LEOPOLD INSTITUTE

THE VALUE OF WILDERNESS WATER

NOTE: This project has been temporarily suspended due to lack of staff and funding.

David Spildie - Leopold Institute

ABSTRACT

The goal of the Value of Wilderness Water project is to develop a framework to explore the aspects of the value of water provided by Wilderness and other protected areas. The benefits of renewable sources of clean water to humans include drinking water, irrigation, industrial uses, and many instream benefits. Clean water will only grow in its value to the nation and the world as populations increase and water quality is affected by development. Wilderness and many other protected areas contain watersheds that have been minimally modified by human disturbance. These areas provide abundant clean water to millions of people. Research on the value of this resource to future generations and its relationship to protected lands is crucial.

Work on the project this summer will entail reference work, a problem analysis, an information needs assessment, and framing the key issues.

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Contribution of Wilderness water to Fresno, California

GIS provides an effective tool to determine the location of water sources, the direction of flow of this water, and the ultimate municipal or urban destination of this flow

GIS provides an effective tool to determine the location of water sources, the direction of flow of this water, and the ultimate municipal or urban destination of this flow

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INTRODUCTION

Wilderness provides many values to the nation. Abundant clean water is one important value, essential to life and the maintenance of human populations. National forest lands provide 14 per cent of the runoff of the contiguous United States land area and the value of this water has been estimated at $3.7 billion per year (USDA - Forest Service, 2000). Portions of this land are designated Wilderness, the most protected of all land categories. Together with other Wilderness lands managed by the Bureau of Land Management, the Fish and Wildlife Service, and the National Park Service, over 106 million acres of Wilderness land exist throughout the nation, representing a wide range of ecosystems. Many of these areas are situated in the headwaters of major drainages that provide water to downstream cities and metropolitan areas.

DATA NEEDS

To assess the importance of Wilderness areas to the Nation's water supply, a Geographic Information System (GIS) provides an effective tool to determine the location of water sources, the direction of flow of this water, and the ultimate municipal or urban destination of this flow. Ultimately, such information can be used to determine the value of water provided by Wilderness. Information needed for this modeling effort includes geographically-referenced data representing Wilderness boundaries, national hydrography, and metropolitan areas. These data are currently available for the conterminous United States. Unfortunately, data for Alaska are not available at this time.

HYDROLOGIC MODELING

The components required to model the values of water from Wilderness are a GIS, the geospatial data representing the aforementioned data categories, and hydrologic modeling software. ArcInfo is the GIS application available to the Forest Service. The data are: digital Wilderness boundaries of the U.S., which I have compiled; the hydrographic data available from the National Hydrographic Dataset (NHD); and the metropolitan area data, which are available from the U.S. Census Bureau. The NHD is based on the content of USGS Digital Line Graph 1:100,000 scale hydrography data integrated with reach-related information from the EPA Reach Files. The NHD depicts drainage of water from confluence to confluence and direction of flow. When these coverages are overlaid in the GIS, it will be possible to join Wilderness areas to the metropolitan areas with the stream network. This will provide baseline information for the location of the source of metropolitan water. The metropolitan area information is built from the Census Bureau metropolitan statistical area data, which is defined as cities with 50,000 or more inhabitants or cities with at least 50,000 inhabitants and a total metropolitan population of at least 100,000. If including smaller cities is necessary for this project, further reference work will be needed to determine how those data can be compiled.

WORK PLAN

The data for this project are available for the conterminous United States. Only metropolitan areas connected to Wilderness through hydrographic reaches will be modeled, so seamless data coverage of the entire United States will not be necessary. Indices depicting the catalogue unit areas will be utilized to download the target areas for digital coverage.

A pilot project will be developed which will determine the feasibility of the available data and the modeling procedures. A subsample of metropolitan areas near Wildernesses will be chosen to determine the resources necessary to identify and download data, create the GIS coverages, and apply the modeling procedures. I will keep notes identifying the time required for each phase and any problems encountered during the pilot period. At that point I will develop a needs assessment to ascertain the time, funding, and personnel required for the modeling effort.

The National Hydrographic Dataset is served in catalogue units, which are approximately 1800 km2 in extent. An index of these units will be laid over the Wilderness and metropolitan area coverages to assess which units are necessary for the modeling effort. Metropolitan areas data are available as one dataset. The metropolitan areas data will not include cities that have less than 50,000 inhabitants. Due to the sparse population of much of the west, this may not accurately portray the value of Wilderness water to smaller cities. The pilot project will assess if this is an issue and determine if standardized demographic data are available for smaller cities.

GIS PROCESSING

To assess the influence of water from Wilderness on metropolitan areas, a GIS overlay process is employed. US Census data are available online and provide a suite of GIS coverages for a number of census categories. In general, metropolitan areas are represented by their county boundaries. To determine the influence of Wilderness water on a city, this is not an accurate representation of the area of the city. The cities coverage is a point coverage, and it too, misrepresents the geographic limits of an incorporated municipality. The best available data to represent this area was Census data titled "2000 Incorporated Places/Census Designated Places". This is a polygon coverage that encompasses the boundary of the municipalities.

Suitability Analysis for Metropolitan Areas

To ascertain a metropolitan area suitable for modeling hydrography associated with Wildernesses areas, three separate data layers were used. The USGS National Atlas website provided 1:2M scale shapefiles for United States metropolitan areas and hydrography networks. The NWPS coverage was then merged with these coverages to identify a metropolitan area with hydrographic connectivity to Wilderness areas. A visual inspection of the relationship between Wilderness areas and cities for the conterminous United States, showed that Fresno, California was suitable candidate for this pilot project. The headwaters in the Sierra Nevada Mountains to the east of the city are encompassed by the Yosemite, Ansel Adams, John Muir, Dinkey Lakes, Kaiser, Monarch, and Sequoia-Kings Canyon Wildernesses.

GIS DATA

Hydrography

The USGS in cooperation with the EPA have created the National Hydrographic Dataset (NHD). This is a comprehensive set of digital spatial data that contains information about surface water features. Within the NHD, these features are combined to form "reaches", which provide the framework for linking water-related data to the NHD surface water drainage network. These linkages enable the analysis and display of these water-related data in upstream and downstream order.

The Fresno metropolitan geographic area consists of 11 hydrography catalogue units (CUs). The spatial extent of these units is identified through an index and then downloaded to the client PC for processing. To allow for modeling of hydrographic networks, the units must be joined into one seamless coverage. This is accomplished through a script called append_nhd.aml and results in a continuous network of stream reaches. The aml was run on the CUs and produced a number of processing errors. These errors were reported to the NHD helpdesk and a dialogue was established over a few days to ascertain the source of the error. It was suggested that the aml and data be moved to Arc Workstation 8.1 and run. This produced different errors, but after consultation with NHD, it appeared there were just checking errors and did not affect the appending of the CUs. The CUs are now joined into one seamless coverage and all line attributes for the reaches are extant.

The NHD provides analysis tools through application extensions that are loaded directly into ArcView 3.2a. These tools analyze the hydrography through processing of reach information. Reach length can be measured, reaches can be navigated upstream or downstream, point events can be added to reaches, and water bodies can be added to the workspace. For purposes of this project, reach navigation can display the mainstream route of water that originates in Wilderness and courses through or near an urban area. This can determine the qualitative value of water from Wilderness.

Census Data

Metropolitan area data from the USGS were used for the initial scoping of a suitable pilot project area. These 1:2 million scale data were sufficient for this task. For the actual pilot itself, finer scale census GIS data were necessary. Metropolitan area data are often generalized to the boundaries of the county in which the target city resides. This is not sufficient for pilot project analysis. Census Bureau data were accessed to identify higher resolution polygon data for an urban area. These data were available as the 2000 Incorporated Places/Census Designated Places shapefile. Census designated places (CDPs) are delineated for each decennial census as the statistical counterparts of incorporated places. CDPs are delineated to provide data for settled concentrations of population that are identifiable by name but are not legally incorporated under the laws of the state in which they are located.

Wilderness

I have maintained a GIS coverage of the NWPS for many years. This provides a current polygon coverage of the boundaries of Wilderness. Most boundaries were originally created from 1:100k source data and names are checked against the NWPS database to ensure correctness. This provides a coverage of suitable resolution for this analysis.

GIS ANALYSIS

Analysis

Desktop ArcView 3.2a was used as the analytical engine for this project. Unlike workstation ArcView 3.2a, the NHD tools can be invoked from Desktop ArcView 3.2a. An overlay procedure was used to display the joined hydrographic reaches, CDPs, and Wilderness boundaries together.

The terminal points of the reaches, which have their sources in the headwaters of the Wilderness areas, can be selected with the NHD navigation tool and it will traverse the hydrographic drainage network through the reach flow relationships. Those that terminate in, flow through, or near the Fresno CDP can be saved as individual navigation results and displayed as a compendium of results in the final display.

Discussion

The resulting display shows the extent and amount of reaches that arise in Wilderness and potentially provide water to the Fresno area (Fig. 1). This shows the geospatial extent of the hydrographic features that ultimately flow to Fresno . The NHD dataset does not provide information on water quantity or quality. To do so would require annual stream volume data from the USGS and a GIS model for assessing volume of water delivered to a downstream area. Additional information would need to be gathered to determine the uses of the water in the CDP; drinking water, irrigation, industry, and so on. This would require significant research for the CDP in question. Scoping should start at the water treatment facility for the municipality to determine the source of drinking water. If it is from a stream source, that stream could be identified in the hydrographic network and if it emanated from Wilderness, the daily volume could provide an estimate of the quantity of water essential to the community from that source. Hydrographic modeling procedures are available that determine water quantity (Luitjen, J., 2000). If the water treatment plant pumps from an aquifer, data may be available on which hydrographic sources recharge it.

LITERATURE CITED

Luitjen, J. 2000. Dynamic Hydrologic Modeling Using ArcView GIS. ArcUser, July-September 2000. pp 20-22.

USDA - Forest Service. 1999. Water & the Forest Service. General Technical Report, RMRS - GTR - 39. Washington, DC: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station.

Wilderness Water
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