Climate
The Verde Valley is located in central Arizona in the northeast portion of Yavapai County. Approximately 100 miles north of Phoenix, the Verde watershed through the Verde Valley is classified as semi-desert with an average annual precipitation of just over 12 inches. However, topography strongly influences rainfall within the Verde watershed; the highest points receive over 20 inches of precipitation a year (Averitt, et al, 1991). All of Arizona falls under the Southwestern or Arizona climatic pattern, which is a bi-seasonal regime characterized by winter precipitation, spring drought, summer precipitation, and fall drought (Lowe, 1964). Prevailing winds are from the southwest.
Elevations in the Verde Valley range from 3,512 feet at Clarkdale to 3,300 feet at Cottonwood to 3,133 feet at Camp Verde. The surrounding mountains, such as Mingus Mountain, Woodchute Mountain, and the nearby Mogollon Rim, rise above the valley to an elevation of 7,500 feet or greater. These surrounding mountains and the Verde River itself contribute to the region's moderate temperatures throughout the year. The flow of cool air off the mountain ranges causes a 30 to 40 F decrease in nighttime temperatures. Temperatures during the winter months are typically 50 to 60 F during the day, with evening temperatures falling to 20 to 30 F. Summer daytime temperatures often reach 100 F, cooling during the evening to 50 to 80 F (ADOC, 1989)
Geology
Landforms
The Verde Valley lies in the mountainous Central Mountains Province of Arizona. This region forms a diagonal band across the mid-portion of the state (Figure 3). The Central Mountains Province is considered the transition zone between the block-faulted Basin and Range deserts of southern and western Arizona and the uplifted Colorado Plateau in the northern portion of the state. The Central Highlands shares some characteristics of both these physiographic provinces, but is characterized primarily by mountains of moderate elevations and deep, steep-walled canyons.
Geologic time is often difficult to comprehend, especially when one tries to grasp the scope of millions of years. Exposed rocks have been found in the surrounding mountains that can be dated about 2 billion years ago. About 60 million years ago, an ancestral Verde River began its southeastward route through the formations now known as the Mogollon Rim and the mountains of central Arizona.
The lava that caps the Black Hills south of the Verde Valley flowed over 15 million years ago (Chronic, 1986). Faulting, uplifting, and erosion continued until an interesting sedimentary formation was created in a large lake in late Pliocene time. This distinctive soft, white limestone that is the Verde Lakes formation was formed about 8 million years ago. The lake formed as a result of the lava flow that dammed the Verde River south of where Camp Verde is now located. The lake was about 15 miles wide by 35 miles long. In time, the river eroded the lava dam and the limestone deposits became the present ground surface. Both Montezuma Castle and Well are in the Verde Lake limestone.
The limestone and salt formations now exposed on the valley hillsides were deposited during this period. These ancient lake beds are a wealth of information containing fossil remains of mastodons, horses, turtles, and shellfish. Tracks can be found of camels, cats, and tapirs (Chronic, 1986). Through natural erosional processes continuing today, the Verde River and its tributaries are still exposing more of this region's geologic history.
Initially, the Verde River meandered across the flat valley floor. As it slowly cut downward through the old lake bed sediments, its curves became more and more deeply entrenched. Eventually the river took a shortcut through one loop leaving its former channel an oxbow lake, which is now known as Peck's Lake (Chronic, 1986).
Two artificial topographic features found along the corridor are very distinct. The mill tailings and tailings pond, both linked to past mining operations at the Clarkdale smelter, are very noticeable. The mill tailings, or slag dump, rise nearly 80 feet from the riverbed forming a distinct black slag mound devoid of vegetation (Averitt, et al, 1991). Southwest of Tuzigoot National Monument, and 200 to 300 yards northeast of the river, lie the tailings pond where iron pyrate was disposed of from the smelter. This 65 acre area is characterized by a sediment, red rust in color, which supports very little plant life (Averitt, et al, 1991).
The diversity of the geologic formations of the Verde Valley region includes a broad range of rocks and minerals. Notable formations include the Verde Formation (consisting of limestone, sand, gravel, and clays), basalt, Redwall and Martin limestone and sandstone, Coconino sandstone, Kaibab limestone, and Supai Formation. The permeable nature of sedimentary rocks makes them important sources of groundwater; much of the base flow for the perennial streams in the Verde Basin is maintained by discharge of groundwater from these units. The upper reaches of the basin, on the Mogollon Rim, are primarily Tertiary-aged volcanic basalt flows and ash-fall tufts (Averitt, et al, 1991).
Soils
The Verde River begins perennial flow just downstream from Sullivan Lake in a vertical walled canyon of volcanic rock with moderate gradient. As it proceeds downstream, the surrounding terrain becomes hilly and the river alternately flows through meadows, where the stream bottom is predominantly sandy, and narrow steep canyons with large bluffs, where the stream bottom is predominantly cobble. Downstream from Perkinsville, the riverbed widens in some areas and gravel bars are formed, particularly where side canyons join the mainstem and leave areas of alluvium. Below Sycamore Canyon, the floodplain narrows and the river overall cuts through a fairly steep walled canyon. Just above Tapco, the canyon widens and there are areas of river-washed gravel and sand deposits.
The river corridor soils are primarily alluvial in nature, classed as riverwash and as terrace deposits. Riverwash consists of poorly sorted, fine to coarse gravel. The terrace deposits border the wide channel of the river and may be 5 to 10 feet high. These deposits consist of a mixture of unconsolidated but finely stratified clay, silt, sand, and gravel. Both the riverwash and terrace deposits are very permeable and form a good table aquifer (Lehner, 1958). Historically, these areas were important for agricultural purposes.
In the Verde Valley downstream to Camp Verde, the floodplain becomes quite broad, the river becomes wider and more meandering, and the stream bottom composition contains more gravel and cobble that form large bars at low flows. The white limestone cliffs adjacent to the river stand out in stark contrast to the red sandstone and limestone in the area. From Camp Verde to Brown Springs, the river bottom is predominantly bedrock material, and the river flows through narrow canyons characterized by a series of wide bends and abrupt drops in slope.
Below Brown Springs, the river passes through large bluff-type mountains, alternating between gentle slopes and steep cliffs on the sides of the river. The river bottom is predominantly cobble and gravel with many large gravel bars exposed at low flows.
The section of the Verde River that the Corridor Project encompasses includes three upland soil associations: the Continental-Whitlock-Cave association, the Retriever- Courthouse association, and the Rockland-Lehmans-House Mountain association.
Of the three associations, the one that borders the most of the Verde River in the corridor area is the Continental-Whitlock-Cave association that extends from Clarkdale southeast to the confluence of the Verde River and West Clear Creek. This asociation is comprised of fine-textured to moderately coarse soils with very low organic matter content and some layers of cemented lime, which range from shallow to deep. It is located in slopes from zero to 30 percent, and elevations range from 2,000 to 3,500 feet.
The principle uses found on these soils are seasonal grazing, wildlife habitat, and mining. Forage production, however, is low because of limited rainfall, high evaporation, and rapid water runoff.
Radiating outward from and surrounding the Continental-Whitlock-Cave association is the Retriever-Courthouse association. The corridor section of the Verde River passes through this association in the area of the Oak Creek and Verde River confluence. The Retriever-Courthouse association consists of shallow to moderately deep medium textured, gravelly calcareous soils on limestone bedrock and rock outcrops. The slopes in this association range from two to 40 percent, and the elevations range from 3,000 to 4,000 feet.
Rangeland and wildlife habitat are the main uses on the Retriever-Courthouse association areas. Because of limited rainfall and shallow soil, forage production is low.
The next most widespread soil association in the Verde River Corridor is the Rockland- Lehmans-House Mountain association, which the Verde River passes through between the Sycamore Creek confluence and Clarkdale to the southeast. This association is characterized by rock outcrops, shallow gravelly to stoney soils that are medium to fine in texture. The soils lay on andesite and basalt bedrock, which form the hills and mountains of the area. The slope of the hills and mountains range from 15 to 60 percent at elevations from 2,000 to 4,000 feet.
The main uses on the Rockland-Lehmans-House association are seasonal grazing, wildlife habitat, and mining of copper and some gold and silver. Forage production ranges from low to medium on this association due to low rainfall and high runoff.
The Verde Watershed
Water, H2O, is such a simple, natural molecule. But there is nothing simple about water when you add humans to the equation. How much water is enough--for who--for what? To be classed "good water quality" depends on the use of the water, such as drinking, swimming, or irrigating crops. Everyone can use the water in a river, can't they, or does someone own all that water? There are no simple answers.
Water Quantity
Beginning in north central Arizona, the Verde River flows southeast for nearly 200 miles until it joins with the Salt River northeast of Phoenix (Figure 4). Some say the headwaters begin at Mt. Floyd near Seligman; the federally designated headwaters begin in Chino Valley at Sullivan Lake at the confluence of the Big Chino Wash and Williamson Valley Wash north of Prescott. The headwaters begin at an elevation of 4,348 feet and fall 3,008 feet to the river's mouth at the confluence with the Salt River.
The Verde River Basin is part of the Central Highlands water province, the smallest of the three water provinces in the state. The Central Highlands contains only 15 percent of the land area in the state, but over 50 percent of the state's streamflow originates in this province (Arizona Water Commission, 1975). There are many high altitude mountain ranges within the Verde Basin. These high altitude zones provide much of the water for streams in the Verde Basin, in the form of direct runoff into stream channels and as groundwater recharge of aquifers.
The watershed of the Verde is in both private and public ownership. The primary land managing entity is the Forest Service (FS) which administers the Prescott, Coconino, Kaibab, and Tonto National Forests. The drainage basin for the Verde covers 6,646 square miles with the major sources of water consisting of winter snows, summer rains, and spring flows. There are eight major perennial tributaries to the Verde: Sycamore Creek, Oak Creek, Beaver Creek, West Clear Creek, East Verde River, Fossil Creek, Wet Bottom Creek, and Tangle Creek. It is estimated that the average annual yield of water is 464, 253 acre feet. The Arizona Game & Fish Department lists 15 lakes in this basin totalling 3,269 acres (ADEQ, 1988).
Historically, surface water diversion was necessary for nearly all economic activities to thrive, but it did not occur in a legitimate and orderly manner under the provisions for the riparian water law doctrine that was used in the eastern United States. The riparian doctrine prohibited diversion and mandated that, in times of shortage, all riparian landowners would share equally whatever water was available. What was needed was a water law doctrine that would allow non-riparian landowners to divert water to lands not adjoining the stream channel to bring the water to mineralized areas or to croplands, while also establishing a priority system of uses and users so that in times of drought, conflict could be avoided.
In 1864 the first Territorial Legislature responded by declaring the rivers, streams, and creeks of flowing waters to be public and to be used for the purposes of mining and agriculture. The Arizona Territorial Supreme Court further institutionalized the predominant water and resource values of the nineteenth century when, in 1888, it rejected the riparian doctrine in favor of the doctrine of prior appropriation (SCORP, 1989a).
This court decision came just prior to the most severe flood and drought episodes the new Arizona residents had ever faced. These climatic events occurred at a time when overgrazing was rampant, and irrigated agriculture and mining were in full force. Large riparian trees were harvested everywhere for building materials, fuelwood, and to build railroads which had reached Arizona by 1880. The flood and drought sequence exacerbated the cumulative effect of these intensive land use practices, and consequently triggered a major episode of severe arroyo cutting and stream channelization (SCORP, 1989a).
Surface water in the Verde is still used for irrigation and for recreation, while groundwater is the principal source of water for both public and domestic uses. Surface runoff can and does impact groundwater portions of the hydrologic cycle in some areas. According to Owen-Joyce and Bell "large scale groundwater development would ultimately decrease the low-flow surface outflow from the basin." Within the Verde Valley, the regional aquifer is made up of river alluvium, Verde Formation and the underlying basalt flows, Supai Formation, and Redwall limestone (Owen-Joyce and Bell, 1983).
As was mentioned earlier, the Verde River's perennial flow begins at Del Rio Springs in Chino Valley. A small dam holds the spring's discharge forming Sullivan Lake which provides water for livestock. The river is frequently dry for a few miles downstream where it drops down into a narrow and highly scenic canyon. One of the Verde's major tributaries, Sycamore Canyon, enters the Verde about 35 miles southeast of Sullivan Lake. Most of Sycamore Creek is a federally designated wilderness area. Tapco, the VRCP's starting point, is located just a few miles downstream from Sycamore Canyon.
The Verde flows essentially undammed for 125 miles until it reaches Horseshoe Dam, about 58 miles northeast of Phoenix. A second dam, Bartlett Dam, is located below Horseshoe. Bartlett and Horseshoe Dams collect and store the water of the Verde for downstream agricultural and domestic uses. These dams also created two storage reservoirs that have become popular recreational resources. Salt River Project has major water rights on the Verde and manages these dams controlling the downstream releases. Twenty communities are located within the Verde River Basin and make use of the many amenities provided by the Verde and its tributaries (USDA FS, 1990).
The flows on the Verde River are extremely variable. The following Table 1 points out this variability. In response to seasonal precipitation patterns, discharge is usually highest following intense summer storms and lowest in late spring. Diversions also substantially influence downstream flows, with late spring and early summer diversions for irrigation resulting in the lowest flows. It should be noted that the highest flow ever recorded for the Verde is over 100,000 cubic feet per second (cfs) (USDA FS, 1990).
Table 1. USGS Gauge Records for the Verde RiverCamp Verde Gauge Tangle Creek Gauge Minimum recorded flow 13 cfs 48 cfs Mean annual flow 378 cfs (6 yr. period) 546 cfs Peak mean daily flow recorded 27,800 cfs (thru 1978) 94,800 cfs Maximum flow recorded 55,000 cfs 112,000 cfs Date of maximum flow 12/19/78 2/15/80 (Source: USDA FS, 1990, Verde Wild and Scenic River Draft Implementation Plan)
The average discharge at the gauging station at Clarkdale is approximately 196 cfs. The historical record reports a high of 51,000 cfs in 1921, with a minimum of 55 cfs in the same year. For 1988, the four highest discharge events were recorded at 8,800, 5,000, 4,900, and 2,600 cfs (USDA FS, 1990).
The Verde River Corridor lies in the Verde Valley groundwater basin. This is a regional aquifer delineated by the Black Hills to the west and by the Mormon Mountain anticline to the east (Twenter and Metzger, 1963). Groundwater discharge from the regional aquifer maintains the perennial surface water flow in the Verde River as well as in its tributaries (Owen-Joyce and Bell, 1983).
Groundwater flow is discharged to springs and streams and is also intercepted by local wells pumped for public and domestic use. Part of this groundwater reaching the surface is lost, due to soil and surface runoff, evaporation, transpiration from vegetation, and diversion for irrigation. The depth of the aquifer varies from the sand surface in the riverbed to 1,279 feet below the surface (Levings and Mann, 1978).
The Verde River Corridor contains numerous agricultural and domestic diversions. Water is drawn from the river by direct diversion and wells. It is partially consumed in agriculture and domestic uses, yet a portion of what is diverted is also returned to the river though delayed by routing through irrigation systems. The dirt irrigation ditches also return water to the river via percolation.
Northern Arizona communities including Prescott, Pine, Payson, Camp Verde Yavapai- Apache Indian Tribe, Camp Verde, and Cottonwood have been granted a share of Colorado River water from the Central Arizona Project (CAP). Salt River Project (SRP) currently claims all unappropriated Verde River water. Some of the communities have expressed an interest in exchanging their CAP allocation to SRP for Verde River water. This could result in additional water being removed directly from the upper and middle Verde River or from its tributaries.
A water balance model was developed by the Environmental Defense Fund to describe quantitatively the current and future water use and supply situations in the upper Verde River basin. This approach balances demand for water with available supply. An estimate of the potential amount of water available from savings through conservation and reallocation can be made by examining water use efficiencies and other variables in the system. The water balance uses information on water supply and demand from 1985 as the baseline cases, and then compares this case to current projections for future water supply and demand in the year 2025. Alternative scenarios for the future are developed using different assumptions about municipal and agricultural demands, levels of conservation, surface water exports, and groundwater mining (EDF, 1989).
If growth occurs in the Verde Valley and Prescott areas as anticipated and all increases in water demand are met, the model predicts that by 2025 instream flows in the Verde River could be reduced by up to 21,000 acre-feet per year (EDF, 1989). (see Other Protective and Management Actions section)
The biggest current threats to flows in the Verde River are from proposed water exchanges that would allow upstream diversion and accelerated ground water pumping within the basin. In an attempt to protect the unique values associated with the Verde River, the Tonto, Prescott, and Coconino National Forests have applied for "instream flow" water rights with the Arizona Department of Water Resources (ADWR). One application begins at Beasley Flat for 25 cfs and increases to 100 cfs at Tangle Creek (USDA FS, 1990). If approved, this application will help ensure that adequate flows are maintained in the river to protect many water dependent resource values such as fish and wildlife.
The process of determining the location and validity of water rights in the Verde Basin is currently taking place as part of the Gila River Adjudication. It is a very large, complex legal process that will take many years to complete.
Natural wetlands in Arizona have been substantially reduced in the last 100 years as a direct result of human developments and uses. The Verde River Corridor harbors two important marshlands that have been altered, but still retain vestiges of their former character and value. Peck's Lake and Tavasci Marsh, both located in the Clarkdale/Cottonwood area, are owned by the Phelps Dodge Corporation. Peck's Lake is one Arizona's few remaining oxbow lakes. Water levels have changed substantially in the last 100 years as a result of a low dam and a water diversion channel on the Verde River. Tavasci Marsh, a spring-fed marsh downstream from Peck's lake, is another unique natural wetland, which is presently drained by a ditch (see Other Protection/Management Actions section).
Water Quality
In general, groundwater from the regional aquifer is suitable for most uses. Water derived from the Verde Formation may exceed the drinking water standards for dissolved solids, sulfate, and some minor elements (Owen-Joyce and Bell, 1983). The Arizona Department of Environmental Quality (ADEQ) has assessed 780 miles of stream reaches in the Verde Basin. Of this total, only 71 miles met or exceeded state water quality standards, and 675 miles were in partial attainment of state standards. The most widespread water quality problem in the basin is elevated sediment/turbidity levels attributed to erosion occurring on lands impacted by grazing, recreation, construction, agriculture, hydrologic/habitat modification, mining, urban runoff, and land disposal (ADEQ, 1988).
A recent biological assessment of the Verde River was made by ADEQ. This assessment used aquatic macroinvertebrates as biological indicators of water quality (ADEQ, 1990). Three sites along the Verde River, one near its headwaters at Paulden, another at Clarkdale, and the third at Beasley Flat, were chosen for study of the effects of non-point source pollution (cattle grazing, irrigation, urban runoff) and point source pollution (sand and gravel mining) on the macroinvertebrate populations.
These sites were sampled during the spring (April) and summer (July) of 1990. A loss of sensitive organisms was seen at Beasley Flat, the site farthest downstream from the reference site at Paulden, which most likely received the greatest quantity of non-point source pollution (ADEQ, 1990). The Arizona Biological Integrity Grading System grade was determined for Clarkdale and Beasley Flat as they compared to the control site at Paulden for both spring and summer flows. A grading system of A to C is used in which A represents sites with least degradation with regard to water quality. The grade of A was determined for Clarkdale during spring and summer and for Beasley Flat during the spring. A grade of B was determined for Beasley Flat during the summer. This investigation concluded that the surface water biological condition at Clarkdale was non-impaired, while at Beasley Flat it was moderately impaired during the summer (ADEQ, 1990).
In addition to this study, information from a Non-Point Discharge Elimination System (NPDES) Compliance Evaluation Inspection Report to the Phelps Dodge Corporation, revealed contamination of the Verde River from a seep 200 to 300 yards (183 to 274 m) away from their tailings disposal ponds. Examination of samples of this contamination in 1989 found concentrations of sulfate (from ore mined at the United Verde Mine) of 20,500mg/L and 25,000mg/L. Magnesium concentrations were found to be 300 times greater than that found upstream of the seeps in the Verde River. Discharges from inactive mine tunnels, tailings, and dumps also cause impacts to the Bitter Creek watershed (Averitt et al, 1990).
The Town of Clarkdale discharges its wastewater from its treatment plant onto the Phelps Dodge tailings for both effluent disposal and dust control. "Oxidation of sulfide minerals in the presence of aerated water causes the formation of sulfate and hydrogen irons. This causes acidification of the water and increases its ability to leach metals. This acidification would serve to dissolve the Verde limestone facie under the tailings and promote subsurface transport of water around Peck's Lake and the tailings area (Averitt et al, 1990).
The development and operation of the Camp Verde Sewer System has contributed to the reduction of seepage of the Town of Camp Verde's effluent into the water course. As other communities within the Verde watershed bring their sewer systems on line within the coming years, a further reduction of effluent seepage into the water course will occur (USDA FS, 1990).
The existing rock product mining within the floodplain of the Verde River Corridor is suspectedto be a cause of increased siltation of the waters of the Verde River. The Prescott National Forest is currently exploring the opportunities for and the feasibility of extracting rock products from lands other than those in the Verde River, especially upstream of the Verde Wild & Scenic River Area. This movement of activity out of the flood channel should reduce siltation, improve water quality, and improve riparian vegetation (USDA FS, 1990).
The Forest Service manages the entire Verde watershed and undertakes watershed improvement projects where deteriorated soil or hydrological conditions create a threat to water quality and other river values. One of the Verde's major tributaries, Oak Creek, was designated as a Unique Water of Recreational and Ecological Significance in 1985 by the State Water Quality Control Council. This is a protective state designation to maintain high water quality for designated streams.
The Environmental Protection Agency (EPA) has established both primary and secondary national guidelines and regulations for the quality of water provided by public water systems. The Verde River supplies high quality water, low in total dissolved solids, for agricultural water and potable purposes. Because of the desirable attributes of this watershed, a high level of protection and priority is essential (ADEQ, 1989). A good source for information concerning the specific water quality in the Verde River Corridor is the Arizona Department of Environmental Quality.
The U.S. Geological Survey (USGS) collects water quality samples from four gauging stations in the corridor (Table 2). These stations are part of the National Stream Quality Accounting Network (Tangle Creek gauging station) and are sampled on a monthly basis. The purpose of the USGS stations are to monitor changes in the watershed. The maximum flows usually occur in the spring and winter months. The minimum flows are recorded during the dry summer months.
Table 2. USGS Gauge Records for the Verde River (USDA FS, 1982)Station Year Maximum cfs Minimum cfs Average cfs Paulden 1963 to 1982 8,080 15 35.7 Clarkdale 1915 to 1921 50,600 55 187 and 1965 to 1982 bel. Camp Verde 1971 to 1982 41,000 13 378 Tangle Creek 1945 to 1982 91,400 61 489
Floodplains
Floodplains are the alluvial lands adjacent to a river which periodically experience flooding. Floodplains in the river corridor are comprised of the floodway, floodway fringe, and those areas encompassing expected 100- and 500-year floods. A 100-year flood is an event which is expected to be equalled or exceeded once on the average during any 100-year period. Similarly, a 500-year flood is expected to occur once in any 500- year period. These findings are based on standard hydrologic and hydraulic study methods. These flood events have been selected by the Federal Emergency Management Agency (FEMA) as having special significance for floodplain management and for establishing insurance rates (Averitt et al., 1990). However, a 100-year flood could occur several times in one year given the right circumstances.
According to the FEMA definition, the floodway includes the channel of the river plus any additional land areas that must be kept free of encroachment in order that the 100-year flood waters may be carried without substantial increases in flood heights. Encroachment such as artificial fill would reduce the flood-carrying capacity of the river, increase its flood heights and increase the flood hazards in areas beyond the encroachment itself (Averitt et al., 1990).
The floodway fringe includes the area between the floodway and the boundary of the 100- year flood. Minimum standards set by FEMA limit increases in flood heights (due to encroachment) to one foot (0.30m), provided that hazardous velocities are not produced. In the case of the Verde River, however, hazardous velocities would be expected to occur with excessive encroachment. Therefore, it was necessary to limit the specified water- surface elevation increases to less than one foot (0.30m). The floodway fringe is essentially that portion of the floodplain that could be completely obstructed without increasing the water surface elevation of the 100-year flood more than one foot (0.30m) at any point (Averitt et al., 1990).
Floodplains (Figure 5) are an important consideration in any river corridor planning endeavor. These natural systems are necessary for overflow during flooding, and help to recharge the river's flows. They contain the upper terraces of a river and support many types of riparian vegetation. Certain types of riparian vegetation, such as cottonwoods and mesquite bosques, have adapted to periodic flooding and require it to stay healthy and regenerate. If the floodplain has been substantially altered to allow for development, the functions of a floodplain may be drastically reduced. Often levees are constructed in the floodplain to protect the development that has been allowed to occur along rivers, further reducing the floodplain's ability to function naturally. Floodplain management entities should consider these natural functions and values of floodplains when determining what actions to take for economic and safety purposes.
Most of the Verde River floodplain areas are undeveloped. The extremely well-delineated river channel and floodplain areas are the likely reason for the lack of past development in these hazardous areas. Historic records of major floods indicate that many of these flows resulted in relatively little damage to property.
Riparian Areas
In 1991, the State of Arizona approved a definition of "riparian areas" as a result of Executive Order 91-6. The definition, developed by the Governor's Riparian Habitat Task Force, defines riparian areas as:
"the aquatic or terrestrial ecosystems that are associated with bodies of water such as streams, lakes, and wetlands, or are dependent on the existence of perennial or ephemeral surface or subsurface water drainage."
The Task Force also approved a set of minimum measurements that further define riparian areas and assist in data collection. The final report details to various state agencies specific tasks regarding riparian inventory, planning, management, and legislation.
Riparian vegetation has never been very abundant in Arizona. Figures vary, but riparian habitat historically comprised approximately three percent of the 68,801,036 acres which make up Arizona (Ohmart, 1982). Presently, only 101,793 acres of the native cottonwood-willow forests and mesquite bosques remain comprising 0.15 percent of the total acreage of Arizona (USDI FWS, 1989). Cottonwood-willow forest communities are the rarest forest communities in North America and mesquite bosques are listed as the fourth rarest (TANC, 1987).
It has been estimated that Arizona has lost or has had altered from 90 to 95 percent of its native riparian areas along the state's major desert streams, such as the Colorado, Gila, Santa Cruz, and lower Salt Rivers (USDI FWS, 1989; SCORP, 1989a). As those figures indicate, desert riparian areas are very limited in Arizona and the remaining areas are of extreme importance to the continued maintenance of fish and wildlife resources.
The riparian vegetation along the Verde River is still in a relatively natural state. The magnificent stands of cottonwood-willow riparian gallery forest, located in the heart of the Verde Valley, are considered globally endangered communities, which means they are found in fewer than twenty places in the world. Only five extensive stands of this rare forest type remain in Arizona; one is the riparian forest along the Verde River Corridor.
In 1986, a landmark act was initiated for the State of Arizona when the legislature appropriated $2 million to Arizona State Parks Board to acquire riparian areas along the Verde River to protect this threatened ecosystem. The result is the six-mile Verde River Greenway between Clarkdale and Cottonwood that is currently undergoing master planning by the Arizona State Parks Board. Additional wetlands and riparian lands within the Greenway may be protected through the recently passed citizen's initiative, the Arizona Heritage Fund.
Much of the state's mid to high elevation riparian areas are still in pretty good shape, but demands and pressure are increasing at an extreme rate. Many of the Verde's tributaries, such as Oak Creek, Beaver Creek, and West Clear Creek fall into this category. As a critical component of Arizona's desert biosystem, these surface waters deserve special attention by state and local policy makers and by the public at large.
Arizona's riparian areas are frequently referred to "those as thin ribbons of green along watercourses." Interior riparian deciduous forests are a diverse community made up of winter deciduous trees. The distribution of these relict forests reflects a contraction of the formerly widespread community of Early Tertiary mixed mesophytic forest, which require a moderate quantity of water. Throughout the second half of the Tertiary period, dry climates expanded over southwestern North America, with corresponding retreats of moisture-dependent forests. These riparian forests have retreated to moist pockets where the warm temperate (ancient) climate persists (Minckley and Brown, 1982).
Fremont Cottonwood (Populus fremontii) and Goodding Willow (Salix gooddingii) are the most frequent native trees along the riparian corridor. These trees are typically found and reach their best development in the alluvial sands, clays, and gravel of the floodplains. Cottonwood-willow associations are believed to be maintained and dependent upon periodic spring floods. They are mainly disseminated by seeds which depend upon receding flood waters to provide a suitable environment for germination (Minckley and Brown, 1982).
Salt cedar (Tamarix pentandra), naturalized from Eurasia, is another common tree along the river corridor. It has invaded many riparian zones in Arizona. Salt cedar has a longer period of seed production (March through October) than either the cottonwood or the willow and many colonize seed beds similar to those used by native trees. Summer flooding may actually enhance this species. Salt cedar can continue to germinate during this time, while summer runoff is of little importance to the regeneration of cottonwoods or willows (Minckley and Brown,1982).
In his study of the riparian habitats along the Verde River, Brock (1987) found several additional trees growing along the stretch of river from Tapco to Bridgeport. Arizona walnut (Juglans major), netleaf hackberry (Celtis reticulata), box elder (Acer negundo), velvet mesquite (Prosopis velutina), desert willow (Chilopsis linearis), and Tree of Heaven (Ailanthus altissima) occurred, but with less frequency than the cottonwood, willow, or salt cedar.
Tree of Heaven, another introduced species, has become widespread in some areas. There is a large stand of this species along the river, west of Dead Horse Ranch State Park. Tree of Heaven produces numerous vegetative shoots from underground tissues and grows rapidly. Brock's study of the riparian area between Tapco to Bridgeport found that Tree of Heaven had the highest relative density values (the ratio of individuals of a species to total individuals of all species) of any tree (Brock, 1987).
The tallest trees encountered along the Verde River, were a "park-like stand of mature Fremont cottonwood trees at the Tapco site" (Brock, 1987, p. 58). Near the mill tailings (within the Greenway) was the site with the greatest average canopy cover, 149 percent, indicating overlap in tree canopy cover (Brock, 1987).
In the riparian habitat along the Verde River, shrubs form a minor component. The most common shrub was seep willow (Baccharris salicifolia). A prevalent species along the quieter bends of the river is the cattail (Typha sp.). The herbaceous layer was dominated by grasses with a few herbaceous broadleaf plants (Brock, 1987). Bermuda grass (Cynodon dactylon), sweet clover (Melitolus sp.) and cocklebur (Xanthium saccharatum), a common weed of cultivated fields, were among the plants observed at one site along the river, growing in wet, alluvial soil. These are all non-native plants, originating outside of North America and introduced to the region.
Peck's Lake and Tavasci Marsh possess some emergent vegetation such as cattails and bulrush (Scirpus sp.) which grow along the edges of the water bodies and many extend several meters from the edge of the shore into the water. Numerous small, semi- aquatic plants typically form understories within the marsh communities along the banks of the Verde River (Minckley and Brown, 1982).
Southeast of Tuzigoot National Monument, there is a large mesquite grove. Mesquite bosques (an Hispanic term for small forests) were numerous in Arizona a century ago, before the rivers were dammed and the groundwater was pumped. Their diminishing numbers can be attributed to the aggressive clearing off the land for agriculture, pasture land, timber, and fuel.
The riparian zone near the headwaters is characterized by a shrub community dominated by seep willow. Velvet ash, Goodding willow, Arizona ash, Arizona walnut, Utah juniper, velvet mesquite, salt cedar, and desert willow are the dominant trees. Downstream, Utah juniper becomes scarce and Fremont cottonwood and Arizona sycamore become more common.
Dead Horse Ranch State Park and the Verde River Greenway, located near Cottonwood, support the largest contiguous stand of mature cottonwood trees on the Verde River. The vegetation changes downstream from Camp Verde and on toward Beasley Flat with younger trees and annual grasses dominating. There are large bosques of velvet mesquite with occasional large sycamore and cottonwood trees.
Benefits of Riparian Areas
Riparian systems are an indicator of the health of a watershed. The Verde River's riparian areas benefit the animal and human residents of the Verde Valley in a number of ways. Riparian areas provide several valuable functions and services which are provided free of charge by Mother Nature. We do not have the technology to replace many of these functions, or, if we do, the replacement costs are very high.
Riparian habitat along the Verde River has a critical role in providing habitat for fish species. The trees help shade part of the river, which keeps water temperatures reduced and helps the water hold more oxygen so the fish can breathe. This shade is especially important in the summer months when the flows in the Verde are at their lowest and a rise in water temperatures occurs easily when the the water volume is low. Overhanging and bank vegetation, plus tree limbs and trunks which fall in the river, provide places for small fish to hide from larger fish. Other benefits include:
- Riparian areas provide homes for one of the largest assemblages of wildlife species in the United States, including several threatened and endangered and rare species.
- Riparian areas form natural floodways that convey floodwaters from upstream to downstream points. Riparian vegetation is adapted to the changing or dynamic flows of a stream. It is an indicator of where past floods have occurred.
- Riparian areas store water during high flows and slowly release this water to downstream areas, which lowers flood peak flows.
- Riparian areas reduce flood flows and the speed of flowing water, which in turn, reduces erosion and cause floodwaters to reduce the quantity of sediment they may be carrying.
- Riparian areas are an important source of ground and surface water, especially with the urban growth in the Verde Valley and its threatened surface and groundwater supplies.
- Riparian areas contribute significantly to the improvement of water quality by removing excess nutrients and other contaminants.
- Riparian areas are of archaeological and historical interest. Former settlements such as Tuzigoot and the significance of the City of Cottonwood's name are two examples.
- Riparian areas provide educational opportunities for scientific studies and nature observation.
- Riparian areas serve as recreation sites for fishing, hunting, picnicking, camping, hiking, horseback riding, and observing wildlife.
- Riparian areas are areas of great diversity and beauty and provide open space for recreational and visual enjoyment.
Both quality and quantity of water for riparian habitats are being threatened in the corridor. Contamination from solid waste dumping and the non-point pollution of the Verde River from the tailings ponds adjacent to Tuzigoot National Monument are a major concern. Air pollution was such a problem earlier in this century that vegetation growth was actually found to have been limited (Averitt et al., 1990).
Human encroachment has also disturbed the riparian areas through industrial use, farming, recreation, and settlement in the areas most valuable to wildlife. Day recreation use alone, by users such as anglers and water enthusiasts, has left much of the soil adjacent to the river barren of vegetation affecting wildlife habitats. Unrestricted road use on both sides of the Verde River has also caused disturbances and areas of rutted, muddy roads (Averitt et al., 1990).
The rapid urbanization of the state has resulted in increased demands on the Verde River watershed. The aquatic and riparian environments are facing degradation due to detrimental management practices from urban construction, mining operations, and livestock grazing, and from uncontrolled recreation activities. The resulting soil erosion, sedimentation, and turbidity increase water pollution. As these industries and the regulatory agencies work toward solutions, it is hoped that the situation will improve.
Wildlife
Wetlands and riparian areas typically have high densities and great diversity of wildlife. The Arizona Game & Fish Department (AGFD) has designated the habitat of the Verde River a "Wildlife Resource Category 1." Habitats in this category are "of the highest value to Arizona wildlife species, and are unique and/or irreplaceable on a statewide or eco-region basis" (AGFD, 1991). The presence or suspected presence of 30 threatened, endangered, or special interest wildlife species is sufficient to support the unique status of the upper Verde. The wildlife habitat value of the Verde River results in significant economic, recreational, and aesthetic value.
The riparian habitats in the Verde River Corridor are a major resource for supporting life in the area. The riparian community and the river itself provide niches for over 60 percent of the vertebrates that inhabit the land surrounding the Verde River Corridor. For example, 255 of the 383 vertebrates known to exist on the Prescott National Forest can be found along the river and its immediate environs. Many of these animals reproduce and complete their entire life cycles in the same community. Others use the river for reproduction or feeding. Still others use the unique riparian zone as a highway for travel from summer to winter areas (USDA FS, 1982).
The riparian habitats along the Verde River constitute an important resource for raptors, songbirds, small mammals, reptiles, and amphibians. Over 200 different species of birds make their homes in the Verde Valley (USDA FS, 1989). The river corridor is well known as a migratory nesting area for hundreds of waterfowl.
The cottonwood/willow, sycamore, and other riparian habitats are especially valuable for the maintenance of the common black hawk, zone-tailed hawk, Cooper's hawk, osprey, bald eagle, and other birds of prey. In addition, riparian dependent songbirds such as yellow-billed cuckoo, vermilion flycatcher, willow flycatcher, black phoebe, Bell's vireo, yellow warbler, and summer tanager, all benefit from the well-structured riparian habitats which currently exist along the upper Verde River system. At least 50 percent of the bird species that nest in the cottonwood trees of the Verde Valley are exclusively dependent on this riparian habitat.
There are many waterfowl and shorebirds that also rely on the Verde River Corridor for their survival including belted kingfisher, snipe, sandpiper, common merganser, great blue heron, green heron, Canada goose, common loon, teal, mallard, and many other species of ducks.
The riparian and aquatic habitats support many amphibians and reptiles, such as Woodhouse's toad, Arizona toad, lowland leopard frog, canyon tree frog, Mexican garter snake, black-necked garter snake, wandering garter snake, narrow-headed garter snake, Clark's spiny lizard, tree lizard, Arizona alligator lizard, California kingsnake, Sonoran mountain kingsnake, and Sonoran mud turtle. The non-native soft-shelled turtle is also found in the Verde River.
The Verde River is an excellent place to observe wildlife. There are many wildlife species present that are found only near water and riparian areas, such beaver, raccoon, muskrat, and river otter. Most other native desert and woodland species gravitate to the river for water, food, shelter, or travel routes. Some of the mammals one can expect to see include: mule deer, white-tailed deer, javelina, an occasional bighorn sheep in the lower stretches, black bear, bobcat, mountain lion, coyote, grey fox, ringtail cat, three species of skunks, Arizona gray squirrel, and a host of bats, mice, pocket gophers, chipmunks, and wood rats.
Fish
The Verde River is rare among streams and rivers of Arizona in that it still maintains a strong native fish community in its headwaters (USDI FWS, 1989). In Arizona, only Aravaipa Canyon is known to sustain more species of native fish. It has high value for the existing native fish community and for recovery of fish listed as threatened or endangered or which are candidates for Federal listing.
The six native species present are longfin dace, desert (or Gila Mountain) sucker, Sonora (or Gila) sucker, roundtail chub, speckled dace, and the federally listed threatened spikedace. Introduced species such as red shiner, mosquitofish, yellow bullhead, carp, channel catfish, trout, and smallmouth bass are present. There are 25 species of fish known or suspected to occur in the river. Of these, 14 are big enough to be caught on a hook and line (USDA FS, 1989).
In the headwaters, native species dominate most habitats with the exception of the backwaters. Below Perkinsville, the dominance of native species begins to decline and by Tapco the non-native fish predominate. Spikedace are essentially absent below Sycamore Creek and speckled dace, longfin dace, and roundtail chub become scarce below the upper end of the Verde Valley.
Flathead catfish are presently replacing channel catfish in the Verde River. In other southwestern rivers, the red shiner appears to be replacing native minnows, including the spikedace, within a relatively short time frame after the shiner's introduction to the area. Although the red shiner became established in the upper Verde River in the mid-1950s, the spikedace still exists and appears able to maintain a coexistence with the shiner in the area.
The AGFD is beginning to stock the middle Verde River with trout in the winter months. The headwaters of the East Verde River are maintained as a put-and-take trout fishery with rainbow trout being the most common, but with brook trout also present.
Sensitive Species
Most Southwestern riparian areas harbor a large percentage of sensitive species, a testament to the important role these wet areas play in supporting fish and wildlife species. These areas must not be only maintained, they must be maintained in a healthy state. Of recent concern to many Southwestern biologists are the disturbing reports that many species of frogs, both common and uncommon, are rapidly disappearing from rivers and streams. Amphibians are the "miner's canaries" of the natural world. Because amphibian skins are more permeable than our own, toxins in the air and water can effect whole populations (TNC, 1991). The cause of decline is not yet known, but monitoring water and air quality is a top priority.
Table 3 lists 46 sensitive plant and animal species that are known to exist along the Verde River and its tributaries. It should not be considered a complete list of sensitive species. There needs to be additional survey work for sensitive plant and animal species. The list does show, however, that the Verde and its riparian lands are critical to the survival of many rare and threatened species.
Table 3. VERDE RIVER SENSITIVE SPECIES LIST
Federal State Common Name Scientific Name Status Status Comments FISH Spikedace Meda fulgida LT/FS ST Proposed Critical Habitat: Verde River from Sullivan Dam to below Sycamore Creek Colorado squawfish Ptychocheilus lucius LE/FS SE Reintroduced from Perkinsville to Childs/experimental population Gila trout Oncorhynchus gilae LE/FS SE Exists in Gap Creek/Verde tributary Woundfin Plagopterus argentissimus LE/FS SE Extirpated/planned reintroduction in lower Verde Razorback sucker Xyrauchen texanus PC1/FS SE Reintroduced from Paulden to Childs-experimental population/Fed listing pending Roundtail chub Gila robusta PC2/FS ST Native fish species Loach minnow Tiaroga cobitus LT ST Extirpated in Verde/possible reintroduction Longfin dace Agosia chrysogaster Native fish species Desert sucker Panoswas clarki Native fish species Sonora sucker Catostomus insignis Native fish species Speckled dace Rhinichthys osculus FS Native fish species BIRDS Bald eagle Haliaeetus leucocephalus LE/FS SE Verde is essential habitat for nesting and wintering for bald eagles Peregrine falcon Falco peregrinus LE/FS SC Southwest (willow) flycatcher Empidonax trailii SE Osprey Pandion haliaetus FS ST Verde is foraging area for osprey Yellow-billed cuckoo (West.) Coccyzus americanus FS ST Common black hawk Buteogallus anthracinus FS SC Belted kingfisher Ceryle alcyon FS SC Zone-tailed hawk Buteo albonotatus FS Black-crowned night heron Nycticorax nycticorax FS MAMMALS Red bat Lasiurus borealis FS SC Camp Verde cotton rat Sigmodon arizonae arizonae SX Considered extinct, last known from 1935 River otter Lutra canadensis sonorae FC/FS SE Louisiana subspecies reintroduced in 1983- 85-L. canadensis lataxina REPTILES & AMPHIBIANS Yavapai (low.) leopard frog Rana yavapaiensis FC SC R. pipiens also occurs on tributaries Arizona Southwestern toad Bufo microscaphus FC2 Mexican garter snake Thamnophis eques FC2 SC Narrow-headed garter snake Thamnophis rufipunctatus FC2 SC Arizona rnountain kingsnake Lampropeltis pyromelana FS Gila monster Helodertm suspectum FS Desert tortoise Gopherus agassizii orxerbates FS PLANTS Arizona cliffrose Cowania (=Purshia) subintegra LE/FS Arizona agave Agave arizonica LE/FS AZ-P Agave toumeyana v. bella FC3 Amsonia palmeri FC3 Erigeron lobatus FC3 Pringle fleabane Erigeron anachna FC2/FS Pectis rusbyi FC3 Echeveria collomae FS Echeveria orpentii FS Astrolagus lentiginous mariapae FC3 Fraxinus anomala var. lowellii FC3 Ripley wild buckwheat Eriogonun ripleyi FC2/FS Apache wild buckwheat Eriogonun capillare FC2/FS Arizona bugbane Cimicifuga arizonica FC1/FS Found in tributaries/Oak Creek Graptopetalurusbyi FC3 Salvia dorrii var.mearnsii FC3/FS Federal Status: LE=listed endangered; LT=listed threatened; PC or FC=candidate; FS=Forest Service Sensitive Species State Status: SE=endangered; ST=threatened; SC=candidate; SX=extinct in AZ; AZ-P=state protected plant
Three wildlife species listed under the Federal Endangered Species Act of 1973, as amended, presently occur near or in the Verde River. The bald eagle and peregrine falcon, both designated endangered species, nest on the cliffs and trees along the river, and the spikedace, a threatened native fish species, lives in the upper Verde River. The Verde River from Sullivan Dam downstream to just below the mouth of Sycamore Canyon has been proposed as Critical Habitat for the spikedace. Another federally listed fish species, the Gila trout, lives in Gap Creek, a Verde tributary. There are also several other rare fish species that are being reintroduced into the Verde as experimental populations. Two endangered plant species, Arizona cliffrose and Arizona agave, occur along the corridor.
The AGFD maintains a list of Threatened Native Wildlife which recognizes four categories of species: extinct, endangered, threatened, and candidate. There are sixteen species on this state list which occur naturally along the Verde River (four additional listed species are reintroductions). Of the species found along the Verde River Corridor, the bald eagle, Southwestern river otter, Gila trout, and willow flycatcher are listed by AGFD as endangered, the spikedace, roundtail chub, osprey, and yellow-billed cuckoo are listed as threatened, and the common black hawk, peregrine falcon, belted kingfisher, Mexican garter snake, narrow-headed garter snake, lowland leopard frog, and red bat are listed as candidates. The Camp Verde cotton rat is listed by the state as extinct. It has not been seen in its only known locality near Camp Verde since 1932.
Several state and federally listed fish species thought to occur historically in the Verde River are now being reintroduced. The razorback sucker is an Arizona endangered species and a federal proposed species and has been reintroduced throughout the upper Verde River from Paulden to Childs. The Colorado squawfish, an endangered species on both the Federal and state lists, has been reintroduced into the Verde as an experimental population in the area from Perkinsville to Childs. Other extirpated fish species, the woundfin and loach minnow, are being studied for reintroduction in the lower and upper Verde River, respectively.
It is not known for certain whether the southwestern river otter, an Arizona endangered species, still exists in the upper Verde River, but it probably has been extirpated (no longer occurs in that locale). However, from 1983 to 1985 a similar but non-native subspecies, the Louisiana river otter, was introduced into the Verde and has survived and reproduced. Many landowners and recreationists have reported sightings of these agile, endearing acrobats of the river.
Five bald eagle nesting territories are known to exist on the Verde River above Horseshoe Dam. Immature and wintering bald eagles also frequent the area. The entire Verde River and one-quarter mile on both sides has been identified as essential habitat for bald eagles. The bald eagle is listed as an endangered species on both the state and federal lists. Bald eagles nesting north of Arizona use the river for wintering, and a local population of bald eagles use it for nesting and rearing young during the spring and summer.
Historically, there were several species known to depend on the riparian and aquatic habitats of the Verde, but are now believed to be extirpated (except for the experimental populations), including the Colorado squawfish, loach minnow, woundfin, and razorback sucker. Tavasci Marsh reportedly supported many wetland bird species such as the wood stork, Virginia rail, and sora rail. With proper management, it is hoped that many of these species can continue to be returned to their historic habitats (see Other Protection/Management Actions section). Coordination is in progress between the FS and AGFD on the reintroduction and/or maintenance of viable razorback sucker, river otter, woundfin, loach minnow, squawfish, and spikedace populations (USDA FS, 1990).
