During medium and high flows, the dissolved-solids concentration is diluted by snowmelt or surface runoff that have a lower dissolved-solids concentration.
The dissolved-solids concentrations range from 32 to 1,570 mg/L for 211 samples collected throughout the study area during all ranges in flow (table 14). Samples collected from perennial streams during low flows seldom have dissolved-solids concentrations less than 200 mg/L except at sites in Oak Creek upstream from Page Springs and in Wet Beaver and West Clear Creeks upstream from where they emerge from their canyons into the Verde Valley. During low flows, the dissolved-solids concentrations generally increase in the downstream direction (fig. 8) owing to increased dissolved solids in ground water from the Verde Formation, particularly in the southern part of the Verde Valley (pl. 3).
In the Verde River upstream from Camp Verde and in the perennial tributaries to the Verde River, the dominant ions generally are calcium, magnesium, and bicarbonate (pl. 3). Exceptions are a sample taken in 1977 from the Verde River near the upstream limit of the study area in which the major ions are calcium, sodium, magnesium, and bicarbonate, and a sample taken in 1979 from Fossil Creek in which the major ions are calcium, magnesium, and sulfate (table 14).
The relation of dissolved solids and specific conductance was determined to compare two sites on the Verde River above and below the area where the water quality changes. Using a least squares best fit method on the data collected during the 1976-79 water years, the relation of dissolved solids to specific conductance is similar at both sites (fig. 9). The major cations and anions can be related also to specific conductance at the Verde River near Camp Verde site as shown on figure 10. Correlation at the near Clarkdale site was poor because the concentrations of sodium, sulfate, and chloride were low. Only calcium, magnesium, and bicarbonate show a relation to specific conductance.
In June 1979 the dissolved-solids concentration of flow in the Verde River increased from 403 mg/L near the mouth of Beaver Creek to 550 mg/L above West Clear Creek (fig. 8). Coincident with the increase in dissolved solids, the sodium and sulfate ions increased; however, calcium, magnesium, and bicarbonate generally continued to be the dominant ions (pl. 3). The increase in dissolved solids and the change in the concentrations of the major ions are the result of ground-water inflow to the river. The increased presence of sodium and sulfate ions probably is the result of the solution of these ions by ground water moving through salt and gypsum deposits in the Verde Formation.
Figure 9 Relation of dissolved-solids concentrations to specific conductance at Verde River near Clarkdale and Verde River near Camp Verde, 1976-79 water years
A similar but less obvious increase in the dissolved-solids concentrations of the Verde River occurs between Clarkdale and U.S. Highway 89A (fig. 8). This increase in dissolved solids probably is the result of ground-water inflow to the river. The ground water is moving through the Verde Formation where solution of limestone probably increases the dissolved-solids concentration. In this instance the relative concentrations of major ions in the river water remain unchanged.
The greatest single use of surface water is for irrigation, and the surface water in the upper Verde River area generally is well suited for that use. The U.S. Salinity Laboratory Staff (1954) devised a classification system that can be used to evaluate the suitability of irrigation water on the basis of the sodium hazard and the salinity or dissolved-solids hazard. Large concentrations of sodium in relation to the concentrations of calcium and magnesium tend to cause a breakdown of soil structure and also may harm plants by causing a toxic accumulation of sodium in the plant tissue. A common measure of the sodium hazard is the sodium-adsorption ratio (SAR) that is defined by the equation
in which the concentrations of the constituents are expressed in milli-equivalents per liter. The salinity hazard is commonly evaluated in terms of specific conductance, which is a measure of the ability of the ions in solution to conduct an electrical current.
In most of the streams in the area the sodium hazard is low, but the salinity hazard generally ranges from low to medium in the tributaries and the Verde River north of Camp Verde and medium to high in the Verde River downstream from Camp Verde (fig. 11). No major diversions for irrigation occur in the reach downstream from Camp Verde, but the possibility exists that with correct selection of crops and proper agricultural practices even the water with a high salinity hazard could be used successfully for irrigation.
The Arizona Water Quality Control Council (written commun., 1979) listed maximum contaminant levels for 16 toxic substances in three categories of surface-water uses (table 7). In general, only a few samples exceeded these standards. In most cases the large concentrations in the total recoverable form are associated with the large sediment concentrations during high flows (table 14). Except for lead and phenols, the chemical quality of surface water is fairly well suited to the current uses. Although some samples contained lead and phenols in excess of the Arizona Water Quality Control Council (written commun., 1979) standards for surface-water uses (table 7), no adverse effects have been documented by local and State agencies.
Table 7 --Surface-water chemical-quality standards(1) for designated uses and number of samples exceeding the limits [T, total recoverable; D, dissolved; and N/S, no standard] Recreational use Agricultural use Concentrations, Full body contact(2) Aquatic and wildlife use irrigation Livestock watering Number Form Parameter of analyzed in micrograms Allowable Number Allowable Number Allowable Number Allowable Number samples for per liter limit, in of limit, in of limit, in of limit, in of micrograms exceed- micrograms exceed- micrograms exceed- micrograms exceed- Min. Max. per liter ences per liter ences per liter ences per liter ences Arsenic 145 T 1 45 D50 0 D5O 0 T2,000 0 T200 0 Barium 145 T 0 1,200 DI,000 1 N/S ---- N/S ---- N/S ---- Boron 201 D 0 530 N/S ---- N/S ---- Tl,000 0 N/S ---- Cadmium 143 T 0 15 T10 3 D10 0 T50 0 T50 0 Chromium (Hexavalent and Trivalent) 145 T 0 60 D50 1 D50 1 Tl,000 0 T1,000 0 Copper 146 T 0 340 N/S ---- D50 3 T5,000 0 T500 0 Lead 141 T 0 150 (2)D5O 16 (3)D50 16 T10,000 0 T1OO 3 Manganese 146 T 0 1,900 N/S ---- N/S ---- T10,000 0 N/S ---- Mercury 143 T 0 4.5 T2 1 T2 1 N/S ---- 10 0 Selenium 143 T 0 9 D10 0 T50 0 20 0 50 0 Silver 145 T 0 30 D50 0 D50 0 N/S ---- N/S ---- Zinc 145 T 0 280 N/S ---- D500 0 25,000 0 25,000 0 Cyanides (As cyanide ion, and complexes) 146 T 0 20 200 0 20 0 N/S ---- 200 0 Phenolics 145 T 0 10 5 6 5 6 N/S ---- 5 6 (1)Standards set by the Arizona Water Quality Control Council (written commun., 1979). (2)When "Partial Body Contact" is the only designated use for a surface-water segment, the allowable limits listed for "Full Body Contact" shall apply until possible adverse health effects are better understood for "Partial Body Contact" use and limits are assigned. (3)of the 141 analyses for total recoverable lead, 60 reported "<1OO ug/L." Some or all of these 60 samples may have exceeded the 50 ug/L; however, for this table it is assumed that they did not exceed the standard.
During 1980, the Arizona Department of Health Services has been sampling the water at the mouth of Bitter Creek and on a tributary stream into which the drainage from the United Verde Mine and adjacent leach dumps flow. The quality of the water in Bitter Creek is affected by the mine drainage (Milne, 1981). Water from the sampling site on the tributary stream exceeds the surface-water standards for sulfate, dissolved solids, copper, zinc, manganese, iron, and cadmium. Water at the mouth of Bitter Creek contains concentrations of sulfate, dissolved solids, copper, zinc, manganese, and iron that exceed the standards for surface-water uses but are dilute compared to the tributary sampling site. At the mouth of Bitter Creek, dissolved-solids concentrations range from about 1,150 to 1,750 mg/L, whereas at the tributary site the range is from about 4,600 to 6,000 mg/L (T. D. Love, Arizona Department of Health Services, written commun., 1980).
Bacteriological Quality
From March 1976 through October 1979, the U.S. Geological Survey analyzed 147 surface-water samples taken at 21 different sites in the area for determination of fecal coliform bacteria. Fecal coliform bacteria are present in the intestines and the feces of warmblooded animals. The presence of fecal coliform organisms may indicate recent and possibly dangerous contamination (Greeson and others, 1977). The fecal coliform counts were from <1 to 1,900 colonies/100 mL (milliliters) (table 14). The most stringent maximum allowable limits set for fecal coliform in surface water by the Arizona Water Quality Control Council (written commun., 1979) is for full body contact or swimming. On the basis of a minimum of five samples, the fecal coliform content of recreation waters shall not exceed a geometric mean of 200 colonies/100 mL. No more than 10 percent of the samples for a 30-day period shall exceed 400 colonies/100 mL nor exceed 800 colonies/100 mL for a single sample.
The bacteriological data collected by the U.S. Geological Survey are too scattered in time to allow an evaluation of the waters in the specific terms of the above standard except under the single-sample category. Six samples, three at Oak Creek near Cornville and three at different sites on the Verde River, exceed the maximum allowable limit of 800 colonies/100 mL. Therefore, the data do indicate that there are sites where, for at least short periods, fecal pollution may be a potential hazard to swimmers.
At three sites on the Verde River and three sites on Oak Creek during 1976-79 (table 14), monthly coliform counts were made for at least 1 year. Although the data are scattered, fecal coliform counts generally were higher in the summer months. The trend toward high fecal coliform counts during the summer may be the result of increased streamside recreation and tourist visitation. Fecal coliform counts at a popular swimming area on Oak Creek increased drastically in response to intensified recreational use during holiday weekends, such as Labor Day, Memorial Day, and Independence Day (Obr and others, 1970). High fecal coliform counts may also result from livestock, wild mammals, and birds defecating in or close to streams.
Suspended-Sediment Concentrations
The suspended-sediment concentrations found in streams in the area are generally less than 50 mg/L at low flow but, during periods of high flow, concentrations have been found to be as much as 9,280 mg/L. Suspended-sediment data collected by the U.S. Geological Survey through September 1979 are given in table 8.
Water-quality criteria for surface water offer few quantitative guides for evaluating suspended-sediment concentrations relative to the suitability of surface water for specific uses. Qualitatively speaking, when concentrations are too high, problems that are likely to result in the study area include: (1) decreasing the esthetic attraction of the streams, (2) clogging the irrigation-distribution systems, and (3) degradation of fisheries. None of these problems appears to be a serious concern in the study area probably because the high flows associated with large suspended-sediment concentrations often cause much more damage than the movement of sediment. Additionally, large suspended-sediment concentrations, because they are related to high flows, are generally of short duration; therefore, the streams tend to clear rapidly.
Table 8 --Suspended-sediment data from selected streamflow sites Instan- Suspended sediment taneous Station Station name Date of Time discharge, Concentration, Discharge, number sample in cubic in milligrams in tons feet per per liter per day second 09503700 Verde River near Paulden 06-22-77 1130 21 23 1.3 03-01-78 1745 7,520 9,280 188,000 11-16-78 1745 29 71 5.6 12-14-78 1430 23 31 1.9 09504000 Verde River near Clarkdale 06-20-77 1700 73 35 6.9 12-12-78 1100 71 26 5.0 01-16-79 1115 78 8 1.7 02-14-79 1530 486 74 97 03-13-79 1620 1,130 25 76 04-18-79 0945 131 4 1.4 05-09-79 1730 81 12 2.6 06-11-79 1600 83 14 3.1 07-12-79 0945 75 18 3.6 08-09-79 1700 72 56 11 09-28-79 1345 77 22 4.6 344557112014600 Verde River at Tuzigoot bridge, near Clarkdale 06-21-77 1500 46 97 12 344318111592400 Verde River at Highway 89A near Cottonwood 06-22-77 1000 32 143 12 09504200 Verde River near Cornville 06-21-77 1200 43 119 14 345954111441800 Oak Creek at Cave Springs near Sedona 06-20-77 1030 4.2 385 4.4 345436111434000 Oak Creek below Indian Gardens 06-20-77 1130 30 9 0.73 344928111482000 Oak Creek at Red Rock Crossing near Sedona 06-20-77 1330 18 19 0.92 09504400 Munds Canyon tributary near Sedona 10-18-72 1515 9.5 25 0.64 09504420 Oak Creek at Sedona 10-11-78 1650 29 7 0.55 12-13-78 1345 42 12 1.4 05-10-79 1400 43 2 0.23 06-14-79 1430 30 2 0.16 07-12-79 1600 27 7 0.51 08-11-79 1300 30 6 0.49 09-26-79 1245 29 2 0.16 09504440 Oak Creek at Red Rock Crossing near Sedona 11-15-78 0930 99 16 4.3 12-13-78 1030 41 6 0.66 02-13-79 1745 158 154 66 04-18-79 1445 303 5 4.1 05-10-79 1130 37 8 0.80 06-13-79 1530 20 15 0.81 07-12-79 1330 14 18 0.68 08-11-79 0900 18 43 2.1 09-26-79 1500 17 5 0.23 09504500 Oak Creek near Cornville 10-20-72 1200 3,230 914 7,970 06-20-77 1430 16 24 1.0 03-01-78 1600 12,200 5,270 174,000 344052111561200 Oak Creek above confluence with Verde River, near Cornville 06-21-77 1000 33 37 3.3 343513111524600 Verde River at 1-17 bridge, near Camp Verde 06-21-77 1000 13 59 2.1 343424111512200 Verde River 600 ft above Beaver Creek at Camp Verde 06-21-77 1500 27 84 6.1 09505200 Wet Beaver Creek near Rimrock 07-27-72 1130 12 211 6.8 04-03-73 1340 110 10 3.0 0900 6.7 6 0.11 02-28-78 1720 70 814 154 09505250 Red Tank Draw near Rimrock 10-19-72 1500 1,060 373 1,070 04-03-73 1605 52 10 1.4 09505300 Rattlesnake Canyon near Rimrock 04-16-73 1230 78 9 1.9 11-13-78 1545 17 15 0.69 12-11-78 1540 3.3 55 0.49 01-15-79 1445 1.2 6 0.02 02-12-79 1330 38 9 0.92 03-13-79 1000 61 5 0.82 04-16-79 1335 38 3 0.31 343752111473500 Wet Beaver Creek at Rusty Spur Ford near Rimrock 06-21-77 0900 3.5 18 0.17 09505350 Dry Beaver Creek near Rimrock 03-02-78 1730 5,720 1,750 27,000 343428111511600 Beaver Creek above confluence with Verde River at Camp Verde 06-21-77 1530 10 163 4.4 09505550 Verde River below Camp Verde 02-28-78 1630 8,310 3,410 76,500 03-06-78 1500 8,930 2,250 54,200 343016111494600 Verde River above West Clear Creek, near Camp Verde 06-21-77 1630 51 74 10 09505800 West Clear Creek near Camp Verde 07-26-72 1400 36 57 5.5 10-07-72 1815 960 333 863 04-11-73 1215 1,300 236 828 04-21-76 1720 526 156 230 06-21-77 1030 14 16 0.60 07-26-79 1400 25 57 3.8 09506000 Verde River near Camp Verde 06-22-77 1200 53 86 12 10-10-78 1410 99 26 6.9 12-12-78 1630 218 38 22 03-14-79 1000 2,000E 54 292E 04-17-79 1000 1,500E 27 109E 05-09-79 1100 153 13 5.4 06-13-79 1000 95 28 7.2 07-11-79 ---- 76 18 3.7 08-10-79 1400 149 45 18 09-27-79 1345 93 95 24 E = Estimated.
