nhdplusv2:hasCOMID Relates an NHDPlusV2 feature to its COMID nhdplusv2:partOfWaterBody Connects an elementary flowpath to a waterbody it lies within hyf:realizedCatchment Identifies the one and only one catchment that is realized by a particular feature hyf:HY_WaterBody A waterbody is part of the hydrographic network and is either standing in a depression or flowing in a channel, which are parts of the channel network nhdplusv2:hasFTYPE Relates an NHDPlusV2 feature to its FTYPE (see also nhdplusv2:hasFCODE) nhdplusv2:partOfFlowPath Connects an elementary flowpath (e.g., NHDFlowline) to any non-elementary flowpath it is a part of hyfo:WaterFeature A complete water feature including water, container, and void; includes surface and subsurface water features wbd:DrainageBasin A HUC12 watershed (drainage area) from the WBD geo:hasGeometry A spatial representation for a given Feature. hyf:HY_DendriticCatchment a catchment which is determined by a single common downstream catchment gwml2:GW_Well A shaft or hole sunk, dug or drilled into the Earth to observe, extract or inject water (after IGH1397) nhdplusv2:divergence Indicates if a nhdplusv2:FlowLine is the main-path or a minor-path of a divergence (no triple if no divergence) topological connection (spatial contact) (sawgraph) nhdplusv2:hasReachCode Relates an NHDPlusV2 feature to its ReachCode hyf:upstreamWaterBody Identifies another waterbody immediately upstream, allowing network navigation without knowing an inflow or outflow of the catchment realized by the waterbody geo:SpatialObject Anything spatial (being or having a shape, position or an extent). qudt:quantityValue gwml2:gwMonitoringHost Identifies the feature hosting the site [GW_MonitoringSite], e.g., a well, spring, lake or stream hyf:downstreamWaterBody Identifies another waterbody immediately downstream, allowing network navigation without knowing an inflow or outflow of the catchment realized by the waterbody hyfo:SurfaceWaterFeature A complete surface water feature including water, container, and void (for example: lake, river, marsh, et al.) nhdplusv2:downstreamFlowPath Identifies another flowpath immediately downstream, allowing network navigation without knowing an inflow or outflow of the catchment realized by the flowpath qudt:Unit nhdplusv2:downstreamFlowPathTC The transitive closure of the nhdplusv2:downstreamFlowPath object property hyf:HY_CatchmentRealization based on the idea that there are multiple hydrology-specific perspectives of the holistic catchment concept that are used to describe a catchment as a unit of study shared across sub-domains and studies qudt:QuantityKind hyf:HY_FlowPath realizes a catchment specifically as a path connecting the inflow and outflow of the catchment it realizes wbd:containingHUC Relates a flowline catchment to any WBD drainage basin it lies within gwml2:GW_AquiferSystem A body of permeable and poorly permeable material that functions regionally as a water-yielding unit; it comprises two or more permeable beds separated at least locally by confining beds that impede groundwater movement but do not greatly affect the regional hydraulic continuity of the system; includes both saturated and unsaturated parts of permeable material (after ASCE, 1987) qudt:hasUnit hyf:HY_Canal a body of surface water, participating in a hydrographic network, that is special due to its artificial origin (man-made) gwml2:GW_AquiferUnit Denotes aquifer-related hydrogeological units: aquifer systems, aquifers, or confining beds nhdplusv2:partOfMainStem Connects an elementary flowpath (e.g., NHDFlowline) to its main stem nhdplusv2:downstreamWaterBodyTC The transitive closure of the nhdplusv2:downstreamWaterBody object property hyf:HY_HydroFeature a basic feature to reflect the properties that all hydrologic features have hyfo:WaterWell A water well, with focus on the hole/shaft itself (see gwml2:GW_Well) hyfo:HydroRockBody a hybrid physical object, such as aquifer, well, or lake, that consists partly of a rock body (a container), empty spaces therein (voids), and a water body inside the space nhdplusv2:MainStem a named river or similar feature, represented from head to outlet (a composition of elemenatry flowpaths (flowlines) per hydrologic fabric logic model) 1 hyfo:SubsurfaceWaterFeature A complete subsurface water feature including water, container, and void (for example, aquifer, well, et al.) gwml2:GW_HydrogeoUnit Any soil or rock unit or zone that by virtue of its hydraulic properties has a distinct influence on the storage or movement of groundwater (after ANS, 1980) qudt:QuantityValue nhdplusv2:FlowLineCatchment The catchment polygon for a nhdplusv2:FlowLine qudt:hasQuantityKind geo:defaultGeometry The default Geometry to be used in spatial calculations. It is usually the most detailed Geometry. nhdplusv2:hasSlope The numeric average slope of a flowline geo:Feature A discrete spatial phenomenon in a universe of discourse. topological connection (spatial contact) (sawgraph) hyf:HY_River a body of surface water, participating in a hydrographic network, which is special due to its property to permanently or temporarily flow hyfo:tapsAquifer Identifies the aquifer a well taps nhdplusv2:FlowPathLength The length of a flowpath nhdplusv2:hasFlowPathLength Relates any flowpath to its length, represented as, for example, a qudt:Quantity object hyf:HY_Lake a body of surface water, participating in a hydrographic network, made special due to its considerable size gwml2:GW_MonitoringSite Site of observation related to groundwater gwml2:GW_Aquifer A body of earth material that contains / potentially contains / potentially contained sufficient saturated permeable material to yield significant quantities of water to wells and springs (after Lohman, 1972) hyfo:AquiferWaterFeature An aquifer water feature including water, container, and void hyfo:isRepresentedByWFR Relates a water feature to a representation of that water feature gwml2:gwAquiferSystemPart Relates an aquifer system with its parts, which can be other systems, aquifers or confining beds nhdplusv2:hasMainStemId Relates a nhdplusv2:MainStem feature to its unique identifier hyf:HY_CatchmentDivide One-dimensional (linear) feature that is a hydrology-specific realization of the holistic catchment wbd:primaryFlowPath Relates a drainage basin (area) to the primary mainstem flowing through it gwml2:gwWellUnit Identifies the aquifers or confining beds intersecting the well nhdplusv2:associatedCatchmentArea Identifies the one and only one catchment area that is associated with a particular flowpath nhdplusv2:FlowLine any atomic/elementary kind of HY_FlowPath within a given framework/context (for example, a single NHDFlowline instance) area of associated catchment may be zero (per hydrologic fabric logic model) can be part of at most one mainstem 2024-09-04 2025-08-01 2025-04-21 This ontology supports querying the SAWGraph Knowledge Graph. It adapts and extends concepts from HY_Features, HyFO, and GWML2 SAWGraph's hydrology (water) ontology - an adaptation and extension of concepts from HY_Features, HyFO, and GWML2 SAWGraph's hydrology (water) ontology - an adaptation and extension of concepts from HY_Features, HyFO, and GWML2 1.0 hyfo:WaterFeatureRepresentation A representation of a water feature (for example, a line or polygon) gwml2:gwAquiferSystem Relates an aquifer system part, which can be another system, aquifer or confining bed, with its aquifer system hyf:HY_Catchment captures the union of catchment and hydro nexus, and the multiple realizations of the holistic catchment concept wbd:contributingDrainageBasin Relates a mainstem to the drainage basin (area) it drains geo:Geometry A coherent set of direct positions in space. The positions are held within a Spatial Reference System (SRS). nhdplusv2:upstreamFlowPath Identifies another flowpath immediately upstream, allowing network navigation without knowing an inflow or outflow of the catchment realized by the flowpath nhdplusv2:FlowPath any non-atomic/non-elementary kind of HY_FlowPath comprised of a contiguous set of atomic/elementary flowpaths hyf:HY_Impoundment a body of surface water, participating in a hydrographic network, seen as being special due to being formed by collecting water, for example in the case of a dam hyf:HY_Lagoon a body of surface water, participating in a hydrographic network, which is special due to its shallow depth and interaction with the open sea nhdplusv2:hasLevelPathId The level path id of a flowline is the hydrologic sequence number of the most downstream flowline feature in the level path and is used to connect flowlines to their corresponding main stem hyf:HY_CatchmentArea Two-dimensional (areal) hydrology-specific realization of the holistic catchment hyf:HY_Estuary a body of surface water, participating in a hydrographic network, made special due to branching and its interaction with the open sea nhdplusv2:containsFlowLine Connects a flowline catchment with its flowline(s) nhdplusv2:hasFCODE Relates an NHDPlusV2 feature to its FCODE (see also nhdplusv2:hasFTYPE) qudt:Quantity