Computing Distribution
Uniformity for Irrigation Management of Citrus
User's Guide for DU
IS004 Quick Answer
R. L. Snyder, Biometeorology Specialist
Department of Land, Air and Water Resources
University of California
Davis, CA 95616, USA
N.V. O'Connell, Farm Advisor
UCCE Tulare County
Ag Bldg Co Civic Ctr
Visalia, CA 93291, USA
Copyright
- Regents of the University of California
Created - July 2000
Last Revision –July 2001
Entering
Data
DU
is an Excel program for calculating distribution uniformity and the
mean
application rate of drip and micro-sprinkler irrigation systems. The companion program ‘DUm’ is the metric
version of the same program. To
obtain a copy, click on DU for
the English
unit version or DUm
for the metric unit version. To
use the DU or DUm
programs, you must collect some data from the irrigation system that
you are
trying to evaluate. Then enter the
following information into the ‘Input’ worksheet. In
cells B2 and B3, enter a block number and the date for record
keeping. The flow rates from
the
emitters can be made in ounces or in milliliters for a pre-selected
rate of
time. Enter the measurement time
interval in seconds into cell G2. Based
on experience, a measurement time interval of 15 seconds works well for
typical
micro-sprinklers used for citrus. In the cell below, enter either "O"
for measurements in ounces or "M" for measurements in milliliters
(cell G3). In the cell G3, enter the
number of emitters per acre for the DU program. Enter
the emitters per hectare in the DUm program. Then
enter the measured flow rates into the
table in cells B7 through P26. Row
(hose) numbers are listed across the top and emitter numbers are given
along
the left-hand side. Entering the data
in the correct order helps to identify problem emitters in your system. A sample entry table for a system with 121
emitters per acre (299 emitters per hectare) is shown below. Sample
flow rates
in milliliters per 15 seconds were entered for nine emitters on each of
six
hoses (rows). The flow rate in
milliliters per 15 seconds would also be entered into the DUm (metric)
program. Note again that the flow rate can
also be
input in ounces per 15 seconds if ‘O’ rather than ‘M’ is input for the
volume
measurement in the DU program.
Results
The
worksheet named "Output" contains the results of the
calculations. The emitter flow rates,
converted to gallons per hour per emitter, are shown in the main body
of the
sample table below. The total number of
samples, the number of low quarter samples, the overall mean flow rate
(gph per
emitter), and the mean of the low quarter are shown above the sample
flow rate
data for each row (hose of emitters).
The results for all of the emitters, are shown in column A. Above the flow rate data, the distribution
uniformity
percentage (DU%) and mean application rates in inches per hour and gpm
per acre
are provided. The overall mean DU% and
application rates are given in column A.
Collecting
Flow Data
The
schematic below shows the laterals and hoses for a typical system. Flow measurements should be taken from a
minimum
of about 20 emitters. Be sure to
measure the flow from emitters from hoses at both the upper and lower
end of
the lateral. Take one measurement near
the riser and one near the end of each hose.
Collect at least two measurements equally spaced between the
riser and
the end.
