SOIL-LIMITING FLOW FROM SUBSURFACE EMITTERS .2. EFFECT ON UNIFORMITY

Soil variability can affect the flow rate of water from subsurface tri ckle emitters. This is because of a buildup of pressure in the soil wh en water cannot be easily transmitted away from the emitter. In this p aper, an analysis was developed showing the relationship between disch arge versus the design discharge as a function of emitter characterist ics and the soil hydraulic properties, When the design how volume incr eases or the hydraulic conductivity of the soil decreases, the pressur e head of the soil next to the emitter increases, which reduces the ho w rate (other factors remaining equal). The subsequent effect on irrig ation uniformity was examined using soil data from a field in the Arav a Valley, Israel. The average of the calculated ratio of the actual di scharge to the designed discharge was 0.905, 0.825, and 0.704 for desi gned discharges of 1, 2, and 4 L/h, respectively. Corresponding coeffi cients of variability were 0.072, 0.124, and 0.193, respectively; like wise Christiansen's uniformities were 0.95, 0.91, and 0.85.