North Fork of South Platte

Source Our computation, no independent reference · computed here from the screened DWR record Source Our computation, no independent reference · no independent reference; see /methods

This year, in context

In the weeks around 2026-09-27 (the newest reading on file), flows at the 13 ranked gages are running at a median 43% of their own long-term norm for this window — 10 below a typical year, 3 at or above. Driest relative to its record: LAKE DITCH, ranking 1st lowest of 4 years.

Gage flow trend & changepoints

Of the 30 gages with enough record, 0 are trending down and 1 up, and 2 carry a detected shift. The clearest is North Fork South Platte River below Geneva Creek, at Grant, its annual mean flow changing +12.23 cfs per decade (+11.5% of its median annual flow) over 60 years (p<0.0001). The other 27 show no clear signal either way. 1 transbasin gage meters imported or exported water — marked ⇆ below and kept out of these counts, because that flow is an operator's decision, not the basin's hydrology (all transbasin diversions).

Drought history, cost, and the four-century context moved to the Drought tab.

⚠️ 1 gage flagged: their records may have quietly shifted against their neighbours, so treat their trends with caution.

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

1 of those show a significant trend once extended backwards from a retired neighbour's record: North Fork South Platte River at Grant (87 yr, increasing). Those are reconstructions, not measurements — each gage's page shows both.

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. 18 gage(s) and 72 structure(s) report in 2026, but structure reporting only reached half its modern level around ~1973. 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 †.

Mass-balance (network closure) trend

Structure divrec-history backfill coverage as of the last check: 16% of 225 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.

Groundwater now has its own tab: 23 monitored well(s), water-table trends, stream corridors, and the advisory depletion screen.

Reservoirs now has its own tab: 12 reservoir(s), end-of-year storage back to 1958, click-to-chart histories.

Cross-gage pattern fingerprint

Over the 42-year window with full coverage (1985–2026), the dominant shared pattern across 3 gage(s) explains 69% 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.

Source DWR administrative record · verify at DWR groundwater wells ↗ Source DWR administrative record · verify at DWR well permits ↗

132 water-level measurements across 23 monitored well(s) — 3 alluvial, 0 bedrock — plus 0 administered well(s) reporting metered pumping.

Well map

3D aquifer x-ray

Every aquifer unit as its own head surface, animated through time.

Water-table trends

Of 3 well(s) with enough record for a trend test: 2 declining, 0 rising.

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.

Source DWR administrative record · verify at DWR structure records ↗

12 reservoir(s) with 2,322 storage measurement(s), 1958–2026. Basin storage as of 2025-10-31 (the record's own end — reservoir records publish ~annually): 70,983 AF across 11 reservoir(s).

Reservoir map — how full is each vessel?

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 row to chart its full storage history, or open its dossier for rights, documents and dam-safety facts.

Source Independent agency measurement · fetched 2026-10-16 · verify at NRCS report generator ↗ Source Our computation, scored against a reference · NRCS forecast, graded here against the gage record

Snow-water equivalent, WY2027

NRCS SNOTEL, daily. Sites are assigned to the district whose boundary contains them — the snow that feeds this district can also sit in a neighboring headwater district.

Two ways a snow year goes wrong (1999–2026)

A bad snow year here comes in two flavors (both called snow droughtA winter that shorts the snowpack. It happens two ways: a dry one, where the snow never comes, and a warm one, where near-normal snow falls but melts off weeks early -- and the river feels them differently.), and the river feels them differently. In 7 of the last 28 winters the snow never came — the pack peaked below 80% of its median. In 0 more, the snow came but left early — a near-normal peak melted out two weeks or more ahead of its usual date, sending the water down before the season needed it.

The snow never came: 2002, 2004, 2005, 2010, 2012, 2022, 2026.

Computed by this site from 1 SNOTEL site’ full daily records (NRCS AWDB, back to 1999). Each year is measured against each site’s own multi-decade median — not the 1991–2020 normal the chart above uses — so the 1980s grade against a fair baseline. Peak and melt-out need 85% of the season’s days on the record; thin years are dropped, not guessed. Derived from snow measurements alone — it cannot tell dry-from-warm causes apart, only what the snowpack did.

Runoff outlook — Cheesman Lake Inflow

NRCS's final issue (2026-06-01) calls it even odds that at least 31 kAF arrives over 06-01 to 09-30 — 40% of a normal season; almost certainly at least 16, probably not more than 45. New forecasts begin in January. How to read these numbers →

Source Our computation, no independent reference · computed here from the screened DWR record Source Independent agency measurement · fetched 2026-10-13 · verify at U.S. Drought Monitor ↗

Right now

This is the 14th-driest week 39 in 102 years of record at SOUTH PLATTE RIVER BELOW CHEESMAN RESERVOIR (as of 2026-09-21; this week’s flow sits at the 14th percentileRank against the record: a river at its 5th percentile is lower than it was in 95 of the past 100 years on this same date. for the date). On this week’s US Drought Monitor, Park County is 34% in D4 exceptional drought (2026-10-13). The law agrees: the most senior active call leaves 98% of this district’s decreed flow rights junior to the calling right this week.

Every year since 1924, week by week

Each thin row is a year at SOUTH PLATTE RIVER BELOW CHEESMAN RESERVOIR; each cell is one week’s flow ranked against the same calendar week of every other year — warm means dry for the date, blue wet, so seasonality cancels and droughts appear as warm bands. Gaps are missing record, never a dry river. Click a year to reconstruct it on the Historical tab.

This year against its analogs

Over the 39 weeks recorded so far, 2026’s weekly trace most resembles 1972 (mean gap 14.7 percentile points; next closest 2023 (14.8), 2012 (16.4)). The analog’s remainder is drawn as context — its ending is what happened to it, not a forecast for this year.

The Drought Monitor’s view since 2000

Mean share of area in each class across Douglas, Jefferson, Park counties — the counties this district’s gages sit in, which overlap the district imperfectly. The Drought Monitor weighs soils, vegetation and local reports; it is CONTEXT beside the river’s own record above, not the water-rights picture.

The law’s own drought gauge

When water runs short, administration answers: calls reach further back in time, and more decreed rights go junior to the calling right. This is that response, weekly since 1950 — the share of this district’s decreed flow rights junior to the most senior active call. Watch it spike in the named droughts below, and linger after the river recovers.

Computed from DWR’s call record (929 calls touching this district) against the district’s rights index. Scoping is deliberately coarse — a call’s own district, or districts named in its comments — and this is administration’s RESPONSE, not a per-structure verdict (each dossier’s curtailment card does that, with stream miles). A deepening call can also reflect growing demand, not only shrinking supply.

1685–1987: this river before anyone measured it

Tree rings record wet and dry years centuries before the first gage. This is the published reconstruction of annual flow at North Fork of South Platte River at South Platte — 303 years, with its uncertainty band drawn, not implied. A reconstruction is an estimate, not a measurement: it answers “is this decade unusual in four centuries?”, and nothing in this site’s statistics uses it.

Woodhouse, C.A. and J.J. Lukas (2006), Multi-century tree-ring reconstructions of Colorado streamflow for water resource planning, Climatic Change 78; data via NOAA NCEI World Data Service for Paleoclimatology / TreeFlow. Source data ↗

This basin’s droughts, by its own record

Detected mechanically: the 26-week smoothed percentile below the 30th for at least 20 weeks; recovered on regaining the 50th. The water-table clock compares each monitoring well against its own pre-drought median (the 3 years before onset) and dates the year the median well got back — the aquifer remembers longest, and “still below” is a finding, not a gap. The knobs are stated because the episode list depends on them — a different reasonable choice merges or splits episodes at the edges. Names are attached where an episode overlaps a drought Colorado already talks about.

What drought has cost here

Since 1996, federal crop insurance has paid $1,316 in drought-caused claims across Douglas, Jefferson, Park counties — 0.4% of all insured crop losses there. The worst year was 1996 ($1,113).

USDA crop-insurance indemnities where the recorded cause of loss is drought, summed over the counties this district's gages sit in. Counties overlap water districts imperfectly, and insured-crop claims are a floor on drought damage, not a total. Source: USDA RMA cause-of-loss files.

When this basin claimed its water

Every bar is a year’s new appropriations (1,096 rights across 103 years of shared record), colored by that year’s wetness from the barcode above. Here the correlation is -0.25 — this basin tended to claim water in dry times, under scarcity pressure. Across the state both behaviors exist: ephemeral southwest basins file after wet demonstrations, transbasin-source basins under drought — and the biggest statewide filing waves sat in the 1950s drought and after 2002, not in the wet 1980s–90s.

Appropriation dates are the CLAIMED initiation of a right, not the courthouse filing date; the record is survivor-biased (abandoned claims are absent, so failed dry-era scrambles are undercounted); and the big 1960s and 2000s spikes sit on legal events — the pre-1969-Act adjudication era and 2000s legislation — not on weather. A correlation here is a description, never a cause.

New to how a dry winter becomes a call on the river? Anatomy of a drought walks the chain in four minutes — snow to rivers to reservoirs to calls to the water table.

Who serves it, who protects it

Two registers the site fetches on their own schedules, read for this district. Neither is a DWR record; each links its own page and its agency.

Public water systems here

Source Register of another agency · fetched 2026-10-06 · verify at EPA SDWIS ↗

5 systems touch this district (5 community systems reporting 2,932 people served, a figure that counts a wholesaler's customers twice); 1 of them carries an open health-based violation on EPA's record.

Instream-flow rights held by the state

Source Register of another agency · fetched 2026-10-11 · verify at CWCB instream flow program ↗

28 reaches over 175.2 miles and 2 natural lake levels, held by the Colorado Water Conservation Board so that water stays in the stream. Every reach, with its schedule and case →

• Elk Creek, 20.6 mi: 5 (1/1 - 12/31) cfs (appropriated 1984, 84CW0646) · dossier
• Craig Creek, 12.2 mi: 8 (1/1 - 12/31) cfs (appropriated 1980, 80CW0209) · dossier
• Wigwam Creek, 12.2 mi: 3 (1/1 - 12/31) cfs (appropriated 1980, 80CW0214) · dossier
• Geneva Creek, 10.8 mi: 2.5 (1/1 - 12/31) cfs (appropriated 1984, 84CW0640) · dossier
• Goose Creek, 10.8 mi: 6 (10/1 - 4/30), 10 (5/1 - 9/30) cfs (appropriated 1980, 80CW0215) · dossier
• Scott Gomer Creek, 10.0 mi: 4 (1/1 - 12/31) cfs (appropriated 1978, 78W9373) · dossier

and 24 more on the district's instream-flow page.

What the water is like -- USGS sensors right now, where it has been sampled, the impaired-waters list, and how the tap water here stands with EPA -- is on the Water quality tab.

Designated groundwater basins are on their own page.

Source Adjudicated record · verify at DWR water-right transactions ↗ Source Adjudicated record · verify at DWR net amounts ↗

Decreed rights on this network run from 1860-12-28 to 2023-02-28. Of the 20 structures with a yield estimate, the median one’s senior right was in priority 8% of a median irrigation season and 0% in a dry one. 25 abandonment screens and 60 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: 1390 across 1261 structure(s); 0 structure(s) carry 0 court-case references. Advisory reading aids on public DWR data — not administrative or legal conclusions.

Is the river getting harder to divert from?

Over 1951–2025, administration on this district has been tightening: 2 of 3 measures (days under callA senior water right demanding its water, which requires everyone junior on that stream to stop diverting until it is satisfied., calls set, seniorityColorado shares water by date: the earlier the right, the stronger its claim when the river runs short. "First in time, first in right." of the controlling call) are moving toward more administration, none the other way.

Why diversions stopped — call-based explanations

Sustained diversion stops matched to senior administrative calls.

• MACK DITCH 1 (8000662) DWR↗☆ stopped 2025-07-27 (21+ days) — call at PIONEER UNION DITCH curtailing 100% of its decreed rate [heuristic-strong]
• LININGER DITCH (8000707) DWR↗☆ stopped 2025-07-25 (14+ days) — call at WESTERN MUTUAL DITCH curtailing 100% of its decreed rate [heuristic-partial, district-confirmed]
• NORTH SIDE DITCH (8000668) DWR↗☆ stopped 2025-07-17 (15+ days) — call at WARD DITCH curtailing 100% of its decreed rate [heuristic-strong]
• SOUTH SIDE DITCH (8000667) DWR↗☆ stopped 2025-07-11 (14+ days) — call at WARD DITCH curtailing 100% of its decreed rate [heuristic-strong]
• KENOSHA DITCH (8000713) DWR↗☆ stopped 2025-07-07 (9+ days) — call at WESTERN MUTUAL DITCH curtailing 100% of its decreed rate [heuristic-strong, district-confirmed]
• CRAIG PARK GULCH DITCH (8000732) DWR↗☆ stopped 2024-10-21 (205+ days) — call at BOULDER WELD CTY DITCH curtailing 100% of its decreed rate [heuristic-strong]
• LININGER DITCH (8000707) DWR↗☆ stopped 2024-09-19 (274+ days) — call at WESTERN MUTUAL DITCH curtailing 100% of its decreed rate [heuristic-partial, district-confirmed]
• CASSEL CREEK DITCH (8000728) DWR↗☆ stopped 2024-09-19 (233+ days) — call at LEE STEWART ESKINS DITCH curtailing 100% of its decreed rate [heuristic-strong]
• CASSEL DITCH 1 (8000729) DWR↗☆ stopped 2024-09-19 (233+ days) — call at LEE STEWART ESKINS DITCH curtailing 100% of its decreed rate [heuristic-strong]
• HEPBURN DITCH 2 (8000657) DWR↗☆ stopped 2024-08-31 (242+ days) — call at JONES DONNELLY DITCH curtailing 100% of its decreed rate [heuristic-strong]
• LININGER DITCH (8000707) DWR↗☆ stopped 2024-07-31 (19+ days) — call at WESTERN MUTUAL DITCH curtailing 100% of its decreed rate [heuristic-partial, district-confirmed]
• KENOSHA DITCH (8000713) DWR↗☆ stopped 2024-07-30 (59+ days) — call at WESTERN MUTUAL DITCH curtailing 100% of its decreed rate [heuristic-strong, district-confirmed]

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.

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 ~1973 — idleness that begins before then may be unreported use, not nonuse (flagged † below).

• LAKE DITCH (8000656) DWR↗☆ (1892-05-30, 10.2 cfs decreed): last active 1973 — 52 years idle
• CRYSTAL LAKE PL (8000672) DWR↗☆ (1903-12-31, 6.6 cfs decreed): last active 1973 — 52 years idle
• LODGE RES PL (8000715) DWR↗☆ (1935-12-31, 2.0 cfs decreed): last active 1973 — 52 years idle
• PROSSER WOODEN PIPELINE (8000791) DWR↗☆ (1908-06-05, 0.2 cfs decreed): last active 1973 — 52 years idle
• BROGAN DITCH (8000717) DWR↗☆ (1898-12-31, 1.8 cfs decreed): last active 1974 — 51 years idle
• BRAINERD GULCH DITCH (8000714) DWR↗☆ (1910-12-31, 5.4 cfs decreed): last active 1975 — 50 years idle
• MEADOW DIVR 1 (8000899) DWR↗☆ (1978-04-01, 0.6 cfs decreed): last active 1975 — 50 years idle
• MEADOW DIVR 2 (8000900) DWR↗☆ (1978-04-01, 0.6 cfs decreed): last active 1975 — 50 years idle
• MEADOW DIVR 3 (8000901) DWR↗☆ (1978-04-01, 0.6 cfs decreed): last active 1975 — 50 years idle
• ASHRAMA DITCH 2 (8000663) DWR↗☆ (1925-09-20, 2.4 cfs decreed): last active 1976 — 49 years idle

Compliance screens (60 advisory flags)

Screened 120 of 1261 structures with rights (132 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.

• BEAVER CREEK DITCH (8000706) DWR↗☆: Observed p99 daily rate 7.0 cfs (max 8.6) exceeds total decreed absolute 4.0 cfs across 6874 recorded day(s).
• WONDER DITCH (8000785) DWR↗☆: Observed p99 daily rate 5.0 cfs (max 5.0) exceeds total decreed absolute 0.5 cfs across 6606 recorded day(s).
• J HIGGINSON DITCH (8000674) DWR↗☆: Observed p99 daily rate 3.9 cfs (max 3.9) exceeds total decreed absolute 3.9 cfs across 5394 recorded day(s).
• SLAGHT DITCH (8000660) DWR↗☆: Observed p99 daily rate 3.0 cfs (max 3.0) exceeds total decreed absolute 0.3 cfs across 9106 recorded day(s).
• LOWER KENOSHA DITCH (8000712) DWR↗☆: Observed p99 daily rate 3.0 cfs (max 3.0) exceeds total decreed absolute 2.4 cfs across 248 recorded day(s).
• ROCKY MTN FUEL DITCH 1 (8000829) DWR↗☆: Observed p99 daily rate 3.0 cfs (max 3.0) exceeds total decreed absolute 2.5 cfs across 2946 recorded day(s).
• SOUTH MENDENHALL D (8000867) DWR↗☆: Observed p99 daily rate 3.0 cfs (max 3.0) exceeds total decreed absolute 1.0 cfs across 1698 recorded day(s).
• FLUME DITCH ALT PT PUMP (8000845) DWR↗☆: Observed p99 daily rate 2.9 cfs (max 2.9) exceeds total decreed absolute 2.9 cfs across 2682 recorded day(s).
• ALKIRE DITCH (8000799) DWR↗☆: Observed p99 daily rate 2.7 cfs (max 2.7) exceeds total decreed absolute 0.3 cfs across 2889 recorded day(s).
• MCARTHUR DITCH & RETURN (8000759) DWR↗☆: Observed p99 daily rate 2.5 cfs (max 3.0) exceeds total decreed absolute 1.4 cfs across 14258 recorded day(s).

Seniority (top structures by decreed rate)

Recent inventory & legal-document changes

• 2026-10-10 — call set: SOUTH FLAT DITCH (39707)
• 2026-10-10 — call set: STERLING IRR CO DITCH 1 (39706)
• 2026-10-10 — call released: 39612
• 2026-10-09 — call released: 39680
• 2026-10-09 — call set: SOUTH PLATTE RIVER AT WATERTON (39697)
• 2026-10-09 — call set: CHATFIELD RESERVOIR (39698)
• 2026-10-09 — call released: 39678
• 2026-10-08 — call set: TRUE WEBSTER DITCH (39693)

Water-court filings this month (division-wide)

20 applications in the 2026-09 resume for this basin's division — new rights, changes, augmentation plans — from the water clerk's statutory monthly notice (C.R.S. 37-92-302), the earliest public signal of a new claim. Filings are division-wide, not district-filtered: check the county column. Full resume PDF at the Judicial Branch →

Anyone affected may file a statement of opposition until 2026-11-30 (45 days left). C.R.S. 37-92-302(3): due by the last day of the second month following the filing month — computed, not legal advice; confirm with the water clerk.

Active substitute water supply plans in this district

Temporary State Engineer approvals to divert out of priority (37-92-308 / 37-90-137). A structure operating under one behaves differently under a call than its decreed rights alone suggest — the priority tables above don't know about these; this list does. Source: DWR’s active-SWSP register, refreshed nightly.