Surge Offers Hope For Surface Irrigation Efficiency

Surge irrigation, while not new, is bringing surface irrigation design and engineering to the forefront of today's technology. Many of America's needs and geographical situations are encouraging improvement in the efficiency of several different types of surface irrigation.

These needs and situations began in the early 1980s as the rising cost of electricity opened the door for natural gas and other power sources for pumping. They sent farmers scrambling to seek out other cost-saving ideas. Research, driven by the energy crisis, was launched at Land Grant Universities in the western United States, including Texas, Nebraska, Colorado, Utah, and Washington. Energy concerns became coupled with pressure from soft farm prices, dropping water tables, and region-wide droughts.

The term "surge irrigation" was coined by Utah State University (J. Keller and G. E. Stringham) in 1979. The practice of intermittently stopping and starting water flows across a field was actually common for decades before then.

In the Great Plains, where long rows were the norm and water table levels were falling, farmers tried something called 'bumping." They found that by interrupting the stream furrow flow and then restarting it, they could advance the water all the way across the field. This idea proved to be effective, however it was very labor intensive.

Automation was needed to solve this labor dilemma. Some of the first automatic valves developed were butterfly types, inflatable bladder types, pneumatically controlled gates and valves, and other highly mechanized products with timers attached. Many of these were adequate for reducing labor during operation. Unfortunately, most of them increased labor for installation, set-up and monitoring. Some of the products were too complicated to market and even required special pipe in some instances.

All of the designs were heavy on the mechanical end and were somewhat prone to failure. Of these valves, the most trouble-free have been the butterfly types.

As agricultural engineers studied the reason that surging worked, they observed two consistent characteristics. First, was a smoothing of the furrow or breakdown of clods during the advance cycle. Secondly, there was a reorientation of the soil particles during the dewatering cycle that produced a sealing of the surface. Together, these changes reduced the infiltration rate of the following surges of water.

W. R. Walker and G. V. Skogerboe at Utah State University stated that the effect of surging is probably associated with the accelerated development of a thin surface seal comprised of very fine soil particles created by the water movement. Walker concluded that during the drainage period, the build-up of negative pressure consolidated this thin seal and altered the permeability of the soil surface.

Following this theory, surge research began to expand into establishing the most efficient surge lengths and determining how the subsequent surge cycle lengths correlate. Surge valve manufacturers took these advances in technology and redeveloped their original timers and clock-type controllers into sophisticated controllers using programmable microprocessors.

This new generation of surge valves allows the grower to tailor his valve controller to soil characteristics, such as texture and infiltration rate. Programmable controllers can be modified any time during irrigation to reduce tailwater or increase opportunity times for deeper penetration of water.

Some controllers have basic built-in programs. All the irrigator has to do is install the unit in the center of his gated pipe between two sets of pipe, enter the appropriate information, press start and let the controller do the rest.

The controller directs the water to half of the gated pipe for a set time and then automatically switches to the other half. Advance cycles are repeated, with an increase in time per side, until the water reaches the end of each row. At this time, the finishing cycles begin to send water all the way down the furrow each time to achieve proper depth of penetration.

By inputting certain information related to a particular field, the program automatically takes into account varying soil types, moisture content, slope, furrow size and compaction. It demonstrates how simple, yet advanced, surge valve operation has become.

The surge valve of today has found many new applications. These include level gated pipe, sloped gated pipe, concrete-lined ditch, and border strip.

The greatest potential for saving water exists with border strip irrigation. This type of irrigation provides a full-field flood. Since more area is covered by water, more water is lost to deep percolation.

In scientific studies, surge irrigation has consistently shown irrigation efficiency increases from 30 to 70 percent and higher. George Dennis of Pacific Gas & Electric in California said, after evaluating the performance of 50 surge valves, that surge has produced water savings and energy savings of up to 38 percent. The company currently offers a cash rebate on all surge valves bought by their customers as a step toward energy conservation, as do many water and conservation districts in several other states. It's clear that surge irrigation offers tremendous savings for farmers who prefer the traditional advantages of surface irrigation.

Editor's Note: Jay Belt is a firm believer in surge irrigation as a salesman for Waterman Industries, Inc., based in the Southwest.