Hydrohistorian
Evolution of the network
Gage flow trend & changepoints
What counts as a trend here
Computed 2026-08-20 08:28 from 10 gage(s) with cached period-of-record data. Mann-Kendall (trend) and Pettitt (changepoint) both require at least 8 years spanning at least 10 years of record. A gage below that reports no signal — which is not the same as “no change.”
Of the 10 gages with enough record, 4 are trending down and 0 up, and 4 carry a detected shift. The clearest is ARIKAREE RIVER AT HAIGLER, NEBR., -68.8 points of its long-term median per decade over 95 years (p<0.0001). The other 6 show no clear signal either way.
| Gage | Trend | Change / decade points of median | Significance | Years | Changepoint |
|---|---|---|---|---|---|
|
▸
ARIKAREE RIVER AT HAIGLER, NEBR. ARIKHANE |
↓ decreasing | -68.8 | p=0.000 | 95 | ~1974 |
|
▸
PIONEER DITCH PIOHDGCO |
↓ decreasing | -11.9 | p=0.000 | 60 | ~1981 |
|
▸
NORTH FORK REPUBLICAN RIVER AT COLORADO-NEBRASKA NRPSTLNE |
↓ decreasing | -9.4 | p=0.000 | 95 | ~1995 |
|
▸
PIONEER DITCH AT THE COLORADO-NEBRASKA STATELINE PIOSTLCO |
↓ decreasing | -8.3 | p=0.000 | 59 | ~1981 |
6 other gage(s) show no significant trend or changepoint (not shown).
How the measurement network itself changed
This basin was not always measured the way it is today — the API-era record is dense and recent, the early record sparse. 6 gage(s) and 10 structure(s) report in 2026, but structure reporting only reached half its modern level around ~1950. 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 | 2 | 0 |
| 1940s | 3 | 0 |
| 1950s | 3 | 9 |
| 1960s | 4 | 8 |
| 1970s | 4 | 8 |
| 1980s | 4 | 14 |
| 1990s | 4 | 14 |
| 2000s | 4 | 8 |
| 2010s | 6 | 9 |
| 2020s | 6 | 11 |
Mass-balance (network closure) trend
Structure divrec-history backfill coverage as of the last check: 0% of 0 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: 2034 monitored well(s), water-table trends, stream corridors, and the advisory depletion screen.
Cross-gage pattern fingerprint
Not enough gages with a long enough common-coverage window yet to fingerprint shared patterns.
Data provenance & quality
Where these numbers come from and how far they can be trusted. Grade B (4/6 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 | current | newest gage reading is 4 day(s) old |
| diversion record | expected-lag | newest diversion record is 293 day(s) old (DWR publishes ~1 year in arrears) |
| structure coverage | sparse | 0% of schematic structures have data |
Independent check: PASS — 100.0000% agreement across 146,030 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 — 99.88% day-level agreement with USGS's own published records for the same gages, across 3 co-listed station(s) and 75,130 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) / 147,171 daily values (1931-03-18–2026-08-16); 39 structure(s) with diversion records; 112 with decreed rights. Methodology has not yet had independent expert review — treat every figure as an advisory screen, not an administrative or legal conclusion.
28,885 water-level measurements across 2034 monitored well(s) — 3 alluvial, 2029 bedrock — plus 0 administered well(s) reporting metered pumping.
What is being counted
Observation wells and pumping wells are different populations and are never conflated: water levels come from monitored observation wells, and metered pumping comes from administered wells reporting through diversion records. Click any well to chart its own record.
Well map
3D aquifer x-ray
Every aquifer unit as its own head surface, animated through time.
How the surfaces are built, and what they are not
Alluvial water table on top, Denver Basin members (Dawson, Denver, Arapahoe, Laramie–Fox Hills) stacked beneath where measured, interpolated from measured water levels. Units are never mixed; a surface exists only inside its own unit's well coverage, with no extrapolation; thin epochs are suppressed and say why. Vertical scale is exaggerated for readability and z is head elevation in feet. These are measured heads, not a calibrated groundwater model.
Water-table trends
Of 459 well(s) with enough record for a trend test: 369 declining, 50 rising.
| Fastest-declining wells | Setting | ft / decade | Span | p |
|---|---|---|---|---|
| ▸ COLO NATIONAL BANK | bedrock | -28.72 | 41 yr | 0.0 |
| ▸ WARD, ALFRED | bedrock | -16.92 | 47 yr | 0.0 |
| ▸ NHP-FR-041 KRAMER | bedrock | -16.76 | 51 yr | 0.0 |
| ▸ NHP-WY-019 BEAUPREZ, E. | bedrock | -16.5 | 57 yr | 0.0 |
| ▸ NHP-WY-003 KOENIG, ROGER | bedrock | -16.44 | 58 yr | 0.0 |
| ▸ NHP-WY-001 HAHN, RODNEY | bedrock | -15.8 | 70 yr | 0.0 |
| ▸ NHP-WY-013 TRAUTMAN, ED | bedrock | -15.8 | 59 yr | 0.0 |
| ▸ NHP-SH-038 ORTNER, T. | bedrock | -15.75 | 50 yr | 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.
Decreed rights on this network run from 1887-06-01 to 2012-02-23. Of the 20 structures with a yield estimate, the median one’s senior right was in priority 23% of a median irrigation season and 0% in a dry one. 1 abandonment screen and 6 compliance flags are listed below as leads for review — a screen is not an abandonment and a flag is not a violation.
Rights on file: 133 across 112 structure(s); 0 structure(s) carry 0 court-case references. Advisory reading aids on public DWR data — not administrative or legal conclusions.
Why diversions stopped — call-based explanations
Sustained diversion stops matched to senior administrative calls.
- CARROLL GILMORE DITCH (6500503) stopped 2025-05-08 (10+ days) — call at LEYNER COTTONWOOD DITCH curtailing 100% of its decreed rate [heuristic-strong]
- CARROLL GILMORE DITCH (6500503) stopped 2025-04-17 (9+ days) — call at TUCKER RES curtailing 100% of its decreed rate [heuristic-strong]
- PIONEER DITCH (HEAD) (6500520) stopped 2025-04-11 (13+ days) — call at TUCKER RES curtailing 100% of its decreed rate [heuristic-strong]
- PIONEER DITCH (HEAD) (6500520) stopped 2024-10-23 (159+ days) — call at INDEPENDENT HIGHLINE DITCH curtailing 100% of its decreed rate [heuristic-strong]
Right yield — how often could these rights actually divert?
Share of irrigation-season days each structure's rights were not called out, derived from the 22-year district-scoped call record (senior right = floor, junior right = ceiling constraint). Call-record-derived; DWR's own analysis governs where available.
| Structure | Senior priority | Senior right: median / dry yr | Junior right: median / dry yr |
|---|---|---|---|
| ROSENKRANS DITCH (6500523) | 1893-09-15 | 23.1% / 0.0% | 23.1% / 0.0% |
| PIONEER DITCH (HEAD) (6500520) | 1890-04-04 | 23.8% / 0.9% | 23.8% / 0.9% |
| PIONEER DITCH LEFT IN STREAM (6502400) | 1890-04-04 | 23.8% / 0.9% | 23.8% / 0.9% |
| LAIRD DITCH LEFT IN STREAM (6502403) | 1888-10-20 | 32.7% / 3.3% | 32.7% / 3.3% |
| WRAY HATCHERY PL (6500525) | 1955-05-10 | 6.1% / 0.0% | 5.6% / 0.0% |
| WRAY DITCH (6500517) | 1888-10-04 | 32.7% / 3.3% | 32.7% / 3.3% |
| N F REPUBLICAN MIN FLOW (6502103) | 1975-09-10 | 6.1% / 0.0% | 6.1% / 0.0% |
| BAR ELEVEN NO 2 DITCH IN STREAM AT HEADG (6502401) | 1888-04-26 | 32.9% / 3.3% | 10.9% / 0.0% |
| RUSH CREEK DITCH 2 (6500516) | 1912-07-04 | 8.2% / 0.0% | 8.2% / 0.0% |
| RUSH CREEK DITCH 1 (6500515) | 1912-07-04 | 8.2% / 0.0% | 8.2% / 0.0% |
| BAR ELEVEN NO 4 PUMP (6500556) | 1894-03-19 | 22.0% / 0.0% | 22.0% / 0.0% |
| O'DONNELL DITCH LEFT IN STREAM (6502402) | 1887-06-01 | 34.3% / 3.3% | 22.0% / 0.0% |
Abandonment radar (1 screen)
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 ~1950 — idleness that begins before then may be unreported use, not nonuse (flagged † below).
- PIERCE MILLER DITCH (6500513) (1904-04-22, 0.5 cfs decreed): last active 1960 — 30 years idle
Compliance screens (6 advisory flags)
Screened 23 of 112 structures with rights (26 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.
- PIONEER DITCH (HEAD) (6500520): Observed p99 daily rate 51.8 cfs (max 140.0) exceeds total decreed absolute 35.0 cfs across 49688 recorded day(s). Structure holds an Augmentation-use decree -- diversions above the direct-flow decree can be lawful under plan operations; interpret with care.
- LAIRD DITCH (6500510): Observed p99 daily rate 14.6 cfs (max 20.0) exceeds total decreed absolute 0.2 cfs across 17102 recorded day(s). Structure holds an Augmentation-use decree -- diversions above the direct-flow decree can be lawful under plan operations; interpret with care.
- BAR ELEVEN NO 2 DITCH (6500500): Observed p99 daily rate 7.0 cfs (max 7.0) exceeds total decreed absolute 3.5 cfs across 4434 recorded day(s).
- CARROLL GILMORE DITCH (6500503): Observed p99 daily rate 3.5 cfs (max 7.5) exceeds total decreed absolute 3.0 cfs across 17012 recorded day(s). Structure holds an Augmentation-use decree -- diversions above the direct-flow decree can be lawful under plan operations; interpret with care.
- OLIVE CREEK DITCH (6500512): Observed p99 daily rate 3.0 cfs (max 3.0) exceeds total decreed absolute 2.0 cfs across 80 recorded day(s).
- PIERCE MILLER DITCH (6500513): Observed p99 daily rate 2.0 cfs (max 2.0) exceeds total decreed absolute 0.5 cfs across 1092 recorded day(s).
Seniority (top structures by decreed rate)
| Structure | Senior priority date | Rights | Decreed abs (cfs) | Decreed abs (AF) | Conditional? |
|---|---|---|---|---|---|
| ROSENKRANS DITCH (6500523) | 1893-09-15 | 1 | 40.0 | 0 | — |
| PIONEER DITCH (HEAD) (6500520) | 1890-04-04 | 1 | 35.0 | 0 | — |
| PIONEER DITCH LEFT IN STREAM (6502400) | 1890-04-04 | 1 | 15.0 | 0 | — |
| LAIRD DITCH LEFT IN STREAM (6502403) | 1888-10-20 | 1 | 11.8 | 0 | — |
| WRAY DITCH (6500517) | 1888-10-04 | 1 | 10.0 | 0 | — |
| WRAY HATCHERY PL (6500525) | 1955-05-10 | 2 | 10.0 | 0 | — |
| N F REPUBLICAN MIN FLOW (6502103) | 1975-09-10 | 1 | 9.0 | 0 | — |
| BAR ELEVEN NO 2 DITCH IN STREAM AT HEADG (6502401) | 1888-04-26 | 2 | 7.0 | 0 | — |
| RUSH CREEK DITCH 1 (6500515) | 1912-07-04 | 1 | 6.0 | 0 | — |
| RUSH CREEK DITCH 2 (6500516) | 1912-07-04 | 1 | 6.0 | 0 | — |
| BAR ELEVEN NO 4 PUMP (6500556) | 1894-03-19 | 1 | 6.0 | 0 | — |
| O'DONNELL DITCH LEFT IN STREAM (6502402) | 1887-06-01 | 2 | 6.0 | 0 | — |
| WILLOW CR RANCH 6-19630 (6505012) | 1893-09-15 | 2 | 4.4 | 0 | — |
| SHIELDS PORTABLE PUMP 1 (6500531) | 1912-07-04 | 1 | 4.0 | 0 | — |
| WILSON RIVER PUMP (6500553) | 1888-10-20 | 2 | 4.0 | 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.
What this does and doesn't model. Seniority arithmetic only: every right junior to the call is treated as curtailed. It does not model reach applicability — structures downstream of the calling point are not administered by it — and it applies no futile-call judgment. Read it as “who is junior to this date, and by how much,” not as a prediction of what the Division Engineer would actually order.
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
DWR administration numbers encode appropriation and adjudication dates; lower is more senior.
Each row shows a streamgage where the upstream walk (headwater seed ± diversions ± returns ± tributaries) disagrees with the gage reading. Possible reasons include ungaged diversions/returns, channel losses, or structures with stale telemetry.
| Stream | Gage | R-mile | Predicted (cfs) | Observed (cfs) | Δ (cfs) | Reach (mi) | Hypothesis |
|---|---|---|---|---|---|---|---|
| MAINSTEM | PIONEER DITCH AT THE COLORADO-NEBRASKA STATELINE (PIOSTLCO) | 32.3 | 14.8 | 0.0 | -14.8 | 5.9 | Unaccounted -14.8 cfs loss over 5.9 mi. Likely cause: stale/missing diversion data at WILEY PUMP 1, PIERCE MILLER DITCH. |
Ribbon width ∝ flow. Hover any diversion/return branch for its data source (live telemetry vs. annual divrec) and age — use that to judge how much to trust a given number.
| Gage ⇅ | Station ⇅ | Avg cfs Aug 10–Aug 16 ⇅ |
% Hist Median ⇅ | Rank ⇅ | Δ1wk ⇅ | Δ4wk ⇅ | Yrs ⇅ | Status ⇅ |
|---|---|---|---|---|---|---|---|---|
| RRCCPLCO | REPUBLICAN RIVER COMPACT COMPLIANCE PIPELINE NEAR LAIRD, CO | 0.0 | 0% | 0 | +0 | +0 | 13.9 | SHORT_RECORD |
| NRPSTLNE | NORTH FORK REPUBLICAN RIVER AT COLORADO-NEBRASKA | 1.9 | 19% | 0 | +1 | +0 | 93.8 | OK |
| PIOHDGCO | PIONEER DITCH | 14.8 | 72% | 1 | -1 | -2 | 59.9 | OK |
| PIOSTLCO | PIONEER DITCH AT THE COLORADO-NEBRASKA STATELINE | 13.4 | 85% | 26 | -0 | -2 | 59.9 | OK |
| ARIKHANE | ARIKAREE RIVER AT HAIGLER, NEBR. | 4.3 | 182% | 60 | +3 | +2 | 94.4 | OK |
Call details in gantt above
3 alert(s) · 1 warning(s) · 3 info. Each gage contributes at most one flag per category (its single most-severe match), so this list shouldn't multiply-count the same underlying condition.