Design Considerations for Subsurface Drip Irrigation (SDI) Systems

Gary A. Clark Research Irrigation Engineer Quick Facts Subsurface drip irrigation (SDI) is a low-pressure irrigation system that uses polyethylene driplines that are permanently buried below the soil surface. Water drips to the surrounding soil through built-in emitters (specialized small openings). SDI places water directly into the root zone of the crop. It may improve yield due to high application uniformity and may have other production benefits, such as reduced weed and disease incidence. SDI systems can have long life expectancy, but good design and maintenance are required. Clogging of dripline emitters is the primary reason for system failure. SDI systems have high initial investment costs as compared to other Kansas irrigation system alternatives. However, cutting corners to save initial investment costs generally results in either poor system operation or reduced system longevity. SDI systems have been successfully operated since 1989 at Kansas State University Northwest Research-Extension Center. A number of studies have shown SDI to have various production advantages and potential for increased water conservation and water quality protection potential as compared to other common types of irrigation systems in the state. In some cases, these benefits will overcome the potential disadvantages, such as high initial cost. SDI systems must be carefully designed, operated, and maintained to ensure a long system life. Proper design and management procedures must be used with SDI systems because water distribution problems may be difficult or impossible to correct if the system is improperly designed or poorly installed. Successful operation of an SDI system begins with a proper hydraulic design, which satisfies constraints dictated by crop and soil characteristics; field size, shape, and topography; and water supply. Disregard of design constraints will likely result in a system that is costly in both time and money and an increased chance of system failure. System failure could result in the loss of the total capital investment. Proper operation and maintenance also are important for satisfactory performance and system longevity. In this publication, SDI design considerations will be discussed. Operation and management considerations for SDI systems are discussed in the publication SDI Management Considerations, MF-2590. Filters and filtration for SDI systems are discussed in Filtration and Maintenance Considerations for Subsurface Drip Irrigation (SDI) Systems, MF-2361. A general description of SDI system components appears in Subsurface Irrigation (SDI) Components: Minimum Requirements, MF-2576. Water quality issues are discussed in MF-2575, Subsurface Drip Irrigation (SDI) Water Quality Assessment Guidelines. This publication is not intended to be a step-by-step design procedure, but rather a review of design concepts that will help a producer who is considering SDI as an irrigation system. It should help producers understand principles of a successful system and allow them to ask and discuss appropriate questions with the designer or seller of SDI components.