Tips For Reducing Evaporation In North Dakota Irrigation Systems

Evaporation is a major loss pathway for irrigation water in North Dakota. With wide open fields, frequent winds, and a continental climate that produces hot, dry periods during the growing season, managers must combine multiple tactics to keep water where crops can use it. This article details practical, field-tested strategies for reducing evaporation in North Dakota irrigation systems, with concrete steps, equipment considerations, and management takeaways you can use this season.

Understand the local drivers of evaporation

Evaporation and crop evapotranspiration are driven by radiation, air temperature, humidity, and wind. In North Dakota these factors combine to produce periods of high water loss:

• Strong daytime solar radiation in summer increases energy available for evaporation and transpiration.
• Low relative humidity and hot afternoon temperatures increase vapor pressure deficit and evaporation rates.
• Frequent winds and gusts accelerate evaporative flux and can carry fine spray droplets away from target areas.
• Soils with low organic matter and coarse texture lose water quickly from the surface.

Practical takeaway: evaluate your field microclimate (wind exposure, slope, soil texture) before choosing equipment or a schedule. Small differences in exposure lead to large differences in evaporative loss.

Selection and optimization of irrigation method

Choosing the right irrigation method is the single biggest lever to reduce evaporation losses. Surface irrigation (furrow or flood) and high-elevation sprinklers expose more water to the air; micro and subsurface systems retain more water in the root zone.

Subsurface drip irrigation (SDI) and drip systems

Subsurface drip irrigation places water below the soil surface, where evaporation from the soil surface is eliminated and most water goes to the root zone.

• Install lateral depth: common depths are 6 to 12 inches for many row crops; adjust depth depending on rooting depth and freeze risk.
• Lateral spacing: 12 to 40 inches depending on crop row spacing and root spread.
• Filtration and maintenance: deploy fine filtration (screen and media) and pressure regulation to prevent emitter clogging. Flush lines regularly and plan backflush or chemical maintenance cycles.
• Emitters and flow rates: choose emitters sized to deliver uniform application matching crop demand. Lower flow per emitter combined with closer spacing gives better wetting uniformity.

Practical takeaway: SDI can reduce surface evaporation dramatically and improve application efficiency, but requires capital investment and disciplined maintenance.

Low-pressure, low-elevation sprinklers and drift control

When sprinklers are required, use low-pressure devices and reduce droplet drift.

• Use drop hoses or low-elevation application systems that present water close to the canopy or soil surface.
• Choose nozzles with larger droplets (higher Volume Median Diameter) to reduce drift and evaporation in windy conditions.
• Operate at recommended pressure ranges; overpressurizing or running rotors at high RPM increases fine droplets and drift.
• Consider Low Energy Precision Application (LEPA) or multi-plant injector nozzles for crops that tolerate localized wetting.

Practical takeaway: lowering the spray height and producing coarser droplets can substantially cut evaporation and off-target loss.

Scheduling and timing to minimize evaporative loss

When you apply water matters nearly as much as how much you apply.

• Irrigate during the coolest, least windy part of the day: late night to early morning is usually best. Early morning application typically minimizes evaporation and improves infiltration.
• Avoid mid-day irrigation when solar radiation and vapor pressure deficit are highest.
• Use short, frequent cycles for sprinkler systems when soils are prone to crusting or have low infiltration, instead of a long single application that encourages runoff.

Numbered checklist for scheduling decisions:

1. Monitor local weather and avoid irrigation when wind speeds exceed 8 to 10 mph.
2. Aim to apply water between midnight and 7 a.m. when humidity is higher and temperatures are lower.
3. Base irrigation timing on soil moisture depletion thresholds (for example, refill when root zone depletion reaches 30-50% of available water) rather than fixed calendar dates.

Practical takeaway: shifting applications several hours can reduce evaporative loss without changing total water delivered.

Soil and crop management to retain soil moisture

Soil surface conditions strongly influence evaporation. Management practices that protect the soil surface and increase water-holding capacity reduce evaporative losses.

Increase surface cover and residue

• Maintain crop residues or apply straw mulch to shade the soil surface and slow surface evaporation.
• Use living mulches or cover crops in fallow periods to reduce bare soil days; terminate cover crops carefully to retain residue.
• Plastic mulch can be effective in horticulture and high-value vegetable production to virtually eliminate soil surface evaporation between rows.

Improve soil structure and organic matter

• Add organic amendments and use practices that increase soil organic matter over time; organic matter increases water-holding capacity and reduces runoff.
• Use reduced-till or no-till practices to preserve residue cover and improve infiltration.
• Correct soil structural problems: address compaction with controlled traffic or deep ripping when appropriate.

Practical takeaway: investments in soil health reduce the frequency and depth of irrigation required and lower evaporation from bare soil.

Windbreaks and field layout

Wind is one of the most powerful drivers of evaporative loss. Simple landscape changes can pay dividends.

• Plant shelterbelts or hedgerows perpendicular to prevailing winds to reduce wind speed across fields. Trees and shrubs with a denser lower canopy are most effective.
• Use temporary wind fences or snow fences in exposed fields where permanent windbreaks are not feasible.
• Orient rows and bed systems to reduce wind channeling; staggered row layouts and alternating heights can disrupt wind flow.

Practical takeaway: even narrow shelterbelts can reduce wind speeds and decrease evaporation across adjacent crop acres.

Instrumentation, monitoring, and automation

Data-driven irrigation management sharply improves water use efficiency and reduces unnecessary surface exposure.

• Soil moisture sensors: capacitance probes, TDR, or neutron probes allow precise knowledge of root zone moisture and scheduling to avoid over-watering.
• Weather-based scheduling: use local ETo estimates and crop coefficients (Kc) to calculate crop water use and schedule irrigation based on actual demand.
• Flow meters and telemetry: monitor system delivery and detect leaks or excessive run times. Integrate alarms for abnormal flow or pressure drops.
• Automation: automatic controllers that combine soil moisture and weather inputs prevent human scheduling errors and avoid irrigating during windy or hot conditions.

Practical takeaway: deploy a small network of sensors and a control strategy and you will avoid many common sources of unnecessary water exposure.

System maintenance and uniformity

A well-maintained system reduces wasted water that would otherwise evaporate.

• Check uniformity: measure distribution uniformity (DU) or Christiansen uniformity (CU) for sprinklers and pivots. Aim for high uniformity; low uniformity leads to over-application on parts of the field.
• Repair leaks and plugged nozzles promptly.
• Use pressure regulators and properly sized piping to maintain intended pressures and droplet sizes.
• Clean filters, inspect laterals in drip systems, and maintain pumps at peak efficiency.

Practical takeaway: maintenance reduces the need to over-apply to compensate for poor uniformity and therefore reduces evaporation.

Water conveyance and storage

Reducing open-water exposure in conveyance also reduces evaporative loss.

• Prefer buried or piped conveyance rather than open ditches where feasible.
• Use gated pipe or lined canals to limit exposed water surface.
• Install small on-farm reservoirs with reduced surface area to volume ratios and cover or shade where possible.

Practical takeaway: conveyance improvements reduce evaporation before water even reaches the field.

Economic and management considerations

Decisions about evaporation reduction require cost-benefit judgment.

• SDI and piping are capital intensive but provide the largest reductions in evaporation and the highest application efficiency.
• Mulches and cover crops are lower-cost options with additional agronomic benefits but may increase labor or machinery costs.
• Prioritize actions with the highest return on investment: scheduling improvements, leak repair, and nozzle adjustments are low-cost and quick wins.

Practical takeaway: combine short-term low-cost fixes with a long-term capital plan for the highest water savings per dollar.

Quick implementation checklist

• Assess field exposure: map wind, slope, and soil texture.
• Improve scheduling: shift irrigation to pre-dawn hours and base timing on soil moisture or ET.
• Reduce spray height and use coarser droplets or low-elevation systems.
• Inspect and repair the system: nozzles, leaks, pressure regulators.
• Increase surface cover: straw, residues, or plastic mulch where appropriate.
• Consider SDI for long-term, high-efficiency irrigation on high-value crops.
• Install windbreaks or temporary fences on exposed fields.
• Deploy soil moisture sensors and automate controllers where possible.

Final thoughts

Reducing evaporation in North Dakota irrigation systems is a multi-faceted challenge that requires matching technology to local conditions and crop needs. No single practice eliminates evaporative loss, but an integrated approach combining smarter scheduling, choice of irrigation method, soil management, and maintenance delivers substantial and durable reductions. Start with low-cost scheduling and maintenance improvements this season, and plan incremental capital investments–piping, SDI, or windbreaks–over multiple years to achieve the best economic and environmental outcomes.