Computed 2026-08-20 08:53 from 16 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 D (2/6 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	stale	newest diversion record is 658 day(s) old (DWR publishes ~1 year in arrears)
structure coverage	sparse	7% of schematic structures have data

Independent check: PASS — 100.0000% agreement across 197,711 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 — 100.00% day-level agreement with USGS's own published records for the same gages, across 6 co-listed station(s) and 91,826 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.

16 gage(s) / 234,482 daily values (1916-04-01–2026-07-06); 165 structure(s) with diversion records; 709 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. 13 gage(s) and 33 structure(s) report in 2026, but structure reporting only reached half its modern level around ~1991. 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)
1910s	1	0
1920s	4	0
1930s	5	0
1940s	5	0
1950s	5	44
1960s	5	42
1970s	5	38
1980s	5	48
1990s	8	64
2000s	10	38
2010s	11	30
2020s	12	32

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
▸ SAND CREEK AT GREAT SAND DUNES NATIONAL PARK☆ SANDUNCO	↓ decreasing	-633.1%	p=0.000	28	~2015
▸ MEDANO CREEK AT GREAT SAND DUNES NATIONAL PARK☆ MEDSANCO	↓ decreasing	-150.9%	p=0.000	31	~2017
▸ MOUNTAIN HOME RESERVOIR (OUTFLOW)☆ MTNOUTCO	no clear trend	-31.1%	p=0.123	27	~2018
▸ SANGRE DE CRISTO CREEK NEAR FORT GARLAND, CO.☆ SANFTGCO	↓ decreasing	-11.5%	p=0.000	103	~1948
▸ TRINCHERA CREEK BELOW SMITH RESERVOIR☆ TRISMICO	↓ decreasing	-10.4%	p=0.022	92	~2009
▸ TRINCHERA CREEK ABOVE MOUNTAIN HOME RESERVOIR☆ TRIMTNCO	↓ decreasing	-5.4%	p=0.000	102	~1949
▸ TRINCHERA CREEK ABOVE TURNER'S RANCH☆ TRITURCO	↓ decreasing	-4.5%	p=0.000	103	~1995
▸ BIG SPRING CREEK AT MEDANO RANCH NEAR MOSCA☆ BIGSPGCO	↓ decreasing	-3.3%	p=0.033	27	~2018

8 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: 7% of 481 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 (1177 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.

• TRINCHERA CREEK BELOW SMITH RESERVOIR: reach shifted from -21 cfs to +1 cfs summer mean (more gaining, p=0.000, 73 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]
• SANGRE DE CRISTO CREEK NEAR FORT GARLAND, CO.: reach shifted from -8 cfs to -26 cfs summer mean (more losing, p=0.000, 72 yr) [alluvial valley: real alluvial aquifer -- a decades-long shift toward losing is the classic signature of alluvial pumping and urbanization] [2 alluvial wells within 2 mi of the gage; pooled water table -17678.2 ft (1991–2025, no_trend)]
• UTE CREEK NEAR FORT GARLAND, CO: reach shifted from +8 cfs to +24 cfs summer mean (more gaining, p=0.008, 75 yr) [alluvial valley: real alluvial aquifer -- a decades-long shift toward losing is the classic signature of alluvial pumping and urbanization]
• TRINCHERA CREEK ABOVE MOUNTAIN HOME RESERVOIR: reach shifted from -14 cfs to -9 cfs summer mean (more gaining, p=0.022, 73 yr) [alluvial valley: real alluvial aquifer -- a decades-long shift toward losing is the classic signature of alluvial pumping and urbanization]

Groundwater now has its own tab: 324 monitored well(s), water-table trends, stream corridors, and the advisory depletion screen.

Reservoirs now has its own tab: 3 reservoir(s), end-of-year storage back to 1951, click-to-chart histories.

Cross-gage pattern fingerprint

Over the 94-year window with full coverage (1933–2026), the dominant shared pattern across 3 gage(s) explains 84% 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 29,262 water-level measurements across 324 monitored well(s) (174 alluvial, 54 bedrock, rest unclassified) — plus 3 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 92 well(s) with enough record for a trend test: 62 declining, 9 rising.

Fastest-declining wells	Setting	ft / decade	Span	p
▸ CC03107214CAA☆	unknown	-11.12	45 yr	0.0
▸ CC03107209BAA☆	unknown	-8.33	45 yr	0.0
▸ CC03107210BCD☆	unknown	-8.0	34 yr	0.0006
▸ CC03107514AD☆	unknown	-7.34	16 yr	0.012
▸ CC03107204CDD☆	unknown	-6.42	34 yr	0.0468
▸ NA03801234BDD1 EW-27U☆	alluvial	-6.38	23 yr	0.0
▸ CC03107207DDA☆	unknown	-6.04	81 yr	0.0
▸ CC03007302BAD☆	alluvial	-5.27	34 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.

SANGRE DE CRISTO CREEK NEAR FORT GARLAND, CO.: 2 alluvial well(s) nearby; pooled water table -17678.2 ft (1991–2025, no_trend, p=0.3202)

UTE CREEK NEAR FORT GARLAND, CO: 1 alluvial well(s) nearby

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.

3 reservoir(s) with 10,637 storage measurement(s), 1951–2025. Basin storage as of 2024-10-31 (the record's own end — reservoir records publish ~annually): 3,634 AF across 3 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
▸ MOUNTAIN HOME RESERVOIR (3503529) ☆	2,533	2024-10-31
▸ SMITH RESERVOIR (3503530) ☆	1,027	2024-10-31
▸ SAN LUIS LAKE (3503531) ☆	74	2024-10-31

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: 1317 across 709 structure(s); 24 structure(s) carry 0 court-case references.

Abandonment radar (25 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 ~1991 — idleness that begins before then may be unreported use, not nonuse (flagged † below).

• LITTLE ALTA D (3500536)☆ (1891-12-31, 1.0 cfs decreed): last active 1954 — 70 years idle † predates modern reporting era — last recorded activity predates this basin's modern reporting era (~1991) -- early absence of record is weak evidence of nonuse
• HOFFMAN D (3500526)☆ (1863-05-31, 1.0 cfs decreed): last active 1971 — 53 years idle † predates modern reporting era — last recorded activity predates this basin's modern reporting era (~1991) -- early absence of record is weak evidence of nonuse
• OJITO CREEK D (3500563)☆ (1864-05-01, 40.0 cfs decreed): last active 1973 — 51 years idle † predates modern reporting era — last recorded activity predates this basin's modern reporting era (~1991) -- early absence of record is weak evidence of nonuse
• LASTRE D (3500534)☆ (1898-04-01, 5.0 cfs decreed): last active 1975 — 49 years idle † predates modern reporting era — last recorded activity predates this basin's modern reporting era (~1991) -- early absence of record is weak evidence of nonuse
• NENNINGER D (3500549)☆ (1863-05-31, 2.0 cfs decreed): last active 1983 — 41 years idle † predates modern reporting era — last recorded activity predates this basin's modern reporting era (~1991) -- early absence of record is weak evidence of nonuse
• W0572 WELL NO 12 (3505088)☆ (1956-03-31, 3.0 cfs decreed): last active 1994 — 30 years idle
• SCOTT SPRING NO 1 (3500652)☆ (1940-12-31, 0.6 cfs decreed): last active 1997 — 27 years idle
• HANK'S POND (3503533)☆ (1952-06-01, 0.0 cfs decreed): last active 1997 — 27 years idle
• MEDANO SAND CR D (3500541)☆ (1908-07-01, 40.0 cfs decreed): last active 1998 — 26 years idle
• SMITH/WAKASUGI D (3500701)☆ (1945-12-31, 2.0 cfs decreed): last active 2000 — 24 years idle

Compliance screens (55 advisory flags)

Screened 97 of 709 structures with rights (104 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.

• SHADY RETREAT D (3500573)☆: Observed p99 daily rate 60.0 cfs (max 60.0) exceeds total decreed absolute 16.7 cfs across 5986 recorded day(s). Structure holds an Augmentation-use decree -- diversions above the direct-flow decree can be lawful under plan operations; interpret with care.
• MEYER D (3500543)☆: Observed p99 daily rate 50.0 cfs (max 50.0) exceeds total decreed absolute 26.7 cfs across 12577 recorded day(s). Structure holds an Augmentation-use decree -- diversions above the direct-flow decree can be lawful under plan operations; interpret with care.
• ZAPATO D 3 (3500592)☆: Observed p99 daily rate 50.0 cfs (max 80.0) exceeds total decreed absolute 16.0 cfs across 3050 recorded day(s). Structure holds an Augmentation-use decree -- diversions above the direct-flow decree can be lawful under plan operations; interpret with care.
• WALSEN D 1 (3500588)☆: Observed p99 daily rate 46.2 cfs (max 117.0) exceeds total decreed absolute 3.5 cfs across 38884 recorded day(s).
• MEDANO SAND CR D (3500541)☆: Observed p99 daily rate 45.0 cfs (max 45.0) exceeds total decreed absolute 40.0 cfs across 1198 recorded day(s).
• NOTLEY BALL OVERFLOW D (3500562)☆: Observed p99 daily rate 40.0 cfs (max 50.0) exceeds total decreed absolute 9.9 cfs across 6596 recorded day(s).
• SEYFRIED STRIBLING D (3500594)☆: Observed p99 daily rate 39.8 cfs (max 100.0) exceeds total decreed absolute 8.0 cfs across 16586 recorded day(s).
• NOTLEY BALL OVERFLOW D 1 (3500597)☆: Observed p99 daily rate 28.7 cfs (max 50.0) exceeds total decreed absolute 1.9 cfs across 3328 recorded day(s).
• GALLOWAY D (3500520)☆: Observed p99 daily rate 20.0 cfs (max 40.0) exceeds total decreed absolute 1.2 cfs across 5632 recorded day(s).
• NORTH ZAPATA CREEK PIPELINE (3500663)☆: Observed p99 daily rate 19.0 cfs (max 25.0) exceeds total decreed absolute 12.0 cfs across 3455 recorded day(s). Structure holds an Augmentation-use decree -- diversions above the direct-flow decree can be lawful under plan operations; interpret with care.

Seniority (top structures by decreed rate)

Structure	Senior priority date	Rights	Decreed abs (cfs)	Decreed abs (AF)	Conditional?
TRINCHERA CANAL (3500579)☆	1864-05-01	14	291.3	0	—
TRINCHERA GARLAND CANAL (3500581)☆	1864-05-01	14	174.9	0	—
GARLAND D,HDGT 2 (3500523)☆	1867-05-01	10	123.0	0	—
GARLAND D,HDGT 1 (3500521)☆	1863-05-31	8	104.7	0	—
USFS QP55A6 (3500723)☆	1905-06-12	1	89.8	0	—
INDIAN CREEK D (3500529)☆	1864-05-01	14	75.0	0	—
TRINCHERA HIGHLINE CANAL (3500582)☆	1864-05-01	14	73.5	0	—
SANGRE CRISTO TRINCHERA (3500570)☆	1863-05-31	8	71.0	0	—
NEWTON D 2 (3500560)☆	1867-05-01	12	64.8	0	—
USFS QP57A2 (3500726)☆	1905-06-12	1	64.4	0	—
SAND CREEK MSF (3500684)☆	1932-03-17	1	58.9	0	—
SANGRE DE CRISTO D (3500571)☆	1863-05-31	8	53.7	0	—
NORTH SWAMP D (3500561)☆	1867-05-01	10	53.0	0	—
SOUTH SWAMP D (3500576)☆	1867-05-01	10	53.0	0	—
OJITO CREEK D 1 (3500564)☆	1864-05-01	14	47.0	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.