Composite clogging characteristics of emitters in drip irrigation systems

Abstract

This study investigated the characteristics of emitter clogging substance in 16 kinds of drip irrigation emitters using 3 kinds of water sources that could typically induce composite clogging in the Yellow River irrigation area. The research results indicate that there was remarkable randomness in the behavior of composite clogging substances in a single emitter, and peak randomness ($\Delta F_{Q}^{t}$) values were 19.5–20.8%, 20.5–22.4% and 25.9–28.2% higher than that with physical, chemical and biological clogging, respectively. Clogging in a single emitter also exhibited recoverability ($R_{Q}^{{{\text{CD}}}}$) which would be lost when the clogging degree reached 60–75%, and recoverability ($R_{Q}^{{{\text{CD}}}}$) showed the opposite variation rule to randomness ($\Delta F_{Q}^{t}$). Though clogging in a single emitter was associated with certain randomness and recoverability, the overall variation of the micro-irrigation system's average discharge variation ratio (Dra) and Christiansen’s uniformity (CU) was not affected. Instead, the two showed relatively consistent dynamic variation of mild fluctuation followed by acute descending. The fluctuation trend during the earlier stage lasted from 128 to 660 h, and descending branch slopes of Dra and CU during the later stage were 0.09–0.12 and 0.13–0.21, respectively. In terms of various types of emitters, $\Delta F_{Q}^{t}$ generally demonstrated dynamic variation for a tape emitter (highest), a single-side labyrinth emitter (slightly lower), a cylindrical emitter (even lower) and a flat emitter (lowest). However, the dynamic variation of $R_{Q}^{{{\text{CD}}}}$, Dra and CU were inverse. As far as various water sources were concerned, mixing water had the highest $\Delta F_{Q}^{t}$, followed by Yellow River water, and surface lake water had the lowest $\Delta F_{Q}^{t}$, while variation characteristics of $R_{Q}^{{{\text{CD}}}}$, Dra and CU among the three water sources were inverse. The present study could provide reference for revealing the characteristics of composite clogging in emitters, thus constructing effective clogging control methods.