Overfladeirrigation

Overfladeirrigation, commonly referred to as surface irrigation, is a method of applying irrigation water by distributing it over the field surface so that it infiltrates into the soil and recharges the root zone. Water movement is driven by gravity, and the field is shaped and leveled to control the depth and path of flow. This category includes basin irrigation, border strip irrigation, furrow irrigation, and flood irrigation.

Design and operation depend on soil infiltration rate, field slope, soil moisture holding capacity, crop water requirements, and climate. Water is released from head ditches or canals through gates and weirs and spreads across the field, then is drained or spills to drainage ditches or tailwater receivers. Management aims to achieve uniform wetting of the root zone while minimizing losses and environmental impacts.

Efficiency varies with method and management. Typical application efficiencies range from about 40 to 70 percent; losses occur through surface evaporation, deep percolation, runoff, and uneven distribution. Poor management can lead to waterlogging, salinization, erosion, and nutrient leaching.

Advantages include low capital cost, simplicity, and compatibility with many soil types, especially in regions with abundant, reliable water supplies. Limitations include dependence on good field leveling, high evaporation losses in hot climates, and lower precision compared with sprinkler or drip systems. Environmental concerns center on tailwater and nutrient runoff, soil salinization, and potential groundwater contamination if drainage is not properly controlled.

Modern practice improves uniformity and efficiency through better field leveling, controlled delivery, and scheduling based on evapotranspiration or soil moisture sensors, sometimes complemented by partially lined canals to reduce tailwater losses.