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Drip Irrigation

Drip irrigation tape with emitters spaced at 18 in. for peppers. Photo: C. Miles.
Drip irrigation tape with emitters spaced at 18 in. for peppers. Photo: C. Miles.


Drip irrigation, also called trickle or micro-irrigation, applies water slowly and directly to the roots of plants. In the Pacific Northwest it is common for vegetable farmers to use a solid set overhead sprinkler irrigation system while fruit growers use drip or trickle irrigation systems. Advantages of drip irrigation systems as compared to overhead sprinkler systems include reduced water use, reduced soil erosion, reduced fertilizer and pesticide runoff potentials, decreased disease, decreased water loss to evaporation, and decreased weed growth.


Drip irrigation tape with emitters spaced at 12 in. for lettuce, and with simple garden hose attachment. Photo: C. Miles.
Drip irrigation tape with emitters spaced at 12 in. for lettuce, and with simple garden hose attachment. Photo: C. Miles.

The installation of an efficient drip irrigation system begins with a good design that includes information regarding soil type, crop needs, water pressure, and appropriate components to be used in the system. It is advantageous to consult with or have an irrigation engineer design the irrigation system. Consultants should have knowledge regarding Federal, State, and County regulations and ordinances for your area. Web resources are listed below to provide suggestions however should not be considered all-inclusive.

Irrigation tutorials; sprinkler & drip systems, design, and installation This web site is very easy to read and provides good basic information regarding design features of drip irrigation systems. You will also find links to irrigation suppliers.

Design Tips For Drip Irrigation Of Vegetables AE260. University of Florida, IFAS Extension. Provides a quick reference regarding important points that should be considered when planning a drip irrigation system for vegetable production. It lists factors that can improve water application uniformity which is necessary for high efficiency of water use.

Drip Irrigation (pdf) Washington State University, Spokane County Extension. Provides a description of components, installation, and calculating water needs. Or view as HTML. Irrigation System Evaluation EM4822. Washington State University, Cooperative Extension, Prosser. How to calculate amount of water applied in your irrigation system. 2005.


Microsprinkler irrigation. Photo: C. Miles.
Microsprinkler irrigation. Photo: C. Miles.

Proper irrigation water management is critical to the success of any irrigation system. Scheduling when and how much to irrigate is critical in order to achieve the full benefit of drip irrigation. Maintenance of filters, soil moisture monitoring, and control of metal deposits, algae and aquatic plants are requirements for optimum success. Web resources are listed below to provide suggestions.

An Introduction to Drip Irrigation Oregon State University, Malheur Experiment Station. Discusses advantages and disadvantages of drip irrigation systems, components and design of systems, and irrigation water management considerations. Includes links to other resources. EM 8782, updated 2006.

Filtration, Treatment, and Maintenance Considerations for Micro-Irrigation Systems Pub. 442-757 (pdf). Virginia State University Cooperative Extension. Discusses causes of emitter plugging, filters and flushing. View as HTML.

Irrigation Management Pub. 456-420, Section C. Virginia State University Cooperative Extension. Soil impacts on irrigation water usage, calculating water application, maintenance issues, and fertigation and chemigation applications. 2009.

Maintaining Drip Irrigation Systems MF-2178. Kansas State University, Agriculture Experiment Station & Coop Ext. Discusses water quality issues impacting drip irrigation systems, maintaining filters and emitters, and includes a troubleshooting guide. 1996.

Rules and Regulations

Solid set irrigation. Photo: C. Miles.
Solid set irrigation. Photo: C. Miles.

Water rights: In the state of Washington water is owned by the public, therefore is not considered property of a single individual or group. Prior to use of water for irrigation individuals and groups are required to have a water right. If you do not already have a water right, it is extremely unlikely that you will receive one in the near future. To find out more about water rights and the permitting process, visit the Department of Ecology website listed below. The overview website listed below contains links to information that will help you navigate the process of understanding and obtaining a water right.

Washington Department of Ecology – Water Right Information Do I Need a Water Right? This online link provides a list of laws and regulations, information regarding water rights, and links to necessary forms to apply for water rights.

Overview of Water Rights in Washington Provides information and links to water right resources. Includes links to laws, regulations, and tribal water rights. Updated July 2008.

Recorded Video Presentation: Water resource Information – Kasey Cykler Washington Department of Ecology. Live presentation recorded at Cloud Mountain Farm Center Farmer Speaker Series: Water Access for Small Farmers 2016. This presentation explains what water rights are, the process to determine whether a piece of property has a water rights, and other tips to navigate the water rights process.

Chemigation, and Fertigation: Applying pesticides (including herbicides, fungicides, rodenticides, and fumigants), spray adjuvants, and plant growth regulators through an irrigation system is called chemigation. Applying commercial fertilizers, soil amendments, lime, and gypsum through an irrigation system is called fertigation. Both processes pose a potential risk as chemicals may end up in drinking water supplies. Washington State Department of Agriculture has regulatory authority over pesticide and fertilizer applications including chemigation and fertigation. Further information and explanations can be accessed through the web sites listed below.

Chemigation and Fertigation Rules (PDF). Chemigation and fertigation- a quick overview of risk and rules. This web page provides contact information and definitions. December 2001.

Backflow Devices: Installing a backflow device is a component of irrigation systems that are regulated under the Federal, State, and County ordinances and regulations. Backflow or anti- siphoning devices prevent contamination of chemicals in drinking water that may occur during irrigation. The Federal Safe Drinking Water Act and the State of Washington have passed rules and regulations that deals with backflow device requirements and monitoring of such devices. To ensure compliance with Federal, State, and County regulations and ordinances, design and installation of irrigation systems is best overseen by an irrigation design specialist.

Backflow Preventers This online link provides a description of a variety of backflow devices.