Nine USGS stations, upstream to downstream. Live instantaneous-values feed;
water-surface elevation derived from published gage datum + stage.
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Longitudinal water-surface profile
Water-surface elevation against approximate downstream distance.
Only the markers are measurements — each is a single point in a separate navigation pool.
The connecting line is interpolation, not a surveyed water surface: the real profile is a
staircase with its drops concentrated at the locks and dams between gages, which this
nine-point sample cannot resolve.
Fetching USGS instantaneous values…
Current conditions by station
Stage and discharge are plotted separately — they are different measures on
different scales and do not share an axis. History loads after the current values;
longer windows are a larger download (7 d ≈ 8 MB).
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Tabulated values
Latest reading at each station, with the datum arithmetic shown so
every elevation is traceable.
Station
Name
Gage ht (ft)
Gage datum (ft)
WSE (ft)
Vert. datum
Q (cfs)
Drainage (mi²)
Reading (CT)
Method, datums, and what to distrust
WSE is derived, not measured. No station in this set publishes a
water-surface-elevation parameter (62614 / 63160). Every elevation here is
gage datum (alt_va) + gage height (00065), using the datum in the USGS
site file. Nothing else is available for these gages.
Six stations publish a gage datum of exactly 0.00 ft NGVD29
(02465000, 02466030, 02467000, 02469525, 02469762 — and 02470629 at 0.13 ft NAVD88).
For those, reported stage is the elevation. This was verified against a year of
daily values: 02466030 at Selden L&D held a 0.93-ft range over 388 days around
el. 95.9, which is only explicable as a regulated navigation pool held near
el. 96 — not a local stage datum.
02452505 (Sipsey Fork) has no published gage datum — alt_va
is null in the USGS site file. Its stage (~35–45 ft) is on an unreferenced local datum
and cannot be converted to elevation. It is shown on the profile as a labeled break,
not as a point, because any elevation for it would be invented. It is also a
tributary, not a mainstem point: Mulberry Fork at Arkadelphia (487 mi²) and
Sipsey Fork (1,100 mi²) both drain into Mulberry Fork above Cordova (1,916 mi²).
The profile mixes NGVD29 and NAVD88. Six stations are NGVD29, three
are NAVD88. In west-central Alabama NAVD88 sits roughly 0.4–0.9 ft below NGVD29.
Across 269 ft of relief that is invisible; across the last two stations — Coffeeville
tailwater to Bucks, roughly 2 ft of total fall — the datum offset is a large fraction
of the signal. Do not read gradient from the lowest reach of this plot.
Converting properly requires VERTCON/VDatum at each site.
Distance is straight-line, not river miles. The x-axis is cumulative
great-circle distance between consecutive mainstem gages. True channel distance is
longer by the sinuosity of the reach, typically 1.3–1.6×. Slopes read off this plot are
therefore biased steep. The shape of the staircase is correct; its horizontal scale is not.
Discharge is not conserved down the list. Readings at lock-and-dam
stations reflect gate and lockage operations at the instant of measurement, and the
Black Warrior and Tombigbee arms merge above Demopolis. Instantaneous Q at a downstream
station will routinely be less than at one upstream. Continuity here needs daily means
and a routed comparison, not a snapshot.
Endpoint note. This page reads
api.waterdata.usgs.gov/ogcapi/v0, not the legacy
waterservices.usgs.gov. The legacy service returns HTTP 403
when a request carries Origin: null — which is what every browser sends for a
page opened from disk — so a file:// dashboard built on it fails silently.
The legacy service is kept only as a fallback for when this page is served over http(s).
Provisional data. USGS instantaneous values are provisional and
subject to revision. Rating shifts at the stage-only sites are not reflected in
real time.
02470629 (Bucks, Mobile R. RM 31) is tidal. Its stage and discharge
oscillate with the tide and reverse on flood; a single instantaneous value there is a
phase sample, not a steady-state condition.
Source: U.S. Geological Survey · api.waterdata.usgs.gov/ogcapi/v0 (collections: latest-continuous, continuous) ·
data are provisional