Full Product Manual

Gather Site Data Page 13
Table 3-3 shows the way water is absorbed in the three different soil types:
• Maximum infiltration rate indicates how fast water can be absorbed into the
soil without runoff.
• Wetting patterns show the relationship between vertical and horizontal
movement of water in the soil up to the maximum wetted diameter. Once the
maximum wetted diameter is reached, water movement is downward,
forming the traditional “carrot,” “onion,” and “radish” profiles.
• Maximum wetted diameter is the greatest distance water will spread hori-
zontally from an emitter.
• Available Water (AW) is the amount of water that is readily available for use
by plants.
Evapotranspiration (ET) is the amount of water passed off as vapor to the
atmosphere from the soil (evaporation) and from plant leaves (transpiration).
Potential evapotranspiration (PET) is the maximum average water requirement
for plants in a given climate. PET is generally expressed in inches per day. Your
system must be designed to satisfy the worst case PET for your area.
On your worksheet, enter information on the general climate of the site, and PET
rates in the area to determine the proper system run time.
In many areas, local newspapers publish PET data. This reference PET is gener-
ally based on the PET rate for a specific variety of grass under the most favorable
soil moisture conditions (field capacity). For areas where specific data is not
readily available, Table 3-4 provides some generic estimates. PET data for specific
cities are available in Appendix B.
➍ Climate and
PET
TABLE 3-3: SOIL INFILTRATION AND WETTING PATTERN
Soil Type Maximum
Infiltration
Rate
Wetting
Pattern
Maximum
Wetted
Diameter
Available
Water
(AW)
Coarse
(sandy loam)
.72 - 1.25
inches per
hour
1.0 - 3.0 feet 1.4 inches
per foot
Medium
(loam)
.25 - .75
inches per
hour
2.0 - 4.0 feet 2.0 inches
per foot
Fine
(clay loam)
.13 - .25
inches per
hour
3.0 - 6.0 feet 2.5 inches
per foot
Medium
Fine
Coarse
®