Events in the NHD Michael Tinker September 2012
Outline
1. Linear referencing
2. Network events
3. NHD events
4. Gages, water quality stations
NWIS
Indexing workflow
5. Dams
6. Divergences
7. Water quality stations
8. Future events in the NHD
9. Wrap up
Linear networks
• Transportation
• Railroad
• Gas pipelines
• Drinking water mains
• Storm drain networks
• Sewer networks
• Rivers systems
Linear referencing
• Points on the network.
• One can always model points on the network using XY coordinates, however…
• It is desirable to model information without having to express it in XY terms.
• For example, route I-12, mile marker 47.
• Multiple attributes can be associated with linearly referenced features.
Network events
• An event is a linearly referenced feature
• Events must have:
– Route
– Measure
NHD point events
• In the NHD, events have:
– ReachCode
– Measure
EventType
Gage
Dam
Flowlines with ReachCode
Flowlines with Measure
Flowlines with ReachCodes, Events with Measures
NHDPointEventFC
EventType
# Water Quality Station
" Dam
! Gaging Station
NHD point events
National Water Information System (NWIS)
Events reference outside information
Sept 19, 2012 240,737 points
NHD point events
• Permanent_Identifier unique identifier
• ReachCode unique reach id
• Measure 0 to 100, for linear referencing
• EventType gage station, dam, diversion, water quality station
• EventDate date the event was created or last modified
Point Event Attributes
• Feature_Permanent_Identifier Permanent_Identifier of NHD feature an event is referenced to. Internal reference.
• Source_DataDescription Name of source data, e.g. NWIS, NID.
• Source_FeatureID ID of feature in the source data, e.g. NWIS site number, or NID ID.
• FeatureDetailURL link to detailed event data at the source e.g. NWIS web page for each unique site number.
Point Event Attributes
Point Events Types in the NHD Sept 19, 2012
Event Type Description Number of points
1 Gaging Station 105,400
2 Dam 60,256
3 Withdrawing Divergence Structure 25
4 General Divergence Structure 818
5 Contributing Divergence Structure 33
6 Water Quality Station 74,205
240,737
Gages
Gaging Station Event Type =1
105,400 points, as of Sept 19 , 2012
Identify gage point events in ArcMap
National Water Information System (NWIS)
National Water Information System (NWIS)
National Water Information System (NWIS)
Snapshot of NWIS Stream gages, Water Quality (QW) stations,
131,902 points, June 2011
Indexing workflow
Clip the NWIS points by HUC 4
NWIS Points in HUC 1201
Remove duplicates from NWIS clip
Hydrography Event Management Tool
Raw NWIS points
NWIS points snapped to NHD
100 meter snapping threshold
100 meter snapping threshold
50 meter move threshold
1000 meter absolute threshold
In lakes > 1000 meter distance flowline is acceptable
Placement Issues
Placement Issues
Placement Issues
Placement Issues
Dams
Dam Event Type = 2
60,256 points as of Sept 19, 2012
National Inventory of Dams (NID)
Fish Passage Decision Support System
Divergences
General Divergence Structure Event Type = 3
25 points as of Sept 19, 2012
Withdrawing Divergence Structure Event Type = 4
818 points as of Sept 19, 2012
Contributing Divergence Structure Event Type = 5
33 points as of Sept 19, 2012
Divergence data sources:
• Bureau of reclamation
• State office of engineer
• State/local water districts
• State/local water rights databases
Colorado Decision Support System
Water Quality Stations
Water Quality Station Event Type = 6
74,205 points as of Sept 19, 2012.
Water quality stations are often coincident with gages
NHDPointEventFC
EventType
# Water Quality Station
" Dam
! Gaging Station
Stream Stats Application
Stream Stats Application
Future Plans for Events
• HUC8 pour points
• “VIP” gages
– HCDN gages
– NSIP (National Streamflow Information Program)
– GAGES II (Geospatial Attributes of Gages for Evaluating Streamflow, Version II)
• Area and line events
• Better integration with USTopo
Pour Points
Pour Points
Pour Points
Pour Points
Weweantic River (Longest river – 27km)
Subbasin 01090002 Downstream Trace
Subbasin 01090002 Upstream Trace
Weweantic River (Greatest number of drainage kilometers – 472)
Subbasins 17040216 and 17040217
Area and line events
Summary
• NHD contains events which link the NHD to external information.
• The events can be used for modeling, such things as stream flows, barriers, water rights, pollution traces, heat pollution.
• Data Information Knowledge