<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="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."/><uf><usefor name="dissolved constituents"/><usefor name="dissolved contaminants"/><usefor name="water-quality"/><usefor name="water-quality data"><usewith><term thcode="2" code="235" name="datasets" parent="808" scope="Digital information in a format suitable for direct input to software that can analyze its meaning in the scientific, engineering, or business context for which the data were collected."/></usewith></usefor></uf><bt><term thcode="2" code="1174" name="topics" parent="1" scope="Themes, subjects, and concerns for which USGS information resources are relevant."/><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="518" name="groundwater quality" parent="1306" scope="Fitness of subsurface water for use based on its composition and properties."/><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="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."/></nt><rt><term thcode="2" code="2274" name="PFAS" parent="769" scope="Per- and polyfluoroalkyl substances (PFAS) are a group of man-made chemical compounds that are an emerging contaminant."/><term thcode="2" code="53" name="aquatic biology" parent="650" scope="The scientific study of organisms living in or near water.  This term is to be used for the science of 'aquatic biology' and for  biological studies in fresh and brackish water. For marine biological studies, use 'marine biology'."/><term thcode="2" code="769" name="contamination and pollution" parent="1174" scope="Introduction of harmful substances into the environment by human action or natural processes."/><term thcode="2" code="283" name="drinking water use" parent="278"/><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."/><term thcode="2" code="1298" name="water chemistry" parent="437" scope="Branch of chemistry that deals with the elements and compounds in water."/><term thcode="2" code="1304" name="water properties" parent="1174" scope="Measurable physical and chemical characteristics of water from different sources."/></rt></descriptor>