Container Gardening Kits
This method is used to determine how many inches of water per day to apply for a dense planting. This method assumes using identical flow rates for each dripper on the line and using preset spacing between the drippers and laterals.
Calculating water requirements for dense plantings
Example:- Dripper flow rate = .5 gph.
- Drippers spaced 12" apart, and in more than one lateral drip line layout.
- Lateral spacing 16" apart.
- Sandy soil.
Formula to determine the application rate per hour
| 231.1 x Dripper Flow Rates (GPH) | = Application Rate Per Hour | |
| Dripline Row Spacing (") x Dripper Spacing (") |
Example:
- Assume our ground cover area is 10' x 8' = 80 sq.ft.
- Assume we have sandy soil.
- We can see from table A5 that we can use 1 gph drippers spaced 12" apart. Let's stay on the safe side and use 16" spacing between the laterals and we will start 4" from the edge of the area being water (see drawing)
- 10' x 12" = 120"
- 120" - 4" - 4" = 112"
- 112 / 16 = 7
- Using 16" lateral spacing divided into 112" allows for 7 drip laterals
- We plug all the numbers into the formula and determine that our application rate is 1.20" per hour.
Example
| 231.1 x 1 GPH Dripper | = 1.20" Per Hour | |
| 16" Row Spacing x 12" Dripper Spacing |
The example shows a higher precipitation rate than for a sprayer or a sprinkler. If you wish to lower the precipitation rate, increase the spacing between drippers and laterals
Average precipitation rate for a sprayer or a sprinkler is around .50 inches per hourAfter determining the application rates, we need to determine the run time necessary to apply 1.20" of water
Formula to determine system run time per day
| ET Plant (Water needed per day in inches) | = Daily Run Time | |
| Application rate of drip system per hour |
Example
| 0.28 | = 23 Minutes per day | |
| 1.20 |
Table A5 Recommended dripper
| Sandy soil | Loamy soil | Clay soil | ||||
| Dripper flow rates | 1- 2 gph | 1 gph | .5 - 1 gph | |||
| Spacing | Drippers | Laterals | Drippers | Laterals | Drippers | Laterals |
| Ground Cover | 12" | 12" - 18" | 12" - 16" | 16" - 24" | 16" - 20" | 18" - 24" |
| Flowers Bed | 12" | 12" - 16" | 12" | 16" - 18" | 18" | 16" - 20" |
| Turf | 12" | 12" - 16" | 12" | 16" - 20" | 18" | 18" - 24" |
Table A6 Generic estimates of ET ( inches per day )
| AZ | .22 to .37 | FL | .22 to .27 | KS | .25 to .27 | NM | .28 to .35 | UT | .20 to .32 |
| CA | .15 to .27 | GA | .22 to .25 | NE | .18 to .25 | OR | .17 to 22. | WA | .14 to .21 |
| CO | .15 to .20 | ID | .20 to .25 | NV | .20 to .25 | TX | .26 to .32 |
The total amount of water that must be supplied to a landscape must be sufficient to replace water loss from the soil surface by evaporation, humidity, temperature and plus that lost by the plant during transpiration processes: this is called evapotranspiration or ET. ET is usually expressed in terms of inches of water per day or inches of water per month. These rates vary with the season and realistically they very by the hour. But for lawn irrigation purposes, average ET rates are more than enough to schedule watering. The best ET data per a week or a month is usually obtained from local sources such as the Cooperative Extension Service, local newspapers or National Weather Service, or you can do it yourself by measuring the depth of water evaporated from an open pan.
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