BIG BEND The Impact of Human Use Upon the Chisos Basin and Adjacent Lands NPS Scientific Monograph No. 4

Chisos Remuda concession

The total impact of the Chisos Remuda Concession upon the vegetation is difficult to assess because of the many factors influenced by its operation. One complex aspect was presented in the previous section with respect to the use of horses on trails. Ecologically, the impact is twofold, the effects upon the vegetation by the maintenance of an unnaturally large population of horses in an unusually small environment, and the effects of the horses in performing their services.

The first aspect has many biological implications which must be understood by the management if destruction of the landscape is to be avoided. Because much energy is needed by the horses in performing the service, they require much food. In turn, the side effects of biological refuse in the form of fecal material and urine are great and must be strictly managed if the surrounding environment is not to be affected. Unmanaged refuse amounts to pollution-enrichment of the environment above natural levels by organic and inorganic substances.

Direct evidence of mismanagement of these biological aspects can be readily observed. indicating that concession management has not confronted the problem. Besides the original removal of the vegetation for establishing the concern, the operation has continued to denude the entire flat and western slope of native vegetation. The area is not bare, but is dominated by unnaturally large, introduced populations of Sorghum halpense, Solanum elaeagnifolium, and Setaria macrostachya, none of which is of any importance in the basin under natural conditions. It is by far one of the most unnatural stands of vegetation in the basin. Dissecting the vegetation near the southwest corner of the corral is a large erosional path along which large quantities of feed, manure, and baling wire occur, waiting to be washed to the ravine below. Nearby are the only remnants of the natural vegetation, Pinus cembroides, Quercus spp., and Rhus virens. Under the dense cover of Solanum elaeagnifolium and Sorghum halpense, Rivina humilis (blood berry) is extremely more common than normal, perhaps due to the increased organic material. At the northwest corner of the corral, an extensive rubbish heap composed of feed, manure, hoof trimmings, and baling wire is washing down the slope to the trail below. In order to determine the immediate extent of the Remuda, the ravine below was followed to near its junction with the Pulliam Ridge drainage. Along the upper third of its course, large dams of manure and feed were found accompanied by clones of Sorghum halpense. As a control area, the ravine to the southwest was traversed and no Sorghum halpense nor manure or feed were found.

The second aspect of the concession's impact, that of supplying horses for visitor use, relates to trail effects. A biological condition which contributes to impact is the excessive amount of manure and urine which are distributed throughout the basin. The exact effect of these materials is not known, but if the horse service continues, a study should be initiated to determine it. The effect is not always an increased growth of the fertilized vegetation, but may be a decreased growth and/or burning under conditions of overfertilization. The well-known fact that many viable seeds are distributed by fecal matter accounts for the extensive clones of Sorghum halpense that appear as one gets progressively closer to the Chisos Remuda and to the tie rack near the Window Pouroff. The odor, large populations of flies, and organically enriched dust, with which the hiker must contend, can all be traced to the extensive impact of the horses. Certainly the effect is not confined to this trail section, but occurs along all trails in the Chisos Basin.

Another form of impact that is due indirectly to the horse is the disregard of the trail bosses for park trail regulations. Special reference is made to their disregard of switchbacks and their encouragement of short-cuts through the native vegetation. Interestingly, this takes place most frequently within view of concession management. The vegetation along the series of switchbacks above the Remuda toward the Upper Basin is much abused and is becoming extremely unnatural in terms of species composition and erosion.

In an attempt to quantify the effect of horses upon natural vegetation, an extensive study was conducted on the southern end of Juniper Flat. This area of the flat is used as a short rest site for horseback riders. On two occasions while I was sampling, riders passed through, with one group of approximately 15 stopping for several minutes to break rank for photographing and smoking. The horses scattered over the flat, some grazing the marginal Stipa tenuissima and others, the shorter Bouteloua hirsuta.

A 200 ft long transect, subdivided into 10-ft sections, spanned from the S. tenuissima-Juniperus deppeana-dominated southeast end to the northwest end dominated by Bouteloua curtipendula-Acacia biuncifera. Figure 5 presents a summary of the vegetation and soil factors. The IP's of two adjacent quadrants were averaged in order to smooth and reduce the number of points. The soils were collected at the end and center of the transect.

Other species common at the more xeric northwest end (southeast exposure) are Agave scabra, Nolina erumpens, Aristida divaricata (poverty threeawn), Bothriochloa barbinodis, and Setaria macrostachya. The latter two are common in disturbed areas and around the Chisos Remuda. The more mesic end (northwest exposure) are Pinus cembroides and Muhlenbergia emersleyi at lower importance.

Two soil factors used in this study, but not at other sites, are water infiltration and bulk density. Infiltration was determined by obtaining the time required for 33 cc of water to penetrate the soil. The water was poured into a cylinder 2-3/8 inches in diameter which had been carefully pushed into the soil to a one-half inch depth. A stopwatch was used to record the time for water disappearance for 10 trials at each of the three points along the transect. Bulk density was determined by measuring the volume of soil removed from five small holes, approximately 2 inches in diameter and 1.5 inches deep. The excavated soil was oven-dried, weighed, and weight divided by the measured volume. The volume was determined by pouring measured quantities of sand from a graduated cylinder into the small holes. Both water penetration and the amount of soil per unit volume are functions of soil compaction.

The data on the physical properties of the soil indicate that the center of the flat has less rock and higher infiltration times and bulk density. The latter two factors point to greater soil compaction. The chemical factors reflect the amount of vegetation cover, the lowest values on the center of the flat, and the higher values on the southeast end. Further soil infiltration data were taken on an isolated group of clones of Stipa tenuissima near the center of the flat and compared with adjacent bare soil within a 3-ft radius of the group. The 10 values for the protected soil between the clones averaged 33.4 seconds, while that from the bare soil averaged 84.9 seconds.

The results of the study indicate that the present bare portion of the flat dominated by Bouteloua hirsuta and Perezia nana (desertholly perezia) is not due to inherent chemical or textural soil qualities, but to physical compaction and removal of the natural vegetation. Compaction of the soil and removal of vegetation create a condition favoring the xerically adapted plants. Another aspect indicating the tendency for growth and reproduction of the natural vegetation is a tree census of the flat. In Table 13 the number of trees and seedlings occurring in the Stipa tenuissima-dominated portion of the flat is compared with a portion of the flat dominated by B. hirsuta. Since the slopes surrounding the flat were not censused, the B. hirsuta area was approximately half the Stipa tenuissima area. Conditions seem favorable for reproduction of four species in the more heavily vegetated area and for only one in the impacted portion.

Fig. 5. Importance Percentage values for Juniper Flat vegetation with respective soil data.

Table 13. Tree and seedling census of Juniper Flat comparing presently grazed and ungrazed portions.

National Park Concessions, Inc.

Initially, this operation had effects on the basin by the removal of the natural vegetation in order to provide space for visitor and personnel housing. After the original removal, the area has remained under constant use and impact, thus providing little opportunity for the remaining vegetation to maintain itself through growth and reproduction. Because of the need to provide an aesthetically pleasing landscape, exotic and other introduced species have been planted. The operation has affected the vegetation indirectly by making great demands upon the water and sewage facilities.

The operation's major effect upon vegetation has been through its gradual encroachment upon the woodland. Unfortunately, the operation is located at the woodland's more critical lower limit which is the area most sensitive to use. The impact has resulted in nearly complete denuding of the woodland area to provide space for the more than 20 buildings which form the complex. These permanent structures and their extensive accesses have contributed significantly to the alteration of natural drainage patterns. Examples can be seen around the lodge, motel, store, and service station. The drainage has been altered to the extent that culverts have been installed to divert lodge drive, motel parking, and personnel quarters' water to the Upper Basin entrance road margin. However, the water is not being directed to its final natural course, which would be the ravine behind the service station and to the area southwest. Even more detrimental to the vegetation are the numerous curbs and walks which prevent even the unnatural flows to assist growth, leaving downfall as the only moisture source.

In conjunction with the decreased moisture from rainfall is the constant impact of man's walking, leaving compacted and denuded sites which are less effective in absorbing rainfall and supporting vegetation. The final results are increased erosion, bare areas, and increased numbers of xerically adapted exotics or introductions. A related factor, the human preference for taking the shortest distance, is overlooked in planning and providing walks which could reduce widespread impact. This is especially evident between the new lodge facility and the store.

The operation, by its unorganized distribution, contributes constantly to the deterioration of the vegetation. This is accomplished either in going from one area to another to perform functions or by damaging the aesthetic qualities of the vegetation in the immediate region, presumably what the operation was established to promote. The latter is questionable when the only replacement plants used in landscaping to alleviate the bareness of removed plants are introduced exotics or plants from the desert. The practice is biologically unsound and wasteful of time and of the introduced species while it also selects against local native species.

An example of introduction is the occurrence of dozens of low elevation, desert cacti inhabiting a man-made planter less than 30 ft from a sheer, badly eroding, desertoid embankment created by construction processes. The cactus, if its pollinators are locally present, could adapt to the new environments and produce offspring, but still would not contribute integrity to the existing local vegetation. The many Yucca thompsoniana (Thompson yucca) and Dasylirion leiophyllum plantings in the lawn of Cynodon dactylon, an exotic around the motel, do not enhance vegetational integrity. The yucca is only native to the desert lowlands and upper slopes of the Dead Horse Mountains in this region. Sotol, however, is common in the lower basin where conditions have been greatly influenced by man's activities, but should it have preference over a pinyon, oak, or juniper removed originally from the site? Because the operation is at the lower limit of the woodland and upper limit of the man-influenced desert, all landscape species should represent the woodland vegetation. Agave scabra, Stipa tenuissima, and Nolina erumpens could lend such integrity for the areas cited above, and there are a number of woodland cacti which could replace the lowland forms presently displayed.

Ranger Station and personnel housing

The Ranger Station and personnel housing facilities required an original denuding to provide space for the structures and accesses to them. Constant human impact around these structures excludes the native vegetation and favors the original denuding process. The impact also encourages the establishment of exotic and introduced species. Both facilities make demands upon water and sewage facilities which indirectly affect the vegetation.

Unfortunately, because of location of the Ranger Station and its accesses, a large area is being affected by human walking, diversion of rainfall, and selected desert plantings. These activities are creating and favoring a xeric condition which is selecting against the natural woodland species, represented here by two struggling Pinus cembroides seedlings and several Agave scabra plants in the mowed Cynodon dactylon lawn. A few other woodland species such as Juniperus pinchoti, Aloysia lycioides, Andropogon gerardi (big bluestem), Bouteloua curtipendula, B. gracilis, and Viguiera stenoloba are behind the station. An incomplete list of the introduced, disturbed area and exotic introductions include Cenchrus incertus, Eragrostis barrelieri, Tribulus terrestris, Alternanthera peploides, Conyza canadensis (horsetail conyza), Setaria macrostachya, Leptochloa dubia (green sprangletop), Xanthocephalum microcephalum, Euphorbia strictospora (slimseed euphorbia), Panicum obtusum and others of a more lowland or desert adaptation. A few of these include Aristida glauca, Machaeranthera pinnatifida, Agave lecheguilla, Acacia constricta, and Larrea tridentata, Several listed are common in the more human-influenced lower basin. but much less common in the woodland formation above the upper basin complex.

The present vegetation in the immediate vicinity of the station could only serve in an interpretational program to demonstrate how man, through his activities, can influence his environment, even to its complete change. The unnatural desertoid area to the east and the unusually dense shrub vegetation to the west demonstrate man's influence. Proper planning, alteration of present drainage, and a natural revegetation program could rectify the situation in time. Such a vigorous program would be applicable around the personnel housing facilities as well. Interested personnel occupying the housing facilities could, through observation and attention, aid in an experimental natural vegetation program, which would benefit the entire impact complex.

Campgrounds

The major effects of the campgrounds are in the maintenance of bare or near-bare areas which provide facilities for the requirements of the camper. Since the camper must circulate through the complex to take advantage of the facilities, impact due to walking and vehicles is inevitable. These activities maintain the desired bare areas and create new sites, increasing the denuding-runoff-erosion cycle. Since campers come from many distant locations, foreign disseminules are introduced into the ecosystem, finding among the many microclimates suitable propagation sites. Facilities such as buildings and roads, by their very existence, decrease the natural vegetation and also increase demands upon water and sewage which have an effect upon the vegetation.

The main campground, the site of major impact. is fortunately confined to a single ridge between two heavily vegetated ravines which restrict approach and impact on the surrounding area. The campground has not altered the natural drainage, but walking and bare areas have increased water runoff into the two ravines. The naturally vegetated areas scattered throughout the campground aid significantly in reducing runoff; however, some natural areas are more densely vegetated because of excess runoff. Runoff and human impact provide great variation in the vegetation.

The main campground provides a variety of campsites, from pleasingly vegetated sites such as 48, 53. 56-59, 62, and 63, to unvegetated sites such as 1-8 and 25. Between these are a range of varying conditions. Isolated between the sites and paved roads are several natural areas such as those between sites 23 and 40, and 15 and 37, which provide pleasing backgrounds. These areas, however, have many unnecessary paths dissecting them which promote erosion and compaction. Large quantities of camping debris litter the areas, impairing vegetation growth and detracting from the aesthetic quality of the natural areas. Landscaped areas, created by the planting of numerous Cupressus arizonica (Arizona cypress) trees, promote alien introductions which exclude local native species and unnecessarily change the physiognomy of the vegetation.

In order to determine the extent of human impact upon the main campground vegetation, a survey of all vacated sites was conducted and a transect, 451 ft long and 2 ft wide, was sampled for vegetation cover. The transect spanned from the northwest corner of the concrete canopy base at site 5 to the northeast corner of the first or upper comfort station. From the northwest corner of the station, the transect continued to the southeast corner of the second station. The transect was divided into 10-ft segments and the individuals were sampled for cover. Those areas occupied by paved road were also recorded. At first, an attempt was made to record natural versus impacted bare areas; however, this was abandoned because of the frequently uncertain status of the bare areas. Little of the bare area could be considered natural.

The results of the transect are presented in Table 14, Immediately evident is the low percentage of vegetation cover (34%). None of the 18 sites sampled in the basin had coverage as low; even site 13 in the Chihuahuan Desert Formation had 43%. The value would be lower if the comfort stations and concrete base of the canopy had been included in the transect as impact. It is of interest that the native vegetation was only about 60% of the total vegetation cover. The coverage of exotic species is quite high, indicating the role man plays in altering species composition. With the exception of Cynodon dactylon and Sorghum halpense, which can cover large areas, the others are relatively small and must be numerous to provide significant cover. The high coverage of Alternanthera peploides in the transect was around the moist water hydrants where Cynodon dactylon, Echinochloa crusgalli, Bromus unioloides, and Sorghum halpense were also common, It is a natural microclimate for mesically adapted species.

Table 14. Distribution of the cover components of a Main Basin Campground transect.

Of the total of nine exotic species collected in this study, seven were encountered in this transect. This aptly demonstrates the influence that human impact processes can have upon a vegetation, from the introduction of exotics to the creation of suitable propagation sites for these species. Of special interest is the collection of Peganum harmala in the campground. The species was first introduced into the United States in 1938 near Pecos, Tex. (Shinners 1948); by 1955 it was reported near San Antonio, Tex. (Sperry et al. 1963); and now in this study it is reported from the Chisos Basin.

Another aspect pertinent to the ecology of exotic species is the degree to which the vegetation in the southern or upper end of the campground has deteriorated, Normally, in and around clumps of Opuntia spp throughout the southwestern United States, one or several species of native grass clones can be observed, Here, however, it is common to observe Opuntia engelmannii harboring large clones of Sorghum halpense with or without native grass species. These natural, protected "seedbeds" are promoting exotic rather than native species, and much time and effort will be required to control this condition. In the ravine to the west of the campground behind sites 10, 12, and 21, Sorghum halpense and Solanum elaeagnifolium is predominate.

The practice of planting introduced species such as Cupressus arizonica, Carya sp. (hickory), and Yucca torreyi (Spanish dagger) falls into a similar category of impact. Table 15 presents a census of the trees and seedlings in the main campground. Over half of the trees are introduced, and most were planted during the expansion program of 1958-59. Cupressus arizonica, comprising 37% of all trees, is the most frequently introduced species. Another variety of the species occurs naturally in Boot and Juniper canyons higher in the Chisos Mountains, but is not found locally near the campground. Since the distance is not great for wind-pollinated species, genetic crosses and diseases undesirable to the local population could result from the introduced population. The introduced yuccas are not common at high elevations and lend no integrity to the campground vegetation.

The transect lacked tree species, except for the presence of the introduced Prosopis glandulosa, Cynodon dactylon, an exotic, is the most common grass, followed by the local dominant, Bouteloua curtipendula, The most numerous plants in the natural area between the two upper comfort stations were the locally common shrubs Acacia constricta and Aloysia lycioides. The most common herb was Alternanthera peploides, a native of unnatural importance, followed by Xanthocephalum microcephalum and Salsola kali, an exotic. Considerable thought and effort must be given to a policy and program concerning these exotic and introduced species which are rapidly reducing native populations as a result of human activity.

The impact of walking was greatest around the comfort stations where the camper can approach from all directions and over any terrain. The south side of the first station demonstrates this damaging effect. Here, the camper from the upper campsites descends a steep, badly eroding slope. In this area Salsola kali was common, accompanied by Setaria macrostachya and Solanum elaeagnifolium. A similar disturbed and eroding situation occurs around the lower comfort station, especially on its east side. Considerable emphasis must be given to controlling impact around these facilities.

Table 15. Tree and seedling census of the Main Basin Campground.

The microclimate created by water hydrants provides a unique habitat for many species, as previously emphasized, and promotes unusual growth in many native species. Because water frequently stands around the hydrants, the microclimate is a constant site for invasion by aliens. Often aiding the cause of the alien is the extremely compacted soil around the site. Adequate drainage should aid in preventing invasion and continued propagation.

A complete survey of nearly all the individual sites revealed lack of vegetation and increasing erosion to be the common maladies. Sites 1-18 and the sites around the second comfort station demonstrate the greatest need for trees, shrubs, and boulders to control the area. Several additional sites had erosional conditions which need control. Sites 47 and 49-52 were the most critical and badly need site-approach control. The area between sites 39 and 42 is in need of stabilization as well as site 42 itself.

Addition of pinyon, oak, and juniper trees would lend integrity to the vegetation, aid in controlling human walking and privacy in the site, prevent erosion, and promote conditions conducive to other woodland species. Care, however, must be taken with their location in order to prevent scorching, as has happened at site 21.

Since Larrea tridentata is not common in the area and those in the campground are situated on roadbed material from lower elevations, these individuals should be removed to prevent further invasion and seed dispersal. This species is occupying potential woodland species sites and producing large quantities of seeds which can invade the numerous eroded areas. Individuals can be found around sites 23, 49, 43. and 60. Some are also found along the road leading to the group campground and in the Campfire Circle parking area.

Sewage

The effect of sewage upon basin vegetation is twofold in nature: both the raw sewage and the sewage lagoons themselves affect the vegetation. Basically, the control of sewage necessitates the creation of denuded areas to contain the materials. By this action the area remains open to erosion and to constant invasion by disturbed-area species. Because the materials are in an aqueous condition and high in organic matter, rich, moist habitats are provided.

The effect of raw sewage upon the vegetation is very apparent to the southwest of the Trailhead in the Upper Basin below the Ranger Station. Here, a sewer cover provides escape of the raw material onto the natural vegetation. I first became aware of this action in 1964, while observing a large flowering clone of Agave chisoensis (Chisos agave) nearby. At that time the vegetation was dominated by Viguiera stenoloba, Xanthocephalum spp., and Acacia constricta. Since that time the vegetation has become more dense to the southwest where the major flow drains. In the last two years the spillage has greatly increased to the extent that it has killed many Viguiera stenoloba and Xanthocephalum spp., which can be observed in the area. Also the area is difficult to approach because of the increased soil moisture.

The effects of the sewage lagoons are numerous, the most direct being the support of large numbers of adventive desert species, disturbed-area species, and exotics. The most common desert plants collected along the eroding slopes of the lagoons were Erioneuron pulchellum, Baccharis glutinosa (seepwillow baccharis), Machaeranthera pinnatifida, Croton pottsii (leatherweed croton), Porophyllum scoparium (poreleaf), Sphaeralcea angustifolia, Senecio longilobus (threadleaf groundsel), Digitaria californica (Arizona cottontop), and Baileya multiradiata. Also collected or observed along the water margin were the exotics Echinochloa crusgalli, Sorghum halpense, and Tamarix pentandra (tamarisk) or T. gallica (salt-cedar). The tall Tamarix individual was dead and difficult to identify by bark characteristics.

Along the water margin of the eroding banks, Echinochloa crusgalli, Conyza canadensis, Chloris virgata (showy chloris), Digitaria californica, and Setaria macrostachya are dominant. The prostrate Boerhaavia coccinea (scarlet spiderling) contributes significantly to ground cover and erosion control around the upper lagoon. Clematis drummondi (Texas virgins bower) covers extensive areas around the lower lagoon in a similar manner. On the upper, more exposed, eroding slopes, Baccharis glutinosa is most common. A few Salix sp. (willow) are becoming established on the lower lagoon. They were not specifically identified because of their lack of leaves and small size in August. Between the two lagoons a remnant of native vegetation is progressing adequately. It consists of Acacia constricta, A. roemeriana, Aloysia lycioides. Rhus microphylla (littleleaf sumac), Opuntia engelmannii, Diospyrus texana (Texas persimmon), and Bouteloua curtipendula.

Other effects of the lagoons upon the vegetation are the infrequent overflow and seepage through the bank, aiding in the establishment of a variety of species at these sites. Also there are algal blooms which could cause death to wildlife visiting the lagoons. While working around the lagoons, the author observed two white-tailed deer within the fence and one dead deer. The cause of death could not be determined; however, an algal bloom was present at the time. The death could have been due to the animal crashing against the fence attempting to escape, as such behavior was observed on two occasions. It was later reported by Chief Naturalist Roland Wauer that other deer had been found dead within this enclosure. If these deaths continue and the effects are not traced to the sewage or algal blooms, the fence should be removed or heightened as policy dictates. The deaths are not significant in number, but the carrion-oriented food chain could be affected,

Pipelines

Pipelines have had three major ecological effects upon the vegetation. The first is the denuding effect required to lay the line; second, the effect of the disturbance upon the soil and revegetation sequence; and third, the erosion paths which can develop because of vegetation reduction. The revegetation sequence has been important in determining local species dynamics and the time required for revegetation, This topic was discussed at the beginning of this section.

Those lines constructed in the Chisos Basin have had all of the above effects. The most extensive line is the water line laid in 1952 from the Window to the water barrel above the Upper Basin complex. The scar is visible for its entire length due to the altered rock and soil strata and the disturbed-area species dominating the scar. The species present are primarily grasses: Bouteloua curtipendula, Aristida glauca, Heteropogon contortus, and Bothriochloa barbinodis. Infrequently, Bouteloua breviseta and Panicum hallii (Halls panicum) are present. A few herbs and shrubs are beginning to invade the scar: Dasylirion leiophyllum, Mimosa biuncifera, Opuntia engelmannii, Viguiera stenoloba, and Croton pottsii.

Other less extensive lines can be observed in the basin. A short line north of the ranger personnel homes is recent (1962-64) and is dominated by Eragrostis intermedia, a disturbed-area species. No other significant species of invader is found here. In a small. year-old scar below the Ranger Station, a sizeable list of invading species was made including Leptochloa dubia, Bothriochloa barbinodis, Sphaeralcea angustifolia, Setaria macrostachya, Panicum obtusum, Euphorbia strictospora, and Ximenesia encelioides (golden crownbeard).

A heavily impacted pipeline scar at the southwest corner of the main campground presents a situation similar to that of the old road scar previously discussed. In this scar many of the species are of low elevation origin, suggesting desert origin of the lighter-colored, gravelly soil. Species include Larrea tridentata, Erioneuron pulchellum, Polygala scoparioides (broom milkwort), Xanthocephalum sarothrae (broom snakeweed). Machaeranthera pinnatifida, Marrubium vulgare, and Sporobolus cryptandrus. Because of the continued impact of the Window Trail dissecting the scar, these species continue to be promoted. A second heavily impacted and eroding scar lies below the lower portion of the main campground and terminates at the pumphouse below. In this disturbed scar Polygala alba (white milkwort) and Aristida glauca are common. This scar must have immediate attention to prevent irreparable damage to the landscape. In no instance should the soil used in such repair be obtained from lower elevations. Any common local shrubs and soil from the eroding bank opposite the pumphouse could be used in stabilization.

Wells

The effect upon the vegetation of the two wells drilled in the basin is difficult to assess. The first well, drilled in 1934, permitted and supported all the activities in the basin until the present Oak Springs water source replaced it in 1952. Several of the facilities initially supported by this first well are still present and still having effect upon the basin vegetation. No direct evidence of effect upon the vegetation other than the road to the well, the pumphouse, and erosion accompanying both can be cited. The margins of the road are in immediate need of stabilization,

The second well, above the present National Park Concessions warehouse, was drilled and abandoned in 1947. The direct effects are still evident around the denuded, eroding site where concrete abutments persist. Perhaps the greatest effect of this project is the steep trail leading to the well site. This trail needs stabilization or, preferably, complete abandonment with controlled planting.

The effect the wells had upon the basin water table, which would affect the vegetation, is not known. This could have been especially serious during the early drought years, when the only major natural spring, Kibbey Spring, ceased its normal flow. That the spring still has only intermittent flow could be due to the previous history of grazing and use of the spring by the animals.