NHD is a digital vector dataset used by geographic information systems (GIS). It contains vector and polygon features such as rivers and lakes, and point features such as stream gages and water quality stations. The NHD allows scientific data such as water flow rates or water quality measurements to be linked by way of a linear referencing system. Links to external scientific data are known in the NHD as events. Because the NHD is designed as a connected flow network, events make many kinds of scientific analysis possible, such as how a source of poor water quality upstream might affect a fish population downstream, or how dams affect water temperatures downstream. The USGS is currently adding point events to the NHD including steam gages, water quality stations, dams, and diversions. Linking scientific information as events to the NHD improves its utility. At the same time, the linked scientific information becomes more useful because it is now connected to other events by way of the NHD network. Events connected in a flow network create a synergy between the data and the network. By adding scientific information to the NHD as events, the USGS is improving the utility of the NHD for customers and scientists.

1. Michael Tinker
Events in the NHD September 2012

2. 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

3. Linear networks
• Transportation
• Railroad
• Gas pipelines
• Drinking water mains
• Storm drain networks
• Sewer networks
• Rivers systems

4. 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.

5. Network events
• An event is a linearly referenced feature
• Events must have:
– Route
– Measure

6. NHD point events
• In the NHD, events have:
– ReachCode
– Measure
EventType
Gage
Dam

7. Flowlines with ReachCode

8. Flowlines with Measure

9. Flowlines with ReachCodes,
Events with Measures
NHDPointEventFC
EventType
# Water Quality Station
" Dam
! Gaging Station

10. NHD point events
Events reference outside information
National Water Information System (NWIS)

11. NHD point events
Sept 19, 2012
240,737 points

12. Point Event Attributes
• 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

13. 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.

14. 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

15. Gages

16. Gaging Station
Event Type =1
105,400 points, as of Sept 19 , 2012

17. Identify gage point events in ArcMap

18. National Water Information System (NWIS)

19. National Water Information System (NWIS)

20. National Water Information System (NWIS)

21. Snapshot of NWIS Stream gages,
Water Quality (QW) stations,
131,902 points, June 2011

22. Indexing workflow

23. Clip the NWIS points by HUC 4

24. NWIS Points in HUC 1201

25. Remove duplicates from NWIS clip

26. Hydrography Event Management Tool

27. Raw NWIS points

28. NWIS points snapped to NHD

29. 100 meter snapping threshold

30. 100 meter snapping threshold

31. 50 meter move threshold

32. 1000 meter absolute threshold

33. In lakes > 1000 meter distance
flowline is acceptable

34. Placement Issues

35. Placement Issues

36. Placement Issues

37. Placement Issues

38. Dams

39. Dam
Event Type = 2
60,256 points as of Sept 19, 2012

40. National Inventory of Dams (NID)

41. Fish Passage Decision Support System

42. Divergences

43. General Divergence Structure
Event Type = 3
25 points as of Sept 19, 2012

44. Withdrawing Divergence Structure
Event Type = 4
818 points as of Sept 19, 2012

45. Contributing Divergence Structure
Event Type = 5
33 points as of Sept 19, 2012

46. Divergence data sources:
• Bureau of reclamation
• State office of engineer
• State/local water districts
• State/local water rights databases

47. Colorado Decision Support System

48. Water Quality Stations

49. Water Quality Station
Event Type = 6
74,205 points as of Sept 19, 2012.

50. Water quality stations are often
coincident with gages
NHDPointEventFC
EventType
# Water Quality Station
" Dam
! Gaging Station

51. Stream Stats Application

52. Stream Stats Application

53. 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

54. Pour Points

55. Pour Points

56. Pour Points

57. Pour Points

58. Subbasin 01090002
Downstream Trace
Weweantic River
(Longest river –
27km)

59. Subbasin 01090002
Upstream Trace
Weweantic River
(Greatest number of
drainage kilometers –
472)

60. Subbasins 17040216 and
17040217

63. Area and line events

64. 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