How Surge Irrigation Works

When Utah State University researchers began studies of surge flow, they were looking for a way to automate surface irrigation by decreasing a furrow stream size from the big one needed to get water to the end of the furrow to one just large enough to keep the furrow wet while the root zone filled up. They conceived the idea of the cutback phase and discovered the advantages of the advance phase during field trials.
Surge Flow Irrigation: Automatic Surface Irrigation Demonstration for Summer Onion Tour, Hill and Stringham, Utah State University Cooperative Extension Service.

Surge irrigation is accomplished by "surging" the water down the furrows on alternating irrigation sets at timed intervals until the water reaches the end of the furrow. The time interval is then cut back to shorter intervals to reduce runoff. Surge irrigation has been shown to reduce the amount of runoff from fields thus reducing losses of sediment carrying nitrates and salts; and, as a result, improve the quality of downstream water in the system. Surge irrigation has also been shown to reduce deep percolation because of more uniform application of irrigation water.
Irrigation Water Management: Surge vs. Conventional Irrigation, Jim Valliant, Colorado State University Cooperative Extension

Several theories exist as to why surge irrigation works; the most accepted version is that the water may continue to penetrate the soil even after the irrigation water is removed from it; this may result in some soil "sealing" and less penetration when the next "surge" of water is applied. Thus, the water may travel further down the furrow with less water applied than if the water had been applied continuously. As a result, vastly improved irrigation efficiencies have been realized by many irrigators.
Report to the USDI, Bureau of Reclamation, Colorado State University Cooperative Extension.

Surge valves typically improve furrow irrigation efficiency an average of 10 to 40 percent. The application efficiency of furrow irrigation with surge is 80-90%, which gives surge the same application efficiency as a center pivot with low heads.
Opportunities to Maximize the Utilization of Water by Irrigators, Leon New, Texas Agricultural Extension Service.

In some field tests, uniformities of more than 90% have been achieved.
Surge Flow Irrigation: Automatic Surface Irrigation Demonstration for Summer Onion Tour, Hill and Stringham, Utah State University Cooperative Extension Service.

Irrigation efficiency was improved to 4.4 bushels per inch of water with surge from 3.8 bushels per inch on conventionally irrigated corn.
Surge Irrigation Saves Water with Top Yields, Jim Valliant, Colorado State University Cooperative Extension.