GMEG - Geology and Geophysics
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What is this project about?
The Navajo Nation (roughly the size of West Virginia) has the largest land base and reservation population of all tribes in the United States. In addition, half of the population is currently under the age of 23 (Census, 2000). Thus, rapid population growth may surpass carrying capacity of ecologically sensitive lands upon which people are dependent for their livelihood. Over time there will be an increasing need for resources and development of infrastructure to accommodate this burgeoning population. Research conducted with participating members of the Navajo Nation will foster community-based land-use planning and science education for Native Americans.
Example of a remote dust monitoring station
Background110 community-based governing bodies on the 65,000 km2 Navajo Nation are in the process of developing land-use plans that require information on geologic hazards, water availability, soils, plant habitats, and environmentally sensitive areas. Information is urgently needed for planning urban development, highways, buildings, bridges, and domestic septic and landfill systems. Even so, most of the Navajo Nation has only cursory geologic mapping available, conducted before a topographic base existed (Cooley, 1969). Soft, erodible bedrock lithologies and extensive surficial deposits dominate the region, making it sensitive to fluctuations in precipitation intensity, percent vegetation cover, and local land use practices. Limited, shallow water resources in the region are controlled by fluctuations in climate and over utilization. Lack of water availability in this arid region, limits economic growth, and lowers the quality of life (including basic sanitation and drinking water availability). Water quality is often significantly affected by the local geology or local system contamination. Bedrock and surficial geologic deposits contribute uranium, arsenic, and other contaminants to groundwater resources and springs. These findings underscore the need for accurate and detailed mapping of bedrock, surficial deposits, landforms, and geologic structures. Arid to semi-arid conditions on the Navajo Nation, combined with a landscape that includes extensive eolian deposits, makes this region especially vulnerable to sand and dust mobility from drought and climate change. Geologic mapping is required to establish local conditions of landscape mobility and stability, and their relation to local environmental conditions. The mapping in this study also serves to document baseline conditions against which to measure expected future landscape changes. Specific sites for detailed study are selected during the mapping process, to address relations of geomorphic change to ecosystem function. Work includes documenting changes in alluvial systems, conditions of eolian sand movement, and land use impacts to augment the foundation of geologic setting in establishing landscape conditions.
WHAT …goals and objectives will the project hope to accomplish?
Our objectives will be to accomplish the following goals:
*Provide the geologic framework for the Navajo Nation that is needed to determine the extent and characteristics of local aquifers and to establish a baseline of landscape conditions for land use planning and natural resource management.
*Document landscape change to provide a foundation for evaluating geologic hazards such as flash floods and dust storms, surface processes related to climate variability and ecosystem function, including plant ecology and landscape mobility. Specific sites for detailed study are selected during the mapping process, such as outlining flood hazards from the Little Colorado River, to be evaluated through mapping from temporal series air photos.
*Determine drought impacts on sand dune activity through combined meteorological monitoring and field evaluation of dunes and vegetation at key sites.
*Evaluate known and suspected conditions that may exacerbate eolian transport processes, by comparing satellite imagery of dune and dust mobility and seasonal vegetation change, to data from monitoring sites and the mapped spatial distribution of climatic variables (such as effective moisture).
* Document changing surface conditions in relation to climate change, and evaluate ecosystem linkages to changing flood hazards.
* Determine composition and potential health effects from dust in the Tuba City uranium milling area of the Navajo Nation.
*Establish clear communication lines with tribal communities and offices making management and planning decisions.
WHAT tasks are part of this project?The project consists of five interrelated tasks: geologic mapping, documentation of changes to alluvial systems, monitoring and evaluation of sand dune mobility, documentation of land use related to observed landscape changes, and outreach.
Task 1 provides a geologic framework for land use planning and natural resource management by conducting geologic mapping at the 1:24,000 scale, compiled into 1:100,000 quadrangles when appropriate. Initial work is conducted within the Winslow, Tuba City, and Sanders Quadrangles, with the intention of continued studies near and on Navajo and Hopi lands, contingent upon funding. Geologic mapping will be conducted with an emphasis on stratigraphic relations, structures, and facies that may influence water quality and availability, and environmental conditions. At least six Holocene to Pleistocene terrace levels are recognized, some containing human artifacts and Pleistocene megafauna. Stratigraphic relations of terrace and dune deposits will be determined whenever possible by field relations, archaeological investigations and absolute dating techniques, as an aid in understanding the chronology and evolution of landscape conditions, drought history, and rates of soil development.
Task 2 uses baseline data from mapping along the Little Colorado River Valley for comparison to conditions recorded by photography and satellite imagery. Changing river morphology and land surface conditions compiled in GIS can be evaluated using data from other tasks to understand changes in flood behavior. Temporal series of air photos from key sites along the Little Colorado River provide a record of past landscape conditions from which to assess effects of perennial vs. ephemeral stream flow, native vs. invasive riparian species, and fluctuations in discharge related to flood hazards and sediment availability for eolian processes.
Task 3 examines natural resource management, by providing information on land use. Land use information on farming projects, grazing practices, and vehicle use will be used to assess observed changes in sediment mobility, surface erosion, and flood history. Whenever possible, we will also conduct small scale experiments on prospective mitigation practices that may be helpful to land use managers.
Task 4 addresses linkages of climate change, drought, and seasonal changes in temperature and precipitation patterns to sand dune mobility and eolian transport processes. This work is a continuation of task 3 of “Effects of climate variability and land use on American Drylands”, in which work on establishing the distribution of dune deposits and sand sheets on the Navajo Nation that are prone to eolian activity began. The current goal is to establish factors needed in a predictive model that describes changing surface conditions, and to describe critical thresholds that are key factors in eolian sediment mobility. Field work and monitoring of eolian activity and meteorological conditions, combined with work remotely sensed vegetation cover, will continue in key areas where dune activity is likely to occur. Monitoring meteorological and soil moisture conditions provides information needed to evaluate the seasonal changes in soil moisture residence time during critical periods of dune plant germination and growth.
Task 5 is devoted to communication and outreach: Information provided by this study is needed for land use plans that are currently in development by local Native American communities, including those affected by the Bennett Freeze Act. Semi-annual reports to local and tribal government offices and community members helps researchers focus attention on local land use issues, and aids in determination of user-friendly research products. We promote participation of tribal members and Native interns in our project to promote and educate tribal communities about our work.
WHY is this research important?
We provide vital information through work on the following: 1) outlining areas prone to geologic hazards and climate change impacts 2) providing basic geologic information for planning and resource management 3) determining the degree of surface vulnerability and sediment transport by eolian and alluvial processes resulting from changes in climate and land use, and 4) determining links between dune deposits, vegetation communities, meteorological conditions, and effects of drought and climate change, 5) outlining areas where geologic conditions may impact human health.
The landscape of the Navajo Nation is characterized by ephemeral streams that have incised easily eroded fine-grained valley-fill, and highly erodible soft bedrock lithologies, such as the Bidahochi and Chinle Formations. Erosion rates are highest, and most sensitive to climatic changes in semiarid regions, including Navajo tribal lands (e.g., Langbein and Schumm, 1958). Thus, the particular geology and climatic characteristics of the region make it especially vulnerable to short-term and long term trends in precipitation and temperature. McFadden and McAuliffe (1997) suggest that changes in precipitation, rather than land use, have been largely responsible for local arroyo formation, because of the highly erodible nature of regional bedrock, and its sensitivity to minor climatic change. Research to date indicates that fluctuating climates are a primary control on alluvial processes, including the rate of vertical and lateral adjustments of the Little Colorado River. Eolian dust sourced from Little Colorado River flood deposits is far traveled, and has the potential to affect snowpack and rates of snowmelt in the Colorado Rockies. Extensive eolian surficial deposits cover more than one-third of Navajo lands. Sand dunes of this region are climatically on the threshold between mobility and stability. Increasing aridity combined with the current demand on resources has the potential to produce dust bowl-like conditions on the southern Colorado Plateau.
In recent years, the Navajo Nation has been experiencing drought conditions that may surpass the severity of all previous droughts in the 20th century. The 1987-1989 drought, attributed to above normal sea surface temperatures related to Global Warming, was the second most costly natural disaster in U.S. history (behind Hurricane Katrina), with damages estimated at $39 billion for the country as a whole (Trenberth et al., 1988; Riebsame, 1991). It has been suggested by current climate models that the recent trend toward increasing aridity in the region can be at least in part attributable to climate change (Seagar et al. 2007) Therefore, understanding interactions of landscape with changing environmental conditions and their relative influence on the severity of drought are important for natural resource planning and land use sustainability.
This information is especially pertinent to those living in this semi-arid environment, where land use sustainability is at risk, and desertification of land threatens the livelihood and culture of local residents. Navajo tribal offices use our information in planning land purchases, infrastructure and development in areas receiving congressional funds for economic rehabilitation. A significant portion of the land where our studies are conducted was affected by the Bennett Freeze Act. The Former Bennett Freeze area (FBFA) covers over 1.6 million acres in the northeast corner of Arizona and forms the westernmost portion of the Navajo Nation. During the forty years it was in effect, the Bennett Freeze curtailed development in affected local communities, and contributed to poor living conditions. Many FBFA residents have lived for years without electricity, plumbing, or the assurance of clean drinking water. Currently, one out of three residents in the western Navajo Nation hauls water for domestic use.
|A frontal system advanced from the across the Navajo Nation on Monday April 5th, 2010 bringing strong southwesterly winds and gusts in excess of 50 mph. The source of the dust was from just north of the Little Colorado River on the Navajo Nation.|
References cited above:
Cooley, M. E., 1969, Regional hydrogeology of the Navajo and Hopi Indian Reservations, Arizona, New Mexico, and Utah: U.S. Geological Survey Professional Paper 521-A, 58 p.
Langbein, B. and Schumm, S. A., 1958, Yield of sediment in relation to mean annual precipitation, Am. Geophys. Union Trans. 39 (1958), p p. 1076–1084.
Riebsame, William E. Changnon, Stanley A., and Karl, Thomas R. (1991) Drought and Natural Resource Management, Impacts and Implications of the 1987-89 Drought; Westview Press, Boulder, Colorado and Oxford, United Kingdom.
Trenberth, Kevin E., Branstator, Grant W., and Arkin, Phillip A. (1988) Origins of the 1988 North American drought: Science v. 242, p.1640-1645.
Seager, R., Mingfang Ting, Held, I., Yochanan Kushnir, Jian Lu, Gabriel Vecchi, Huei-Ping Huang, Nili Harnik, Ants Leetmaa, Ngar-Cheung Lau, Cuihua Li, Jennifer Velez, and Naomi Naik 2007, Model Projections of an Imminent Transition to a More Arid Climate in Southwestern North America: Science, v. 316 no. 5828, 1181-1184.