The contour-levee irrigation method has been used for many years for flooding rice fields. This method is adapted to medium- to fine-textured soils having an available water holding capacity of no less than 1.25 inches per foot of depth nor less than 2.5 inches for the root zone depth of the crop being irrigated.
The contour levee type of surface irrigation is similar to the level border method, except it is adapted to sloping land. The strips have been graded until they are level, and instead of rectangular fields bordered by ridges, the fields are bounded on the contour by levees at the lower edge of the strip.
This method of irrigation is often used on fields where the slope is greater than 0.2% but less than 4%, and where land leveling would be impractical or too expensive. The distance between levees depends on the slope and crop to be irrigated, but typically the difference in elevation between levees should not exceed 10 cm; therefore, the distance between levees varies between 3 to 15 m.
When irrigating, the procedure is the same as for the level border system. Water is applied from a head ditch, and it spreads rapidly over the area where it infiltrates into the soil. Since contour levee systems consist of leveled areas on the side of a slope, there are more strips below the highest one. Therefore, water can be reused from the higher strips to the lower strips. The excess water from a strip is directed into the one immediately below. Good drainage must be provided at the lowest strip to remove all excess water. This type of irrigation is well suited to rice cultivation and can be used with crops that can tolerate being submerged in water for long periods of time, such as cotton and some forage grasses.