October 2006 Datum Change Information

October 2006 Datum Change Information

On October 1, 2006, the California Department of Water Resources(DWR) will change the reporting of all tide data collected at 44 locations in the Sacramento-San Joaquin Delta and Suisun Marsh from National Geodetic Vertical Datum 1929 (NGVD29) to the North American Vertical Datum 1988 (NAVD88) standard. Tide stage forecasts for four delta locations (Rio Vista, Antioch, Mallard Island and Venice Island) and river stage forecasts for three river forecast points (Mokelumne River at Bensons Ferry near Thornton, San Joaquin River at Mossdale Bridge, and Yolo Bypass at Lisbon) will be displayed in NGVD29 datum until October 1, 2006...where it will then be displayed as NAVD88. The change to NAVD88 will affect the monitor stage and flood stage at four locations.

The new monitor and flood stages effective October 1, 2006:

Location

New Monitor Stage (feet)

New Flood Stage (feet)

Old Monitor/Flood Stage (feet)

Mokelumne River at Bensons Ferry near Thornton

12.0

17.0

13.0 / 18.0

Sacramento River at Rio Vista Bridge

7.4

11.9

8.0 / 12.5

San Joaquin River at Mossdale Bridge

19.5

28.5

17.0 / 26.2

Yolo Bypass at Lisbon

13.0

19.0

14.0 / 20.0

National Geodetic Survey (NGS) Adjustments to NAVD88 Survey effective October 1, 2006:

Station
Transmitted
to CDEC
Station Name
CDEC ID
New
Adjustment
values based
on NGS
Elevations to
get NAVD88
back to old
NGVD29
valuesa
A02104
N
Sacramento River at Bryte
 
-0.54
B91212
Y
Sacramento River at Rio Vista
RVB
-0.6
B91510
Y
Yolo Bypass at Liberty Island
LIR
2.59
B91560
Y
Yolo Bypass near Lisbon
LIS
-1.04
B91560
N
Sacramento River at Walnut Gr.
-0.36
B91750
N
Sacramento River at Snodgrass
-0.45
B94100
N
Georgiana Slough at Moke. R
-0.46
B94150
N
Mokelumne R at New Hope
-0.41
B94175
Y
Mokelumne R at Thornton
BEN
-0.75
B95020
Y
San Joaquin at Antioch
ANH
-0.11
B95060
N
Threemile Sl at SJ River
-0.66
B95100
N
San Joaquin River at San Andreas
-0.27
B95220
Y
Rock Slough at CC Canal
RSL
-0.45
B95250
Y
Old River at Bacon Island
BAC
-0.59
B95260
Y
Discovery Bay at Indian Sl
DBI
-0.36
B95261
Y
Discovery Bay at Disc Bay Blvd
DBD
-0.31
B95270
Y
Old River nr Byron
ORB
-0.28
B95283
Y
Italian Sl Headwater nr Byron
ISH
-0.38
B95290
Y
Old River at Coney Island
CIS
-0.66
B95300
Y
Grantline Canal at Tracy Blvd.
GCT
-0.58
B95310
N
Grantline Canal above Dam
-0.58
B95325
Y
Doughty Cut above GLC
DGL
-0.53
B95340
N
Old River at Clifton Court
-0.49
B95365
Y
Old River near DMC (below)
OBD
-0.42
B95366
Y
Old River near DMC (above)
OAD
-0.42
B95380
Y
Old River at Tracy Road
OLD
-0.49
B95400
Y
Old River at Head
OH1
-0.52
B95420
Y
Tom Paine Slough above Mouth
TPS
-0.48
B95421
Y
Tom Paine above Intake
TPI
-0.48
B95425
Y
Tom Paine at P.P. #6
TPP
***
B95460
N
Middle River at Bacon Isl
-0.27
B95468
N
Middle River at Middle River
-0.2
B95500
N
Middle River at Borden Hwy
-0.47
B95503
Y
Middle River at Tracy Road
MTB
-0.54
B95530
Y
Middle River at Howard Rd.
MHR
-0.79
B95540
N
Middle River at Mowry
-0.71
B95580
Y
San Joaquin at Venice Isl
VNI
-0.35
B95620
N
San Joaquin at Rindge Tract
-0.5
B95660
Y
Stockton Ship Channel at Burns
RRI
-0.87
B95740
Y
San Joaquin at Brandt Bridge
BDT
-0.73
B95765
Y
San Joaquin River below Old River 
SJL
-0.73
B95820
Y
San Joaquin River at Mossdale Bridge
MSD
2.38
EOB80261551
Y
Sacramento River at Mallard Island
MAL
2.68
EOB80172083
Y
Martinez
MRZ
2.68
*      The Gage Height correction is the difference between NGVD29 datum + 3 feet and NAVD 88 datum.
**   Previously set to M.S.L. 
*** Station re-established and set to NAVD 88 datum
a(NAVD 88 value) - (New adjustment value) = (Old NGVD29 value)
 (NGVD 29 value) +  (New adjustment value) = (New NAVD 88)
NOTES:
B94175 -  Maps & Surveys BM destroyed.  USED N.G.S. elevation for BM N463 for this station.
B95290 -  Maps & Surveys NAVD-88 elevation of 6/15/04 used for this station. 
B95425 -  N.G.S. elevation for AI7593 used for establishment of new station. Not associated with GPS Survey value 
B95280 - N.G.S. elevation from HS0515 used for establishment of NAVD-88 elevation for staff not associated with GPS Survey value
Mallard - Value set based on BM identified as Tidal 1 and elevation is from N.G.S. not associated with GPS survey value
Martinez - Value set based on BM identified as 145672, 1990 Contra Costa Co. and elevation is from N.G.S. not associated with GPS Survey value
 




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