The classification codes and descriptions are broad subject headings that are specific to various databases. The codes appear in the Classification, CL=, field in an IDS record and, due to the interdisciplinary nature of much of the material covered, one record may have several classifications, e.g.:

CL: Classification

SW 0815 Precipitation; SW 5040 Data acquisition

Each code is prefaced by another two-character code SW that indicates the Water Resources database.

To find a suitable code(s) to use when searching the Water Resources database, use the 'Find' feature on your browser and look for relevant words. When you have found a code or codes, you can search for these by entering them in the 'Words in any field' query box, e.g.:

cl=0815
cl=5040
cl=(0840 or 2040)

The database has 10 main divisions each with separate sub-divisions within. Scope notes of each chapter and sub-division are listed.

NATURE OF WATER
Fundamental research on the water substance.

0540 Properties of Water
         Study of the physical and chemical properties of pure water and its thermodynamic behavior in various states.

0560 Aqueous Solutions and Suspensions
         Study of the effects of various solutes on properties of water; surface interactions; colloidal suspensions.

WATER CYCLE
Analysis and interpretation of the natural occurrence, character, transport, and distribution of water. This category covers research of the dimensions of the hydrologic cycle, in contrast to the application of research to water management problems. The category represents an essential supporting effort to applied problems in later categories.

0810 General
         Studies involving two or more phases of the water cycle such as hydrologic models; rainfall-runoff relations; surface and groundwater relationships; watershed          studies.

0815 Precipitation
         Investigation of spatial and temporal variations of precipitation; physiographic effects; time trends; extremes; probable maximum precipitation; structure of          storms.

0820 Snow, Ice, and Frost
         Studies of the occurrence and thermodynamics of water in the solid state in nature; spatial variations of snow and frost; formation of ice and frost; breakup of          river and lake ice; glaciers; permafrost.

0830 Evaporation and Transpiration
         Investigation of the process of evaporation from lakes, soil, transpiration process in plants; methods of estimating actual evapotranspiration or energy balance.

0835 Streamflow and Runoff
         Mechanics of flow in streams; mechanics of overland flow; flood routing; bank storage; space and time variations (including high and low-flow frequency);          droughts; floods.

0840 Groundwater
         Mechanics of groundwater movement; multiphase systems; sources of natural recharge; mechanics of flow to wells and drains; subsidence; properties of          aquifers.

0845 Water in Soils
          Infiltration, movement and storage of water in the zone of aeration, including soil.

0850 Lakes
         Hydrologic, hydrochemical, hydrobiological, and thermal regimes of lakes and reservoirs; water level fluctuations; currents; waves.

0860 Water and Plants
          Role of plants in the hydrologic cycle; water requirements of plants; interception.

0870 Erosion and Sedimentation
         Erosion process; prediction of sediment yield; sedimentation in lakes and reservoirs; stream erosion; sediment transport. (erosion and sediment control          classified in 2080)

0880 Chemical Processes
         Chemical interaction between water and its natural environment; chemistry of precipitation.

0890 Estuaries
         Tidal effects on flow and stage; effects of sediment deposition, sea water intrusion, or other special problems of the estuarine environment.

WATER SUPPLY AUGMENTATION AND CONSERVATION
Quantitative increases in the availability of water through improved management and conservation practices.

1010 Saline Water Conversion
         Methods of desalting sea water and brackish water.

1020 Water Yield Improvement
          Increasing streamflow or improving its distribution through land management; determining hydrologic response to artificially induced rainfall; water harvesting           from impervious area; phreatophyte control; reservoir evaporation suppression.

1030 Use of Water of Impaired Quality
         Use of low-quality water for specific agricultural, industrial, or municipal purposes; agricultural use of water of high salinity.

1040 Conservation in Domestic and Municipal Use
         Methods of reducing domestic and municipal water use without impairment of service.

1050 Conservation in Industrial Use
         Reduction in both consumption and diversion requirements for industry.

1060 Conservation in Agricultural Use
         More efficient irrigation practices; chemical control of evaporation and transpiration; lower water-use plants.

WATER QUANTITY MANAGEMENT AND CONTROL
Practices or processes for management of water exclusive of conservation, and for determining the effects of man's nonwater activities on water quantity. Emphasis for this category is on the evaluation of man's water quality control efforts.

2010 Control of Water on the Surface
         Effects of land management on runoff; land drainage; seepage control; effects of control programs and devices on the stage and time distribution of streams,          lakes and estuaries; stream forecasts; control of noxious weeds and objectionable plant growth in surface channels.

2040 Groundwater Management
         Artificial recharge; conjunctive operation; irrigation effects.

2060 Effects on Water of Man's Nonwater Activities
         Effects of urbanization, highways, logging or urban land use on water yields and flow rates.

2080 Watershed Protection
         Methods for controlling erosion which reduces sediment load and conserves soil.

WATER QUALITY MANAGEMENT AND PROTECTION
Methods for identifying, describing, and controlling pollution caused by increasing quantities of municipal, industrial, agricultural, and other wastes containing physical, chemical and biological pollutants entering ground and surface waters. This category includes studies on the fate of pollutants in the environment and the effects of pollution on various uses of water resources. Routine sampling and data collection are excluded.

3010 Identification of Pollutants
         Techniques for detection, identification, and quantification of physical, chemical, and biological pollutants; analytical techniques; analytical equipment.

3020 Sources and Fate of Pollutants
         Determination of sources of pollutants in water; determination of pathways by which pollutants move from sources through surface, ground, and coastal          waters; studies on changes in their character or composition due to physical, biological or chemical action; acidification.

3030 Effects of Pollution
         Definition of the effects of pollutants, singly and in combination on different water uses: municipal, industrial, agricultural, recreational, and on the propagation of          aquatic life and wildlife; studies on the cause of eutrophication in fresh and marine waters; toxicity studies on aquatic life; bioaccumulation.

3040 Wastewater Treatment Processes
         Single or combined physical, chemical, and biological treatment processes to remove or modify impurities found in wastewaters; improvement of conventional          treatment methods for more complete purification of wastewaters, including treatment for direct reuse; collection systems.

3050 Ultimate Disposal of Wastes
         Treatment and disposal of waste concentrates resulting from the treatment of contaminated waters. Such wastes include material removed from municipal,          industrial, and agricultural wastes during treatment, the waste brines from desalting plants or oil fields, radioactive waste concentrates, wash water from filters          of water treatment plants.

3060 Water Treatment and Distribution
          Protection of water supply sources to minimize need for or load on, treatment facilities; development of more efficient and economical methods of water           treatment for municipal, industrial, agricultural, or recreational uses; alteration of water quality for health; deterioration during storage and distribution.

3070 Water Quality Control
          Research on methods to control surface and groundwater quality (except wastewater treatment) such as: production modification or substitution, process           changes, improved agricultural practices for preventing pollution from pesticides and other agricultural chemicals; management of groundwater impoundments,           estuaries, and streams to improve water quality, and supplemental aeration; groundwater pollution treatment studies.

WATER RESOURCES PLANNING
Methods, procedures, and techniques for improving the planning and decision-making process. Primary emphasis of this category throughout is on development of methodologies and criteria for providing meaningful decision rules in planning which will adequately reflect the physical, economic, legal, and social aspects of water management. This category excludes economic, legal, or social analyses which represent and integral phase of research activities conducted under other major categories, and is not limited to evaluation of the physical aspects only of applied management techniques.

4010 Techniques of Planning
         Applications of systems analysis to project planning; treatment of uncertainty; probability studies.

4020 Evaluation Process
         Methods, concepts, and criteria for evaluating project benefits; discount rate; project life; economic, social, and technological projections; reliability of          projections; value of water in various uses.

4030 Cost Allocation, Cost Sharing, Pricing/Repayment
         Methods of calculating repayment and establishing prices for vendible products; techniques of cost allocation; cost sharing pricing, and repayment policies.

4040 Water Demand
         Water quantity and quality requirements of various uses, both diversion and consumption.

4050 Water Law and Institutions
          State, local, and federal law studies on changes and additions to encourage more efficient water use; institutional structure and constraints which influence           water decisions at all levels of government.

4060 Nonstructural Alternatives
         Achievement of water resources development aims by nonstructural methods such as flood plain zoning, flood insurance.

4070 Ecologic Impact of Water Development
         Effects of water resources management operations on the overall ecology of an area.

RESOURCES DATA
Strategies for establishing field data collection programs, developing more efficient data acquisition methods or equipment, and initiating programs. This category includes studies to determine data needs as well as most efficient methods to meet these needs. Design of instrument networks which are incidental to the primary purpose of the effort should be placed under the other appropriate categories.

5010 Network Design
         Data requirements and methods of collecting data.

5040 Data Acquisition
         New and improved instruments and techniques for collection of water resources data; telemetering equipment; measuring instruments; remote sensing.

5080 Evaluation, Processing and Publication
         Methods of processing data; form and nature of published data; maps of data.

ENGINEERING WORKS
Improved technology for designing, constructing, and operating works which are required to implement water development plans. This category excludes works relevant to a specific goal, such as water treatment or desalination.

6010 Structures
         Design or construction criteria and techniques for all structures associated with the development of water resources or the control of surface or ground water.
         Included are dams, locks, bridges, conduits, lined tunnels, floodwalls, water supply intakes, wells pipelines, and storage reservoirs (earth and rockfill
         structures are under 6040).

6020 Hydraulics
         Studies on the static and dynamic behavior of water as it influences design theory for spillways, penstocks, conduits, tunnels, canals, riprap, breakwaters,
         floodwalls, and other similar structures; design of wells and well systems, including both collecting and relief wells.

6030 Hydraulic Machinery
         Design and performance of hydraulic machinery and equipment, including gates, valves, pumps, turbines and similar facilities. Includes associated control          facilities, generators, transmission systems and power system operation to the extent each is unique to problem of water utilization.

6040 Soil Mechanics
         Design theory, criteria, techniques, and engineering properties of soils as related to the design, construction, and performance of cut slopes, earth foundations,          embankments, and rockfill structures.

6050 Rock Mechanics and Geology
         Behavior of rock masses and rock foundations; engineering characteristics; structural properties of rock materials; design techniques applicable to foundations          for large structures.

6060 Concrete
         Cementing materials, aggregates, and other concrete components; engineering characteristics of concrete construction methods and techniques.

6070 Materials
         Miscellaneous materials other than soil, rock, concrete and concrete components; detection measuring, and material testing techniques and equipment. Areas          included are: bituminous, chemical, synthetic, plastic or metallic materials; paints; materials corrosion where associated with structures for water control.

6080 Rapid Excavation
         Mechanical chemical, and nuclear explosive techniques and equipment for rapidly excavating and moving large volumes of earth or rock.

6090 Fisheries Engineering
         Development of techniques and design of facilities to attract and pass fish past dams and other water control structures; methods for improving the design,          maintenance, and functioning of fish spawning areas.

MANPOWER, GRANTS, AND FACILITIES
Support of education and training as an essential ingredient of water resources research programs as well as the planning and design of water development projects. This category also includes grant and contract programs for which allocation to other categories is impossible.

7010 Education-extramural
         Support of education in water resources at universities.

7020 Education-in-house
         Government employee training programs.

7060 Research Facilities
         Laboratories, field stations or other.

7080 Grants, Contracts and Research Act Allotments

SCIENTIFIC AND TECHNICAL INFORMATION
Development of adequate manual or mechanized procedures for acquisition, storage, retrieval, and dissemination of scientific and technical information is a vital and an integral part of a successful research program. This category includes all separately identifiable activities involved in the handling of recorded knowledge resulting from basic or applied research in the water-related aspects of the physical, life, and social sciences.

8010 Acquisition and Processing
         Identification, acquisition, storage or exchange of documents in the full size or reduced form and the organization or arrangement of these documents for          retrieval.

8020 Reference and Retrieval
         Selected search and retrieval of an organized document collection in response to a specific user request.

8030 Secondary Publication and Distribution
         Selective review, indexing, subject classification, coding, abstracting, announcing, listing or distribution of documents or their bibliographical surrogates to          provide service such as current awareness or selective dissemination of information, abstract bulletins, and topical bibliographies.

8040 Specialized Information Center Services
         Activities described under groups 8010, 8020, and 8030 where performed by a separate functional element whose mission includes additional subject are          technical competence to critically review, digest, analyze, evaluate or summarize scientific and technical information in specially defined areas, or to provide          advisory and other services.

8050 Translation
         Conversion, to or from English, of scientific or technical documents in whole or in part, where performed as a separate or specific activity.

8080 Preparation of Reviews
         Preparation of state of the art critical reviews and compilation in specified technical subject areas, where performed as a separate activity exclusive of the          output of group 8040.