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Old 01-27-2013, 04:31 PM
Kiril Kiril is offline
LawnSite Fanatic
Join Date: Jun 2007
Location: District 9 CA
Posts: 18,360
All this talk about irrigation scheduling, but nary a mention of proper methodology. Your basic water requirements on a per hydrozone (or valve zone) basis assuming no rain inputs, soil moisture content is at field capacity to start with and soil is homogeneous throughout root zone (both current and potential). A proper audit needs to be conducted.

Interval: INTz = (AWHC * RZ * MAD) / (ETo * Kl)
INTz = Zone Interval (days)
AWHC = Soil Plant Available Water Holding Capacity (in/foot)
RZ = Root zone depth (feet)
MAD = Management allowable depletion (%)
ETo = reference evapotranspiration (in/day)
Kl = landscape/crop coefficient (%) (see WUCOLS)
Runtime: RTz = [(60 * INTz * ETz) / ARze] * RTM
RTz = Irrigation zone runtime (mins)
INTz = Interval between irrigation events (days)
ETz = Zone adjusted ET (in/day) --> ETz = (ETo * Kl)
ARze = Zone effective application rate (in/hr) --> from catch can audit (most accurate)
RTM = Runtime multiplier (a factor of DU) --> RTM = 100/DULH

Note: Other considerations need to be made here, but this will get you started in the right direction.
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