« PreviousContinue »
accumulate in the soil and has a long-term The reduction in streamflow has caused
impact on agricultural production. Reduced a hydroelectric-power generation decrease,
Annual 1872–1990 departure from average discharge in the Sacramento River flows from the upper Sacramento, Feather, Yuba, and American River basins, basin. Solid areas are years classified as critically dry by the California Depart- adjusted to represent unimpaired runoff. Flows from 1872 to 1905 are estimated ment of Water Resources. The Sacramento River basin discharge is the combined from historical data (Data from the California Department of Water Resources.)
communities, are also adversely affected by the drought. Low streamflows and reservoir levels restrict boating and fishing. Extreme fire danger has led to the closing or restricted use of wildlands. The drought has been extremely hard on fish and wildlife. Decreased releases of water downstream from reservoirs and high air temperatures have resulted in a fourth straight year of poor anadromous fish spawn. For some species, the problem is now compounding: reduced populations that hatched during the first year of drought are returning to even worse conditions. Reservoir fisheries are also being adversely affected by low water levels. The flooding of some waterfowl refuges is incomplete, and forage and cover for upland wildlife is reduced. The drought has had a devastating effect on California's timberlands. Trees weakened by the drought are being killed by insects and disease. In the Lake Tahoe basin, about 20 percent of the trees are already dead, and even more trees are in jeopardy this year.
The danger of forest fires is exacerbated by the presence of this added dry fuel. In Yosemite National Park, California's famed sequoias were sprayed with a fire-retardant to protect them from threat of fire.
Forecast for 1991
DWR forecasters estimate that if runoff is 70 percent of normal next year, there is a 65 percent chance that most of the State's water needs would be met. Carryover storage in reservoirs is well below normal, however, so reservoir storage would not recover from depleted levels. The forecasters also estimate that if runoff is 5 percent above normal, reservoir storage levels would return to normal and that most of the State's water need would be met as well. Because the winter storm season brings most of the State's annual precipitation, it may be spring 1991 before we know if California is in for a fifth straight year of drought or if the dry spell will be broken.
National Mapping Program
Continuing Evolution in Mapping Technology
By Lindy Mann
r | Whe initial cycle of detailed topographic
mapping covering the conterminous
48 States, begun more than 50 years ago, was completed by the USGS during fiscal year 1990. Having accomplished this significant milestone, the USGS National Mapping Division is focusing on updating the more than 57,000 maps generated and making them available in digital form. New automated methods for processing spatially related data are streamlining map production techniques as well as revolutionizing the application of this information to land and resource management issues.
The conterminous United States and Hawaii are mapped as quadrangles, each covering 7.5 minutes of latitude and longitude. The 7.5-minute mapping program began in the late 1930's in a cooperative effort with the Tennessee Valley Authority. Most of the 7.5minute quadrangle maps are printed at a scale of 1:24,000 (1 inch on the map represents 2,000 feet on the ground). For a few areas, 1:25,000-scale maps are published in which contours are depicted in meters.
The mainland of Alaska has been mapped at a scale of 1:63,360 (1 inch represents 1 mile). A few areas of the Alaska peninsula and most of the Aleutian Islands are mapped with very general reconnaissance maps because the persistent cloud cover over these areas makes it difficult to acquire the aerial photography needed for map compilation. The final map completed in the first cycle of the national program was the Seneca quadrangle south of Canyon City in Grant County, Oreg.
One of the key components in the evolution of the National Mapping Program is the conversion of the 1:24,000- and 1:25,000-scale topographic maps to digital form. The resulting data will be made available to Federal, State, and public users through the National Digital Cartographic Data Base, which the USGS is assembling as the largest repository of map information on the United States and its territories.
Geographic information system (GIS) technology has emerged as a powerful new means of handling spatially related information and is a major element in the new digital direction of USGS mapping efforts. GIS's capture, store, and process data according to their geographic or spatial relationships. From these systems scientists can produce maplike layers of digital data that can be merged, separated, manipulated, and analyzed by computers to support more informed decisionmaking for many scientific, engineering, and planning purposes.
The completion of the initial cycle of topographic mapping marks the beginning of a major new responsibility for the USGS. As fiscal year 1991 began, the USGS was assigned the role for the Interior Department of coordinating and standardizing digital cartographic data through the Federal Geographic Data Committee (as directed in the Office of Management and Budget Circular A–16, Revised). In this role, the bureau will serve as the Federal data base manager and coordinator for spatially referenced digital data.
Building Partnerships for Geographic Data Sharing
By Michael A. Domaratz
geographic and cartographic information
in computer-readable form—is a requisite part of understanding and responding to complex societal problems. Computerized tools for handling spatial data, such as geographic information systems, are cost-effective means of managing large volumes of spatial data and performing these analyses. As important as these tools have become, their effectiveness ultimately depends on the availability and quality of the digital spatial data analyzed. The immediate need for highquality spatial data and the cost of collecting the data are two factors that encourage new partnerships among users in Federal, State, and local governments. These partnerships prevent wasteful duplication of effort and permit increased dedication to solving problems rather than to collecting data.
I ncreasingly, the analysis of spatial data—
he National Mapping Division provides accurate and up-to-date basic cartographic information for the United States in forms that can be readily applied to present-day problems. Maps, digital data, aerial photographs, satellite images, and geodetic control information represent some of the cartographic products available. Topographic maps at various scales, which illustrate detailed and precisely referenced information about natural and mammade features on the Earth's surface, continue to be important products. These maps provide basic cartographic information that is needed by Federal, State, and local government agencies in dealing with key issues ranging from satisfying energy demands to conserving natural resources, from identifying environmental problems to developing acceptable solutions, and from locating commercial facilities to designing public works. In addition to maps, cartographic data in computerreadable form are becoming increasingly important. These data are used in computer-based resource and geographic information systems to evaluate alternative management plans and to study the effects of different management policies.
Building innovative partnerships and improving coordination processes also increase the Nation's ability to solve future societal problems and to compete more effectively in the world marketplace. The development of a national digital spatial data infrastructure, including linkages at all levels of society, will enable sharing and efficient transfer of digital spatial data between producers and users, thus increasing the availability and timeliness of spatial information. The Federal Interagency Coordinating Committee on Digital Cartography (FICCDC) coordinates the digital cartographic data activities of Federal agencies. In a 1989 memorandum rechartering the FICCDC, the Director of the Office of Management and Budget (OMB) noted the evolving nature of data handling technology and the need for Federal Government programs to evolve with this technology. The Director asked the FICCDC to evaluate its role in coordinating Federal digital spatial data use and to review and recommend revision to OMB Circular A–16, the coordinating mechanism. In its report, the FICCDC recommended that the breadth of coordination activities be increased by adding such types of spatial data as geologic, resource, cultural and demographic, and ground transportation; that the name of the committee be changed to the Federal Geographic Data Committee to reflect the broader coordination responsibility; and that the new committee and its responsibilities be incorporated in a revised and expanded Circular A–16. The primary objective of the new Federal Geographic Data Committee is to promote the coordinated development, use, sharing, and dissemination of surveying, mapping, and related spatial data. Subcommittees will coordinate activities related to 10 spatial data Categories, including topographic map, soil, wetland, geologic, geodetic, vegetation, cadastral, ground transportation, cultural and demographic, and certain international boundaries. These activities will identify standards of accuracy, content, and format, facilitate exchange of information and transfer of data, and coordinate collection of spatial data. Working groups will respond to issues common to all spatial data categories, such as standards, technology, and liaison with the non-Federal spatial data user community. The new committee will promote the development, maintenance, and management of spatial data bases. Specifications for these systems will ensure data reliability, compatibility, and consistency so data may be used with confidence. The committee will also encourage the development of standards and specifications that foster the exchange and multiple
use of data and promote data sharing. An additional important focus of the new committee is to provide guidance and promote coordination among Federal, State, and local government agencies, the private sector, and academia with the objective of developing a partnership for a national digital spatial data infrastructure.
The revision of Circular A–16 provides the framework for coordinating the programmatic and technical aspects of expanding Federal spatial data activities and for coordinating activities for certain categories of spatial data that are national in scope. The revision also supports development of common standards and specifications that remove the impediments to sharing data; promotes technology development, transfer, and exchange; and encourages sharing of data not only among Federal agencies, but also among State and local government agencies, the private sector, and academia.
Cartographic Data Aid Response to National Emergencies
By Lindy Mann
urrent cartographic information in
both digital and graphic form assists in
local and regional planning and in responding to national emergencies. The cartographic data depicted on the more than 57,000 topographic maps covering the Nation at scales of 1:24,000 (49 States) and 1:63,360 (Alaska) are periodically reviewed for updating. These topographic maps and related digital cartographic data are critical national resources that can be used to provide a benchmark for environmental analysis, for planning purposes to help mitigate national emergencies, for determining damages from natural disasters, and as source data for preparing other map products.
Maps are periodically revised to reflect
recent natural and cultural changes and to correct deficiencies and inaccuracies in older maps. To accomplish a national map revision program in a systematic manner and to ensure that the highest priorities are addressed, the USGS annually solicits map requirements from Federal, State, and local agencies.
Joint funding agreements between individual
States and the USGS help expedite the needed revision of existing topographic maps. Annually, the USGS has mapping agreements with 25 or more States, and the support provided by the USGS ranges from
revision of existing maps to preparation of cartographic data in digital form. The revision program is managed by the National Mapping Division, and cartographic production is done in centers in Reston, Va.; Rolla, Mo.; Denver, Colo.; Menlo Park, Calif.; and Sioux Falls, S. Dak. More than 3,000 topographic maps are currently in the revision program, and between 3,000 and 5,000 maps are inspected annually to determine the need for revision. Some maps require only minor updates, while others require major changes. Revision may require scheduling new aerial photography; establishing field control and, when needed, field inspecting map features depicted on a map manuscript before printing; and obtaining source information such as boundary and coastline changes and names that are to be shown on the revised maps. Often, priorities change suddenly when a natural disaster occurs. Hurricane Hugo is a prime example. Many areas in South Carolina were declared disaster areas by the Federal Emergency Management Agency. These areas are depicted on parts of 280 1:24,000-scale maps, 55 of which cover areas that sustained severe damage. Several of these maps are now scheduled for revision. To generate up-todate maps of the State areas affected, suitable source materials, such as aerial photographs, are needed to revise existing maps and digital cartographic data. To provide current information for production of topographic and soil classification maps, orthophotographs, map products for land management and land use and land cover and for damage assessments of natural events and planning purposes to mitigate risks associated with natural disasters, a National Aerial Photography Program was developed and implemented. This Federal program, which is managed by the USGS, is funded by five major Federal agencies and a few States. Under contract, private companies photograph selected State areas annually. The program is designed to provide complete photographic coverage of the conterminous United States about every 5 years. This national data
base of current information is available to all users through the USGS Earth Science Information Centers (see “Guide to Information and Publications,” p. 94) and provides an easily accessible source to help in many aspects of national emergencies. Revision of existing maps still requires cartographers to perform field work in the areas affected by natural and cultural changes, to search for documentation on boundary changes, and to acquire horizontal and vertical map control where needed. However, most revision work is done in offices where information from aerial photographs, existing map data, and cartographic data in digital form is reviewed and analyzed. The USGS is implementing new technologies and acquiring modern digital equipment to expand and improve the production of new maps and data and to accelerate map revisions and, therefore, accessibility to the latest cartographic data. Users of maps and cartographic data repeatedly tell us that current information is a critical need. Likewise, it is important to have current information readily available for land management studies, including wetlands and
More than 3,000 of the 57,000 U.S. topographic maps are being revised in fiscal year 1990 as part of the USGS National Mapping Program.
Hurricane Hugo left its mark on many coastal communities in South Carolina, as evidenced by these beach homes and a parking lot in the Folly Beach area.