North Platte River Basin

Evolution of the network

Gage flow trend & changepoints

Of the 33 gages with enough record, 2 are trending down and 0 up, and 3 carry a detected shift. The clearest is MICHIGAN RIVER AT WALDEN, CO., -13.0 points of its long-term median per decade over 43 years (p<0.0001). The other 30 show no clear signal either way.

30 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. 5 gage(s) and 387 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: 53% of 123 schematic-relevant structures. Kink count trend: increasing (p=0.000), kink magnitude trend: increasing (p=0.003) across 48 qualifying year(s).

Reach gain/loss shifts (1974–2026)

Mass-balance kinks computed for every summer month back to 1974 (244 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.

• MICHIGAN RIVER AT WALDEN, CO.: reach shifted from +13 cfs to -47 cfs summer mean (more losing, p=0.012, 24 yr) [sedimentary uplands: moderate groundwater connectivity -- gain/loss shifts can be real aquifer response; corroborate with nearby well records] [2 alluvial wells within 2 mi of the gage; pooled water table -0.1 ft (1976–2024, no_trend)]

Groundwater now has its own tab: 52 monitored well(s), water-table trends, stream corridors, and the advisory depletion screen.

Reservoirs now has its own tab: 204 reservoir(s), end-of-year storage back to 1974, click-to-chart histories.

Cross-gage pattern fingerprint

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

326 water-level measurements across 52 monitored well(s) — 17 alluvial, 12 bedrock — plus 4 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 4 well(s) with enough record for a trend test: 1 declining, 1 rising.

Stream corridors — the surface connection

Where a reach's gain or loss has shifted, the wells within two miles of its anchoring gage and what their water table did over the same era.

MICHIGAN RIVER AT WALDEN, CO.: 2 alluvial well(s) nearby; pooled water table -0.1 ft (1976–2024, no_trend, p=0.6922). Glover screen: 0.3 cfs of nearby metered alluvial pumping → est. lagged depletion 0.3–0.3 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.

204 reservoir(s) with 16,908 storage measurement(s), 1974–2026. Basin storage as of 2025-10-31 (the record's own end — reservoir records publish ~annually): 21,106 AF across 62 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 reservoir to chart its full storage history.

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.