How to read a depth-to-water figure

Four things about these numbers that decide whether you are reading them right.

1. Both figures are depth to water, measured downward

A bigger number means the water is deeper. A section that has fallen 40 ft is one where you now have to go forty feet further down to reach water than before irrigation began. The change column is the second figure minus the first: + is deeper, − is shallower.

2. It is a surface, not a reading

These are interpolated surfaces, not readings at a point. The Survey builds them from measured wells; a figure for one section is an estimate for that square mile, not a measurement of any particular well on it.

The Survey measures wells and fits a surface between them. The figure over one section is what that surface says there. It is the right number for « how much has this area changed » and the wrong number for « how deep is my well ».

3. A shallower reading is real

5,151 sections — 19.9% of those with both figures — sit higher than before development.

On 5,151 sections the water table sits higher than before development. That is real, not a fault in the file — recharge, return flow from surface irrigation and reduced pumping all raise a water table. The site shows it as measured.

4. And zero is a floor, not a measurement

659 sections read exactly 0.0 ft before development and 1,309 read exactly 0.0 ft today — against five occurrences for the next most common value, and not one negative figure anywhere in the file. A continuous surface does not land on the same number 659 times by chance: it is floored at ground level and cannot express a water table standing above the ground. Where either figure is 0.0, the change shown is a floor, not an exact amount, and this site marks it « at least ».

Measured on the file we hold: 659 sections read exactly 0.0 ft before development, 1,309 read exactly 0.0 ft in 2022–2024, and there are 0 negative depths anywhere in the file. Missing values are stored separately — 5,708 sections carry no predevelopment figure at all — so 0.0 is not a disguised blank. It is a clamp, and where it appears the change we show is marked ≥.

What the numbers look like across the file

Start from the counties, the townships, or see what is covered.

Need this for one particular parcel?

A surface figure is not a well depth. Someone on the ground can tell you what it means where you are. Tell us where; we pass the request on.

We are nobody's agent and have no arrangement with any firm today. What we do with this.