Understanding Border Strip Flooding Irrigation

Border strip flooding is a surface irrigation method where the land is divided into a series of strips by parallel ridges or levees. Water is applied to the upper end of each strip and flows down the slope as a sheet, advancing towards the lower end. This method is suitable for lands with gentle slopes and certain soil types.

Characteristics of Border Strips

The effectiveness of the border strip flooding method depends significantly on the dimensions of the strips. These dimensions are typically determined by factors like:

• Soil type (infiltration rate)
• Slope of the land
• Stream size or flow rate of water

Choosing the correct strip width and length ensures uniform water distribution and efficient irrigation without excessive runoff or deep percolation.

Typical Dimensions for Border Strips

Based on common agricultural practices and engineering guidelines for border strip flooding, the typical dimensions of the strips fall within a specific range. These dimensions help manage the flow of water effectively across the strip.

The strips are generally:

• Width: The width of the strips is usually between 10 meters and 20 meters. Wider strips can be used with larger water flow rates or on heavier soils where water spreads slowly.
• Length: The length of the strips can vary more widely, typically ranging from 100 meters to 300 meters. The length is influenced by the slope, soil type, and the available stream size. Steeper slopes or soils with high infiltration rates might require shorter strips.

These dimensions ensure that water covers the strip surface adequately before it reaches the end, allowing sufficient time for infiltration into the soil while minimizing water loss.

How Border Strip Flooding Works

In this method, parallel levees are constructed along the primary direction of the slope. Water is released from a head ditch into the top end of each strip. The water flows down the strip as a thin sheet. When the water front reaches the end of the strip, the water supply is cut off. The water left on the strip continues to infiltrate into the soil.

Factors Influencing Border Strip Design

• Slope: Ideal slopes are gentle, typically between 0.1% and 0.5%. Steeper slopes might require shorter borders to prevent erosion.
• Soil Type: Heavy soils (like clay) allow water to spread faster and infiltrate slower, potentially allowing for wider and longer strips. Sandy soils have high infiltration rates, requiring narrower and shorter strips, or a larger flow rate.
• Stream Size: A larger flow rate allows for wider strips and faster water advance, which can be beneficial on soils with high infiltration rates or for longer strips.
• Crop Type: The irrigation requirement and rooting depth of the crop can also influence the desired infiltration depth and thus the design.

Revision Table: Border Strip Dimensions

Additional Information: Surface Irrigation Methods

Border strip flooding is one of several surface irrigation methods. Others include:

• Basin Flooding: Suitable for flat lands and crops planted in basins (like paddy rice). Entire area is flooded.
• Furrow Irrigation: Water is applied in small channels (furrows) between crop rows. Suitable for row crops on various slopes.
• Wild Flooding: Water is applied over the entire field without much control or specific borders/furrows. Less efficient and often used on pastures or lands with irregular topography.

The choice of surface irrigation method depends on land topography, soil type, water availability, crop type, and economic factors. Border strip flooding offers better water control than wild flooding and is more adaptable to slightly sloping lands than basin flooding.