Emitters Wetted Diameter Spacing NumberTree Natural Resources Conservation

Emitters: Wetted Diameter, Spacing, & Number/Tree Natural Resources Conservation Service

Why should I be concerned with wetted diameter and spacing? u From a practical perspective, one needs to get water to a significant portion of the potential root zone of the tree/shrub/plant so it doesn’t die from an inability to intake water, or fall over during a windstorm from lack of an anchoring root system u From a standards and specifications perspective: v PS 441 (Irrigation System, Trickle, 4/82) requires that “Emitters shall be located to provide an overlap of the wetting pattern within the root zone. ” v Draft PS 441 (Irrigation System, Microirrigation, 2/00) requires that “The number and spacing of emitters along the lateral line shall be adequate to provide water distribution to the plant root zone and percent plant wetted area (Pw). ”…. Pw from NEH 623, Ch. 7 Natural Resources Conservation Service

What exactly is Pw? u Pw is the “average horizontal area wetted in the top 6 to 12 inches of the root zone as a percentage of the total crop area. ” (NEH 623, Ch. 7) For a lone tree Pw=Aw/Arz emitter Aw Tree trunk Surface area wetted Natural Resources Conservation Service Arz

Percent Wetted Area & Number of Emitters Sw e= # of emitters/tree Sp Se Sr Natural Resources Conservation Service

Wetted diameter overlap Natural Resources Conservation Service

Percent Wetted Area & Number of Emitters Eq. 7 -1, NEH 623 33 Pw 50 NEH 623 40 Pw 50 NEH 652 Se. 8 Sw NEH 623 BUT, what is Sw (wetted diameter) ? ………. Natural Resources Conservation Service

Wetted diameter is a function of: u emitter type, if not a point source u emitter discharge u duration of operation u soil layering (horizontal) u soil type u any others? …. . Natural Resources Conservation Service

Wetted diameter is a function of soil Also see Table 6 -16 of NEH 652 and BE CAREFUL Natural Resources Conservation Service

Wetted diameter is a function of soil layering Area in ft 2 wetted from point source emitter discharge of 1 gph Taken from Table 7 -2, NEH 623 Natural Resources Conservation Service

Wetted diameter is a function of discharge & duration - to a limit 1 gph for 2 hrs 1 gph for 8 hrs Natural Resources Conservation Service 4 gph for 2 hrs

Wetted diameter is a function of emitter type Micro sprinkler Point source emitter Natural Resources Conservation Service

Considerations for Emitter type and # u # increases wetted area u zigzag, pigtail etc…. . increases # u pulsing u micro sprays u cost (more emitters w/ less q) u increase duration of flow u FIELD TEST Natural Resources Conservation Service

Emitter Spacing & Number Recommendations for Windbreaks Taken from Table 7 -2, NEH 623 Natural Resources Conservation Service