Calculate border strip irrigation volume from strip dimensions and application depth. Determine inflow rate needed for uniform water distribution.
Border irrigation applies water to long, narrow strips of land bounded by low ridges (borders). Water is released at the upstream end and flows as a thin sheet across the strip, infiltrating as it advances. The strip width, length, and application depth determine the total volume, while the inflow rate must be matched to advance the water front at a pace that achieves the target depth.
Border strips are simpler to manage than individual furrows and work well for close-grown crops like alfalfa, wheat, and pasture. They require well-leveled fields with a gradual slope (0.1–0.5%) in the flow direction. Strip widths range from 20 to 100 feet and lengths from 300 to 1,500 feet.
This calculator computes the volume of water needed and the inflow rate required to irrigate a border strip efficiently. Whether you are a beginner or experienced professional, this free online tool provides instant, reliable results without manual computation.
Border irrigation is cost-effective for crops that cover the entire soil surface. This calculator helps you determine the right inflow rate and volume to achieve uniform distribution along the strip without excessive runoff at the tail end. Having a precise figure at your fingertips empowers better planning and more confident decisions.
Volume (gal) = Width (ft) × Length (ft) × Depth (in) × 0.623 Inflow Rate (GPM) = Volume (gal) / Advance Time (min) Volume (ac-ft) = Width × Length × Depth / (12 × 43,560)
Result: Volume = 74,760 gal; Inflow = 415 GPM
Volume = 50 × 800 × 3 × 0.623 = 74,760 gal. Inflow = 74,760 / 180 = 415 GPM. This is a moderate inflow suitable for a silt loam on a 0.2% slope.
Designing a border strip system involves selecting strip width, length, and slope to match the available water supply and soil intake characteristics. NRCS design manuals provide tables and equations relating these variables for different soil types.
The cutoff ratio is the fraction of the strip length water has advanced when inflow is stopped. For efficient irrigation, the cutoff ratio should be 0.80–0.90. Water momentum and continued tail-water recession carry the front to the end of the strip after cutoff.
Border irrigation is more uniform than wild flooding but less precise than graded furrows. It requires less labor than furrow irrigation because fewer individual streams need management. For flat, well-leveled fields growing broadcast crops, borders are often the most practical surface irrigation method.
Close-grown crops like alfalfa, pasture grasses, small grains (wheat, barley), and orchards on flat ground work well with border irrigation. Row crops are generally better served by furrow or drip systems.
Strip width depends on available flow: 20–40 ft for small supplies, 40–80 ft for moderate supplies, and up to 100 ft for large canal deliveries. Wider strips need higher inflow rates.
Strip length depends on soil intake rate and slope. Typical lengths are 300–600 ft for fast-intake sandy soils, 600–1,000 ft for medium soils, and up to 1,500 ft for slow-intake clay soils.
Cross-slope variations cause water to concentrate on the low side, leaving the high side dry. Laser-leveling to within ±0.05 ft ensures uniform lateral distribution across the strip.
Border irrigation has lower capital cost but higher labor cost and lower efficiency (50–70% vs 80–90%). Pivots automate the process, saving labor on large fields.
Partially. Automated check gates and timers can start and stop inflow, but the water advance and distribution rely on gravity and field preparation.