AHGW:Arc Hydro Groundwater Data Model

File:Archydrogw overview.JPG

Overview diagram of the Arc Hydro Groundwater Data Model

Arc Hydro Groundwater is a geodatabase design for representing groundwater datasets within ArcGIS. The data models helps archive, display, and analyze multidimensional groundwater data, and includes several components to represent different types of datasets including representations of aquifers and wells/boreholes, 3D hydrogeologic models, temporal information, and data from simulation models. The data model is compatible with the surface water data model and will share the same framework.

Background

The Arc Hydro data model started as a data model for representing surface water systems within an ArcGIS geodatabase. In 2002 the Arc Hydro data model was published as an ESRI book entitled: Arc Hydro GIS for Water Resources. Arc Hydro has been highly successful and has been widely adopted in industry. The groundwater data model has been developed as a companion to the surface water data model. The data model is based on a newly designed Arc Hydro framework which is shared by the surface water and groundwater data models. Users can add groundwater and surface water components to the framework as necessary, or develop their own components. This new componentized approach enables tailoring the geodatabase design to meet specific project needs. Each component of Arc Hydro Groundwater data model is described below.

The groundwater data model is being documented as an ESRI Press book: Arc Hydro Groundwater Data Model, which will be available in the coming months. This wiki compliments the book but is not a replacement for it.

Framework Component

The Arc Hydro framework provides a simple data structure for storing basic spatial datasets describing hydrologic systems. The framework supports basic water resources analysis such as tracing water as it flows over the terrain in watersheds, streams, and water bodies, creating groundwater level and groundwater quality maps, and viewing time series data related with monitoring stations and wells.

File:Archydrogw framework.JPG

Arc Hydro framework

• Aquifer – Polygon features representing aquifer boundaries. The features can be classified to represent different zones such as outcrop and confined sections of the aquifer.
• MonitoringPoint – Point features representing locations where hydrologic variables are measured, such as stream-gage stations and precipitation gages.
• SeriesCatalog – Table for indexing and summarizing time series stored in the TimeSeries table.
• TimeSeries – Table for storing time varying data such as water levels, flow, and water quality.
• VariableDefinition – Table for storing time series values.
• WaterBody – Polygon features representing areas such as ponds, lakes, swamps, and estuaries.
• WaterLine – Line features representing hydrographic “blue lines”, which represent mapped streams and water body center lines.
• WaterPoint – Point features representing hydrographic features such as springs, water withdrawal/discharge locations, and structures.
• Watershed – Polygon features representing drainage areas contributing water flow from the land surface to the water system.
• Well – Point features representing well locations and their attributes.

Aquifer
Polygon Feature Class
Field name	Type	Description
HydroID	Long Integer	Unique feature identifier in the geodatabase used for creating relationships between classes of the data model.
HydroCode	Text	Permanent public identifier of the feature used for relating features with external information systems.
Name	Text	Text attribute representing the name of the aquifer.
HGUID	Long Integer	Relates aquifer polygons with more detailed descriptions of hydrogeologic units defined in the HydrogeologicUnit table.
FType	Text	Distinguishes between types of aquifers or zones within an aquifer (e.g., unconfined and confined).

MonitoringPoint
Point Feature Class
Field name	Type	Description
HydroID	Long Integer	Unique feature identifier in the geodatabase used for creating relationships between classes of the data model.
HydroCode	Text	Permanent public identifier of the feature used for relating features with external information systems.
Name	Text	Text attribute representing the name of the aquifer.
JunctionID	Long Integer	Relates a MonitoringPoint feature with a river network by associating the point feature with a junction on the network. The JunctionID of MonitoringPoint feature is equal to the HydroID of a related HydroJunction feature.
FType	Text	Distinguishes between types of monitoring points (e.g., stream and precipitation gages, water quality monitoring sites).

SeriesCatalog
Table
Field name	Type	Description
FeatureID	Long Integer	Unique feature identifier. Is equal to the HydroID of the feature associated with the time series summarized in the catalog.
FeatClass	Text	Name of the feature class to which the related feature belongs.
VarID	Long Integer	Numerical identifier for the variable within the geodatabase. Matches the HydroID of the associated record in the VariableDefinition table.
TsTable	Text	Table containing the time series record.
StartTime	Date	The start date/time value of the series.
EndTime	Date	The end date/time value of the series.
ValueCount	Long Integer	Number of time-series values in the series.

TimeSeries
Table
Field name	Type	Description
FeatureID	Long Integer	Unique feature identifier. Is equal to the HydroID of the feature associated with the time series value.
VarID	Long Integer	Numerical identifier for the variable within the geodatabase. Matches the HydroID of the associated record in the VariableDefinition table.
TsTime	Date	Time stamp specifying the date and time associated with the time series value.
UTCOffset	Double	Number of hours the time coordinate system used to define TsTime is displaced from Coordinated Universal Time.
TsValue	Double	Numerical value of the variable at the given location and time.

VariableDefinition
Table
Field name	Type	Description
VarID	Long Integer	Unique numerical identifier for the variable within the geodatabase.
VarName	Text	The name of the variable.
VarDesc	Text	The description of the variable.
VarUnits	Text	Units of measure for the variable.

WaterBody
Polygon Feature Class
Field name	Type	Description
HydroID	Long Integer	Unique feature identifier in the geodatabase used for creating relationships between classes of the data model.
HydroCode	Text	Permanent public identifier of the feature used for relating features with external information systems.
Name	Text	Text attribute representing the name of the water body.
JunctionID	Long Integer	Relates a WaterBody feature with a river network by associating a water body with a junction on the network. The JunctionID of a WaterBody feature is equal to the HydroID of a related HydroJunction feature.
NextDownID	Long Integer	Relates a WaterBody feature to its downstream feature, thus creating feature to feature connectivity. NextDownID of a WaterBody feature is equal to the HydroID of the next downstream feature.
AreaSqKm	Double	Area of the WaterBody feature in square km units. This attribute is commonly used for modeling purposes and analytic calculations.
FType	Text	Distinguishes between types of water bodies (e.g., lake, pond, and estuary).

WaterLine
Line Feature Class
Field name	Type	Description
HydroID	Long Integer	Unique feature identifier in the geodatabase used for creating relationships between classes of the data model.
HydroCode	Text	Permanent public identifier of the feature used for relating features with external information systems.
Name	Text	Text attribute representing the name of the river or stream.
FlowDir	Double	Direction of flow for the feature (e.g., with digitized, against digitized).
NextDownID	Long Integer	Relates a WaterLine feature to its downstream feature. NextDownID is equal to the HydroID of the next downstream feature.
LengthKm	Double	Length of the WaterLine feature in km units. This attribute is commonly used for modeling purposes and analytic calculations.
FType	Text	Distinguishes between types of wells (e.g., domestic, water supply, industrial).

WaterPoint
Point Feature Class
Field name	Type	Description
HydroID	Long Integer	Unique feature identifier in the geodatabase used for creating relationships between classes of the data model.
HydroCode	Text	Permanent public identifier of the feature used for relating features with external information systems.
Name	Text	Text attribute representing the name of the water point.
JunctionID	Long Integer	Relates a HydroPoint feature with a river network by associating a watershed with a junction on the network. The JunctionID of a HydroPoint feature is equal to the HydroID of a related HydroJunction feature.
FType	Text	Distinguishes between types of HydroPoint features (e.g., spring, diversion point, structure).

Watershed
Polygon Feature Class
Field name	Type	Description
HydroID	Long Integer	Unique feature identifier in the geodatabase used for creating relationships between classes of the data model.
HydroCode	Text	Permanent public identifier of the feature used for relating features with external information systems.
Name	Text	Text attribute representing the name of the watershed.
DrainID	Long Integer	Index associating Watershed features with a specific drainage area. The DrainID of a Watershed feature is equal to the HydroID of the reference drainage area feature.
JunctionID	Long Integer	Relates a Watershed feature with a river network by associating a watershed with a junction on the network. The JunctionID of a Watershed feature is equal to the HydroID of a related HydroJunction feature.
NextDownID	Long Integer	Relates a Watershed feature to its downstream feature, thus creating feature to feature connectivity. NextDownID is equal to the HydroID of the next downstream feature.
AreaSqKm	Double	Area of the watershed in square km units. This attribute is commonly used for modeling purposes and analytic calculations.
FType	Text	Distinguishes between types of Watershed features.

Well
Point Feature Class
Field name	Type	Description
HydroID	Long Integer	Unique feature identifier in the geodatabase used for creating relationships between classes of the data model.
HydroCode	Text	Permanent public identifier of the feature used for relating features with external information systems.
LandElev	Double	The elevation of the land surface at the well location. Is commonly used to reference vertical information (measured as depth along the well).
WellDepth	Double	The depth of the well. Together with the LandElev provides a description of the well’s 3D geometry.
AquiferID	Long Integer	Relates a Well feature with an Aquifer feature. The AquiferID of a Well feature is equal to the HydroID of an Aquifer feature.
AqCode	Text	Text describing the aquifer. Is used to symbolize wells based on the related aquifer.
HGUID	Long Integer	Relates the well to a hydrogeologic unit.
FType	Text	Distinguishes between types of wells (e.g., domestic, water supply, industrial).

Geology Component

File:Archydrogw geology.JPG

Geology component for representing data from geologic maps

The Geology component conations a set of feature classes for representing data from geologic maps and to integrate geologic data with other groundwater-related datasets.

• GeologyPoint – Points that represent locations such as springs, caves, sinks, and observation points.
• GeologyLine – Line features that describe objects such as faults, contacts, and dikes.
• GeologyArea – Polygon features describing areal features such as rock units and alteration zones.

GeologyPoint, GeologyLine, and GeologyArea
Point, line and polygon features
Field name	Type	Description
HydroID	Long Integer	Unique feature identifier in the geodatabase used for creating relationships between classes of the data model.
HydroCode	Text	Permanent public identifier of the feature used for relating features with external information systems.
GeoAbbrev	Text	Abbreviation of the geologic feature. Used in map legends and labeling.
Description	Text	A text description of the feature.
HGUID	Long Integer	Hydrogeologic unit identifier. Relates the feature with a hydrogeologic unit.
HGUCode	Text	Text code for storing the permanent identification code of hydrogeologic units.
FType	Text	Distinguishes between types of geologic features.

Borehole data

The Borehole component contains classes for representing 3D information recorded along boreholes. The data can be stored as tabular information related to well features or as 3D point and line features that can be visualized in ArcScene.

File:Archydrogw wellsandboreholes.JPG

Arc Hydro framework

• BoreholeLog – Table for representing vertical data along boreholes. Each row in the BoreholeLog table represents a point or interval along the borehole.
• BorePoint – 3D point feature class for representing point data along boreholes
• BoreLine – 3D line feature class for representing interval data along boreholes.

BoreholeLog
Table
Field name	Type	Description
WellID	Long Integer	References the HydroID of a Well feature.
RefElev	Double	A reference elevation (e.g., land elevation, top of casing) giving the starting elevations for data measured as depth along the borehole.
FromDepth	Double	The top elevation of an interval measured as depth along the borehole.
ToDepth	Double	The bottom elevation of an interval measured as depth along the borehole.
TopElev	Double	Top elevation of an interval represented in absolute elevation units (e.g., feet above mean sea level).
BottomElev	Double	Bottom elevation of an interval represented in absolute elevation units (e.g., feet above mean sea level).
ElevUnits	Text	Units of elevations stored in the TopElev and BottomElev attributes.
Material	Text	Description of strata observed along a borehole. Usually documented in drilling logs and later classified into geologic/hydrogeologic units.
HGUID	Long Integer	Hydrogeologic unit identifier. Classifies borehole data into hydrogeologic units defined in the HydrogeologicUnit table.
HGUCode	Text	Hydrogeologic unit code. Text for classifying, symbolizing, and labeling hydrogeologic units.
LogType	Text	Distinguishes between types of borehole logs (e.g., well completion, hydrostratigraphy).

BorePoint
Point Z Feature Class
Field name	Type	Description
HydroID	Long Integer	Unique feature identifier in the geodatabase used for creating relationships between classes of the data model.
HydroCode	Text	Permanent public identifier of the feature used for relating features with external information systems.
WellID	Long Integer	References the HydroID of a Well feature.
GeoSectionID	Long Integer
Material	Text	Description of strata observed along a borehole. Usually documented in drilling logs and later classified into geologic/hydrogeologic units.
HGUID	Long Integer	Hydrogeologic unit identifier. Classifies borehole data into hydrogeologic units defined in the HydrogeologicUnit table.
HGUCode	Text	Hydrogeologic unit code. Text for classifying, symbolizing, and labeling hydrogeologic units.
PointElev	Double	Elevation of the BorePoint feature.
FType	Text	Distinguishes between types of BorePoint features (e.g., stratigraphic picks, sampling ports).
HorizonID	Long Integer

BoreLine
Polyline Z Feature Class
Field name	Type	Description
HydroID	Long Integer	Unique feature identifier in the geodatabase used for creating relationships between classes of the data model.
HydroCode	Text	Permanent public identifier of the feature used for relating features with external information systems.
WellID	Long Integer	References the HydroID of a Well feature.
Matieral	Text	Description of strata observed along a borehole. Usually documented in drilling logs and later classified into geologic/hydrogeologic units.
HGUID	Long Integer	Hydrogeologic unit identifier. Classifies borehole data into hydrogeologic units defined in the HydrogeologicUnit table.
HGUCode	Text	Hydrogeologic unit code. Text for classifying, symbolizing, and labeling hydrogeologic units.
TopElev	Double	Top elevation of the BoreLine feature.
BottomElev	Double	Bottom elevation of the BoreLine feature.
FType	Text	Distinguishes between types of BoreLine features (e.g., well completion, hydrostratigraphy).

Hydrostratigraphy

The hydrostratigraphy component represents hydrogeologic units using 2D and 3D features. Classes in the component enable the representation of hydrogeologic models including 2D polygons representing the extent of hydrogeologic units, cross sections, surfaces representing the top and bottom of hydrogeologic units, volume elements. In the Arc Hydro Groundwater data model, the 2D representation of cross-sections is implemented with multiple feature classes, and these are given the “XS2D” prefix (e.g., XS2D_Boreline and XS2D_Panel).

File:Archydrogw hydrostratigraphy.JPG

Hydrostratigraphy component

• GeoArea – Polygon feature class for representing the 2D extent of hydrogeologic units or parts of them.
• GeoRasters – Raster catalog for storing rater surfaces. The catalog enables storing rasters within the geodatabase and adding attributes describing raster datasets.
• GeoSection – 3D multipatch feature class representing vertical cross sections.
• GeoVolume – 3D volume objects representing hydrogeologic units.
• HydrogeologicUnit – Table for defining conceptual hydrogeologic units.
• SectionLine – Line feature class for representing 2D section lines.

File:Archydrogw XS2D.JPG

XS2D component

• XS2D_Catalog – Table for managing XS2D feature classes and their association with SectionLine features.
• XS2D_BoreLine – Polyline feature class for representing vertical borehole data projected on a vertical plane along a section line. Usually, when creating a new cross-section, a set of wells is selected near the line defining the cross-section, and hydrostratigraphic data along the boreholes is projected on the cross-section plane.
• XS2D_Panel – Polygon feature class for representing hydrogeologic units as 2D cross-section "panels." Usually a cross-section will be formed by a set of XS2D_Panel features, each representing a hydrogeologic unit along a section line.
• XS2D_PanelDivider – Polyline feature class representing vertical lines on a cross-section plane, showing the location where a section line changes direction (i.e., the location of vertices of the section line). Panel dividers are used as guides for orientation when viewing the 2D cross-section.
• XS2D_MajorGrid and XS2D_MinorGrid – Polyline feature classes representing grid lines showing the vertical and horizontal dimensions in a 2D cross-section. Major grid lines are typically drawn as vertical and horizontal lines across the cross-section, while minor grid lines are indicated by tick marks along the border of the cross-section.

GeoArea
Polygon Feature Class
Field name	Type	Description
HydroID	Long Integer	Unique feature identifier in the geodatabase used for creating relationships between classes of the data model.
HydroCode	Text	Permanent public identifier of the feature used for relating features with external information systems.
HGUID	Long Integer	Hydrogeologic unit identifier. Relates GeoArea polygons with more detailed descriptions of hydrogeologic units defined in the HydrogeologicUnit table.
HGUCode	Text	Text descriptor of hydrogeologic units used for labeling, symbolization, and queries.
HorizonID	Long Integer	Index for describing the depositional sequence of hydrogeologic units.
FType	Text	Distinguishes between types of GeoArea features.

GeoRasters
Raster Catalog
Field name	Type	Description
Name	Text	Generic raster catalog attribute (created automatically when you create a raster catalog) used to store the name of a raster dataset.
Description	Text	Text descriptor of the raster (e.g., formation top, formation bottom).
RasUnits	Text	The raster units (e.g., feet above mean sea level).
HGUID	Long Integer	Hydrogeologic unit identifier. Relates rasters in the catalog with more detailed descriptions of hydrogeologic units defined in the HydrogeologicUnit table.
HGUCode	Text	Text descriptor of the hydrogeologic unit used for labeling, symbolization, and queries.
HorizonID	Long Integer	Index for describing the depositional sequence of hydrogeologic units.
AquiferID	Long Integer	Relates rasters with Aquifer features. The AquiferID attribute of a GeoRaster relates to the HydroID of an Aquifer feature.
AqCode	Text	Aquifer code. Text descriptor of aquifers used for labeling, symbolization, and querying.
Clip	Long Integer
Fill	Long Integer

GeoSection
3D MultiPatch Feature Class
Field name	Type	Description
HydroID	Long Integer	Unique feature identifier in the geodatabase used for creating relationships between classes of the data model.
HydroCode	Text	Permanent public identifier of the feature used for relating features with external information systems.
SectionID	Long Integer	Equal to the HydroID of a SectionLine feature. Relates GeoSection features with SectionLine features.
SName	Text	Section name. Text descriptor of the section line for labeling, symbolization, and queries (e.g., A-A’).
HGUID	Long Integer	Hydrogeologic unit identifier. Relates GeoSection features with more detailed descriptions of hydrogeologic units defined in the HydrogeologicUnit table.
HGUCode	Text	Text descriptor of the hydrogeologic unit used for labeling, symbolization, and queries.
FromWell	Long Integer
ToWell	Long Integer
FType	Text	Distinguishes between types of GeoSection features.
HorizonID	Long Integer	Index for describing the depositional sequence of hydrogeologic units.

GeoVolume
3D MultiPatch Feature Class
Field name	Type	Description
HydroID	Long Integer	Unique feature identifier in the geodatabase used for creating relationships between classes of the data model.
HydroCode	Text	Permanent public identifier of the feature used for relating features with external information systems.
HGUID	Long Integer	Hydrogeologic unit identifier. Relates GeoVolume features with more detailed descriptions of hydrogeologic units defined in the HydrogeologicUnit table.
HGUCode	Text	Text descriptor of the hydrogeologic unit used for labeling, symbolization, and queries.
HorizonID	Long Integer	Index for describing the depositional sequence of hydrogeologic units.
FType	Text	Distinguishes between types of GeoVolume features.

HydrogeologicUnit
Table
Field name	Type	Description
HydroID	Long Integer	Unique identifier in the geodatabase used for creating relationships between classes of the data model. Used to relate between hydrogeologic units defined in the table and spatial features within the hydrostratigraphy component.
HGUCode	Text	Hydrogeologic unit code. The permanent identification code of hydrogeologic units, used to establish a linkage with external information systems.
HGUName	Text	Text descriptor of hydrogeologic units used for labeling and symbolization.
AquiferID	Long Integer	Aquifer identifier for grouping hydrogeologic units. AquiferID is also used to relate hydrogeologic units in the table with Aquifer features.
AqCode	Text	Aquifer code. Text descriptor of the aquifer used for labeling, symbolization, and querying.
Description	Text	Text for storing detailed descriptions of hydrogeologic units.
HorizonID	Long Integer	Index for describing the depositional sequence of hydrogeologic units.

SectionLine
Line Feature Class
Field name	Type	Description
HydroID	Long Integer	Unique feature identifier in the geodatabase used for creating relationships between classes of the data model.
HydroCode	Text	Permanent public identifier of the feature used for relating features with external information systems.
SName	Text	Section name. Text descriptor of the section line for labeling, symbolization, and queries (e.g., A-A’).
VertExag2D	Double	Vertical exaggeration that will be applied when creating XS2D features (see section on representing vertical cross sections in 2D).
FType	Text	Distinguishes between types of SectionLine features.

XS2D_Catalog
Table
Field name	Type	Description
SectLineFC	Text	Name of the SectionLine feature class containing the referenced SectionLine feature.
SectionID	Long Integer	HydroID of the associated SectionLine feature.
SName	Text	Name of the associated SectionLine feature.
XS2D_FC	Text	Name of the XS2D feature class.
XS2DType	Text	Role that the XS2D feature class plays in the cross section (e.g., Boreline, Panel, Grid, etc.).

XS2D_BoreLine
Polyline Feature Class
Field name	Type	Description
HydroID	Long Integer	Unique feature identifier in the geodatabase used for creating relationships between classes of the data model.
HydroCode	Text	Permanent public identifier of the feature used for relating features with external information systems.
WellID	Long Integer	HydroID of the associated Well feature.
TopElev	Double	Top elevation of the XS2D_BoreLine feature.
BottomElev	Double	Bottom elevation of the XS2D_BoreLine feature.
Material	Text	Description of strata observed along a borehole. Usually documented in drilling logs and later classified into geologic/hydrogeologic units.
HGUID	Long Integer	Hydrogeologic unit identifier. Is equal to the HydroID of a hydrogeologic unit defined in the HydrogeologicUnit table.
HGUCode	Text	Text descriptor of the hydrogeologic unit used for labeling, symbolization, and queries.
Offset	Double	Distance from the well related to the XS2D_BoreLine feature to the nearest point on the section line (distance units are the same as the units of the SectionLine feature class).
Measure	Double	Distance along the section line to the Well feature associated with the XS2D_BoreLine feature. The distance is measured from the starting point of the section line to the point on the section line closest to the Well feature.
IsLeft	Long Integer	TRUE if the Well feature associated with the XS2D_BoreLine is on the left side of a section line in the direction of digitization. FALSE if it is on the right side.
FType	Text	Distinguishes between types of XS2D_BoreLine features.

XS2D_Panel
Polygon Feature Class
Field name	Type	Description
HydroID	Long Integer	Unique feature identifier in the geodatabase used for creating relationships between classes of the data model.
HydroCode	Text	Permanent public identifier of the feature used for relating features with external information systems.
HGUID	Long Integer	Hydrogeologic unit identifier. Is equal to the HydroID of a hydrogeologic unit defined in the HydrogeologicUnit table.
HGUCode	Text	Text descriptor of the hydrogeologic unit used for labeling, symbolization, and queries.
FType	Text	Distinguishes between types of XS2D_Panel features.

XS2D_PanelDividier
Polyline Feature Class
Field name	Type	Description
HydroID	Long Integer	Unique feature identifier in the geodatabase used for creating relationships between classes of the data model.
HydroCode	Text	Permanent public identifier of the feature used for relating features with external information systems.
Measure	Double	Distance along the section line to the vertex of the line where the direction changes. The distance is measured from the starting point of the section line to the point of direction change.

XS2D_MajorGrid and XS2D_MinorGrid
Polyline Feature Class
Field name	Type	Description
HydroID	Long Integer	Unique feature identifier in the geodatabase used for creating relationships between classes of the data model.
HydroCode	Text	Permanent public identifier of the feature used for relating features with external information systems.
GridValue	Double	Elevation or measure (distance along section line) value used for labeling grid lines, using the same distance units as the coordinate system of the SectionLine feature associated with the cross section.
IsVertical	Long Integer	TRUE if the grid line is vertical; FALSE if it is horizontal.

Time Series

The Time Series component provides a new design for dealing with temporal data within Arc Hydro. The new design provides better support for utilizing multiple representations of time series data and a new table to describe time series variables.

The Arc Hydro Groundwater Temporal Component.

• AttributeSeries – Table for archiving time-series data where multiple variables are indexed with the same feature and time.
• DatasetCatalog – Table for indexing time-series datasets.
• FeatureSeries – Collections of features indexed by time representing a series of geometries varying in location or shape.
• RasterSeries – Raster catalog for storing collections of raster datasets indexed by time.
• SeriesCatalog – Table for indexing and summarizing time series stored in the TimeSeries table.
• TimeSeries – Table for storing single-variable time series.
• VariableDefinition – Table for defining temporal variables.

AttributeSeries
Table
Field name	Type	Description
FeatureID	Long Integer	Unique feature identifier. Is equal to the HydroID of the feature associated with the time series value.
TsTime	Date	Time stamp specifying the date and time associated with the time series value.
UTCOffset	Long Integer	Number of hours the time coordinate system used to define TsTime is displaced from Coordinated Universal Time.
VarKey 1	Double	For a given value field, the field name indicates the variable whose TSValues are stored in that field. This variable is linked to the VariableDefinition table via the VarKey field.
VarKey 2	Double	For a given value field, the field name indicates the variable whose TSValues are stored in that field. This variable is linked to the VariableDefinition table via the VarKey field.
...	...	...
VarKey N	Double	For a given value field, the field name indicates the variable whose TSValues are stored in that field. This variable is linked to the VariableDefinition table via the VarKey field.

DatasetCatalog
Table
Field name	Type	Description
VarID	Long Integer	Numerical identifier for the variable within the geodatabase. Matches the HydroID of the associated record in the VariableDefinition table.
DsType	Text	Type of time-series dataset described, e.g., RasterSeries, FeatureSeries, Feature Layer.
DsSource	Text	Name of the time-series dataset described.
TsTable	Text	Name of the time-series table that contains time-series values, used in cases where features are associated with a time series of values stored in a separate table (e.g., wells related with water levels, or polygons related with precipitation)
StartTime	Date	Start date/time of the series.
EndTime	Date	End date/time of the series.
StepCount	Long Integer	Number of unique time steps in the time-series dataset.

FeatureSeries
Collection of Feature Classes
Field name	Type	Description
HydroID	Long Integer	Unique feature identifier in the geodatabase used for creating relationships between classes of the data model.
VarID	Long Integer	Numerical identifier for the variable within the geodatabase. Matches the HydroID of the associated record in the VariableDefinition table.
TsTime	Date	Time stamp specifying the date and time associated with the feature.
UTCOffset	Long Integer	Number of hours the time coordinate system used to define TsTime is displaced from Coordinated Universal Time.
GroupID	Long Integer	Index for grouping a set of features into a “track” showing the change of a feature’s shape, location, or both.

RasterSeries
Raster Catalog
Field name	Type	Description
Name	Text	Generic attribute (created automatically when you create a raster catalog) used to store the name of a raster dataset.
VarID	Long Integer	Numerical identifier for the variable within the geodatabase. Matches the HydroID of the associated record in the VariableDefinition table.
TsTime	Date	Time stamp specifying the date and time associated with the raster.
UTCOffset	Long Integer	Number of hours the time coordinate system used to define TsTime is displaced from Coordinated Universal Time.

SeriesCatalog
Table
Field name	Type	Description
FeatureID	Long Integer	Unique feature identifier. Is equal to the HydroID of the feature associated with the time series summarized in the catalog.
FeatClass	Text	Name of the feature class to which the related feature belongs.
VarID	Long Integer	Numerical identifier for the variable within the geodatabase. Matches the HydroID of the associated record in the VariableDefinition table.
TsTable	Text	Table containing the time series records.
StartTime	Date	The start date/time value of the series.
EndTime	Date	The end date/time value of the series.
ValueCount	Long Integer	Number of time-series values in the series.

TimeSeries
Table
Field name	Type	Description
FeatureID	Long Integer	Unique feature identifier. Is equal to the HydroID of the feature associated with the time series value.
VarID	Long Integer	Numerical identifier for the variable within the geodatabase. Matches the HydroID of the associated record in the VariableDefinition table.
TsTime	Date	Time stamp specifying the date and time associated with the time series value.
UTCOffset	Double	Number of hours the time coordinate system used to define TsTime is displaced from Coordinated Universal Time.
TsValue	Double	Numerical value of the variable at the given location and time.

VariableDefinition
Table
Field name	Type	Description
HydroID	Long Integer	Unique numerical identifier for the row within the geodatabase. Matches VarID in related tables.
VarKey	Text	Unique text ID for a variable, used when a variable is indexed in an attribute series table via field names.
VarName	Text	The name of the variable.
VarDesc	Text	The description of the variable.
Vocabulary	Text	Name of the list of variables in which a particular VarCode is defined (e.g., USGS NWIS).
VarCode	Text	Public identifier for a variable (e.g., "00060" for discharge in USGS NWIS).
Medium	Text	Medium in which the variable is observed or occurs (e.g., "Groundwater“)
VarUnits	Text	Units of measure for the variable.
DataType	Text	Describes whether the time series contains instantaneous measurements, cumulative values, etc.
IsRegular	Short Integer	Integer field that stores 1 (TRUE) if the time series values are regularly spaced in time, or 0 (FALSE) if the time series is irregular.
TimeStep	Long Integer	For regular time series, the number of TimeUnits between each occurrence of a time series value.
TimeUnits	Text	For regular time series, the time unit used to describe the length of time between occurrences of a time series value.
NoDataVal	Long Integer	Numerical value used to indicate a "No Data Value" (e.g., a missing value) in the time series table.

Simulation

The AHGW simulation feature dataset is a set of vector feature classes that can represent common modeling objects and it is designed to allow for representation of finite element and finite difference systems in a GIS. The simulation feature dataset includes four feature classes: Boundary, Cell2D, Cell3D, Node2D, and Node3D. These feature classes enable storage and representation of model inputs and outputs related to the simulation objects.

The Arc Hydro Groundwater Simulation Feature Dataset.

• Boundary – Polygon feature class that represents the two-dimensional extent of a model. It is not an essential part of the model representation but it can be useful to illustrate the location of the simulation model to support a simple spatial reference or database query.
• Cell2D – Polygon feature class used to represent cells or elements associated with two-dimensional simulation models or a single layer of a three-dimensional model.
• Cell3D – Multipatch feature class for representing three-dimensional cells and elements of simulation models.
• Node2D – 2D Point feature class that represents nodes in a 2D model grid/mesh or the nodes in a single layer of a 3D model grid/mesh.
• Node3D – 3D Point feature class that represents nodes in a model grid/mesh.

Boundary
Polygon Feature Class
Field name	Type	Description
HydroID	Long Integer	Unique feature identifier in the geodatabase used for creating relationships between classes of the data model.
HydroCode	Text	Permanent public identifier of the feature used for relating features with external information systems.
ModelDesc	Text	A text descriptor of the model.
OriginX	Double	X coordinate of the model origin.
OriginY	Double	Y coordinate of the model origin.
Angle	Double	The model angle of rotation.
FType	Text	Distinguishes between types of Boundary features.

Cell2D
Polygon Feature Class
Field name	Type	Description
HydroID	Long Integer	Unique feature identifier in the geodatabase used for creating relationships between classes of the data model.
HydroCode	Text	Permanent public identifier of the feature used for relating features with external information systems.
CellID	Long Integer	Index of the cell within the numbering scheme used for an individual layer of the computational grid.
FType	Text	Distinguishes between types of Cell2D features.

Cell3D
3D MultiPatch Feature Class
Field name	Type	Description
HydroID	Long Integer	Unique feature identifier in the geodatabase used for creating relationships between classes of the data model.
HydroCode	Text	Permanent public identifier of the feature used for relating features with external information systems.
CellID	Long Integer	Global index of the cell within the numbering scheme used for the computational grid.
Cell2DID	Long Integer	Index relating Cell3D features with a Cell2D feature. The Cell2DID of a Cell3D feature is equal to the CellID of a Cell2D feature.
FType	Text	Distinguishes between types of Cell3D features.

Node2D
Point Feature Class
Field name	Type	Description
HydroID	Long Integer	Unique feature identifier in the geodatabase used for creating relationships between classes of the data model.
HydroCode	Text	Permanent public identifier of the feature used for relating features with external information systems.
NodeID	Long Integer	Index of the node within the numbering scheme used for an individual layer of the computational grid.
Cell2DID	Long Integer	Index relating Node2D features with a Cell2D feature.
FType	Text	Distinguishes between types of Node2D features.

Node3D
3D Point Feature Class
Field name	Type	Description
HydroID	Long Integer	Unique feature identifier in the geodatabase used for creating relationships between classes of the data model.
HydroCode	Text	Permanent public identifier of the feature used for relating features with external information systems.
NodeID	Long Integer	Global index of the node within the numbering scheme used for the computational grid.
Cell3DID	Long Integer	Index relating Node3D features with a Cell3D feature. The Cell3DID of a Node3D feature is equal to the CellID of a Cell3D feature.
Node2DID	Long Integer	Index relating Node3D features with a Node2D feature. The Node2DID of a Node3D feature is equal to the NodeID of a Node2D feature.
FType	Text	Distinguishes between types of Node3D features.

See also

• Arc Hydro (surface water) Data Model on the ESRI website
• Arc Hydro Groundwater Data Model on the ESRI website

• MODFLOW Data Model