Tips For Reducing Water Use In North Dakota Irrigation Systems

Overview of North Dakota irrigation and water constraints

North Dakota sits in a region where growing seasons are short, summer evaporative demand can be high, and precipitation is variable from year to year. Much of the irrigated acreage in the state uses groundwater from alluvial aquifers or surface water from reservoirs and rivers. Water availability, rising pumping costs, and pressure to maintain aquifer levels make efficient irrigation both an economic and environmental priority.
Reducing water use without sacrificing yield requires a systems approach: matching the right irrigation method to soil and crop, measuring and managing soil water and crop demand, improving the hydraulic performance of equipment, and changing operations and cropping practices where appropriate. The guidance below focuses on practical, implementable steps for North Dakota conditions.

Understand the water balance: ETo, Kc, and soil available water

Irrigation decisions should be based on crop water demand and how much water is stored in the soil profile. Two core concepts:

• Reference evapotranspiration (ETo): the atmospheric demand for water, driven by temperature, solar radiation, wind, and humidity. ETo is expressed as depth per time (inches/day or mm/day).
• Crop coefficient (Kc): a crop-specific multiplier that converts ETo to crop evapotranspiration (ETc). ETc = ETo x Kc.

Practical takeaway: use local weather station ETo (or a nearby ag weather station) and appropriate Kc curves for your crop to estimate daily and seasonal water use. For many row crops in North Dakota during peak summer, ETc commonly ranges from 0.15 to 0.40 inches per day depending on crop and stage. Weekly water needs can therefore vary from about 1 to 3 inches during high demand.
Measure soil moisture and rooting depth to determine available water. Avoid guessing. Soil texture and organic matter control plant available water; sandy soils hold far less water per foot of depth than loams or silts. Common rule-of-thumb thresholds for irrigation initiation are based on percent of total available water depleted (read below under scheduling).

Scheduling and monitoring: move from calendar to data-driven irrigation

Shift from calendar-based or fixed-interval irrigation to a data-driven schedule that uses soil moisture, crop stage, and weather.

• Use soil moisture sensors (capacitance probes, TDR, or gypsum blocks) to measure the root zone. Place sensors at multiple depths and representative positions in the field.
• Track crop stage and Kc. Apply more frequently during rapid growth stages (e.g., corn tassel and grain fill).
• Use on-farm or nearby weather station ETo to adjust for hot, windy spells.

Soil moisture thresholds and depletion levels
A practical and commonly used threshold is to irrigate when 40 to 50 percent of the plant available water (PAW) in the root zone has been depleted for high-value crops. For deficit-tolerant crops or when water is limited, allow 60 percent depletion before irrigating. Translate these percentages into inches by multiplying rooting depth (feet) by PAW per foot.
Example: a crop with a 2.5 ft rooting depth on a loam with PAW of 1.5 in/ft has total PAW = 3.75 inches. At 50% depletion you would plan an irrigation when approximately 1.9 inches has been used from the profile.
Use flow meters and stationing to measure delivered water
Install and log flow meters on pivots, wheel lines, and pumps. Compare delivered volumes with expected ET-based needs. Discrepancies signal leaks, misapplied water, or inaccurate scheduling.

Irrigation system choices and hardware upgrades

Choosing and optimizing the right system yields large savings.
Center pivot and lateral move optimization
Center pivots dominate in North Dakota. Key improvements include:

• Nozzle selection and maintenance: match nozzle sizes to pump capacity and desired application rate to preserve system pressure and uniformity. Replace worn or eroded nozzles; test and catalog flow rates.
• Pressure management and drop nozzles: reduce operating pressure where possible and use lower-angle low-pressure nozzles or drop tubing to reduce drift and evaporation loss.
• Variable rate irrigation (VRI): where field variability exists in soil depth or yield potential, VRI can tailor water application across management zones and reduce total water use while maintaining yield.
• End-gun management: avoid unnecessary use of end guns which increase application and runoff at the end of pivots. Use shutoff or reduced output where appropriate.

Drip and subsurface drip irrigation (SDI)
Drip and SDI significantly reduce losses to evaporation and runoff and increase water use efficiency, especially for high-value specialty crops or where fertigation provides additional value. For broadacre row crops, SDI requires capital investment and careful filtration and maintenance but can reduce applied water 20 to 50 percent compared with overhead systems in some conditions.
Pumping and hydraulic efficiency

• Right-size pumps and motors; oversized or undersized pumps waste energy and may reduce uniformity.
• Use variable frequency drives (VFDs) where practical to adjust motor speed to actual demand and reduce energy use.
• Inspect and minimize head losses: check pipe diameters, fittings, air valves, and strainer condition.

Concrete action: perform a hydraulic audit once every few years to identify losses and opportunities for energy and water savings.

Field management, soil health, and crop choices

Improving soil water retention and reducing evaporative losses lowers irrigation demand.

• Increase soil organic matter through cover crops, reduced tillage, and residue retention. Organic matter improves water-holding capacity and infiltration.
• Use crop rotations and variety selection to match crops to water supply. Deep-rooting crops can access more stored water.
• Maintain residue cover and consider strip-till or no-till to reduce evaporation and improve infiltration.
• Use mulches or inter-row cover where feasible to limit topsoil evaporation.

Practical numbers: adding 1 percent organic matter to the top foot of soil can increase plant available water by roughly 0.5 to 1.0 inches per foot depending on texture. That equates to one or more irrigation events saved over a season.

Operational tactics to reduce waste

• Apply smaller, more frequent irrigations when soils are coarse-textured and infiltration is limited. This reduces runoff and deep percolation losses.
• Avoid irrigation during the hottest, windiest part of the day; schedule applications near dawn or evening to reduce evaporation losses for overhead systems.
• Minimize tail-water and return flows with proper field leveling and grading. Use tail-water recovery basins where practical.
• Reduce overlap and adjust travel speed on center pivots to maintain uniform application.
• Use surge or pulsed irrigation techniques in furrow systems where infiltration rates are low; this can improve infiltration and reduce runoff.

Maintenance practices to preserve uniformity and efficiency

Uniformity is central to reducing overall water use: poor uniformity drives higher average application to avoid under-irrigation of dry spots.

• Inspect and calibrate nozzles, sprinklers, and emitters every season.
• Clean and monitor filters, strainers, and screens; a clogged filter reduces flow and can change pressure and distribution.
• Check lateral movement lines for leaks and repair promptly.
• Regularly test system uniformity using catch-can tests or flow checks for pivots. Aim for a distribution uniformity (DU) above 80 percent for pivots and above 85 percent for drip systems.

Economic and programmatic considerations

• Track water and energy costs per acre-inch applied. Reducing application even modestly can yield significant cost savings in high-energy pumping environments.
• Investigate cost-share and conservation programs at federal and state levels that support efficiency upgrades such as VRI, SDI installation, and pump modernization.
• Evaluate return on investment for upgrades by comparing expected water and energy savings to capital and maintenance costs. Some upgrades pay back in a few years when energy costs are high.

Practical checklist: startup, season, and end-of-season actions

1. Before season start: inspect pumps, motors, belts, bearings, filters, and pressure gauges; calibrate flow meters and map field zones.
2. At startup: test nozzles and sprinklers for correct flow rates; verify pressure settings and adjust regulators.
3. During season: monitor soil moisture at multiple depths and locations; log flow meter data and compare delivered water to ETc-based target volumes.
4. Mid-season check: test distribution uniformity and repair defective emitters or damaged pipe; tune pressure and travel speed on pivots.
5. End of season: flush lines, clean filters, and service pumps and motors; review seasonal irrigation logs and document lessons for next year.

Conclusion: integrated steps for measurable savings

Reducing water use in North Dakota irrigation systems is achievable through coordinated action in scheduling, hardware optimization, soil management, and maintenance. Key priorities that deliver the most benefit for most operations:

• Adopt data-driven scheduling using soil moisture sensors and local ETo.
• Improve distribution uniformity through nozzle maintenance, pressure control, and system audits.
• Upgrade pumping and control equipment where payback is clear and consider VRI or SDI for variable fields or high-value crops.
• Build soil health to increase water storage and reduce irrigation frequency.

Start with an assessment: measure current water use and uniformity, then implement the most cost-effective changes first. Track the results and iterate. Over time, these actions reduce total water applied, lower energy and input costs, and increase the resilience of irrigated cropping systems in North Dakota.