Water Demand Forecast
Predicted system demand from seasonal pattern, day of week, and the live weather forecast. Ranges are 80% confidence. Windows begin with today — today’s meter total is still accumulating, so today is shown as a prediction rather than an actual.
Next 3 Days
Next 7 Days
Next 30 Days
Est. Monthly Water Sales
Est. Annual Water Sales
At the current combined base and consumption rate of $30.80 per 1,000 gallons.
The week ahead
| Day | Expected use | Likely range | Temp | Rain |
|---|---|---|---|---|
| Sun, Sep 13 | 169,095 | 150K – 191K | 61° | — |
| Mon, Sep 14 today | 164,057 | 145K – 186K | 59° | — |
| Tue, Sep 15 | 158,028 | 139K – 180K | 58° | — |
| Wed, Sep 16 | 157,001 | 137K – 180K | 59° | — |
| Thu, Sep 17 | 157,231 | 137K – 181K | 60° | — |
| Fri, Sep 18 | 157,575 | 136K – 182K | 60° | — |
| Sat, Sep 19 | 157,664 | 136K – 183K | 58° | — |
What the data shows
Our water year
These figures come from 3,458 days of whole-system meter readings, Jan 1, 2021 to Sep 12, 2026. The busiest day on record used 258,978 gallons on Aug 3, 2023, and the quietest just 48,838 gallons on Nov 26, 2017.
Summer demand runs roughly 1.9 times winter demand — almost entirely irrigation and summer visitors. Year-to-year totals are essentially flat, so what moves the needle is the weather, not the number of homes.
Why it matters
Knowing what demand is likely to do lets EWUA schedule pumping and keep storage topped up before a hot spell rather than during it — which protects both water pressure and fire-flow reserves.
It also shows where conservation counts most. A dry, warm stretch is when the system works hardest, so easing back on irrigation during those runs makes a far bigger difference than the same effort in winter.
How this forecast is calculated
- The model
- A statistical regression fitted in log space, so influences combine proportionally — a hot spell lifts demand by a percentage rather than a fixed number of gallons.
- Season
- A smooth annual curve (three Fourier harmonics of the day of year) rather than month-by-month averages, plus an allowance for the day of the week.
- Weather
- Average temperature, an extra term for heat above 60 °F (irrigation switches on rather than rising smoothly), same-day and three-day rainfall, and how long it has been dry.
- History used
- 1,928 days of actual metered use, weighted by ridge-regularised least squares.
- Weather outlook
- A live forecast for Eastsound covers the first 16 days; beyond that the model uses long-run seasonal norms from the Orcas Island airport weather station.
- The shaded range
- An 80% likelihood band from the model’s own historical error (about ±12.9% a day out), widening further ahead as real weather data gives way to averages.
- Accuracy
- Checked by hiding the most recent 60 days from the model and scoring its predictions against them. It currently lands within 6.5% of actual use on average.
- Worth knowing
- The next few days are the most dependable because they use real forecast weather. The 30-day figure leans on seasonal norms, so read it as a planning range rather than a promise.
Projected system-wide water use, updated several times a day. The forecast combines the season, the day of the week, and the local weather outlook for Eastsound — warm, dry stretches push demand up; rain brings it down. Recent accuracy is within 6.5% of actual use on average. Figures are whole-system totals; the shaded range is the likely spread rather than a guarantee.
Updated Sep 13, 2026 11:45 pm
About This Forecast
This is EWUA’s water demand forecast: our best estimate of how much water our community will use over the coming days and weeks, before the demand arrives. Picture our reservoirs like the gas tank in your car, a buffer that fills overnight and draws down through the day. This tool helps us stay ahead of that tank, especially in a hot, dry summer.
What You’re Looking At
The cards show expected use for the next 3, 7, and 30 days, each with a “likely range” instead of a single false-precision number. The chart traces recent actual use (solid line) flowing into the forecast (dashed line), with a shaded band for the 80% confidence range. The table breaks the week ahead down day by day, next to the temperature and rain shaping each day.
How It Works
The forecast learns from more than five years of daily, system-wide meter readings, then weighs three things that move demand: the season (summer use runs nearly double winter), the day of the week, and the live weather forecast for Eastsound. Warm, dry days push the prediction up; incoming rain pulls it down. It refreshes automatically every day and typically lands within about six or seven percent of what actually happens.
Why We Built It
Water demand is never steady, and guessing wrong is costly. Guess low and we’re caught flat-footed when a heat wave hits; guess high and we pump and treat more than we need. With a reliable headsup, we can top off storage before a hot spell rather than during it, run pumps on the right schedule, and protect two things you rely on without thinking about them: steady pressure at your tap, and the reserves our fire district counts on.
Where You Come In
The single biggest driver this forecast watches is outdoor watering on hot, dry days, and it’s the one most within our control. Watering at night, easing back on irrigation, and fixing small leaks flatten exactly the peaks you see the forecast light up. As a member-owner, this data belongs to you too.