Computed 2026-08-20 08:47 from 97 gage(s) with cached period-of-record data. Statistical tests (Mann-Kendall trend, Pettitt changepoint) require at least 8 years spanning at least 10 years of record -- gages below that report no signal, not "no change."

Data provenance & quality

Where these numbers come from and how far they can be trusted. Grade C (3/6 points) — the components below are the finding; the letter alone is not. Sources: DWR HydroBase snapshot HydroBase_CO_20260707 (imported 2026-08-19) for history, plus the CDSS REST API for current conditions.

Check	State	What was measured
gage freshness	stale	newest gage reading is 45 day(s) old (target 7)
diversion record	expected-lag	newest diversion record is 293 day(s) old (DWR publishes ~1 year in arrears)
structure coverage	sparse	4% of schematic structures have data

Independent check: PASS — 100.0000% agreement across 262,508 stored values re-checked against DWR's authoritative record (HydroBase_CO_20260707), over 20 structures. 0 disagreement(s) beyond a 0.01 cfs tolerance. Checked 2026-08-19; a rotating sample covers the whole basin across successive runs, and the structures this report cites are checked every time.

Federal cross-check: PASS — 99.67% day-level agreement with USGS's own published records for the same gages, across 31 co-listed station(s) and 777,166 overlapping days (within max(2%, 0.5 cfs) daily). Pre-1950 records at some gages carry known between-agency day-stamp and transcription differences — scored at each year's best ±1-day alignment; residual disagreement is real historical divergence, flagged for review.

97 gage(s) / 1,214,326 daily values (1889-01-01–2026-07-06); 619 structure(s) with diversion records; 8016 with decreed rights. Methodology has not yet had independent expert review — treat every figure as an advisory screen, not an administrative or legal conclusion.

Read this first: the measurement network itself evolved

This basin was not always measured the way it is today — the API-era record is dense and recent, the early record sparse. 70 gage(s) and 311 structure(s) report in 2026, but structure reporting only reached half its modern level around ~1957. Every historical claim below is checked against this: long-term shifts that co-move with the growth of the network carry an explicit measurement-evolution caution, and abandonment screens whose idleness begins before the modern reporting era are flagged †.

Decade	Gages with data (median yr)	Structures reporting (median yr)
1880s	1	0
1890s	2	0
1900s	3	0
1910s	9	0
1920s	11	0
1930s	14	0
1940s	18	0
1950s	28	140
1960s	32	184
1970s	36	194
1980s	34	208
1990s	37	272
2000s	45	262
2010s	51	286
2020s	48	273

Gage flow trend & changepoints

Every located gage with a period of record — dot size scales with the strength of its flow trend (|Sen slope| in %/decade, the same statistic as the table below), color with direction. An amber ring marks a detected Pettitt changepoint. Click a gage to chart its trend and shift.

Gage	Trend	Change / decade	Significance	Years	Changepoint
▸ SAN FRANCISCO CREEK AT UPPER STATION, NEAR DEL NORTE☆ SAFUPPCO	↓ decreasing	-1039.2%	p=0.000	26	~2017
▸ RIO GRANDE BELOW ELEPHANT BUTTE DAM, NM☆ RIOELENM	↓ decreasing	-65.3%	p=0.000	110	~1953
▸ RIO GRANDE CANAL NEAR DEL NORTE☆ RIOCANCO	↓ decreasing	-47.1%	p=0.000	39	~1999
▸ CLOSED BASIN PROJECT CANAL NEAR ALAMOSA☆ CBPALACO	↓ decreasing	-28.3%	p=0.000	39	~2010
▸ NORTH CLEAR CREEK BELOW CONTINENTAL RESERVOIR☆ NCLCONCO	↓ decreasing	-25.2%	p=0.000	98	~1986
▸ SAN MARCIAL CONVEYANCE CHANNEL ON RIO GRANDE, NM☆ SMCRIONM	↓ decreasing	-18.9%	p=0.000	72	~1975
▸ RIO GRANDE AT WASON, BELOW CREEDE, CO.☆ RIOWASCO	↓ decreasing	-14.2%	p=0.000	48	~1929
▸ RIO GRANDE FLOODWAY AT SAN ACACIA, NM☆ RGFSANNM	no clear trend	+11.0%	p=0.164	68	~1978
▸ RIO GRANDE AT ALBUQUERQUE, NM.☆ RIOALBNM	↓ decreasing	-10.9%	p=0.008	61	~2000
▸ RIO GRANDE NEAR LOBATOS☆ RIOLOBCO	↓ decreasing	-8.3%	p=0.001	128	~1930
▸ RIO GRANDE FLOODWAY AT SAN MARCIAL, NM☆ SMFRIONM	no clear trend	+7.3%	p=0.411	77	~1974
▸ RIO GRANDE AT THIRTY MILE BRIDGE NEAR CREEDE☆ RIOMILCO	↓ decreasing	-6.2%	p=0.001	115	~1943
▸ RIO GRANDE AT ALAMOSA☆ RIOALACO	no clear trend	-4.7%	p=0.189	115	~1929
▸ RIO GRANDE AT EMBUDO, NM.☆ RIOEMBNM	↓ decreasing	-4.0%	p=0.000	128	~1949
▸ RIO GRANDE AT MONTE VISTA☆ RIOMONCO	↑ increasing	+3.8%	p=0.024	101	~1967
▸ RIO CHAMA BELOW EL VADO DAM, NM☆ RCHELVNM	no clear trend	+3.2%	p=0.150	91	~1978
▸ RIO GRANDE NEAR DEL NORTE, CO☆ RIODELCO	↓ decreasing	-2.4%	p=0.001	129	~1929
▸ RIO GRANDE AT OTOWI BRIDGE NEAR SAN ILDEFONSO, NM.☆ RIOOTANM	↓ decreasing	-2.0%	p=0.042	125	—

79 other gage(s) show no significant trend or changepoint (not shown).

Mass-balance (network closure) trend

Structure divrec-history backfill coverage as of the last check: 4% of 2377 schematic-relevant structures. 0 year(s) clear the 30% coverage gate so far -- the trend activates automatically once qualifying years span a full decade. No action needed; the nightly backfill keeps extending the record.

Reach gain/loss shifts (1950–2026)

Mass-balance kinks computed for every summer month back to 1950 (4600 reach-snapshots) — which reaches gain or lose water, and how that has shifted across decades. Each shift is cross-checked against the observation record above: as more diversions became metered, "unaccounted" water shrinks mechanically, which can masquerade as a hydrologic shift.

• RIO GRANDE AT MONTE VISTA: reach shifted from -934 cfs to +377 cfs summer mean (more gaining, p=0.000, 77 yr) [sedimentary uplands: moderate groundwater connectivity -- gain/loss shifts can be real aquifer response; corroborate with nearby well records] [measurement-evolution caution: this shift co-moves with the growth of the gage/metering network (rho=0.64) -- part of it may be unaccounted water becoming accounted, not hydrologic change] [3 alluvial wells within 2 mi of the gage; pooled water table -1.4 ft (1946–1975, no_trend)]
• EMPIRE CANAL NEAR MONTE VISTA: reach shifted from -384 cfs to +9 cfs summer mean (more gaining, p=0.009, 29 yr) [sedimentary uplands: moderate groundwater connectivity -- gain/loss shifts can be real aquifer response; corroborate with nearby well records] [4 alluvial wells within 2 mi of the gage; pooled water table -1.1 ft (1968–2024, decreasing)]
• PRAIRIE DITCH NEAR SEVEN-MILE PLAZA: reach shifted from -239 cfs to -91 cfs summer mean (more gaining, p=0.004, 17 yr) [sedimentary uplands: moderate groundwater connectivity -- gain/loss shifts can be real aquifer response; corroborate with nearby well records] [4 alluvial wells within 2 mi of the gage; pooled water table -5.6 ft (1947–2005, no_trend)]
• RIO GRANDE AT ALAMOSA: reach shifted from -291 cfs to +194 cfs summer mean (more gaining, p=0.000, 77 yr) [sedimentary uplands: moderate groundwater connectivity -- gain/loss shifts can be real aquifer response; corroborate with nearby well records] [measurement-evolution caution: this shift co-moves with the growth of the gage/metering network (rho=0.62) -- part of it may be unaccounted water becoming accounted, not hydrologic change] [2 alluvial wells within 2 mi of the gage; pooled water table +1.2 ft (1949–2021, increasing)]
• PINOS CREEK NEAR DEL NORTE, CO.: reach shifted from -369 cfs to +30 cfs summer mean (more gaining, p=0.000, 77 yr) [mountain crystalline canyon: minimal groundwater storage -- large or shifting unaccounted losses here are more consistent with data/measurement issues or unmodeled plumbing than with aquifer exchange] [measurement-evolution caution: this shift co-moves with the growth of the gage/metering network (rho=0.63) -- part of it may be unaccounted water becoming accounted, not hydrologic change]
• RIO GRANDE ABOVE TRINCHERA CREEK NEAR LA SAUSES: reach shifted from +43 cfs to +206 cfs summer mean (more gaining, p=0.000, 77 yr) [sedimentary uplands: moderate groundwater connectivity -- gain/loss shifts can be real aquifer response; corroborate with nearby well records] [measurement-evolution caution: this shift co-moves with the growth of the gage/metering network (rho=0.66) -- part of it may be unaccounted water becoming accounted, not hydrologic change]

Groundwater now has its own tab: 605 monitored well(s), water-table trends, stream corridors, and the advisory depletion screen.

Reservoirs now has its own tab: 66 reservoir(s), end-of-year storage back to 1975, click-to-chart histories.

Cross-gage pattern fingerprint

Over the 115-year window with full coverage (1912–2026), the dominant shared pattern across 3 gage(s) explains 94% of year-to-year variance (almost certainly a basin-wide climate/snowpack driver).

All gages in this window move with the shared pattern -- no localized outlier.

The basin's aquifer story, from 52,552 water-level measurements across 605 monitored well(s) (350 alluvial, 117 bedrock, rest unclassified) — plus 2 administered well(s) reporting metered pumping through diversion records. Observation wells and pumping wells are different populations and are never conflated. Click a well to chart its record.

Well map

Every monitored well with a location — hover for identity, click to chart its water-level record below. ● alluvial   ● bedrock / confined (Denver Basin, High Plains, etc. — one-way, no human-timescale recharge)   ● unclassified — marker size scales with the strength of the well's water-level trend (|Sen slope| in ft/decade — the same Mann-Kendall/Sen statistic as the trends table below); the smallest, faintest dots have too little record to test.

3D aquifer x-ray

Every aquifer unit as its own 3D head surface — alluvial water table on top, Denver Basin members (Dawson, Denver, Arapahoe, Laramie–Fox Hills) stacked beneath where measured — interpolated from measured water levels and animated through time. Units are never mixed; surfaces exist only inside each unit's well coverage (no extrapolation); thin epochs are suppressed with their reason shown. Vertical scale exaggerated for readability; z is head elevation in feet. Advisory — measured heads, not a calibrated model.

Load 3D x-ray

Water-table trends

Of 149 well(s) with enough record for a trend test: 101 declining, 8 rising.

Fastest-declining wells	Setting	ft / decade	Span	p
▸ NA04000732CCC☆	alluvial	-10.46	14 yr	0.0228
▸ NA04100636DDD RG33B☆	alluvial	-10.45	25 yr	0.0
▸ NA04000801AAD1 RG29A☆	alluvial	-10.37	10 yr	0.0006
▸ NA04000931BAB1☆	unknown	-8.34	34 yr	0.0001
▸ NA04101032ABB1 EW-40U☆	alluvial	-8.2	33 yr	0.0
▸ NA04101032ABB2 EW-40C☆	alluvial	-7.96	33 yr	0.0
▸ NA04100936DDA RG28A☆	alluvial	-7.53	42 yr	0.0
▸ NA04000804BCC2☆	alluvial	-7.17	56 yr	0.0

Stream corridors — the surface connection

For each reach whose gain/loss has shifted (Trends tab), the wells within 2 miles of its anchoring gage, their pooled water-table history over the same era, and an advisory Glover screen of lagged stream depletion from nearby metered pumping. v1 proximity = distance to the reach's anchoring gage; segment-based reach join is a flagged upgrade.

RIO GRANDE AT MONTE VISTA: 3 alluvial well(s) nearby; pooled water table -1.4 ft (1946–1975, no_trend, p=0.2643). Glover screen: 0.4 cfs of nearby metered alluvial pumping → est. lagged depletion 0.2–0.3 cfs (uncalibrated T/S ranges; flagged for SPDSS calibration, AWAS cross-check, and expert review — DWR's AWAS is the authority).

EMPIRE CANAL NEAR MONTE VISTA: 4 alluvial well(s) nearby; pooled water table -1.1 ft (1968–2024, decreasing, p=0.0)

PRAIRIE DITCH NEAR SEVEN-MILE PLAZA: 4 alluvial well(s) nearby; pooled water table -5.6 ft (1947–2005, no_trend, p=0.0892)

RIO GRANDE AT ALAMOSA: 2 alluvial well(s) nearby; pooled water table +1.2 ft (1949–2021, increasing, p=0.0)

Wells labeled by administrative world before anything else is said about them: tributary alluvium participates in the priority system; designated-basin and Denver Basin bedrock aquifers are governed differently and are excluded from stream-connection reasoning. Read bedrock declines differently too: deep bedrock aquifers recharge negligibly on human timescales, so a falling bedrock level is storage mining — effectively permanent — not a drought response that a wet year undoes. All screens advisory.

66 reservoir(s) with 27,950 storage measurement(s), 1975–2026. Basin storage as of 2025-10-31 (the record's own end — reservoir records publish ~annually): 48,114 AF across 16 reservoir(s). Storage change is real water the mass balance must credit — a losing reach beside a filling reservoir isn't losing water, it's banking it.

Reservoir map — how full is each vessel?

Each reservoir drawn as a vessel: bubble size ∝ its record-high storage, fill level = last recorded storage as a share of its surveyed capacity (USACE National Inventory of Dams) where a confident NID match exists — the tooltip names the matched dam — and of its own record high otherwise (a wrong capacity would be worse than an honest record high, so only confident joins upgrade). Hover for numbers, click to chart its history below the map. A dashed teal ring marks reservoirs reporting live DWR telemetry — their fill reflects yesterday's storage, drawn as a dotted tail on charts and treated as provisional until the next verified HydroBase snapshot supersedes it. ● <25% ● 25–60% ● 60–90% ● >90%

Basin storage, end of each water year

End-of-water-year totals; per-year reservoir counts shown because reporting coverage varies -- a total is only comparable to years with similar counts.

Largest reservoirs on record

Click a reservoir to chart its full storage history.

Reservoir	Last recorded storage (AF)	As of
▸ RIO GRANDE RES (2003554) ☆	23,219	2025-10-31
▸ CONTINENTAL RES (2003536) ☆	12,320	2025-10-31
▸ SANTA MARIA RES (2003558) ☆	5,176	2025-10-31
▸ BEAVER PARK RES (2003532) ☆	2,714	2025-10-31
▸ BIG MEADOWS RES (2003589) ☆	2,269	2025-10-31
▸ ROAD CANYON RES (2003555) ☆	1,281	2010-10-31
▸ LOST LAKES RESERVOIR (2003546) ☆	835	2025-10-29
▸ LAKE HUMPHREYS RES (2003587) ☆	715	2010-10-31

Decrees, seniority, and administrative calls connected to this basin's flow network. Advisory reading aids on public DWR data — not administrative or legal conclusions. Rights on file: 9212 across 8016 structure(s); 117 structure(s) carry 0 court-case references.

Abandonment radar (16 screens)

Absolute rights with 10+ years of no recorded diversions. Screens only — storage, alternate points, and plan operations can explain nonuse lawfully. And diversion REPORTING itself only reached its modern level ~1957 — idleness that begins before then may be unreported use, not nonuse (flagged † below).

• EAGLE D (2000613)☆ (1875-05-05, 5.3 cfs decreed): last active 1962 — 34 years idle
• LOHR OVERFLOW SEPG D #1 (2000718)☆ (1897-06-28, 9.0 cfs decreed): last active 1962 — 34 years idle
• WINTZ D (2000908)☆ (1910-10-14, 2.1 cfs decreed): last active 1962 — 34 years idle
• MEADOW LAKE RES (2003547)☆ (1916-06-01, 0.0 cfs decreed): last active 1965 — 31 years idle
• LARICK D 5 (2000708)☆ (1874-05-01, 2.0 cfs decreed): last active 1966 — 30 years idle
• MACLEOD D 2 (2000724)☆ (1882-05-31, 1.0 cfs decreed): last active 1970 — 26 years idle
• MACLEOD D 5 (2000727)☆ (1878-04-01, 1.0 cfs decreed): last active 1970 — 26 years idle
• SHERIDAN NORTH D (2000841)☆ (1883-04-01, 2.0 cfs decreed): last active 1970 — 26 years idle
• SHERIDAN SOUTH D (2000842)☆ (1882-09-30, 3.0 cfs decreed): last active 1970 — 26 years idle
• BOWEN DRAIN DIST LAT SYS (2000549)☆ (1922-06-21, 53.5 cfs decreed): last active 1974 — 22 years idle

Compliance screens (184 advisory flags)

Screened 342 of 8016 structures with rights (413 have diversion history on file). A flag is a lead for expert review — augmentation plans, exchanges, and free-river conditions can make over-decree diversions lawful and are deliberately not modeled.

• EMPIRE CNL (2000623)☆: Observed p99 daily rate 516.0 cfs (max 613.0) exceeds total decreed absolute 505.9 cfs across 49601 recorded day(s).
• RIO GRANDE RES (2003554)☆: Observed p99 daily rate 224.0 cfs (max 2039.3) exceeds total decreed absolute 3.7 cfs across 250131 recorded day(s). Structure holds an Augmentation-use decree -- diversions above the direct-flow decree can be lawful under plan operations; interpret with care.
• PRAIRIE DRAIN D (2000799)☆: Observed p99 daily rate 188.0 cfs (max 216.0) exceeds total decreed absolute 40.0 cfs across 2199 recorded day(s).
• COSTILLA D (2000587)☆: Observed p99 daily rate 134.0 cfs (max 191.0) exceeds total decreed absolute 103.3 cfs across 28368 recorded day(s).
• SANTA MARIA RES (2003558)☆: Observed p99 daily rate 109.4 cfs (max 1696.0) exceeds total decreed absolute 3.7 cfs across 146061 recorded day(s). Structure holds an Augmentation-use decree -- diversions above the direct-flow decree can be lawful under plan operations; interpret with care.
• EXCELSIOR D (2000627)☆: Observed p99 daily rate 106.0 cfs (max 154.0) exceeds total decreed absolute 89.7 cfs across 40685 recorded day(s).
• CENTENNIAL D (2000566)☆: Observed p99 daily rate 97.0 cfs (max 132.0) exceeds total decreed absolute 82.4 cfs across 35085 recorded day(s).
• CONTINENTAL RES (2003536)☆: Observed p99 daily rate 95.3 cfs (max 1647.6) exceeds total decreed absolute 3.7 cfs across 162004 recorded day(s). Structure holds an Augmentation-use decree -- diversions above the direct-flow decree can be lawful under plan operations; interpret with care.
• CHICAGO D (2000575)☆: Observed p99 daily rate 85.0 cfs (max 196.0) exceeds total decreed absolute 66.4 cfs across 33392 recorded day(s).
• WESTSIDE D (2000903)☆: Observed p99 daily rate 50.0 cfs (max 80.0) exceeds total decreed absolute 35.8 cfs across 22621 recorded day(s).

Seniority (top structures by decreed rate)

Structure	Senior priority date	Rights	Decreed abs (cfs)	Decreed abs (AF)	Conditional?
USFS QP37N (2001965)☆	1905-06-03	1	2044.0	0	—
RIO GRANDE CNL (2000812)☆	1879-11-30	23	1648.5	0	—
RGWUA RECHARGE PROJECT (2001675)☆	1959-11-01	1	1018.0	0	yes
USFS QP37K (2001964)☆	1905-06-03	1	960.0	0	—
USFS QP39F (2001984)☆	1907-03-02	1	880.0	0	—
FARMERS UNION CNL (2000631)☆	1887-04-01	10	801.4	0	—
EMPIRE CNL (2000623)☆	1882-08-10	6	505.9	0	—
SAN LUIS VALLEY CNL (2000829)☆	1885-01-05	13	501.0	0	yes
USFS QP37D (2001958)☆	1905-06-03	1	447.0	0	—
USFS QP39D (2001979)☆	1905-06-03	1	390.2	0	—
USFS QP31F (2001929)☆	1905-06-03	1	373.2	0	—
PRAIRIE D (2000798)☆	1872-05-01	19	367.0	0	—
MONTE VISTA CNL (2000753)☆	1882-05-31	12	340.8	0	—
USFS QP37B (2001956)☆	1905-06-03	1	324.6	0	—
USFS QP37H (2001962)☆	1907-03-02	1	293.4	0	—

No inventory or legal-document changes detected since the daily watch began.

If a call were placed at a given seniority, which structures in this basin would be out of priority, and how much of their decreed rate would be curtailed? Computed from this basin's cached decrees.

Pick a calling right

Real decrees from this basin, ordered by administration number — that is, by actual seniority. The years will look out of order, and that is correct: an administration number encodes the adjudication date as well as the appropriation date, so a right appropriated in 1970 can be administered ahead of one from 1950. A senior call curtails almost everything; a junior one curtails almost nothing.

Or enter an administration number directly

Administration number
Simulate

DWR administration numbers encode appropriation and adjudication dates; lower is more senior.