Cycle ratios typically range from 0.25 to 0.75. By regulating these two parameters, a wide range of surge flow regimes can be produced which can significantly improve irrigation efficiency and uniformity. It is perhaps worth noting that surge flow, while appearing quite simple, is nevertheless an advanced irrigation technology.- The design and evaluation require a level of hydraulics beyond this guide and the equipment needed to implement surge flow fully is often feasible only in large farming operations. This is not to imply that surge flow cannot or should not be considered in developing countries, only that special adaptations will be necessary. 7.2.1 Effects of surging on infiltration Since its introduction in 1979, surge flow has been tested on nearly every type of surface irrigation system and over the full range of soil types.
Results vary depending on the selection of cycle time, cycle ratio and discharge.
To effect infiltration rates, the flow must completely drain from the field between surges. If the period between surges is too short, the individual surges overlap or coalesce and the infiltration effects are generally not created. Research shows that the surging effect on infiltration is primarily due to the consolidation of the thin layer of fine material deposited in the bottom of the furrow or on the border or basin surface by the destruction of soil aggregate and erosion caused by the water flow. As the water drains from the field between surges, the negative pressure that develops in the soil consolidates the surface layer, collapsing the larger pores, attracting small particles into the lattice between larger particles, and orienting clay and silt into a layered structure. As a result the permeability of the field surface is reduced and thereafter infiltration rates are lowered.