Computed 2026-08-20 09:42 from 10 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	14% of schematic structures have data

Independent check: PASS — 100.0000% agreement across 154,523 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 — 99.52% day-level agreement with USGS's own published records for the same gages, across 7 co-listed station(s) and 50,101 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.

10 gage(s) / 60,439 daily values (1936-10-01–2026-07-06); 170 structure(s) with diversion records; 366 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. 2 gage(s) and 58 structure(s) report in 2026, but structure reporting only reached half its modern level around ~1974. 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)
1930s	3	0
1940s	4	0
1950s	2	0
1960s	2	32
1970s	2	67
1980s	1	86
1990s	2	88
2000s	2	94
2010s	2	62
2020s	2	58

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
▸ PIEDRA RIVER NEAR ARBOLES, CO.☆ PIEARBCO	↓ decreasing	-10.5%	p=0.033	63	~1999

9 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: 14% of 135 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 (–)

Mass-balance kinks computed for every summer month back to (0 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.

No reach shows a statistically significant long-term gain/loss shift.

Groundwater now has its own tab: 44 monitored well(s), water-table trends, stream corridors, and the advisory depletion screen.

Reservoirs now has its own tab: 28 reservoir(s), end-of-year storage back to 1970, click-to-chart histories.

Cross-gage pattern fingerprint

Not enough gages with a long enough common-coverage window yet to fingerprint shared patterns.

The basin's aquifer story, from 243 water-level measurements across 44 monitored well(s) (33 alluvial, 0 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 1 well(s) with enough record for a trend test: 1 declining, 0 rising.

Fastest-declining wells	Setting	ft / decade	Span	p
▸ WS-25☆	alluvial	-0.53	42 yr	0.0043

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.

28 reservoir(s) with 5,424 storage measurement(s), 1970–2024. Basin storage as of 2023-10-31 (the record's own end — reservoir records publish ~annually): 14,465 AF across 8 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
▸ WILLIAMS CREEK RESERVOIR (7803642) ☆	8,482	2023-10-31
▸ STEVENS RESERVOIR DAM (7803645) ☆	1,825	2022-10-31
▸ G S HATCHER RESERVOIR (7803626) ☆	1,635	2022-10-31
▸ LINN AND CLARK RESERVOIR (7803629) ☆	1,239	2022-10-31
▸ TOWN CENTER LAKE (7803646) ☆	641	2022-10-31
▸ LAKE FOREST (7803644) ☆	452	2022-10-31
▸ PARGIN RESERVOIR (7803633) ☆	337	2011-10-31
▸ PINON LAKE (7803636) ☆	125	2022-10-31

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: 435 across 366 structure(s); 30 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 ~1974 — idleness that begins before then may be unreported use, not nonuse (flagged † below).

• STEVENS SPRING (7800735)☆ (1999-04-10, 0.0 cfs decreed): last active 1968 — 57 years idle † predates modern reporting era — last recorded activity predates this basin's modern reporting era (~1974) -- early absence of record is weak evidence of nonuse
• BUCY WATER LINE (7800514)☆ (1963-07-07, 0.0 cfs decreed): last active 1970 — 55 years idle † predates modern reporting era — last recorded activity predates this basin's modern reporting era (~1974) -- early absence of record is weak evidence of nonuse
• HERSCH DITCH (7800561)☆ (1949-08-01, 8.0 cfs decreed): last active 1970 — 55 years idle † predates modern reporting era — last recorded activity predates this basin's modern reporting era (~1974) -- early absence of record is weak evidence of nonuse
• MARTIN SPG D AND PL NO 1 (7800581)☆ (1928-07-15, 1.0 cfs decreed): last active 1974 — 51 years idle
• PIEDRA STATION PIPE LINE (7800606)☆ (1913-10-01, 0.1 cfs decreed): last active 1974 — 51 years idle
• SANDFORD WATERLINE (7800615)☆ (1968-09-01, 0.0 cfs decreed): last active 1974 — 51 years idle
• YELLOW JACKET PIPE LINE (7800651)☆ (1912-06-10, 0.1 cfs decreed): last active 1974 — 51 years idle
• LINN AND CLARK RESERVOIR (7803629)☆ (1902-06-14, 0.0 cfs decreed): last active 1974 — 51 years idle
• J B MARTINEZ DITCH (7800564)☆ (1883-06-14, 1.2 cfs decreed): last active 1975 — 50 years idle
• TRES PIEDRAS DITCH (7800639)☆ (1943-10-01, 2.0 cfs decreed): last active 1975 — 50 years idle

Compliance screens (85 advisory flags)

Screened 118 of 366 structures with rights (139 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.

• PIEDRA FALLS DITCH (7800604)☆: Observed p99 daily rate 26.1 cfs (max 33.0) exceeds total decreed absolute 26.0 cfs across 25808 recorded day(s).
• GORDON CREEK WETLANDS DIVERSION DITCH (7800756)☆: Observed p99 daily rate 20.0 cfs (max 20.0) exceeds total decreed absolute 4.0 cfs across 1681 recorded day(s).
• FARROW AND PETERSON D (7800545)☆: Observed p99 daily rate 18.4 cfs (max 23.3) exceeds total decreed absolute 16.6 cfs across 26551 recorded day(s).
• J B MARTINEZ DITCH (7800564)☆: Observed p99 daily rate 17.0 cfs (max 20.0) exceeds total decreed absolute 1.2 cfs across 322 recorded day(s).
• CIMARRON DITCH (7800524)☆: Observed p99 daily rate 15.0 cfs (max 15.0) exceeds total decreed absolute 5.0 cfs across 7748 recorded day(s).
• G S HATCHER DITCH (7800550)☆: Observed p99 daily rate 15.0 cfs (max 16.8) exceeds total decreed absolute 7.5 cfs across 1550 recorded day(s).
• M E AND M DITCH (7800580)☆: Observed p99 daily rate 14.4 cfs (max 21.0) exceeds total decreed absolute 12.0 cfs across 15526 recorded day(s).
• CLAYTON-REED DITCH (7800525)☆: Observed p99 daily rate 13.0 cfs (max 13.1) exceeds total decreed absolute 10.0 cfs across 19001 recorded day(s).
• HOSSACK CREEK DITCH (7800562)☆: Observed p99 daily rate 13.0 cfs (max 24.7) exceeds total decreed absolute 10.0 cfs across 10971 recorded day(s).
• J C R DITCH (7800565)☆: Observed p99 daily rate 12.9 cfs (max 19.0) exceeds total decreed absolute 10.0 cfs across 6994 recorded day(s).

Seniority (top structures by decreed rate)

Structure	Senior priority date	Rights	Decreed abs (cfs)	Decreed abs (AF)	Conditional?
PIEDRA RIVER MIN FLOW (7801903)☆	1978-03-16	1	70.0	0	—
PIEDRA RIVER MIN FLOW (7801910)☆	1979-03-14	1	70.0	0	—
PIEDRA RIVER MIN FLOW (7801902)☆	1978-03-16	1	53.0	0	—
PIEDRA RIVER MIN FLOW (7801901)☆	1978-03-16	1	44.0	0	—
LINN AND CLARK DITCH (7800578)☆	1902-06-14	1	36.5	0	—
PIEDRA RIVER MIN FLOW (7801900)☆	1978-03-16	1	30.0	0	—
PIEDRA FALLS DITCH (7800604)☆	1934-07-18	2	26.0	0	yes
LITTLE PAGOSA CREEK DIVR (7800659)☆	1939-12-31	1	26.0	0	—
BARNES-MEUSER AND SHAW D (7800507)☆	1903-12-31	3	22.5	0	—
BUCKSKIN-NAILOR DITCH (7800513)☆	1900-03-20	7	21.9	0	—
PERKINS DITCH - STOLLSTEIMER CREEK (7800600)☆	1963-07-28	1	20.0	0	—
ABRAHAM DAVIS DITCH (7800501)☆	1900-04-01	4	18.0	0	—
WEMINUCHE CR MIN FLOW (7801909)☆	1978-03-16	1	18.0	0	—
FARROW AND PETERSON D (7800545)☆	1879-04-10	6	16.6	0	—
F S MOCKLER IRR DITCH (7800544)☆	1901-10-01	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.