Number 51 January 1992
The Rural Clean Water Program (RCWP) was designed to provide financial and technical assistance to farm operators within RCWP project critical areas to tall best management practices (BMPs) to control water pollution. Over the past year, evaluation teams composed of NWQEP staff members and USDA agency have been conducting on-site evaluations of the 21 RCWP projects nationwide as part of an overall effort to evaluate the effectiveness and lessons learned from the RCWP. RCWP water quality improvements depend on changes in farm operators' knowledge, attitudes, and behavior. A survey of eligible RCWP participants and non-participants in each RCWP project area was designed by North Carolina State University faculty members Thomas Hoban and Ronald Wimberley (Dept. of Sociology and Anthropology) and Steven Coffey (Water Quality Group, Dept. of Biological and Agricultural Engineering).
Funded by USDA, the survey will provide information that will ultimately be related to other indicators of project effectiveness being collected through the on-site evaluations of RCWP projects. Both aspects of the evaluation and a final report on the RCWP will be submitted to USDA in September, 1992.
Objectives of the farm operators' survey are to: 1) analyze the factors that influenced participation in the RCWP and adoption of recommended BMPs; 2) analyze attitudes about the benefits and costs of participation in the RCWP; 3) determine respondents' willingness and ability to maintain BMPs adopted as a result of participation in the RCWP and the potential for adoption of additional BMPs in the future; and 4) determine perceptions of the effectiveness of technical and financial assistance programs, as well as education and information efforts, associated with the RCWP.
Data collection for the farm operators' survey are being accomplished through telephone interviews with a representative sample from the RCWP project areas.
Approximately 1000 telephone interviews are planned; 750 interviews have already been completed.
For further information about the survey contact:
Thomas Hoban
Dept. of Sociology,
Anthropology, and Social Work
Box 8107, NCSU
Raleigh, NC 27695-8107
Tel: 919-515-2670.
This article is the third in a series designed to share the experience and lessons learned by RCWP project personnel by highlighting the projects' ten- year reports.
John W. Stanley, Polk County Florida Agricultural Stabilization and Conservation Service
The Taylor Creek - Nubbin Slough Rural Clean Water Program (RCWP) Project lies on the north
shore of Lake Okeechobee. Two basins, Taylor Creek and Nubbin Slough, were combined by a
drainage project in the 1960s and now empty into Lake Okeechobee through one outlet, the
S-191 structure. Flow from this structure provides 4% of the total inflow into Lake Okeechobee
and contributes 27% (the highest of any tributary) of the phosphorus loadings and a significant
proportion of the nitrogen loadings to the lake. The primary source of these loadings were cattle
lounging in and around streams, runoff from dairy barns and holding areas, and runoff from
improved pastures. The critical area includes essentially the entire Taylor Creek - Nubbin Slough
Basin, a depressional type watershed covering 110,000 acres.
Lake Okeechobee provides public drinking water supplies for Belle Glade, Clewiston,
Okeechobee City, Pahokee, and South Bay and is a secondary source of drinking water for the
lower east coast of Florida and Miami. As salt water encroachment increases along the lower east
coast, the lake is expected to play an increasingly important role in the water supply for this
growing area. The lake is used by commercial fishermen to catch panfish, catfish, and frogs
valued at $5 million annually. Lake Okeechobee is also a natural winter habitat for many species
of ducks. The local tourist industry depends on the lake as a drawing card for year-round
recreational activity. About 49% of sport fishing activity in the area, valued at $3.6 million
annually, occurs in the north end of the lake and is immediately influenced by project area
waters. Agricultural interests use water from the lake to irrigate about 500,000 acres of vegetable
crops, sugar cane, pastures, and some row crops, especially in the organic soils on the south side
of the lake. The loss of Lake Okeechobee to hyper- eutrophication would be catastrophic to the
region's economy and water supply.
When the RCWP project was initiated, the project area contained 24 multiple farm dairies on
30,000 acres with approximately 28,000 animals and 56 cattle ranches occupying 49,000 acres
with 25,000 head of cattle. In addition, roughly 1,400 acres were devoted to citrus production.
Limited vegetable crops were grown in the project area.
The goals of the Taylor Creek - Nubbin Slough project were: 1) to achieve a 50% reduction of
phosphorus and nitrogen concentrations entering Lake Okeechobee through the S- 191 structure;
2) to have at least 47,331 critical acres in the Taylor Creek - Nubbin Slough Basin (75% of the
critical area) under contract; and 3) to have all dairy farms in the critical area under contract. All
goals were met or exceeded.
The key to the success of the project was the implementation of an administrative subcommittee.
This subcommittee was made up of the Agricultural Stabilization and Conservation Service,
Cooperative Extension Service, Soil Conservation Service, and South Florida Water Management
District. The subcommittee met regularly to coordinate project activities and each member
participated in all phases and activities of the project.
BMPs were originally selected from the list of nationally approved BMPs designed to reduce
nutrient runoff and keep animals from direct access to streams. Later, pasture and hayland
management and irrigation management BMPs were added to the project. Early in the project,
waste management BMPs were added, along with management BMPs and components. Dairies
were targeted because of their size, location, and animals concentrated near streams. Because
project team members found that farmers did not understand the operation and design of animal
waste systems, management practices were written into the contracts to ensure that the systems
were operated and maintained appropriately.
John W. Stanley, District Director Boyd Gunsalus, Water Quality Environmentalist
This article begins a new series on nonpoint source (NPS) modeling. Geographic information
systems (GIS) represent a new data management technology that is increasingly being used to
manage data for models for a wide range of NPS applications. These applications include
evaluating the effectiveness of best management practices (BMP) in controlling NPS pollution;
identifying high priority areas for implementation of stormwater management techniques;
estimating pollutant loadings for current and projected land use scenarios within a watershed;
defining and mapping critical areas for NPS control projects; and many others. Readers interested
in contributing to the series are encouraged to contact Judith Gale, NWQEP NOTES editor.
Gerard McMahon
Geographic information systems (GIS) are computer programs linking features commonly seen
on maps, such as roads, town boundaries, and water bodies, with related information not usually
presented on maps, such as type of road surface, population, or water quality information. This
article outlines the basic concepts associated with a GIS, beginning with the maps and other
information that comprise a GIS and including a summary of the functional capabilities of a GIS.
Historically, maps have been used for navigation through unfamiliar territory, communicating
information to the map user about the relative locations of objects of interest, such as cities,
countries, and oceans (Berry, 1987). In a sense, maps are models revealing how objects are
distributed or located in space. Spatially distributed objects or phenomena shown on most maps
include points, lines, or areas. For any of these objects, data can be collected on both the location
and associated attributes or variables.
Some maps are composed of information on only one type of spatial phenomena (either point,
line, or area) for a single variable (e.g., a map of census tracts might portray information about
a single variable such as population). Other maps show information on multiple types of
phenomena for multiple variables.
Four basic characteristics of maps are important from a GIS perspective (Robinson et al., 1984).
First, all maps are concerned with two fundamental aspects of planning-related data: location of
the object for which the data are being collected, and attributes of that object. An example of
such an object is a parcel of land. Location refers to position in two or three dimensional space,
while attributes are qualities or magnitudes associated with the object, such as size, zoning
designation, or type of land use.
Second, a map is always smaller than the region it portrays, so that each map has a defined
dimensional relationship between reality and the map. This relation is called scale, a measure that
shows the proportion between the map dimensions and those of reality. U.S. Geological Survey
(USGS) topographic maps, with a scale of 1:24,000, are commonly used. This scale indicates that
every inch of distance shown on the map corresponds to 24,000 inches (or 2,000 feet) of actual
"on the ground" distance.
Third, location of a feature shown on a map is referenced by either a spherical coordinate system,
such as latitude-longitude, or a rectangular coordinate system, such as the state plane coordinate
system (Huxhold, 1991). The latitude-longitude system accurately portrays location and distance
over the entire spherical surface of the globe, although it is cumbersome to use for local
application. Rectangular, or plane coordinate, systems require that the curved surface of the earth
be mathematically transformed to create a two- dimensional surface. Such a transformation is
called a map projection. Plane coordinate systems then place a two-dimensional grid on top of
the transformed map, making the calculation of distance and direction easy.
Finally, all maps are abstractions or generalizations of reality, portraying data chosen to fit the
intended use of the map. These data are usually subjected to operations such as classification
(i.e., dividing all the observations into several useful categories) and simplification (i.e.,
generalizing the portrayal of a creek on a town road map), which enhance the comprehensibility
of the map for that particular use.
A GIS is a data management system in which spatial phenomena of interest (points, lines, areas)
can be referenced by spatial or geographic location, as well as by any other variable contained
in the information system. For example, a GIS containing maps of soil type, land use, and slope
can be queried to list not only soil types prone to erosion (based on slope), but also areas of
coincidence between such soils and agricultural land uses.
A GIS is structured to take advantage of this location information in several ways. Because
location is measured for each of the units of observation in the information system (e.g., for each
of the land parcels), the GIS knows where each of the parcels is located with respect to all the
other parcels. That is, it knows which parcels are adjoining, and the distance between parcels.
The GIS, by knowing the location of all points along each parcel boundary, can also calculate
the size of each parcel by using the coordinates and simple conversion routines (e.g., using state
plane coordinates, measured in feet, to determine area in acres). The mathematical property that
allows a GIS to generate information about spatial "connectedness" is called topology. The
addition of location information, along with the capacity to develop topological relationships
between the units of observation, allow a GIS to produce maps that are "smart".
A GIS can make use of "layers" of information contained on separate maps (e.g., a layer of
parcel boundary information, a layer of land use type, a layer of stream location, etc.). The key
to the utility of a GIS is that these layers are each referenced to a common geographic coordinate
system that allows the maps to be compared or analyzed with reference to each other. In this
regard, a GIS can be conceptualized as a set of floating layers or maps with common spatial
registration.
The data structure allows questions to be asked about individual maps (how many parcels with
an area greater than 10 acres?; how much agricultural land on which conservation tillage has
been implemented?) and about the relationship between maps (how much agricultural land
without conservation tillage within 500 feet of a stream?).
A GIS, then, is an information system, organized around a series of observations on a number
of variables. The observations are typically on either points, line segments, or area. A GIS is a
unique information system in which individual observations can be spatially referenced to each
other. This connectedness, or topology, allows the GIS user to perform tasks not possible with
an ordinary information system. Some of the questions that might be answered using a GIS are
discussed in the next section.
The functional capabilities of a GIS are best introduced by considering the categories of questions
a GIS might be expected to help answer. The first category can be thought of as
descriptive or inventory oriented questions. An inventory question might be asked of either a
single map (how many acres of agricultural land in a county?) or of multiple maps (how many
agricultural acres on which animal waste management best management systems have been
implemented lie within 100 feet of a stream?).
The second category of questions concerns analysis oriented questions. Unlike inventory oriented
questions, which ask for a description of some aspect of the GIS data base, analysis oriented
questions can involve making a claim using the data within the GIS. As with inventory questions,
analysis oriented questions can involve a single map (is there a spatial trend in agricultural land
values in a county? ) or multiple maps (is there a relationship between water quality and land use
within 500 feet of a stream?). Developing answers to spatially oriented analytical questions
involves a collaborative use of a GIS with other analytical software, particularly statistical
analysis software.
To address both inventory and analysis oriented questions, a GIS relies on two general types of
operations: capturing and storing the data to be used by the GIS and processing the spatial and
non-spatial data contained in the GIS.
There are three basic options for bringing new data into the GIS: 1) digitizing existing maps to
serve as "base maps" for use in the GIS; 2) digitizing new maps created especially for the GIS;
and 3) transferring digital mapped information directly into the GIS (Huxhold, 1991). Map
digitizing is an exacting and time consuming process. A map to be digitized is attached to a
"digitizing table" (which, in turn, is connected to a computer and the GIS program), and features
shown on the map are traced using an electronic pointer and transferred into the GIS.
Transferring an already created digital map into the GIS involves much less work, although the
digital version of the map, which was probably created for other applications, may not meet all
the desired specifications, in terms of scale, date, and spatial extent, for the new application.
The advisability of using an existing set of maps for entry into the GIS depends on the answer
to several questions (Huxhold, 1991). Are the existing maps accurate? If existing features such
as field boundaries are not portrayed accurately on the base maps, the digitizing process can do
nothing to improve the portrayal of this information, and may actually compound the inaccuracies
of the base maps. Are the base maps up to date? Are the base maps clean and on a "stable"
material? Paper base maps that have been folded, rolled, or stored in unprotected locations can
become distorted relative to maps produced on stable base material such as mylar. Also,
accumulation of dirt and stains on paper maps may make it difficult to identify all the features
shown on the map. Are the base maps tied to a coordinate system? No matter how accurate or
stable the material on which a base map is drawn, if the map does not have registration marks
tying the map to a coordinate system such as latitude-longitude or the state plane coordinate
system, it is impossible to make use of the information shown on the map in a GIS. Finally,
were the existing maps compiled at a scale sufficient to support the level of detail needed to
complete the desired study? If the existing maps cannot meet these tests, new maps may have
to be created. Although it is possible to make use of less than ideal base maps to provide data
for a GIS, recommendations based on the GIS operations using these data may have to be
substantially qualified.
Once data have been entered into the GIS, there are a variety of data processing functions
enabling the GIS user to answer both inventory and analysis oriented questions.
Three major types of inventory-type operations are commonly used in a GIS. The first operation,
data base queries, is the most intuitively obvious and widespread use of a GIS in urban and
environmental planning. The simultaneous access to both location and attribute information, for
one or multiple maps, allows the GIS user to extract a wide range of information from the GIS
data base.
A second type of descriptive use of the information in a GIS is to develop what have been
referred to as "descriptive spatial statistics" (Berry, 1987). A GIS enables the analyst to move
beyond the understanding conveyed by conventional statistics, such as the average acreage of
corn planted in a county, to summarize the influence that spatial processes might have on the
variable of interest. For example, a map of all agricultural parcels in a county, color coded to
reflect crop type, would permit a much more useful summary of corn planting information.
A third important descriptive capability of a GIS is the ability to create maps that are tailored to
specific questions. A disadvantage of the common practice of hand drafting information onto
existing maps, such as a USGS topographic map, is that a map created for one use may contain
either too much or too little information when used in a different situation, thus limiting the
map's usefulness in the new situation. Drafting information about agricultural activities onto
existing USGS topographic maps, which already contain a great deal of information, may
frustrate or confuse the non- technical audience for which the information is intended.
Other data processing operations address analytical rather than descriptive information needs. At
least four analytical operations can be applied when the information in a GIS is to be used for
making or defending a claim, rather than just describing the values taken on by one or more
mapped variables.
The first set of operations has been called "map algebra" operations (Tomlin, 1983; Berry, 1987).
In one map algebra operation, map overlay, the value assigned to every location in the new map
is computed as a function of the values associated with the same locations on several "input"
maps, such as land use, soil type, type of best management systems installed, and so forth.
Another map algebra operation is the ability to characterize and summarize neighborhoods,
resulting in new maps based on variable characteristics in the vicinity of target locations. An
example of this function would be the ability of the GIS to create a "buffer" around a feature,
such as a stream network, as part of an effort to identify areas that should remain undisturbed
by residential development or agricultural activity.
Map algebra operations can be combined to form equations, or "cartographic models", in a
manner similar to traditional algebraic operations. For example, an agricultural land suitability
analysis might screen parcels by first using the GIS to establish a buffer zone around a stream
and then running a USLE (Universal Soil Loss Equation) model within the buffer zone to assess
erosion potential in a riparian area.
Another analysis oriented use of GIS is the preparation of a data set for entry into other computer
programs. Data on spatially distributed units of observation can be captured, edited, organized,
and manipulated prior to analysis by a statistical package or a distributed pollutant loading model
such as AGNPS.
Berry, J.K. 1987. A mathematical structure for analyzing maps, Environmental Management
11(3):317-325.
Huxhold, W.E. 1991. An Introduction to Urban Geographic Information Systems. New York:
Oxford University Press.
Robinson, A.H., R.D. Sale, J.L. Morrison, and P.C. Muehrcke. 1984. Elements of Cartography
(5th edition). New York: Wiley and Sons.
Tomlin, C.D. 1983. Digital Cartographic Modelling Techniques in Environmental Planning. PhD
Dissertation, Yale University, New Haven, CT.
Author's Note: Much of the material presented in this article was generated as part of the
development of a manual entitled Policies and Procedures for Joint Military-Civilian Land Use
Planning prepared for the Division of Community Assistance, North Carolina Department of
Economic and Community Development and the Office of Economic Adjustment, U.S.
Department of Defense.
U.S. EPA. 1991. Seminar Publication - Nonpoint Source Watershed Workshop.
EPA/625/4-91/1027. 209 p.
The proceedings from the Nonpoint Source Watershed Workshop held in New Orleans, LA,
January 29-31, 1991, are now available. The workshop was jointly sponsored by EPA's Nonpoint
Source Control Branch and the EPA Center for Environmental Research Information. Papers
presented at the workshop and included in the publication addressed ten topics: water quality
problem identification in priority watersheds, developing goals and objectives for watershed
projects, designing institutional arrangements that work, developing the watershed plan, site
planning and selection of nonpoint source (NPS) controls, developing a monitoring system,
building successful technology transfer programs, planning and implementing an effective
information and education program, evaluating a NPS watershed implementation project, and
innovative state and local regulatory programs that support local NPS projects.
The proceedings can be obtained free from the Center for Environmental Research Information
in Cincinnati, OH (Tel: 513-569-7562 or FTS 684-7562) or the NCSU Water Quality Group (see
enclosed publication order form).
NWQEP NOTES is issued bimonthly. Subscriptions are free (contact: Publications Coordinator at the address below or via email at wq_puborder@ncsu.edu). A list
of publications on nonpoint source pollution distributed by the NCSU Water Quality Group is
included in each hardcopy issue of the newsletter.
I welcome your views, findings, information, and suggestions for articles. Please feel free to
contact me.
Judith A. Gale, EditorTaylor Creek - Nubbin Slough (Florida) Rural Clean Water Program Project
Boyd Gunsalus, South Florida Water Management DistrictProject Synopsis
Project Goals
Project Administration and Coordination
BMPs Implemented
Selected Findings and Recommendations
For Further Information Contact
Polk County ASCS
P.O. Box 688, Bartow, FL 33830
Tel:
813-533-2051
South Florida Water
Management District
1000 NE 40th Ave.
Okeechobee, FL 34973
Tel: 813-763-3776
TECHNICAL NOTES
Introduction to Geographic Information Systems
Department of City and Regional Planning, University of North Carolina at Chapel HillIntroduction
Geographic Information Systems
Functional Elements of a GIS
Capturing, Storing, and Retrieving Spatial Data
Data Processing Operations
References
INFORMATION
EDITOR'S NOTE
Water Quality Extension Specialist
North Carolina State University Water Quality Group
Campus Box 7637
North Carolina State University
Raleigh, NC 27695
Tel: 919-515-3723
Fax: 919-515-7448
email: notes_editor@ncsu.edu