Paper No. 973033

An ASAE Meeting Presentation



Nick C. Parker
Unit Leader
 <>TX Coop. Fish & Wldlf Res. Unit
Raymond Sims
Research Associate
<> Agric. Sci. & Natural Res.
Rodolfo Estrada
Research Associate
Agric. Sci. & Natural Res.
Clifford B. Fedler
Associate Professor
Civil Engineering
Raquel Leyva
Research Assistant
TX Coop. Fish & Wldlf. Res. Unit
Jeff Johnson
Director, Ag Operations
Agric. Sci. & Natural Res.
Yonglun Lan
Research Associate
Agric. Sci.. & Natural Res.

Texas Tech University Lubbock, Texas

Written for presentation at the 1997 International Summer Meeting sponsored by THE AMERICAN SOCIETY OF AGRICULTURAL ENGINEERS

Minneapolis, Minnesota August 10-14, 1997


Landsat Thematic Mapper imagery and aerial videography are being used in the National GAP Analysis program to classify vegetation and develop models of vertebrate distribution for assessment of biodiversity. The GIS spatial technologies used in this program make possible extensions into agriculture and natural resource management far beyond the scope of TX-GAP.

Keywords: computers, economics, farming, GAP

The author(s) is solely responsible for the content of this technical presentation The technical presentation does not necessarily reflect the official position of ASAE and its printing and distribution does not constitute an endorsement of views v hich may be expressed.

Technical presentations are not subject to the formal peer review process by ASAE editorial committees; therefore, they are not to be presented as refereed publications.

Quotation from this work should state that it is from a presentation made by (name of author) at the (listed) ASAE meeting

EXAM PLE - From Author's Last Name, Initials. "Title of Presentation." Presented at the Date and Title of meeting, Paper NO. X. ASAE, 2950 Niles Road, St. Joseph, MI 49085-9659 USA.

For information about securing permission to reprint or reproduce a technical presentation, please address inquires to ASAE.

ASAE, 2950 Niles Road, St. Joseph. MI 49085-9659 USA

Voice: 616.429.0300 FAX: 616.429.3X52 E-Mail: <>

Nick C. Parker1 , Raymond Sims 2 3 , Rodolfo Estrada2,4, Clifford B. Fedler5 ,  Raquel Leyva2 , Jeff Johnson6 and Yonglun Lan7

1 USGS-Biological Resources Division; Texas Cooperative Fish and Wildlife Research Unit, Texas Tech University, Lubbock, TX 79409-2120
2 Texas Cooperative Fish and Wildlife Research Unit, Texas Tech University, Lubbock, TX 79409-2120
3 Cur rent address: 155 Allen Dr., #43; Lumberton, TX 77656
4 Current address: 1565 Moline St., Apt. #33, Aurora, CO 81026.
5 Department of Civil Engineering, Texas Tech University, Lubbock, TX 79409-1023
6 College of Agricultural Science and Natural Resources, Texas Tech University, Lubbock, TX 794092123
7Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China


The Texas Cooperative Fish and Wildlife Research Unit in partnership with Texas Tech University, and with other Federal and state agencies operates a geographic information system (GIS) laboratory for applications in agricultural and natural resource management. As part of a national GAP Analysis Program (the GAP program) remotely sensed imagery such as, Landsat Thematic Mapper and aerial videography is being used to classify vegetation and develop vertebrate distribution models for use in assessment of biodiversity. The hardware, software, and personnel associated with this project make possible extension into agriculture and natural resource management far beyond the scope of the GAP program. For example, using these resources, and ancillary data sets, three dimensional animated models of cattle prices at selected markets in Texas for a period of 1-year were used to demonstrate the value of spatial technologies to understanding site-specific economic conditions. Specifically, cattle prices at selected markets in Texas during a 1-year period were displayed as 52 three-dimensional animated models reflecting weekly sales in these markets. Other applications have included differentiation of irrigated and non-irrigated crop lands on the Texas High Plains, identification of center-pivot irrigation systems, the water levels in playa lakes, and design and placement of a constructed wetland to remove nutrients from sewage plant effluent. We have also identified the distribution of vegetation, including noxious weeds and plants such as salt cedar, in the riparian zone of the Red River. Numerous additional applications include the potential for coordinated state and nation-wide management of crops, agricultural resources, and pests.


Agriculturists and natural resource managers in Texas have a growing wealth of GIS data layers available to support scientifically sound decisions regarding resource allocation. The Texas Geographic Information Systems Planning Council members include 31 state agencies, three statewide associations, two regional entities, and four educational institutions (Texas GIS Planning Council 1994). Extensive GIS capability exists in state agencies such as the Texas Parks and Wildlife Department, Texas Natural Resources Conservation Commission, and the Texas Natural Resources Information System. The Texas Department of Agriculture is a member of the Texas GIS Planning Council, along with the Texas State Soil and Water Conservation Board, the General Land Office and the Texas Water Development Board. GIS is now used at all levels of government including Federal agencies working together with state agencies. The statewide GIS Implementation Plan was developed to provide coordination of GIS activities and management of data on natural resources, socioeconomics and all related indices of Texas data.

The state and federal agencies in Texas have completed digital data layers developed by the U.S. Geological Survey for county boundaries, rivers, streams and lakes, ecoregions, highways, railroads, landcover and land use, digital elevation models, political boundaries, hydrography, transportation, cemeteries, and airports (Texas GIS Planning Council 1994). GIS layers of endangered species and vegetation have been developed by the Texas Parks and Wildlife Department. Geology, surface mines, bathymetry of near shore continental shelf, playa lakes, and reservoirs have been prepared as GIS layers by the Bureau of Economic Development. Soil maps developed by the Soil Conservation Service (now the Natural Resources Conservation Service), the Texas Agriculture Experiment Station and the U.S. Department of Agriculture are available through the Texas State Soil and Water Conservation Board. Most of these data sets, including those of the U.S. Census Bureau, are available through the Texas Natural Resources Conservation Commission.

The U. S. Geological Survey, through the Mapping Division and the Biological Resources Division, seeks to develop and maintain a national digital cartographic database of the nation's natural resources (Texas GIS Planning Council 1994). Geospatial technologies have developed as indispensable tools for many researchers and natural resource managers. For example, these tools have been used in response to oil spills in Texas coastal waters (Garrett 1995; Garrett et al. 1995). Real-time data are used to pinpoint locations of spills using Global Positioning Systems (GPS) and satellite imagery in GIS databases to deploy equipment and personnel for containment and clean-up. An example of one national application of these technologies is the National GAP Program of the Cooperative Research Units in the Biological Resources Division of the U.S. Geological Survey.

The National GAP Program originated in the Idaho Cooperative Research Unit of the U.S. Fish and Wildlife Service, prior to realignment of the Coop Units with formation of the National Biological Service (NBS) in 1993. In October 1996, the NBS was reorganized into the Biological Resources Division of the U. S. Geological Survey to provide the scientific understanding and technologies needed "to support sound management and conservation of the Nation's biological resources." (Biological Resources Division 1997). The development and refinement of geospatial technologies to manage natural resources and develop maps for the Nation were clearly defined as roles of the U.S. Geological Survey.


The Texas GAP Analysis Program (TX-GAP) was implemented as part of the National GAP Analysis Program (GAP) (Scott et al. 1996) to assess statewide biodiversity and stewardship for Texas public lands. Vegetation and vertebrate species distribution are being mapped as indicators of biodiversity. Landsat Thematic Mapper (Landsat TM) satellite images, aerial photography, aerial videography, digital thematic data, natural resource inventories, museum specimens, and other sources of information are all being used in the analysis process. Geographic Information Systems are being used to bring the volumes of disparate data together for analysis and the production of maps displaying spatial data.

Because Texas is so large in area and diverse, new tools had to be developed to meet the challenges of TX-GAP. In addition to it's size enormity, Texas is about 97% privately owned. Private land ownership causes unique challenges. Therefore, early GAP programs were started in states with large public land holdings. Access to private lands and assessing conservation measures taken on those lands is very difficult in Texas. A decision was made to base the TX GAP analysis on Landsat TM satellite imagery. The satellite imagery is being "ground truthed' with aerial videography, and supplemented with field data collections as well as individual site specific resource inventories. All field sites are identified by location with Universal Transverse Mercator (UTM) coordinates obtained from Global Positioning Systems (GPS) and entered into a relational database for development of GIS layers.

Vegetation is being mapped at the pixel level (30m), and aggregated up to a 10 ha minimum mapping unit for reporting purposes. Terrestrial vertebrate species distributions are being modeled by habitat type and filtered with a variety of thematic layers on different environmental features. Public land stewardship is based on public information, observation, and land use plans. Biodiversity is based on vegetation, habitat, and vertebrate species distributions.

Geographic Cattle Prices

As a demonstration of its potential application in agriculture, the GIS equipment and software available in the TX-GAP program were used to develop a spatial representation of cattle prices in selected Texas markets for a full year. Cattle prices are routinely reported in financial publications following weekly sales at livestock auctions throughout Texas. During a given week, prices for 500-800 lb steers ranged from $49.50 to $60.00 per hundred pounds (live weight) in Texas. Prices may be influenced by abundance of cattle, amount of rainfall, time of year, price of feed and distance of feedlots to processing plants.

Cattle prices were displayed as the third dimension (elevation) on a two-dimensional map of Texas. The resulting three-dimensional map was updated to reflect weekly prices in six markets in Texas --- Amarillo, San Antonio, San Angelo, Victoria, Alice, and Huntsville. When displayed sequentially as 52 computer snapshots in an animated "gif" format, the weekly changes in cattle prices were readily apparent in geographically diverse markets for the year of 1996. Such display of data readily detects volatile markets and provides a geographical framework in which importance of transportation systems (roads, rail, and waterways), environmental conditions, and location of farm sites may be evaluated. While only currently a demonstration, this model could easily be manipulated to perform statistical analyses in order to make predictions and evaluate individual component impacts upon the market. Additional layers such as hay prices, precipitation, and range conditions could be included to examine interactions and geographic influence on cattle prices.

Red River riparian zone

Saltwater inflows into the Red River and other surface water bodies is considered to be a serious liability. The U.S. Congress has authorized three saltwater retention dams in the Red River Basin, of which only one has been constructed. Truskett Dam south of Vernon, Texas is currently the only salt water retention dam constructed in the Texas drainage of the Red River. The 1993 Landsat TM imagery, in concert with aerial videography and limited on-the-ground field verification, was used to map vegetation in the 7.5-minute USGS map of Vernon, Texas which includes a portion of the Red River along the Texas-Oklahoma border (Figure 1). Readily evident were halophytic noxious plants such as salt cedar of which there were 31,110 A, or 2.4% of the total acreage (1,276,813) in the scene, in the Vernon scene (Figure 2). Identification of such plants can be used to delineate areas with inflows of brackish and saline waters that degrade the quality of freshwater supplies. Identification and estimation of flow of inland salt water sources can be used to prioritize management activities to protect freshwater resources. Similarly, identification of saltwater resources in arid areas provides the potential to move ocean-based industries, such as the farming of marine fish, shellfish and plants, to protected inland sites.


Fresh water is increasingly seen as one of, if not the most, valuable resource in the world and especially in arid climates. The High Plains of Texas is one of the most productive agricultural sites in the world. This region accounts for 46% of the $3.4 billion produced annually from field crops in Texas (personal communication, D. Ethridge, Texas Tech University). Roughly half of the three million bales ($936 million) of cotton produced on the Texas High Plains in 1996 were from farms using ground water for irrigation. An expansion of irrigated farm lands may place agriculture in conflict with the need for water in urban areas, for recreation and for in-stream flow -- conflicts found throughout the west (Reisner 1993).

A spatial analysis of irrigated and non-irrigated crop lands provides a planning tool for landowners and government officials. We prepared such an analysis as a demonstration of application in Lubbock, Texas. Landsat TM scenes from 1993 were used to identify irrigated and non-irrigated lands in Lubbock County located in Lubbock County on the Texas High Plains (Figure 3). A Landsat TM scene for Lubbock County, Texas was classified using Spectrum software (Khoros Research, Inc., Albuquerque, New Mexico ). This supervised classification was obtained by color signature of 30x30 m pixels. Twelve attributes were identified (Table 1). These attributes were identified to be part of three main land use types: urban areas, vegetated areas, and water bodies. Urban areas included paved and bare soil areas. Vegetated areas included six main group classes: grassland, mesquite, mesquite -juniper, Harvard oak orchard, and agricultural fields. The supervised classification was verified by ground truthing at selected sites. A descriptive analysis was developed for Lubbock County using the software ArcTools by ESRI (Redlands, California). The program ArcGrid by ESRI was used to estimate total area for Lubbock County as well as for each attribute. Total land area for Lubbock County was estimated to be 576,548 acres (Table 1) as compared to the 899.52 (575,680 acres) reported by Romas (1995).

Irrigated fields were distinguished from non-irrigated fields in Lubbock County using two main criteria -- shape and color signature of the pixel. Irrigated fields (Figure 3) represented 40% of the total area (Table 1) whereas, non-irrigated fields (Figure 4) were 8%. The number of center pivot irrigation units (whole-circle units and not 1/4- 1/2 circle units) were estimated manually by shape. Within Lubbock County an area of 576,000 acres, 48 % of the land, was in crop production. Eighty-five percent of the crop land ( 279,385 A total) was irrigated ( 233,323 A) in 1993. This calculation for irrigated lands in 1993 compares very favorably with the 23,000 acres reported by Ramos (1995) for 1995. There were 217 full circle center pivot irrigation systems with actively growing crops in Lubbock County. Records of the High Plains Underground Water District indicated that in 1995 there were 539 center pivot irrigation units. However, partial circle units were included in the count. Application of remote sensing technologies to evaluate agricultural practices saved time and provided an easily repeatable method for collecting such data. Aulbach (1991) used Landsat imagery and ancillary data to examine land use patterns during and 8-year period (1974-1982) in Hockley County. In this area, before the widespread introduction of center pivot irrigation units, he reported irrigated lands were converted to nonirrigated lands as water level in the aquifer declined. With future development, analysis of Landsat and other remotely sensed imagery could be fully automated to provide data much faster and more efficiently on a routine basis. With refinement, the process could also be used to identify pivot irrigation units of less than a full circle and predict ground water levels.

Playa Lakes

The High Plains of Texas is a very flat area transversed by only a few rivers. Most of the precipitation that falls on the High Plains and ground water pumped to the surface for agricultural, industrial and municipal use does not drain off of the High Plains. Surface waters drain to one of the approximately 20,000 shallow basins known as playa lakes (Gustavson et al. 1994). Some playas with undisturbed bottoms may retain water throughout the year. Others are only ephemerally wet; however, all playas are recognized as important recharge zones for the underlying Ogallala Aquifer (Wood and Sanford 1994). The Bureau of Economic Geology at the University of Texas has prepared digital data layers with polygons representing playa lakes throughout the Panhandle of Texas (Texas GIS Planning Council 1994). These data provide historical information that can be used for future analysis of the area water resources, more specifically associated with the modifications of the playa lakes.

As another demonstration project, we used Landsat TM imagery taken from a single date in 1993 and ancillary data to identify water bodies, including 227 playa lakes in Lubbock County (Figure 5). Water bodies were classified in the same fashion as other attributes. Water bodies included playa lakes, reservoirs, rivers and creeks with water present at the time the Landsat image was made. The total area, 2,854 acres, for water bodies was estimated using ARC/GRID. The number of playa lakes with water was obtained manually. However, by actual count (E. Fish, Texas Tech University, personal communication) there are 1068 playa lakes totaling 14,803.5 A in Lubbock County. The playas without water may have been planted with crops and, therefore, in our analysis classified as irrigated croplands. In scenes taken immediately following rainfall events all playas would be flooded and could be properly classified. A series of multiple Landsat TM scenes would be required due to the spatial variation of rainfall in Lubbock County. If these 1068 plays lakes are the major source for recharge of the Ogallala Aquifer, then each acre of each plays would be required to infiltrate 16 feet of water per year to replace the water used for agricultural irrigation. Based on the 230,000 acres of irrigated cropland (Ramos 1995) commonly irrigated at about 1 foot of water per year, would require a total of 230,000 acre-ft of water. This calculated rate of recharge through the playas, an area 2.57% of Lubbock County, seems to be unlikely. Since the water level of the Ogallala Aquifer in Lubbock County has remained relatively stable during the past decade, then there must be other significant areas of recharge.

Constructed wetlands

Waste water treatment facilities are designed and permitted to meet minimum water quality discharge standards for biochemical oxygen demand (BOD), ammonia (NH3), suspended solids (TSS) and pH. Nutrients such as total nitrogen and phosphorous are typically not regulated, but are of environmental concern. Constructed wetlands have been used to reduce nutrient levels in discharges from wastewater treatment plants to protect both surface and groundwater.

GIS equipment and software were used to design the slope and placement of a constructed wetland to reduce nutrients in the discharge of a municipal wastewater treatment plant (Fedler and Parker 1995). Water from this facility in Amarillo, Texas passed via a pipeline into the Prairie Dog Fork of the Red River downstream of Tanglewood Lake. GIS data were used to analyze water levels in Tanglewood Lake and to design the constructed wetlands to fit within the local terrain. With the GIS analysis we were able to estimate evaporation values and required inflows to maintain water at any given level in the lake.

Related Projects

The distribution of plants and animals throughout Texas is of more than academic interest. Landowners, managers and state agencies use these data to manage natural resources for recreation (hunting, fishing and bird watching), commercial harvest, and conservation. For example, spatial distribution of mammals in Texas can be obtained from publications such as The Mammals of Texas (Davis and Schmidly 1994) or from interactive GIS data layers now being developed to include the maps prepared by Davis and Schmidly to show distribution of mammals in Texas. These interactive maps will include numerous other data from the literature. These data, when layered with maps of land cover, soil type, etc., can be used to model distribution of mammals at scales much finer than previously, or currently, available on county maps.

Baker et al. (1997) describes applications of GIS layers when structured to include museum records and records of the Texas Department of Health. One application of this technology has been to display the spatial distribution of bats and incidence of rabies in bats in Texas. Similarly, the distribution of the Four Corners Disease (hantavirus pulmonary syndrome) can best be understood by examining distribution of its primary host, the deer mouse (Peromyschs maniculatus) (McGarigle 1996). We have yet to examine land-use practices as they influence availability of habitat, distribution of the deer mouse, and thus distribution of hantavirus.

Projects Under Development

In cooperation with the U.S. Agriculture Research Service and visiting scientists from China and Mexico we are using Landsat TM imagery and ancillary data to analyze soil erosion in response to agricultural practices. Landsat TM scenes have been previously used to assess regional soil compaction (Rober et al. 1996) and to differentiate cropland with no-tillage, chisel-point plowing and mold-board plowing (Schaal 1986 and Lyon 1995). GIS techniques and mathematical models of wind-driven soil erosion will be used to analyze agricultural systems to conserve both soil and water.

When agricultural crops are stressed by drought, insects, disease or other environmental and biological challenges their photosynthetic activity declines. Stressed plants are less tolerant of strong sunlight due to their depressed level of evapotranspiration and are therefore typically hotter and reflect less infrared light than non-stressed plants. The health of plants can thus be sensed remotely by satellite imagery and aerial videography. These data can be used in precision farming to economically apply site specific treatment to correct problems. Applications include irrigation, treatment with pesticides, fertilizers, and other chemicals and tillage.


Agriculturists and resource managers are increasingly learning the power of spatial technologies, GPS units and GIS data layers. Plans are being developed to put a real time differential GPS radio tower on the High Plains that will service approximately a 300-mile radius. This tower will allow individual GPS units to obtain a geographic fix in real time with an accuracy of better than 5m. The high level of accuracy will allow tractors and other farm equipment to use GPS linked with GIS for precision farming allowing precise and efficient application of chemical and water resources and more timely harvesting and planting on a sub-field level.

Another evolving technology is commercialization of space-housed remote sensing platforms. Over the course of 1997 and 1998 several new satellites will be launched with multiple levels of resolution in multispectral and panchromatic sensors. Several new satellites including the EarlyBird and QuickBird by EarthWatch, Inc. (Longmont, Colorado) and Carterra by Space Imaging EOSAT (Thornton, Colorado) are designed to target the agricultural market. These satellites will provide 1 m resolution in panchromatic black and white and 4 m resolution multispectral images. EarlyBird and QuickBird also return to the same location every 60 h and the data can be downloaded from the Internet. When these GIS, GPS, remote sensing applications and other automated samplers and sensors are build into agriculture practices the long-term possibilities of increased efficiency are virtually unlimited.

The GIS applications discussed in this paper are only a few of the agricultural applications currently being developed. Today, at least one landowner in Dickens County, Texas has his own GIS and GPS capability. He employs SPOT (SPOT Image Corp., Reston, Virginia) imagery to map noxious plants and identifies GPS coordinates for the precision application of herbicides used in control of brush and weeds. As more data, better hardware, and more robust software are wrapped into easier to use and less expensive packages, GIS solutions to current agricultural problems will become more prevalent. Several advances in technology should make GIS a more feasible option on the High Plains and throughout Texas in the next few years.


We thank Don Ethridge, Ernest Fish, Carlos Gonzales-Rebeles, Jeff Lee, and Sherman Phillips and for review of this manuscript. The Texas Cooperative Fish and Wildlife Research Unit is jointly sponsored by Texas Parks and Wildlife Department, Texas Tech University, the Wildlife Management Institute, and the U.S. Geological Survey-Biological Resources Division. This is publication T-10-110 of the College of Agricultural Sciences and Natural Resources.


Aulbach, C.S. 1991. Detecting, evaluating, and monitoring land-use change on the Southern High Plains of Texas. Ph.D. Dissertation, Texas Tech University, Lubbock, Texas. 129 PP

Baker, R.J., B. Albin, R.D. Bradley, J.J. Bull, J. Burns, G. Edson, R.E. Estrada, E. Farley, C.B. Fedler, B.M. Gharaibeh, R.L. Hammer, C. Jones, K.A. Clark, R.R. Monk, J.T. Montford, G. Moore, N.C. Parker, J. Rawlings, A Sansom, D.J. Schmidly, R.W. Sims, H. Wichman, and F.D. Yancey. 1997. Natural Science Database: Resource management and public health. Pages 10-20 in M. Shaughnessy (ed.) Collaboration: The 'Key' to Success. Proceedings of the 4th Annual Conference, Organization of Fish and Wildlife Information Managers, Key Largo, FL. 96 pp.

Biological Resources Division. 1997. Geospatial technology strategic plan 1997-2000. U.S. Geological survey, Office of Biological Informatics and Outreach, Reston, Virginia.

Davis, W.B. and D.J. Schmidly. 1994. The mammals of Texas. Texas Parks and Wildlife Press, Austin, Texas.

Fedler, C.B. and N.C. Parker. 1995. Constructed wetlands for nutrient reduction at Lake Tanglewood, Amarillo, Texas. Project Report, Dept. (: ivil engineering, Texas Tech University, Lubbock, Texas.

Garrett, M. 1995. GIS for oil spill response: database needs, uses, and case studies from Florida and Texas. Pages 193-203 in J.C. Lyon and J. McCarthy (editors), Wetland and environmental application of GIS. Lewis Publ., Boca Raton.

Garrett, M., G.A. Jeffress, and D.A. Waechter. 1995. Incorporation of real-time environmental data into a GIS for oil spill management and control Pages 231-240 in J.C. Lyon and J. McCarthy (editors), Wetland and environmental application of GIS. Lewis Publ., ., Boca Raton.

Gustavson, T.C., V.T. Holliday, and S.D. Hovorka. 1994. Development of playa basins, Southern High Plains, Texas, and New Mexico. Pages 5-21 in L.V. Urban and A.W. Wyatt ((eds).) Proceedings of the Playa Basin Symposium, Texas Tech University, Lubbock, Texas.

Lyon, J.G. 1995. Remote sensing of sediments and wetlands in Lake Erie. Pages 107-124 in J.C. Lyon and J. McCarthy (editors), Wetland and environmental application of GIS. Lewis Publ., Boca Raton.

McGarigle, B. 1996. Hantavirus risk assessed by GIS. Pages 28-30 in Geographic Information Systems Executive Handbook: A supplement to government technology.

Reisner, M. 1993. Cadillac desert: The American West and its disappearing water. Revised and updated. Penguin Books, New York, New York.

Ramos, M.G. (E.). 1995. 1996-1997 Texas Almanac. The Dallas Morning News, Inc. Dallas, TEXAS .

Rober, M.L., D. Wood, and R.A. McBride. 1996. Use of digital image analysis and GIS to assess regional soil compaction risk. Photogrammetric Engineering and Remote Sensing 61(12: 1397-1404.

Schaal, G. 1986. Residue studies. Ohio Dept. of Natural Resources, Div. of Soil and Water Conservation, Columbus, Ohio (Reported in Lyon 1995).

Scott, J.M., T.H. Tear, and F.W. Davis (eds.) 1996. GAP analysis: A landscape approach to biodiversity planning. American Soc. Photogram~netry and Remote Sensing, Bethesda, Maryland.

Texas GIS Planning Council. 1994. Texas Geographic Information Systems Implementation Plan: Building Texas GIS infrastructure. Austin, Texas.

Warren, W.W. and W..E. Sanford. 1994. Recharge to the Ogallala: 60 years after C.V. Theis's analysis. Pages 23-33 in L.V. Urban and A.W. Wyatt (eds.) Proceedings of the Playa Basin Symposium, Texas Tech University, Lubbock Texas.

Table 1. Attributes for Lubbock County, Texas. Attributes were determined by color signature of 30x30 m pixels from Landsat Thematic Mapper images.

Attributes Acres Percent
Irrigated 233,323 40.47
Grassland 194,331 33.71
Paved and bare soil 50,963 8.84
Non-irrigated 46,061 7.99
Mesquite 22,663 3.93
Harvardshinoak 7,952 1.38
Juniper 7,407 1.28
Riparian 4,254 0.74
Orchard 3,500 054
Water 2,854 0.50
Mesquite-juniper 1,747 0.30
Acacia 1,493 0.26
TOTAL 576,548 100.00

Figure 1. Lubbock County and location of the 7.5-minute quadrangle map for Vernon, Texas.

Figure 2. Salt cedar as classified from Landsat TM imagery of 1993 in the area of the 7.5-minute quadrangle map prepared by the U.S. Geological survey for Vernon, Texas.

Figure 3. Irrigated fields in Lubbock County, Texas as analyzed from 1993 TM scenes. Note the circular center-pivot irrigation units.

Figure 4. Non-irrigated fields in Lubbock County, Texas as analyzed using TM scene from 1993. Note the large area void of fields is the city of Lubbock, Texas.

Figure 5. Water bodies in Lubbock County, Texas as estimated from spectral signatures for water in 1993 Tm scenes. The area and shape of each dot represents the area and shape of the water bodies. The round bodies are playa lakes, the squares represent reservoirs and the linear bodies are impoundments on the few streams in Lubbock County.

p1641.gif (73727 bytes) p164fig2.gif (161804 bytes)
p164fig3.gif (146733 bytes) p164fig4.gif (84860 bytes)

p164fig5.gif (71615 bytes)