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

2. 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 (P w ).”…. P w from NEH 623, Ch. 7

3. Natural Resources Conservation Service What exactly is P w ? u P w 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 P w =A w /A rz AwAw A rz emitter Tree trunk Surface area wetted

4. Natural Resources Conservation Service Percent Wetted Area & Number of Emitters e= # of emitters/tree SeSe SpSp SwSw SrSr

5. Natural Resources Conservation Service Wetted diameter overlap

6. Natural Resources Conservation Service Percent Wetted Area & Number of Emitters Eq. 7-1, NEH 623 33  P w  50 NEH 623 40  P w  50 NEH 652 S e .8S w NEH 623 BUT, what is S w (wetted diameter) ?……….

7. 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?…..

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

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

10. 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 1 gph for 2 hrs 4 gph for 2 hrs

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

12. 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

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