Water Needs of Windbreaks for Trickle Irrigation System Design

Forestry Technical Note Number MT-33 (Rev. 1)

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This technical note is also available in Acrobat Reader format.

Forestry Technical Note Number MT-33 (Rev. 1) (PDF; 73 KB)

February 2009
Robert D. Logar, State Staff Forester

Establishment, survival and optimum growth of windbreaks is necessary to provide the planned level of protection for adjacent fields, farmsteads or feedlots. The majority of windbreaks in Montana occur in a semi-arid to arid environment and water needs for temporary or permanent irrigation are a consideration. The accompanying procedure aids in determining the degree of irrigation development needed, taking into consideration the climatic conditions, soil, and plant species.

The objective of the Natural Resources Conservation Service is to insure optimum plant growth and deep root establishment for windbreaks as they develop. This is accomplished by providing adequate water during critical growth periods in a timely manner and with proper placement of lines and emitters to insure balanced root growth. The amount of water supplied depends on the specific species requirements, the annual moisture received and the capacity of the soil to retain sufficient moisture for the desired plant species response.

Species suited to various soils and their expected growths are contained in Section II of the Field Office Technical Guide (FOTG). To achieve the expected growth indicated in Section II, four-system design levels can be considered for optimum and sustained plant growth and vigor. Based upon well-drained, non-saline soils and species suitability, they are:

Level 1: Permanent full irrigation designed for peak use.

Level 2: Permanent irrigation to the fifth year of growth with capacity to supply supplemental water during drought years or above-average temperature growth season.

Level 3: Temporary irrigation installation to the third year of establishment (the system removed thereafter); however, it is recommended that the system be retained to maintain High water use group species during drought years or above-average temperature growing season.

Level 4: No system is needed unless the landowner desires accelerated tree and shrub growth, or to insure survival of plants during drought years or above-average temperature growing seasons.

The design level will insure compliance with the purpose of farmstead and field windbreak standards: To protect the soil resources; manage snow deposition; reduce wind damage; protect farmsteads, crops, livestock; provide wildlife food and cover; or increase the natural beauty of the area.

Table 1 - Water Use Factor, Table 2 - Windbreak Species Root/Crown Widths and Table 3 - Climatic Area Factor are used to complete the attached Windbreak Trickle Irrigation Water Needs Worksheet (Attachment 1). The results of the worksheet will establish the amount of water needed and system requirements for the planned or existing windbreak being evaluated. The Windbreak Trickle Irrigation Water Needs Worksheet (Attachment 1) is intended for use with trickle irrigation supply systems. However, the determination of windbreak water needs is applicable to all forms of irrigation.

Trickle irrigation supply systems need to meet the water needs of the plant as it matures and grows. The Water Needs Worksheet provides what the water needs of the plant are when it is mature or at 20 years old. The trickle irrigation supply systems are designed to deliver the 20 year old water needs. You want the capacity to provide that supplemental water after 20 years but you won’t need it the first year. The system can easily be adjusted to deliver less water in the earlier stages of establishment and growth. Changes in size of emitters and length of time each plant is watered can be changed as the planting grows and gets established.

There are some guidelines to meet the water needs of new and early establishing windbreaks. In the first year supply 5 gallons per plant per week, 7 gallons per plant per week the second year, 10 gallons per plant per week the third, etc., until you approach what the mature, or 20 year water needs are of the plant.

An excel spread sheet Windbreak Trickle Irrigation Water Needs Worksheet (Attachment 2) has been created to assist in establishing the water needs of windbreaks for trickle irrigation system designs. This tool has drop down menus, performs the calculations, and looks up the information from the tables based on the information that is selected. The excel spread sheet is another tool that can be used and expresses the information in Attachment 1 just in a different format. Montana was divided into five climatic areas of consumptive use. Weather data was used to create these climatic areas. The map in the Montana Irrigation Guide provides more detail. Table 3 is a general guide and site-specific information may be available.

• Table 1 - Water Use Factor
• Table 2 - Windbreak Species Root/Crown Widths
• Table 3 - Climatic Area Factor

Windbreak Trickle Irrigation Water Needs Worksheet

Windbreak Trickle Irrigation Water Needs Worksheet Text Description

The worksheet is also available in the following formats. These documents require Microsoft Excel or Acrobat Reader.

Windbreak Trickle Irrigation Water Needs Worksheet - Attachment 1 - Manual Fillable Form (PDF; 137 KB)
Windbreak Trickle Irrigation Water Needs Worksheet - Attachment 2 (XLS; 133 KB)

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Last Modified: 01/30/2009