<descriptor thcode="2"><thesaurus thcode="2" name="USGS Thesaurus" scope="Topics and methods of scientific study carried out by USGS, with product types, scientific disciplines, geologic time, and types of institutional structure and activities.  Broad and shallow, used to help people find scientific information." creator="U.S. Geological Survey" rights="Public domain" edition="2.0" date="2020-01-09" codetype="number" prefix="topic" uri="https://www2.usgs.gov/science/USGSThesaurus" tblname="term" nonpref="nonpref" relterm="relterm" root_code="1" contact="pschweitzer"><category><term thcode="25" code="29" name="distinct labels" parent="26" scope="Preferred labels (descriptor texts) are distinct within the thesaurus. A concept can be specified either by its unique identifier (code) or by the text of its descriptor."/><term thcode="25" code="16" name="hierarchical" parent="11" scope="Substantive broader-narrower relationships exist among the terms."/><term thcode="25" code="13" name="transitive" parent="12" scope="Narrower terms have an &quot;is a&quot; relationship with their broader terms, and generally can be described as part-of, type-of, or instance-of the broader term."/><term thcode="25" code="21" name="disciplines" parent="2" scope="Broad categories of human inquiry or activity, such as scientific disciplines."/><term thcode="25" code="20" name="methods" parent="2" scope="Actions taken to obtain or analyze information"/><term thcode="25" code="19" name="organizational functions" parent="2" scope="Things that organizations do, typically including various types of programs, projects, and services."/><term thcode="25" code="7" name="temporal" parent="2" scope="Terms indicate periods of time, such as chronostratigraphic units, named historical periods or intervals surrounding known historical events, or seasons."/><term thcode="25" code="5" name="theme" parent="2" scope="Terms indicate domains of human concern, such as scientific discipline, societal problems, or characteristics of earth, space, oceans, and living things."/><term thcode="25" code="29" name="distinct labels" parent="26" scope="Preferred labels (descriptor texts) are distinct within the thesaurus. A concept can be specified either by its unique identifier (code) or by the text of its descriptor."/><term thcode="25" code="16" name="hierarchical" parent="11" scope="Substantive broader-narrower relationships exist among the terms."/><term thcode="25" code="13" name="transitive" parent="12" scope="Narrower terms have an &quot;is a&quot; relationship with their broader terms, and generally can be described as part-of, type-of, or instance-of the broader term."/><term thcode="25" code="21" name="disciplines" parent="2" scope="Broad categories of human inquiry or activity, such as scientific disciplines."/><term thcode="25" code="20" name="methods" parent="2" scope="Actions taken to obtain or analyze information"/><term thcode="25" code="19" name="organizational functions" parent="2" scope="Things that organizations do, typically including various types of programs, projects, and services."/><term thcode="25" code="7" name="temporal" parent="2" scope="Terms indicate periods of time, such as chronostratigraphic units, named historical periods or intervals surrounding known historical events, or seasons."/><term thcode="25" code="5" name="theme" parent="2" scope="Terms indicate domains of human concern, such as scientific discipline, societal problems, or characteristics of earth, space, oceans, and living things."/></category><altlabel><altlabel>USGSThesaurus</altlabel><altlabel>USGSThesaurus</altlabel></altlabel></thesaurus><term thcode="2" code="560" name="hydrology" parent="291" scope="Branch of earth science that deals with water as it occurs in the atmosphere, on the surface of the ground, and underground."/><uf><usefor name="hydrologic maps"><usewith><term thcode="2" code="700" name="maps and atlases" parent="808" scope="Representation, usually on a flat surface, of a part or whole of the Earth or other parts of the universe.  Collections of maps linked digitally or bound together in a book are called atlases."/></usewith></usefor></uf><bt><term thcode="2" code="291" name="earth sciences" parent="1019" scope="Broad term for all science related to the study of the earth."/><term thcode="2" code="1019" name="sciences" parent="1" scope="Major educational fields, fields of study, and professional groupings within USGS."/><term thcode="2" code="1" name="Categories" scope="Thematic terms for categorizing information resources.  This thesaurus is intended to support finding and understanding scientific information."/></bt><nt><term thcode="2" code="1678" name="hydrodynamics" parent="560" scope="Principles of fluid dynamics applied to water bodies."/></nt><rt><term thcode="2" code="278" name="domestic well water use" parent="1313" scope="Use of self-supplied water for household purposes, such as drinking, food preparation, bathing, washing clothes and dishes, flushing toilets, and watering lawns and gardens."/><term thcode="2" code="353" name="erosion" parent="451" scope="The process whereby materials of the earth's crust are loosened, dissolved, or worn away and simultaneously moved from one place to another."/><term thcode="2" code="398" name="floods" parent="1667" scope="Relatively high water that overflows the natural or artificial banks of a stream or coastal area that submerges land not normally below water level."/><term thcode="2" code="451" name="geologic processes" parent="101" scope="All types of processes involving geological structures."/><term thcode="2" code="518" name="groundwater quality" parent="1306" scope="Fitness of subsurface water for use based on its composition and properties."/><term thcode="2" code="554" name="hydrogeology" parent="464" scope="Study of subsurface waters and geologic aspects of surface waters."/><term thcode="2" code="562" name="hydrothermal processes" parent="451" scope="Natural phenomena relating to heated water generated by igneous activity."/><term thcode="2" code="581" name="industrial water use" parent="1313" scope="Use of water for industrial purposes such as fabrication, processing, washing, and cooling, and including such industries as steel, chemical and allied products, paper and allied products, mining, and petroleum refining."/><term thcode="2" code="607" name="irrigation" parent="1313" scope="Artificial application of water on lands to assist in the growing of crops and pastures or to maintain vegetative growth in recreational lands such as parks and golf courses."/><term thcode="2" code="657" name="limnology" parent="291" scope="Scientific study of the physical and biological characteristics of inland bodies of water such as lakes and ponds."/><term thcode="2" code="708" name="marine water quality" parent="1306" scope="Observed intrinsic characteristics of marine waters affecting their ability to support life or facilitate biological processes such as waste decomposition."/><term thcode="2" code="731" name="meteorology" parent="68" scope="Branch of science dealing with the short-term variations of atmospheric conditions including wind, precipitation, temperature, humidity, cloud cover, and air pressure."/><term thcode="2" code="751" name="mining water use" parent="1313" scope="Water use for the extraction of naturally occurring mineral deposits by mining or quarrying."/><term thcode="2" code="806" name="nutrient content (water)" parent="1304" scope="Contaminants in water that nourish organisms, especially plants. Includes nitrogen and phosphorus, either of which can lead to the harmful growth of algae and other plants when present to excess in a body of water."/><term thcode="2" code="818" name="ocean sciences" parent="291" scope="Sciences involved in the study of geological, biological, chemical, and physical characteristics and processes of the oceans."/><term thcode="2" code="854" name="oxygen content (water)" parent="1304" scope="Measurement of the concentration of oxygen dissolved in water, which is an important indicator of the condition of a water body."/><term thcode="2" code="925" name="power generation water use" parent="1313" scope="Use of water in the process of producing electric energy by transforming other forms of energy."/><term thcode="2" code="927" name="precipitation (atmospheric)" parent="63" scope="Any or all forms of water particles that fall from the atmosphere, such as rain, snow, hail and sleet."/><term thcode="2" code="1001" name="river reaches" parent="1002" scope="Continuous parts of streams between two specified points."/><term thcode="2" code="1002" name="river systems" parent="1124" scope="Long water courses including main streams and tributaries."/><term thcode="2" code="1010" name="salinity" parent="1304" scope="Measure of the concentration of salts dissolved in a solution."/><term thcode="2" code="1034" name="sediment transport" parent="451" scope="Transport of solid particles of unconsolidated rock and mineral fragments, chemical precipitates, or biological materials."/><term thcode="2" code="998" name="stream discharge" parent="1113" scope="Volume of water in a stream passing a given point at a given moment in time, expressed as a measure of volume per unit of time, i.e. cubic feet per second, million gallons per day, or gallons per minute."/><term thcode="2" code="1116" name="stream-gage measurement" parent="375" scope="Use of specialized instruments designed for observing, checking, and recording the water discharge that occurs in a natural channel."/><term thcode="2" code="1113" name="streamflow" parent="1667" scope="A type of channel flow, applied to a specific part of surface runoff in a stream, whether or not it is affected by diversion or regulation."/><term thcode="2" code="1124" name="surface water (non-marine)" parent="1308" scope="Open bodies of water, such as lakes, rivers, or streams.  All non-marine waters on the  surface of the earth, including fresh, brackish, and salt water."/><term thcode="2" code="1125" name="surface water quality" parent="1306" scope="Chemical, physical, and biological characteristics of water in lakes, rivers, or streams related to its fitness for use."/><term thcode="2" code="1129" name="suspended material (water)" parent="1304" scope="Sediment or organic material carried in suspension in the water column, in contrast to material that moves on or near the bottom. May be measured directly by sampling, or indirectly by acoustic or optical backscatter or transmission."/><term thcode="2" code="1295" name="wastewater discharge" parent="1311" scope="Water that is returned or reused after release from a wastewater treatment plant."/><term thcode="2" code="1299" name="water circulation" parent="1667" scope="The flow of water in a body of water due to wind or other forces or variations in density or temperature. Use 'water circulation' for situations that are not specifically covered by narrower terms. Use 'ocean circulation' for water circulation in the oceans."/><term thcode="2" code="1301" name="water hardness" parent="1304" scope="Indicator of the concentration of alkaline salts in water, mainly calcium and magnesium, as a measure of water quality."/><term thcode="2" code="1302" name="water pH" parent="1304" scope="The negative logarithm of the hydrogen ion concentration or activity of a water solution. Used for expressing both acidity (pH less than 7) and alkalinity (pH greater than 7), with 7 considered neutral."/><term thcode="2" code="1304" name="water properties" parent="1174" scope="Measurable physical and chemical characteristics of water from different sources."/><term thcode="2" code="1306" name="water quality" parent="1174" scope="The chemical, physical, and biological characteristics of water, usually in respect to its suitability for a particular purpose."/><term thcode="2" code="1308" name="water resources" parent="777" scope="Stocks of water, the liquid derived from precipitation. A constituent of living matter and necessity for all life, it covers a large proportion of the earth's surface."/><term thcode="2" code="1309" name="water sampling" parent="379" scope="Methods of collecting a representative part of a body of water for testing in controlled conditions."/><term thcode="2" code="1312" name="water temperature" parent="1304" scope="The degrees of heat of water from a given source at a specific time."/><term thcode="2" code="1313" name="water use" parent="1311" scope="Water withdrawal for a specific purpose, such as domestic use, irrigation, or industrial processing."/><term thcode="2" code="1327" name="wetland functions" parent="315" scope="Processes related to wetlands such as support of ecosystems, evaporation effects on weather, nutrient cycles, etc."/></rt></descriptor>