Aquifer Forecast
The resting (“static”) water table, isolated from pumping drawdown — the true state of the aquifer. Higher = more water. The dashed line projects the statistical trend forward; the shaded band is 80% confidence and widens with the horizon.
Aquifer Now
Long-Term Trend
Net Since 2022
+3-Year Projection
+5-Year Projection
+10-Year Projection
Read with caution This is a short 4.6-year record. The fitted trend is weaker than the year-to-year noise, so it is not statistically firm, and today's reading (-0.06) is slightly below where the record began (+0.30). The projection simply extends that weak slope — read it as a direction, not a forecast.
Vertical axis is the A-Score (standard deviations from each well’s normal); up = more water.
Vertical axis is the A-Score (standard deviations from each well’s normal); up = more water.
Vertical axis is the A-Score (standard deviations from each well’s normal); up = more water.
The resting (“static”) water table, isolated from pumping drawdown — the true state of the aquifer. The dashed line projects the statistical trend forward; the shaded band is 80% confidence and widens with the horizon.
How it works
- Resting level
- Each well transducer is filtered to its flat, recovered plateaus — the static water table between pump cycles. Pumping drawdown and recovery ramps are discarded, so this measures the aquifer, not our pumping.
- A-Score
- Every well is normalized to its own baseline (so a 110-ft Filtronics well and a 20-ft Greer well count equally), then averaged into one index. Higher = more water.
- Z-Score
- Each reading restated as standard deviations from its own well’s average, so wells at different depths share one scale. The A-Score is the resting-only refinement of this raw z-score, which still includes pumping.
- Projection
- A linear trend plus annual seasonality is fit to the history and extended 3510 years. The shaded band is 80% confidence and widens with the horizon.
- Trend line
- The amber line is the deseasonalized ordinary least-squares (OLS) centerline of the same fit — the long-run direction with the yearly cycle removed. Its slope is ≈ +0.012 A-units/yr (~0.06 ft/yr shallower), i.e. statistically flat.
- Rainfall
- A weak secondary input (deseasonalized r ≈ 0.26 at ~1-month lag; even weaker day-to-day). The table tracks cumulative seasonal recharge, not individual storms.
- Reading it
- Over 2022-01–2026-08 the resting table is essentially flat (within year-to-year noise) — on this record recharge is keeping pace with withdrawals, though the movement is within normal year-to-year variation. With 4.6 years of history, treat the far end as a direction, not a guarantee.
- Model
A(t) = a₀ + b·t + Σ Fourier(annual)- Fit
β = (XᵀX + λI)⁻¹XᵀY— ridge least squares, minimizing Σ(Aᵗ − Âᵗ)²- Drawn
a₀ + b·t— the deseasonalized trend only- Band
±1.28·σ · √(1 + k/24)— 80% confidence, widening at horizon k months
Updated Aug 16, 2026 · 8 wells combined
Rainfall
KORS · Orcas Airport, via MeteostatMonthly rainfall (bars) at Orcas Airport, with total system water use overlaid (green line, ×1,000 gal — Badger BEACON) where metering data is available.
| Year | Rainfall | Water used |
|---|---|---|
| 2021 | 47.7″ | 46.3 M |
| 2022 (partial) | 39.9″ | 32.6 M |
| 2023 | 33.5″ | 51.6 M |
| 2024 | 47.8″ | 50.1 M |
| 2025 | 40.1″ | 49.6 M |
| 2026 (partial) | 13.4″ | 22.7 M |
Water used = total metered consumption (Badger BEACON) — the closest stand-in for volume produced (actual production runs ~10% higher). Partial years don’t yet have all 12 months of metering.
Net balance = how far a year’s rainfall ran above/below its average, minus how far water use ran above/below its average (percentage points). Positive (green) = a surplus year (wetter and/or less use); negative (red) = a deficit. The line is that year’s average aquifer level (A-score). Full metering years only.
The same same-year balance stated plainly: that year’s total water use divided by that year’s rainfall (million gallons of use per inch of rain). Higher bars = more water used per inch that fell — a drier, higher-demand year. The line is that year’s average aquifer level (A-score).
Updated Aug 16, 2026
About the A-Score
This is EWUA’s Aquifer Forecast: a first-of-its-kind window into the health of the groundwater beneath our water system, and where it’s headed. It began with a decision. In early 2021, the EWUA Board approved the first ongoing, long-term aquifer monitoring project in the association’s history, a commitment to watch our most important resource continuously, for years and decades to come. This page is what that foresight can now show you.
What You’re Looking At
Every one of our wells (eight today, soon to be nine) has a sensor that measures the depth to water every few minutes, around the clock. But raw readings bounce around all day, because every time a pump runs it draws its well down, and the level recovers once the pump rests. It’s a bit like checking the oil in your car: you don’t get an honest reading with the engine running, you let it settle first. So we keep only the resting, “static” water level, the true state of the aquifer with our own pumping filtered out. Because our wells sit at very different depths, we measure each against its own normal and combine them into one easy-to-read number: the A-Score. Higher means more water; lower means a leaner stretch.
What It’s Telling Us
With about four and a half years of resting-level history, the aquifer has held steady. It dips each summer as demand climbs and recovers each winter as the rains return, but the long-run trend is essentially flat, even leaning slightly toward recovery. In plain terms, natural recharge has been keeping pace with what we withdraw. The dashed line projects that trend ten years forward, with a widening band of uncertainty the further out we look. We treat the far end as a direction, not a promise.
Why It Matters
You can’t steward what you can’t measure. If the water table ever begins a real decline, this tool will catch it early, long before it would show up at your tap, giving our operators time to act rather than scramble. It also grounds our biggest decisions, like the Clark Well and treatment plant now under construction, in real evidence about how much the system can sustainably give.
Where You Come In
A healthy aquifer depends on recharge keeping up with demand, and the biggest lever on demand is how much we use during the hot, dry months. Cutting back on irrigation, watering at night, and fixing small leaks are deposits back into the same account this A-Score tracks. As a member-owner, the data is yours to watch anytime.