Water Use Efficiency Calculator

Crop WUE divides your full irrigated yield by total seasonal ET, so it credits both rainfall and irrigation for however much yield the crop produced overall. Irrigation WUE instead divides only the yield gained above your dryland baseline by the inches of irrigation you actually applied, isolating the marginal bushels per inch that irrigation specifically contributed. A field could have solid Crop WUE from favorable rainfall while showing a weak IWUE if the irrigation itself added little on top of what rain alone would have produced.

The rating (1=Excellent down to 4=Poor) is based only on Crop WUE against fixed bushel-per-inch cutoffs (9, 7, and 5 bu/in), not on IWUE or on the economic outputs. A field can have excellent Crop WUE from a productive season overall while still showing a modest IWUE if the dryland yield was already close to the irrigated yield, meaning irrigation added comparatively little marginal benefit even though total water productivity looks strong.

ROI is the marginal revenue from the yield gain (yield gain times crop price) divided by irrigation cost (inches applied times cost per acre-inch) — so an ROI of 2.0 means every dollar spent on irrigation returned two dollars in additional crop revenue. A value below 1 means the irrigation cost that season exceeded the extra revenue it generated, which can happen with a small yield gain, a low crop price, or high per-inch irrigation costs, even if the crop still yielded well in absolute terms.

It compares irrigation applied against net irrigation need — seasonal ET minus effective rainfall — expressed as a percentage, so 100% means you applied exactly what the crop needed beyond what rain supplied, above 100% means you likely over-irrigated relative to net demand, and below 100% suggests the crop may have been under water stress for at least part of the season. It's a water-balance check independent of yield or economics, useful for spotting scheduling mismatches even when the yield-based metrics look fine.