ABOUT THE COLLECTION

Proceedings of the Hydrology section of the Annual Meeting of the Arizona-Nevada Academy of Science. Full text manuscripts of work presented. Research related to water resources, water management, and hydrologic studies primarily focused regionally on southwestern US.

Digital access to Hydrology and Water Resources in Arizona and the Southwest has been made possible by a collaboration between the Arizona-Nevada Academy of Science and the University of Arizona Libraries.

The collection consists of current and back issues from Volume 1 (1971) - Volume 44 (2015). The content is available both as complete issues, and as individual articles. Content is available open access.

There was no Proceedings published in 2013 due to a joint meeting with AAAS-Pacific Division that did not have a separate Hydrology section. There will similarly be no Proceedings volume published for the 2018 meeting which was co-sponsored by ANAS and the Arizona/Southern Nevada Branch of the American Society for Microbiology. Volumes for 2016 and 2017 Annual Meetings are still in production.


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  • Hydrology and Water Resources in Arizona and the Southwest, Volume 43 (2014)

    Unknown author (Arizona-Nevada Academy of Science, 2014-04-12)
  • EFFECTS OF CLIMATE CHANGE ON LAND USE AND LAND COVER ON THE SAN PEDRO RIVER, ARIZONA

    Klotz, Jason; Tecle, Aregai; Northern Arizona University (Arizona-Nevada Academy of Science, 2014-04-12)
  • RESTORATION BENEFITS TO NATURAL SPRINGS IN THE LAKE MARY WATERSHED

    Nash, Clairisse; Tecle, Aregai; Craig, Ashley; Sanchez-Meador, Andrew; Yocom, Larissa; Northern Arizona University (Arizona-Nevada Academy of Science, 2014-04-12)
  • WATER QUALITY IMPACTS OF FOREST FIRES

    Tecle, Aregai; Neary, Daniel; Northern Arizona University; Rocky Mountain Research Station (Arizona-Nevada Academy of Science, 2014-04-12)
    This paper is concerned with the effects of forest fires on water quality, especially surface water quantity. The topic is important since surface water constitutes the main source of water for most domestic, industrial and commercial uses in the United States. The bulk of the surface water is the product of runoff from precipitation that falls as snow or rain on our forested and rangeland watersheds. In many areas such as the arid and semi-arid Southwest, the vegetation in these watersheds is dry and susceptible to wildfires. Oftentimes, fire in the form of prescribed burning is used to protect these areas from wildfire. However, such fire suppressions have resulted in overcrowded and dense vegetation and the production of abundant fuels in watersheds. Such a situation and the frequently recurring drought and extensive insect infestation have most forest systems susceptible to catastrophic fires that scorched many of the Nation's forests, rangelands, parks and other large-scale real estate properties (Neary et al. 2008, Lutz et al. 2009, Stein et al. 2013). In 2013, there were a total of 9,230 lightening started fires in the United States burning 3,057,566 acres. In the same year, there were 38,349 humancaused fires that burned 1,261,980 acres. This made the total acreage burned by the two types of fires in 2013 to be 4,319,546 acres (National Interagency Fire Center 2014). Such fires accounted for $13.7 billion in total economic losses and $7.9 billion in insured losses from 2000 through 2011 in the United States (Haldane 2013, International Association of Wildland Fire 2013). These burns also have tremendous effects on the characteristics of water-producing watersheds and the quality of the water coming out of them. This paper discusses the effects of wildland fires on water quality and suggests ways of managing fire-prone forested water source areas to prevent their degradation from wildland fires. The paper uses information from recently occurred catastrophic fires in Arizona to demonstrate the effects of wildland fires on water quality.
  • TRACE METAL AND PHOSPHATE PARTITIONING BETWEEN STORMWATER RUNOFF, GROUNDWATER AND SEDIMENTS ADJACENT TO LAKE HAVASU, ARIZONA

    Wilson, Doyle C.; Lake Havasu City Operations Department (Arizona-Nevada Academy of Science, 2014-04-12)
    A baseline study was established to characterize heavy metal, arsenic, selenium, and nutrient levels in stormwater runoff from Lake Havasu City, Arizona. It also lead to investigating the fate of those constituents in lake water, shallow groundwater and surficial sediments at the mouths of five washes draining from the city into Lake Havasu. Composite core and pit sediment samples collected at wash mouths before and during historic low lake water levels, reveal a fairly consistent metal and total phosphate presence at most wash sites. Two sites have generally higher concentrations where clay is a more significant component in the sediment. Regression correlations support that nickel has a strong association with chromium and cobalt in all sample types as well as with barium in runoff and groundwater. Copper and cobalt also show strong affinities with several other transition metals in groundwater and sediments. Reducing conditions prevail within 1-2 inches of the sediment surface at all locations, yet metal concentrations within 1.5 feet of the surface display a spatial change from increasing with depth at northern wash sites to a more variable pattern at southern sites. Phosphate concentration with depth is more variable and may contradict the local metal trends. Metal ion and complex adsorption to mineral and organic surfaces is expected though total organic carbon levels, reflected by the presence of freshly buried vegetation, are highly variable. Black color of sediment cores converts to yellow-brown overnight indicating chemical changes and the subordinate effect of organic matter in the sediment. Wash mouth sediments appear to be a repository for most metals and for total phosphate, though more work is needed to determine the mechanisms involved associating stormwater runoff with chemical and sediment deposition.
  • WATER HARVESTING IN ARID AND SEMI-ARID REGIONS

    Ffolliott, Peter F.; Brooks, Kenneth N.; Neary, Daniel G.; Univ Arizona; Univ Minnesota; USDA Forest Service, Rocky Mountain Research Station (Arizona-Nevada Academy of Science, 2014-04-12)
    Water harvesting, also called rainwater harvesting, is a technique of developing surface water resources to augment the quantity and quality of water available to the people in arid and semi-arid regions where other water sources are not readily available or too costly to develop and use. A waterharvesting system consists of facilities for collecting and storing rainfall and the resulting surface runoff until the water is used for livestock, small-scale agricultural production, or domestic uses. A distribution facility can also be required unless the collected water is immediately concentrated in the soil profile to grow plants. For example, a distribution facility is needed when the stored water is used to irrigate an agricultural crop or provide water to households.Water harvesting is potentially applicable in almost any area receiving at least 100 millimeters (mm) of annual rainfall (National Academy of Science 1974). Larger volumes of water can be stored on sites where the annual rainfall is 250 mm or more and an adequate storage facility is available.
  • EFFECTS OF PRESCRIBED FIRE AND A WILDFIRE ON OAK SAVANNAS IN THE PELONCILLO MOUNTAINS OF THE SOUTHWESTERN BORDERLANDS REGION

    Gottfried, Gerald J.; Ffolliott, Peter F.; Neary, Daniel G.; Decker, Donald D.; U.S. Forest Service; Univ Arizona; USDA Natural Resources Conservation Service (Arizona-Nevada Academy of Science, 2014-04-12)
    The Southwestern Borderlands Region of Arizona, New Mexico, and northern Mexico are known for its biological diversity and beauty. The area is characterized by its mountains surrounded by deserts and grasslands. The region contains representative animals and plants from the Rocky Mountains in the north to the Sierra Madre Mountains to the south. Madrean oak woodlands and savannas are common within the area covering millions of acres. Periodic fires caused by lightning or Native American people maintained the grasslands and reduced the encroachment of woody vegetation and the accumulations of woody fuels. However, the role of fire declined after the transcontinental railroad was completed and large herds of cattle were introduced into the area. Fires are still ignited but do not spread throughout the landscape largely because overgrazing caused a decline in herbaceous vegetation which carried fires. Aggressive fire suppression by land managers also contributed to the reduced influence of fire. Public and private land managers are concerned that the lack of fires in the Borderlands Region is to blame for the increase in woody species and the decline in biological diversity and productivity of the grasslands and savannas. The Peloncillo Programmatic Fire Plan was developed by the Coronado National Forest to re-introduce landscape level prescribed and managed fires into Forest Service and Bureau of Land Management lands within the Peloncillo Mountains (Gottfried et al. 2009). One of the issues was whether it was best to burn in the cool-season (November-April) or the warm-season (May-October) because of concerns about potential harm to the threatened New Mexican ridge-nosed rattlesnake (Crotalus willardi obscurus) and the endangered Palmer agave (Agave palmeri). The agave is important because it provides food for the endangered lesser long-nosed bat (Leptonyceris curasoae). The area usually burns during the warm period prior to the monsoon season.
  • CONTRIBUTIONS OF SILVICULTURE TO WATERSHED EXPERIMENTS IN ARIZONA'S PONDEROSA PINE FORESTS: A HISTORICAL REVIEW

    Gottfried, Gerald J.; Ffolliott, Peter F.; Neary, Daniel G.; U.S. Forest Service; Univ Arizona (Arizona-Nevada Academy of Science, 2014-04-12)
    Silvicultural studies on the Fort Valley Experimental Forest, the oldest experimental forest in the United States, have been the basis for planning and implementing watershed management experiments in ponderosa pine (Pinus ponderosa) forests. The primary purpose of these experiments had been to evaluate the potentials for increasing streamflow volumes while maintaining or improving other ecosystem-based, multiple-resource values. Knowledge gained from these experiments has provided today's managers with a better appreciation of the past management of Arizona's ponderosa pine forests. The effects of applying silvicultural treatments formulated largely from studies on the Fort Valley Experimental Forest and effects of these treatments on forest structures are reviewed in a historical context in this paper.
  • CONTRIBUTIONS BY THE ROCKY MOUNTAIN RESEARCH STATION TO THE FOUR FOREST RESTORATION INITIATIVE: SILVICULTURE, WILDLIFE AND WATERSHED MANAGEMENT

    Gottfried, Gerald J.; Ffolliott, Peter F.; Neary, Daniel G.; Rocky Mountain Research Station, U.S. Forest Service; Univ Arizona, Sch Nat Resources & Environm (Arizona-Nevada Academy of Science, 2014-04-12)
    The 2.4 million acres of ponderosa pine (Pinus ponderosa) forests and the many resources that they provide are the basis for the wide range of interests and concerns relative to their stewardship by management agencies, special interest groups, and the general public. As might be expected, therefore, there are conflicts of interest among stakeholders. These conflicts often concern the impacts of tree cutting activities on non-market benefits such as wildlife habitats, streamflow regimes, and scenic beauty. A recent issue of conflict has been the application of prescribed or managed fires to reduce the large accumulations of flammable fuels that can cause damaging wildfires when ignited - especially ignitions in the wildland-urban-interface. However, silvicultural practices such as the application of prescribed fire or mechanical forest stand treatments that can reduce the accumulations of fuels are opposed by some members of society. Collaboration among the supportive but sometimes conflicting interests of the involved parties is necessary to resolve any difficult conflicts and thus provide more unified management of ponderosa pine forests.
  • BEST MANAGEMENT PRACTICES FOR PROTECTING WATER QUALITY IN BIOENERGY FEEDSTOCK PRODUCTION

    Neary, Daniel G.; USDA Forest Service, Rocky Mountain Research Station (Arizona-Nevada Academy of Science, 2014-04-12)
    In the quest to develop renewable energy sources, woody and agricultural crops are being viewed as an important source of low environmental impact feedstocks for electrical generation and biofuels production (Somerville et al. 2010, Berndes and Smith 2013). In countries like the USA, the bioenergy feedstock potential is dominated by agriculture (73%) (Perlack et al. 2005). In others like Finland the largest potential comes from forest resources. Forest bioenergy operational activities encompass activities of a continuing and cyclical nature such as stand establishment, mid-rotation silviculture, harvesting, product transportation, wood storage, energy production, ash recycling, and then back to stand establishment (Neary 2013). All of these have the potential to produce varying levels of disturbance that might affect site quality and water resources but the frequency for any given site is low (Berndes 2002, Shepard 2006, Neary and Koestner 2012). Agricultural production of feedstocks involves annual activities that have a much higher potential to affect soils and water resources. The way forward relative to assessing the soil and water impacts of bioenergy systems and the sustainability of biomass production rests with three approaches that could be used individually but are more likely to be employed in some combination (Neary and Langeveld 2013). These approaches are: (1) utilizing characteristics that can be quantified in Life Cycle Assessment (LCA) studies by software, remote sensing, or other accounting methods (e.g.,greenhouse gas balances, energy balance, etc.; Cherubini and Strømman 2011); (2) measuring and monitoring ecosystem characteristics that can be evaluated in a more or less qualitative way (e.g., maintaining soil organic carbon) that might provide insights on potential productivity and sustainability, and (3) employing other proactive management characteristics such as Best Management Practices that are aimed at preventing environmental degradation.
  • USE OF CUMULATIVE EFFECTS ASSESSMENTS IN DETERMING THE IMPACTS OF HERBICIDE APPLICATION PROGRAMS ON WATER QUALITY

    Neary, Daniel G.; USDA Forest Service, Rocky Mountain Research Station (Arizona-Nevada Academy of Science, 2014-04-12)
  • ARIZONA WATERSHED SYMPOSIA: A FORUM FOR REPORTING EARLY WATERSHED MANAGEMENT ACTIVITIES

    Ffolliott, Peter P.; Univ Arizona (Arizona-Nevada Academy of Science, 2014-04-12)
    The role of the Arizona Water Resources Committee and the goal of the Arizona Watershed Program in the early watershed management activities of the state are presented in the introduction of this paper to place its contents in perspective. The Arizona Watershed Resources Committee was a “citizen's advisory committee” that was formed in 1956 to assist in implementing the recommendations made in historic Barr Report to increase water yields and enhance the other natural resources found on the watersheds in the Salt and Verde River Basins of north-central Arizona (Fox et al. 2000). The Barr Report had been released to the public in the form of a short summary publication (Part I) and a more detailed and comprehensive document (Part II), both with the intriguing title of “Recovering Rainfall - More Water for Irrigation,” in the fall of 1956 (Barr 1956a, 1956b, respectively). Contents of the report supported the belief of members of the Arizona Water Resources Committee and many other people that the state's watersheds were in “bad shape” while providing what was called a “scientific basis” for improving these conditions by more intensive watershed management to primarily increase streamflow volumes. The Arizona Watershed Program was a collaborative initiative of the Arizona Water Resources Committee, the Watershed Management Division of the Arizona State Land Department, and the U.S. Forest Service and their cooperators to investigate the effects of vegetative management practices on the hydrologic processes affecting water yields and incorporate the findings obtained into watershed management practices (Fox et al. 2000). It was planned that this general goal would be met by three “highly integrated” programs – a research program, an action program, and a public relations program. Findings of the research and action programs have been reported by Ffolliott and Thorud (1974, 1975), Hibbert (1979), Baker and Ffolliott (1998), Baker (1999), Neary et al. (2002, 2008), DeBano et al. (2004), Solomon and Schmidt (1981), and others. A main component of the public relations program – the Arizona Watershed Symposia – is the focus of this paper.
  • IMPACTS OF URBAN DEVELOPMENTS ON HYDROLOGIC PROCESSES

    Ffolliott, Peter P.; Brooks, Kenneth N.; Univ Arizona; Univ Minnesota (Arizona-Nevada Academy of Science, 2014-04-12)
    Urbanization has been a significant cause for the fragmentation of wildland watersheds since the early 1950s. Furthermore, it is anticipated that urban developments will account for additional losses of natural landscapes into the 21st century. The National Resource Inventory of the U.S. Department of Agriculture indicated that millions of acres of forests, woodlands, agricultural croplands, and other open spaces were converted to urban and other developed areas in the 5 years beginning in 1992 as the rate of urbanization increased when compared to the earlier 10-year period (Alig et al. 2004). Aligned with a projected increase of more than 120 million people in the United States by 2050, urban developments will grow substantially into the future with the fastest rate in the western and southern regions. How urbanization impacts on hydrologic processes and how these impacts might be mitigated when necessary is the focus of this paper.
  • Hydrology and Water Resources in Arizona and the Southwest, Volume 44 (2015)

    Unknown author (Arizona-Nevada Academy of Science, 2015-04-18)
  • DETERMINING SUCCESS IN WATERSHED RESTORATION USING INTERDISCIPLINARY METRICS: RIO SALADO ENVIRONMENTAL RESTORATION PROJECT, PHOENIX, ARIZONA

    Schmidt, Carly H.; Environmental Science and Management, Northern Arizona University. (Arizona-Nevada Academy of Science, 2015-04-18)
    Ecological restoration has yet to gain an indepth understanding of the social dynamics that inform restoration design and enable improved watershed performance in urban environments. The Rio Salado Environmental Restoration Project is unique in that the scale of the project expands to new reaches of the Salt River with each successful venture. The 40-year project has been most successful in recent years due to innovative strategies that capitalize on public outreach and inclusion. Adoption of multi-purpose objectives that include partnerships, public stakeholders, and learning achievement have contributed to the project's success. The ability of the restored system to withstand flood events is one of the many examples demonstrating the project's qualifications as a model for future urban restoration efforts. Lessons about the social dynamics that inform urban restoration success have the potential to augment scientific learning in ecological restoration.
  • RESTORATION OF THE LAS VEGAS WASH AND ASSOCIATED WETLANDS IN LAS VEGAS, NEVADA

    Burke, Megan; Northern Arizona University, Flagstaff, Arizona (Arizona-Nevada Academy of Science, 2015-04-18)
    This paper evaluates the historical growth of the Las Vegas Wash, its subsequent degradation, and the current efforts to restore and stabilize its channel. The Las Vegas Valley Metropolitan Area is located in the Mohave Desert in a drainage basin surrounded by mountain ranges. This drainage basin and its dynamic system of stream channels constitute the Las Vegas Watershed in which the Wash is located. The condition of the Las Vegas Wash is unique, as is a perennial stream that evolved from an ephemeral wash in response to the rapid urbanization and subsequent production of treated wastewater input into the stream channel. The situation has created a series of wetland ecosystems along the Wash, and valuable riparian habitat in such an arid environment. The Wash and its associated wetlands system provide a variety of ecological services to the city of Las Vegas, including storm water conveyance, wastewater effluent filtration, flood protection, and a green space for residents to enjoy. However, continuous increase in volume and intensity of the stream flow has resulted in severe channel degradation and bank erosion in numerous locations along the stream channel. After an examination of the historic and present-day conditions of the Wash and its restoration activities, this essay suggests that future evaluations of the Las Vegas Wash case study may provide evidence to support the propagation of collaborative management efforts.
  • RESTORING THE WATER QUALITY OF THE SAN PEDRO RIVER WATERSHED

    Klotz, Jason; Tecle, Aregai; School of Forestry, Northern Arizona University, Flagstaff, AZ (Arizona-Nevada Academy of Science, 2015-04-18)
    This paper is concerned with restoring the quality of water in some portions of the San Pedro River. There are high concentrations of bacteria in some parts of the San Pedro River. Our aim is to find ways of improving the situation. Specifically, there are two objectives in the study. The first one attempts to identify the possible sources of the bacterial contamination and assess its trends within the watershed. The second objective is to determine appropriate methods of restoring the water quality. The main water quality problem is nonpoint source pollution, which enters the stream and moves along with it. The magnitude of the problem is affected by the size and duration of the streamflow, which brings bacteria-laden sediment. The amount of sediment brought into the system is large during the monsoonal events. At this time, the streamflow becomes highly turbid in response to the organic and inorganic sediments entering the system. Based on research done for this paper, the amount of bacterial concentration is strongly related to turbidity. Best management practices (BMPs) have been designed and implemented to restore the water quality problem in the area. The BMP's consist of actions such as monitoring, educational outreach, proper signage, and other range/watershed related improvement practices. Other issues that contribute to the increasing amount of bacteria that are briefly addressed in this paper are bank and gully erosion, flood control, and surface water and streamflow issues that occur on the stream headwaters.
  • WATERSHED RESTORATION EFFORTS AT HART PRAIRIE IN NORTHERN ARIZONA

    Kursky, Joshua; Tecle, Aregai; Northern Arizona University, Flagstaff, AZ (Arizona-Nevada Academy of Science, 2015-04-18)
    Hart Prairie is a high-elevation upland riparian ecosystem on the west slope of the San Francisco Peaks in northern Arizona. The location is unique, not only as an upland riparian area in the semi-arid Southwest, but also for having a wet meadow ecosystem dominated by Bebb willow (Salix bebbiana). The ecosystem has experienced a high degree of change since the time of Euro-American settlement. Along with fire suppression, increased wild ungulate herbivory rates, and conifer encroachment into a historically short-grass prairie, several humaninduced changes have been made to the topography of the watershed. Stock tanks, an earthen berm with associated diversion channels, and a road that cuts perpendicularly across the direction of water flow near the base of the watershed have contributed to the altered drainage patterns and the decreased water availability to the flora and fauna in the area. As a result, the Bebb willows and the associated meadow vegetation are at risk. Most of the willows, which constitute the majority of the canopy in the ecosystem, are at a decadent, over-mature stage that allows a limited recruitment of younger plants (Maschinski 1991, Waring 1992). Under these conditions, the plant community may die off leading to the loss of this rare riparian area forever. Research on restoration efforts have been undertaken since the mid-1990s on The Nature Conservancy’s Hart Prairie Preserve and the adjacent US Forest Service Fern Mountain Botanical Area. This paper summarizes the efforts that have been made; most of which targeted to improve the low germination rates of willow seeds, and to restore the geomorphology and surface flow patterns to their pre-disturbance conditions.
  • CASE STUDIES IN STREAM AND WATERSHED RESTORATION (URBAN, AGRICULTURAL, FOREST AND FISH HABITAT IMPROVEMENT)

    MacDonald, Kit; U.S. Forest Service, Kaibab National Forest, Williams, AZ (Arizona-Nevada Academy of Science, 2015-04-18)
    Stream and watershed restoration projects have become increasingly common throughout the U.S., and the need for systematic post-project monitoring and assessment is apparent. This study describes three stream and watershed ecological restoration projects and the monitoring and evaluation methods employed or planned to evaluate project successes or failures. The stream and watershed restoration and evaluation methods described in this paper may be applicable to projects of similar types and scales. Rivers and streams serve a variety of purposes, including water supply, wildlife habitat, energy generation, transportation and recreational opportunities. Streams are dynamic, complex systems that not only include the active channel, but also adjacent floodplains and riparian vegetation along their margins. A natural stream system remains stable while transporting varying amounts of streamflow and sediment produced in its watershed, maintaining a state of “dynamic equilibrium.” (Strahler 1957, Hack 1960). When in-stream flow, floodplain morphology, sediment characteristics, or riparian vegetation are altered, this can affect the dynamic equilibrium that exists among these stream features, causing unstable stream and floodplain conditions. This can cause the stream to adjust to a new equilibrium state. This shift may occur over a long time and result in significant changes to water quality and stream habitat. Land-use changes in a watershed, stream channelization, installation of culverts, removal or alteration of streambank vegetation, water impoundments and other activities can dramatically alter ecological balance. As a result, large adjustments in channel morphology, such as excessive bank erosion and/or channel incision, can occur. A new equilibrium may eventually be reached, but not before the associated aquatic and terrestrial environment are severely impaired. Stream restoration is the re-establishment of the general structure, function and self-sustaining characteristics of stream systems that existed prior to disturbance (Doll et al. 2003). It is a holistic approach that requires an understanding of all physical and biological processes in the stream system and its watershed. Restoration can include a broad range of activities, such as the removal or discontinuation of watershed disturbances that are contributing to stream instability; installation of control structures; planting of riparian vegetation to improve streambank stability and provide habitat; and the redesign of unstable or degraded streams into properly functioning channels and associated floodplains. Kauffman et al. (1997) define ecological restoration as the reestablishment of physical, chemical and biological processes and associated linkages which have been damaged by human actions.
  • HYDROGEOMORPHIC AND BOTANICAL ASSOCIATIONS OF BAJADA EPHEMERAL DRAINAGES IN THE WHITE TANK MOUNTAINS, SONORAN DESERT

    Haberkorn, Matt; Phoenix College Bioscience Department, Phoenix, AZ (Arizona-Nevada Academy of Science, 2015-04-18)
    Ephemeral drainage plant communities of the Sonoran Desert compose a highly significant yet relatively unexplained portion of the ecosystem. Eighty-one percent of all southwestern and 94% of Arizona drainages are categorized as ephemeral drainages (Levick et al. 2008). Small but significant portions of the bajada environment are also composed of ephemeral drainages. These drainages carry out important landscape scale functions in water movement, groundwater recharge, nutrient movement and cycling, sediment transportation, geomorphology, plant habitat, seed disbursement, as well as wildlife habitat and corridors. In decades past, Sonoran Desert bajada research relating the physical earth sciences to ecology has focused on explaining upland plant community patterns along this landform (Yang and Lowe 1956, Phillips and MacMahan 1978, Key et al. 1984, McAuliffe 1994, Parker 1995, McAuliffe 1999). This body of research, however, has very little information pertaining to ephemeral drainages dissecting the upland bajada environment. The bajada geomorphic environment is a composition of geomorphic surfaces of varying soil development proceeding away from a mountain (Peterson 1981, McAuliffe 1994). Each of these geomorphic surfaces is characterized by a unique lithology, slope, age and degree of argillic and caliche soil horizon development. Generally, geomorphic surfaces containing highly developed argillic or caliche soil horizons are found near the mountain while surfaces of undeveloped soils are furthest away from the mountain. Depending on the bajada, local geomorphic history, however, may result in different landscape scale patterns of geomorphic surfaces and soil development. This physical environment forms the template from which the ephemeral drainage develops its channel morphology, hydrology and botanical associations. It was expected that the various geomorphic surfaces composing the bajada found at the study sites would determine the specific channel morphology, hydrology and plant community associations of the examined ephemeral drainage. The goal of this study was to explain (1) channel morphology, (2) hydrology or ephemeral flow patterns and (3) plant communities found along the ephemeral drainage. Plant communities of drainages were also compared to upland communities. These factors were then utilized to give an overall explanation for the distribution of hydrogeomorphic and botanical associations found along the bajada ephemeral drainage.

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