Characterization of Drip Emitters and Computing Distribution Uniformity in a Drip Irrigation System at Low Pressure Under Uniform Land Slopes

摘要

Characteristics of emitters under low pressure are essential for designing dripirrigation systems. Low pressure data for drip emitters are not available frommanufacturers. A laboratory test was conducted to evaluate the performance of fivetypes of newly manufactured drip tapes, especially under a low pressure distributionsystem. The five drip products that were tested were (i) Toro Drip in PC (PCS 1810-18-100), (ii) T-Tape (TT15-1245-0100), (iii) Mister_LS (MLD-HDT100), (iv) Mister_PS(MLD-1PC 25), and (v) Netafim (Techline CV 560 050). Drip tapes tested in this studyhave design discharge rates of 4.00 L/hr @ 206.84 Kpa (1.06 gph @ 30 psi), 1.02 L/hr@ 55.16 Kpa (0.27 gph @ 8 psi), 3.785 L/hr @ 172.37 Kpa (1.00 gph @ 25 psi), 3.785L/hr @172.37 Kpa (1.00 gph @ 25 psi), and 0.984 L/hr @ 206.84 Kpa (0.26 gph @20psi), respectively. All of them, except T-Tape, were pressure compensating (PC)emitters; the T-Tape was non-pressure compensating (NPC). For all products, exceptToro, the emitter spacing was 0.305 m (12 inches) and for Toro, it was 0.46 m (18inches). Mister_PS (MLD-1PC 25) was the point source (PS) emitter and all others were line source emitters. Drip products were tested with 15 different operating pressuresranging from 5.97 KPa (0.87 psi) to 344.74 KPa (50.00 psi).From an evaluation of 60 emitters from each product, the Toro brand showed anaverage uniformity coefficient (UC) of 91.24 %, with a coefficient of variation (Cv) of0.06, T-Tape drip products showed an average UC of 96.63 % with a Cv of 0.04, Mister_LS showed an average UC of 93.12 % with a Cv of 0.08, Mister_PS showed an averageUC of 96.33 % with a Cv of 0.04, and Netafim showed an average UC of 97.92 % with aCv of 0.02. Flow rate vs. pressure head (Q-H) curves were also developed for each dripemitter tested. From emitter exponent values it was observed that all of the pressurecompensating (PC) products behaved like NPC emitters at low pressures, although theybehaved like PC emitters under normal operating pressures. From statistical analysis, itwas determined that except for Netafim product, all other tested products were effectiveunder low operating pressures as were under high operating or recommended pressures.Netafim product had no emission under low pressures.Using the measured average emission rate and developed Q-H curves, thedistribution uniformities of all products except Netafim were calculated under lowpressure ranges of 5.97 KPa (0.87 psi) to 23.88 KPa (3.50 psi ) for different lengths oflaterals and under 0%, 1%, 2%