Management, Maintenance, and Water Quality Effects on the Long-term Performance of Subsurface Drip Irrigation Systems

Abstract

The longevity of subsurface drip irrigation (SDI) systems is a key factor in the profitability of these systems when used for lower-value commodity crops (typically the fiber and grain crops). The system management and maintenance protocols, as well as the source water quality, can greatly impact the longevity of these systems. This study evaluated 10 subsurface drip irrigation systems in 2008 and 8 additional systems in 2009 that had been in operation between 6 and 20 years. System uniformity was evaluated by the uniformity parameters, emitter discharge variation, qvar, and the lower quartile distribution uniformity of emitter discharge, DUlq. Pressure measurements along the dripline also were used to determine if qvar was primarily explained by friction losses. Two-thirds of the evaluated SDI systems had qvar less than 20% and DUlq greater than 80 which would be acceptable and one-third of the systems had qvar less than 10% and DUlq greater than 90 which would be good to excellent uniformity. There was very little correlation in system uniformity and system life with the oldest system (20 years) having the greatest uniformity. Uniformity problems on nearly two-thirds of the systems appeared to have been exacerbated by incorrect operating pressure (both too low and too high) with the six best performing systems operating between 65% and 100% of the manufacturer's specified nominal operating pressure. Water hardness and total dissolved salts were the major water quality concerns. Poor maintenance (e.g., no or infrequent chlorination; inadequate filtration system backflushing) appeared to reduce uniformity in between one-third and one-half of the systems. The producer's lack of installation records and operator's guides likely negatively impacted system uniformity through these poor management and maintenance procedures. The use of both qvar and DUlq to evaluate performance of SDI systems appeared to enhance the determination of the primary causes of SDI system nonuniformity.