Computed 2026-08-20 08:40 from 35 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	1% of schematic structures have data

Independent check: PASS — 100.0000% agreement across 44,226 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 — 99.70% day-level agreement with USGS's own published records for the same gages, across 25 co-listed station(s) and 200,086 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.

35 gage(s) / 290,248 daily values (1896-10-01–2026-07-06); 277 structure(s) with diversion records; 735 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. 18 gage(s) and 103 structure(s) report in 2026, but structure reporting only reached half its modern level around ~1953. 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)
1890s	1	0
1900s	2	0
1910s	1	6
1920s	2	5
1930s	1	13
1940s	1	25
1950s	4	97
1960s	5	107
1970s	6	79
1980s	13	94
1990s	10	84
2000s	13	64
2010s	19	120
2020s	18	114

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
▸ LONG CANYON CREEK NEAR MADRID, CO.☆ LONMADCO	no clear trend	+211.3%	p=0.081	18	~1979
▸ VAN BREMER ARROYO NEAR MODEL, CO☆ VANMODCO	↓ decreasing	-77.4%	p=0.043	59	~1988
▸ MODEL CANAL☆ MODCANCO	↓ decreasing	-58.8%	p=0.019	18	—
▸ PURGATOIRE RIVER AT ROCK CROSSING NR TIMPAS, CO.☆ PURRCKCO	↓ decreasing	-38.8%	p=0.006	44	—
▸ JOHNS FLOOD DITCH☆ JOHDITCO	↓ decreasing	-30.4%	p=0.028	18	—
▸ PURGATOIRE RIVER NEAR THATCHER, CO.☆ PURTHACO	↓ decreasing	-18.2%	p=0.027	61	~2010
▸ PURGATOIRE RIVER AT TRINIDAD☆ PURTRICO	↓ decreasing	-9.1%	p=0.000	115	~1970

28 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: 1% of 3815 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 (1955–2026)

Mass-balance kinks computed for every summer month back to 1955 (1515 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.

• JOHNS FLOOD DITCH: reach shifted from -30 cfs to +1 cfs summer mean (more gaining, p=0.000, 18 yr) [sedimentary plains/foothills: moderate groundwater connectivity -- gain/loss shifts can be real aquifer response; corroborate with nearby well records]
• PURGATOIRE RIVER NEAR HOEHNE, CO.: reach shifted from -112 cfs to -32 cfs summer mean (more gaining, p=0.009, 20 yr) [sedimentary plains/foothills: moderate groundwater connectivity -- gain/loss shifts can be real aquifer response; corroborate with nearby well records]
• CHILILI DITCH: reach shifted from -22 cfs to -16 cfs summer mean (more gaining, p=0.036, 19 yr) [sedimentary plains/foothills: moderate groundwater connectivity -- gain/loss shifts can be real aquifer response; corroborate with nearby well records]
• PURGATOIRE RIVER AT TRINIDAD: reach shifted from +46 cfs to -2 cfs summer mean (more losing, p=0.000, 50 yr) [sedimentary plains/foothills: moderate groundwater connectivity -- gain/loss shifts can be real aquifer response; corroborate with nearby well records]

Groundwater now has its own tab: 258 monitored well(s), water-table trends, stream corridors, and the advisory depletion screen.

Reservoirs now has its own tab: 27 reservoir(s), end-of-year storage back to 1950, click-to-chart histories.

Cross-gage pattern fingerprint

Over the 50-year window with full coverage (1977–2026), the dominant shared pattern across 3 gage(s) explains 54% 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 652 water-level measurements across 258 monitored well(s) (140 alluvial, 0 bedrock, rest unclassified) — plus 1 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 8 well(s) with enough record for a trend test: 2 declining, 2 rising.

Fastest-declining wells	Setting	ft / decade	Span	p
▸ SC03005818BBB☆	alluvial	-0.88	13 yr	0.0005
▸ SC02905815DAA☆	alluvial	-0.64	13 yr	0.0049

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.

CHILILI DITCH: 0 alluvial well(s) nearby. Glover screen: 0.0 cfs of nearby metered alluvial pumping → est. lagged depletion 0.0–0.0 cfs (uncalibrated T/S ranges; flagged for SPDSS calibration, AWAS cross-check, and expert review — DWR's AWAS is the authority).

PURGATOIRE RIVER AT TRINIDAD: 0 alluvial well(s) nearby. Glover screen: 0.0 cfs of nearby metered alluvial pumping → est. lagged depletion 0.0–0.0 cfs (uncalibrated T/S ranges; flagged for SPDSS calibration, AWAS cross-check, and expert review — DWR's AWAS is the authority).

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.

27 reservoir(s) with 2,689 storage measurement(s), 1950–2013. Basin storage as of 2012-10-19 (the record's own end — reservoir records publish ~annually): 9 AF across 1 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
▸ TRINIDAD RESERVOIR (1903935) ☆	14,200	2010-10-31
▸ NORTH LAKE RESERVOIR (1903855) ☆	3,658	2005-07-14
▸ MONUMENT LAKE RESERVOIR (1903857) ☆	1,552	2005-10-06
▸ LAKE DOROTHY (1903941) ☆	326	2006-04-18
▸ RUSSELL RESERVOIR (1903856) ☆	290	2005-09-08
▸ GAGLIARDI (JOE/LD WARD) RESERVOIR (1903530) ☆	185	2004-10-10
▸ RUSSELL LAKE DITCH (1900551) ☆	150	2002-10-15
▸ SUENO RESERVOIR (1903940) ☆	50	2006-09-07

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: 960 across 735 structure(s); 42 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 ~1953 — idleness that begins before then may be unreported use, not nonuse (flagged † below).

• UPLAND DITCH (1900696)☆ (1914-12-16, 8.0 cfs decreed): last active 1957 — 67 years idle
• MIGUEL TRUJILLO DITCH (1900754)☆ (1922-04-11, 3.0 cfs decreed): last active 1965 — 59 years idle
• EARL FLOOD DITCH (1900648)☆ (1912-08-08, 30.0 cfs decreed): last active 1966 — 58 years idle
• BLACK HILLS RESERVOIR (1903782)☆ (1977-09-01, 0.0 cfs decreed): last active 1966 — 58 years idle
• BAKER RESERVOIR (1903784)☆ (1916-05-08, 0.0 cfs decreed): last active 1970 — 54 years idle
• BROWN RESERVOIR NO 1 (1903794)☆ (1909-11-14, 0.0 cfs decreed): last active 1970 — 54 years idle
• HART DITCH (1900617)☆ (1905-06-30, 15.0 cfs decreed): last active 1978 — 46 years idle
• DOHERTY DITCH (1900692)☆ (1913-03-04, 15.0 cfs decreed): last active 1978 — 46 years idle
• CANONCITA DITCH (1900627)☆ (1902-03-07, 5.0 cfs decreed): last active 1983 — 41 years idle
• PARSONS DITCH NO 1 (1900671)☆ (1895-04-04, 2.0 cfs decreed): last active 1986 — 38 years idle

Compliance screens (88 advisory flags)

Screened 131 of 735 structures with rights (146 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.

• JOHN FLOOD DITCH (1900572)☆: Observed p99 daily rate 46.0 cfs (max 224.0) exceeds total decreed absolute 1.2 cfs across 57136 recorded day(s). Structure holds an Augmentation-use decree -- diversions above the direct-flow decree can be lawful under plan operations; interpret with care.
• HOEHNE DITCH (1900571)☆: Observed p99 daily rate 30.3 cfs (max 260.0) exceeds total decreed absolute 22.2 cfs across 55327 recorded day(s).
• MAXWELL DITCH NO 20 (1900522)☆: Observed p99 daily rate 22.0 cfs (max 32.0) exceeds total decreed absolute 6.8 cfs across 12262 recorded day(s). Structure holds an Augmentation-use decree -- diversions above the direct-flow decree can be lawful under plan operations; interpret with care.
• MAXWELL DITCH NO 2 (1900603)☆: Observed p99 daily rate 18.6 cfs (max 24.2) exceeds total decreed absolute 0.4 cfs across 3092 recorded day(s).
• PIONEER DITCH NO 1 (1900653)☆: Observed p99 daily rate 15.0 cfs (max 40.0) exceeds total decreed absolute 3.8 cfs across 6602 recorded day(s).
• JEANNIN DITCH (1900702)☆: Observed p99 daily rate 14.0 cfs (max 14.0) exceeds total decreed absolute 4.0 cfs across 5426 recorded day(s).
• O'NEAL DITCH (1900682)☆: Observed p99 daily rate 13.0 cfs (max 16.0) exceeds total decreed absolute 8.5 cfs across 11030 recorded day(s).
• ANTONIO LOPEZ DITCH (1900583)☆: Observed p99 daily rate 12.4 cfs (max 19.0) exceeds total decreed absolute 8.0 cfs across 22774 recorded day(s).
• SALAS NORTH DITCH (1900559)☆: Observed p99 daily rate 12.0 cfs (max 33.5) exceeds total decreed absolute 8.8 cfs across 23575 recorded day(s).
• MAXWELL DITCH NO 19 (1900523)☆: Observed p99 daily rate 10.0 cfs (max 10.0) exceeds total decreed absolute 1.6 cfs across 2066 recorded day(s).

Seniority (top structures by decreed rate)

Structure	Senior priority date	Rights	Decreed abs (cfs)	Decreed abs (AF)	Conditional?
TRINIDAD RESERVOIR (1903935)☆	1861-05-31	21	729.9	92378	yes
MODEL DITCH (1900552)☆	1862-03-20	9	293.8	0	—
PULASKI DITCH (1900660)☆	1863-06-30	11	154.0	0	—
BACA IRRIGATING DITCH (1900783)☆	1861-05-31	8	103.7	0	—
NORTH LAKE INLET (1900554)☆	1861-05-31	6	65.8	0	—
SAN YSIDRO HIGHLINE (1900713)☆	1908-05-31	1	56.0	0	—
EARL FLOOD DITCH (1900648)☆	1912-08-08	1	30.0	0	—
HOEHNE DITCH (1900571)☆	1863-01-01	3	22.2	0	—
PURGATOIRE RIVER MIN FLOW (1903025)☆	2009-01-27	1	21.0	0	—
HALL & HOWARD DITCH (1900607)☆	1892-01-01	1	19.9	0	—
S FK PURGATOIRE MIN FLOW (1903002)☆	2009-01-27	1	18.0	0	—
MOCK DITCH NO 2 (1900823)☆	1897-12-29	1	17.9	0	—
LEWELLING-MCCORMICK (1900575)☆	1864-01-01	3	17.8	0	—
TRINCHERA DITCH (1900726)☆	1866-02-28	1	16.8	0	—
HART DITCH (1900617)☆	1905-06-30	1	15.0	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.