South Platte: Balzac to Stateline

Evolution of the network

Gage flow trend & changepoints

Of the 44 gages with enough record, 5 are trending down and 2 up, and 7 carry a detected shift. The clearest is SOUTH PLATTE RIVER AT JULESBURG (LEFT CHAN. #4), -432.6 points of its long-term median per decade over 29 years (p=0.0001). The other 36 show no clear signal either way.

36 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. 36 gage(s) and 299 structure(s) report in 2026, but structure reporting only reached half its modern level around ~2007. 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: 7% of 2910 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 (1950–2026)

Mass-balance kinks computed for every summer month back to 1950 (2708 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.

• STATELINE DITCH AUG. RETURN TO SOUTH PLATTE: reach shifted from +9 cfs to -394 cfs summer mean (more losing, p=0.028, 25 yr) [alluvial valley: real alluvial aquifer -- a decades-long shift toward losing is the classic signature of alluvial pumping and urbanization] [37 alluvial wells within 2 mi of the gage; pooled water table +1.0 ft (1947–2026, no_trend)]
• SOUTH PLATTE RIVER AT JULESBURG (RIGHT CHAN. #2): reach shifted from -150 cfs to +97 cfs summer mean (more gaining, p=0.000, 42 yr) [alluvial valley: real alluvial aquifer -- a decades-long shift toward losing is the classic signature of alluvial pumping and urbanization] [measurement-evolution caution: this shift co-moves with the growth of the gage/metering network (rho=0.54) -- part of it may be unaccounted water becoming accounted, not hydrologic change] [34 alluvial wells within 2 mi of the gage; pooled water table +0.5 ft (1947–2026, no_trend)]
• LEWIS CREEK DIVERSION: reach shifted from +27 cfs to -7 cfs summer mean (more losing, p=0.000, 20 yr) [alluvial valley: real alluvial aquifer -- a decades-long shift toward losing is the classic signature of alluvial pumping and urbanization] [13 alluvial wells within 2 mi of the gage; pooled water table -0.5 ft (1966–1984, no_trend)]
• POWELL BLAIR DITCH: reach shifted from -48 cfs to -30 cfs summer mean (more gaining, p=0.005, 20 yr) [alluvial valley: real alluvial aquifer -- a decades-long shift toward losing is the classic signature of alluvial pumping and urbanization]
• BRAVO DITCH: reach shifted from -37 cfs to -13 cfs summer mean (more gaining, p=0.014, 19 yr) [alluvial valley: real alluvial aquifer -- a decades-long shift toward losing is the classic signature of alluvial pumping and urbanization] [17 alluvial wells within 2 mi of the gage; pooled water table -0.4 ft (1947–2025, no_trend)]
• SOUTH RESERVATION DITCH: reach shifted from -26 cfs to -14 cfs summer mean (more gaining, p=0.025, 20 yr) [alluvial valley: real alluvial aquifer -- a decades-long shift toward losing is the classic signature of alluvial pumping and urbanization] [17 alluvial wells within 2 mi of the gage; pooled water table +2.5 ft (1962–2013, no_trend)]

Groundwater now has its own tab: 1116 monitored well(s), water-table trends, stream corridors, and the advisory depletion screen.

Reservoirs now has its own tab: 4 reservoir(s), end-of-year storage back to 1950, click-to-chart histories.

Cross-gage pattern fingerprint

Over the 32-year window with full coverage (1995–2026), the dominant shared pattern across 3 gage(s) explains 55% 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.

Structures most implicated by reconciliation (as of 2026-08-16)

Which structures' data absorbed the most correction when the current mass-balance snapshot was reconciled -- see the Historical tab for the full picture on any date.

• PAWNEE DITCH CITY OF STERLING AUG RT (return): +138.8 cfs (100% of that reach's correction)
• SOUTH PLATTE DITCH RT (return): -109.3 cfs (100% of that reach's correction)
• SCHNEIDER DITCH RT (return): +90.5 cfs (100% of that reach's correction)
• STERLING IRR CO D SAND CHUTE RT (return): -43.7 cfs (50% of that reach's correction)
• STERLING IRR CO D PIONEER AUG RT (return): -43.7 cfs (50% of that reach's correction)
• PAWNEE RIDGE DEWATERING RETURN (return): +21.3 cfs (100% of that reach's correction)
• LOWLINE DITCH RT (return): -16.7 cfs (100% of that reach's correction)
• LEWIS CREEK RT (return): -16.4 cfs (100% of that reach's correction)
• JULESBURG TOWN OF AUG RT (return): -15.4 cfs (100% of that reach's correction)
• TETSEL SOUTH DITCH RETURN (return): -6.9 cfs (50% of that reach's correction)

171,347 water-level measurements across 1116 monitored well(s) — 871 alluvial, 9 bedrock — plus 141 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 122 well(s) with enough record for a trend test: 33 declining, 23 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.

STATELINE DITCH AUG. RETURN TO SOUTH PLATTE: 37 alluvial well(s) nearby; pooled water table +1.0 ft (1947–2026, no_trend, p=0.3626). Glover screen: 0.9 cfs of nearby metered alluvial pumping → est. lagged depletion 0.7–0.9 cfs (uncalibrated T/S ranges; flagged for SPDSS calibration, AWAS cross-check, and expert review — DWR's AWAS is the authority).

SOUTH PLATTE RIVER AT JULESBURG (RIGHT CHAN. #2): 34 alluvial well(s) nearby; pooled water table +0.5 ft (1947–2026, no_trend, p=0.6761). Glover screen: 0.5 cfs of nearby metered alluvial pumping → est. lagged depletion 0.3–0.4 cfs (uncalibrated T/S ranges; flagged for SPDSS calibration, AWAS cross-check, and expert review — DWR's AWAS is the authority).

LEWIS CREEK DIVERSION: 13 alluvial well(s) nearby; pooled water table -0.5 ft (1966–1984, no_trend, p=0.0689). Glover screen: 12.4 cfs of nearby metered alluvial pumping → est. lagged depletion 7.2–11.3 cfs (uncalibrated T/S ranges; flagged for SPDSS calibration, AWAS cross-check, and expert review — DWR's AWAS is the authority).

POWELL BLAIR DITCH: 20 alluvial well(s) nearby. Glover screen: 14.3 cfs of nearby metered alluvial pumping → est. lagged depletion 8.9–13.2 cfs (uncalibrated T/S ranges; flagged for SPDSS calibration, AWAS cross-check, and expert review — DWR's AWAS is the authority).

BRAVO DITCH: 17 alluvial well(s) nearby; pooled water table -0.4 ft (1947–2025, no_trend, p=0.1588). 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).

SOUTH RESERVATION DITCH: 17 alluvial well(s) nearby; pooled water table +2.5 ft (1962–2013, no_trend, p=0.0632). Glover screen: 0.2 cfs of nearby metered alluvial pumping → est. lagged depletion 0.1–0.2 cfs (uncalibrated T/S ranges; flagged for SPDSS calibration, AWAS cross-check, and expert review — DWR's AWAS is the authority).

RAMSEY DITCH: 32 alluvial well(s) nearby; pooled water table -0.1 ft (1967–1984, no_trend, p=1.0). Glover screen: 11.7 cfs of nearby metered alluvial pumping → est. lagged depletion 8.8–11.1 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.

4 reservoir(s) with 11,495 storage measurement(s), 1950–2025. Basin storage as of 2024-10-31 (the record's own end — reservoir records publish ~annually): 44,646 AF across 3 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.