Selection of suitable drip-emitters for Yellow River water drip irrigation

Abstract: Diversified irrigation water has become an increasingly urgent need, due mainly to the limited fresh water resources and water pollution in China. Consequently, Yellow-river water irrigation has attracted more attention in recent decades. Since the Yellow River is the most sediment-filled river on earth, emitter clogging by a high concentration of sand has confined to the application of drip irrigation. Naturally, anti-clogging performance has been a commonly-used indicator to select the appropriate emitters. However, resource waste, high costs, and carbon footprint have posed a great challenge on both the anti-clogging performance and service life, when selecting the emitter products. In this study, an experimental field test was conducted to select emitter and lateral products suitable for drip irrigation with Yellow-River water, concurrently considering the anti-clogging performance, service life, system cost, and carbon footprint. SPSS Principal Component Analysis (PCA) was used to establish selection indexes, and then to screen the suitable emitter products for various crops in different years. 16 kinds of emitters were also analyzed using Cristiansen Uniformity (CU) coefficient, including inlaid plain channel emitters, inlaid cylindrical emitters, single-wing labyrinth, and inlaid strip emitters. 3 crops were selected to evaluate the drip irrigation laterals. The experimental water was taken from the Wushen Canal in Hetao Irrigation District, and then filtered with sedimentation basin before entering into the drip irrigation system. Irrigation water was treated through the homogeneous filtration of a sand filter and a laminated filter. The work pressure was maintained at 0.1 MPa in operation. The Yellow-River water was operated for 9 h/d with a flushing frequency of once every 60 h at a flow rate of 0.45 m/s and a flushing time of 6 min, a total of 600 h (flushing water) and 720 h (non-flushing water). The results showed that there were significant differences in life cycle, cost and carbon footprint in different types of drip-emitters. The longest life cycle was found in flat emitters, followed by cylindrical emitters, strip emitters, and single wing labyrinth emitters. The highest cost was found in cylindrical emitters, followed by flat emitters, strip emitters, and single wing labyrinth emitters. CU of all emitters showed a slow and then rapid downward trend. The highest carbon footprint was cylindrical emitters, followed by flat emitters, strip emitters, and single wing labyrinth emitters. Taking the no-flushing capillary for one-year life cycle as an example, the costs of single wing labyrinth emitters are 52.7%-67.5%, 17.1%-63.5% and 28.7%-54.7% lower than that of cylinder emitters, flat emitters and strip emitters, respectively, and the carbon footprint is 10.6%-14.7%, 0-13.2% and 8.9%-12.6% lower. Consequently, it was recommended to use the single wing labyrinth drip emitter with 2.7 L/h for a 1-year usage period (sunflower), the flat emitter with 1.4 L/h for a 3-year usage period (Chinese wolfberry), and the flat emitter with 2.8 L/h (with capillary flushing) for a 5-year usage period (alfalfa) in the crop irrigation in Inner Mongolia Hetao Irrigation Area. Capillary flushing demonstrated relatively low effects on the 1 and 3-year period (sunflower and Chinese wolfberry), however, the effects were more obvious on the 5-year use period (alfalfa). This finding can provide a new perspective for the selection of drip-emitter products in large-scale drip irrigation with the high-sand Yellow-River water.