Calculate gross irrigation depth per application from net depth and application efficiency. Plan how much water your system must deliver.
When you irrigate, not all water applied reaches the crop's root zone. Some is lost to evaporation, wind drift, deep percolation, or runoff. The gross irrigation depth accounts for these losses so that the net amount actually needed by the soil is delivered.
The relationship is straightforward: gross depth equals net depth divided by application efficiency. If your system is 80% efficient and the soil needs 1.0 inch of water, you must apply 1.25 inches gross. Knowing this number lets you set run times, flow rates, and pivot speeds correctly.
This calculator converts your target net irrigation depth into the gross depth your system must deliver, given its measured or estimated application efficiency. It also shows the volume in gallons per acre for operational planning. Whether you are a beginner or experienced professional, this free online tool provides instant, reliable results without manual computation. By automating the calculation, you save time and reduce the risk of costly errors in your planning and decision-making process.
Applying the wrong depth wastes water and energy or leaves your crop short. This calculator bridges the gap between what the soil needs (net) and what your system must deliver (gross), giving you a number you can act on at the pump panel or pivot control. Having a precise figure at your fingertips empowers better planning and more confident decisions.
Gross Depth (in) = Net Depth (in) / (Application Efficiency / 100) Volume (gal/ac) = Gross Depth × 27,154 Loss (in) = Gross Depth − Net Depth
Result: Gross Depth = 1.25 in
Gross = 1.0 / 0.80 = 1.25 inches. The system must apply 1.25 inches so that 1.0 inch reaches the root zone. Loss = 0.25 inches. Volume = 1.25 × 27,154 = 33,943 gal/ac.
Surface irrigation (flood, furrow, border) ranges from 40–75% efficiency. Sprinkler systems (hand-move, wheel-line, center pivot) range from 65–90%. Drip and micro-irrigation achieve 85–95%. Choosing a higher-efficiency system reduces gross water requirements but involves higher capital costs.
Place at least 16–24 cans in a grid pattern across one span or set of the system. Run the system for its normal duration. Measure the depth in each can with a graduated cylinder. Average the values and divide by the applied depth (from flow meter or nozzle charts) to get application efficiency.
Once you know the gross depth, divide it by the system's application rate (in/hr) to get run time. For center pivots, convert depth to rotation speed (% timer setting). For drip, multiply depth by area per emitter to get run time per zone.
Application efficiency is the fraction of water applied that is stored in the root zone and available for crop use. It accounts for evaporation, drift, deep percolation, and runoff losses.
The catch-can test is the most common field method. Place cans at regular intervals under the irrigation system, run it for a set time, and measure the water collected. Compare collector averages to the applied depth.
Net depth depends on MAD and soil AWC. For a silt loam with 1.8 in/ft AWC and 3 ft roots at 50% MAD, the net depth is 2.7 inches. Lighter irrigations may target 0.5–1.5 inches.
No. Conveyance losses (canal seepage, pipe leaks) are separate. Overall system efficiency = conveyance efficiency × application efficiency. This calculator addresses application efficiency only.
Wind speeds above 10 mph can reduce sprinkler efficiency by 10–20% due to drift and increased evaporation. Irrigating at night or using low-angle nozzles reduces wind losses.
No real-world system achieves 100%. Ignoring losses leads to under-irrigation and crop stress. Using measured efficiency ensures the soil actually receives the intended amount of water.