Caltrans Water Conservation Measures in Highway Landscaping

The California Department of Transportation (Caltrans) began using a variety of new materials and techniques to address drought conditions by reducing or eliminating water use on roadside landscaping following the onset of multi-year severe drought conditions in 2011.  New roadside landscaping projects began utilizing recycled water, native grasses and plants that require little or no watering, innovative water collection techniques, and smart irrigation controls. Caltrans’ water conservation efforts are designed to help meet or exceed state water use reduction goals and address growing water scarcity.

Caltrans owns and manages over 30,000 acres of irrigated landscaping, which performs important functions to help maintain the safety and condition of roads and improve the environment. Roadside landscaping provides important environmental functions: it prevents erosion, reduces stormwater runoff, and provides natural habitat. Water shortages and use restrictions could impair the ability of landscaping projects to perform these functions.  In response, Caltrans instituted measures to protect the state’s $1.4 billion investment in highway plantings while significantly reducing water use.

Caltrans convened a state operations drought workshop in February 2014 to identify actions the agency could take to meet water conservation requirements and to estimate timelines and funding necessary for implementation. These actions included:

  • Water collection- Testing the use of plastic lining around roadside trees, which can trap condensation, allowing it to drip back to the soil and water the trees.
  • Reduced pruning - Limiting tree pruning so that larger shaded areas can help retain soil moisture, except where pruning is necessary for safety reasons. Caltrans is also adding mulch to portions of highway landscaped areas to further help retain soil moisture.
  • Irrigation system changes and upgrades - Increased installation of smart irrigation controls, which take advantage of soil conditions and weather predictions in determining whether or not the landscaping needs watering. Caltrans anticipates that six of the state’s transportation districts will transition exclusively to using smart irrigation controls in 2014-2015. In addition to increasing the use of smart controls, Caltrans districts have been inventorying existing conditions of irrigation systems, identifying deficiencies and conducting needed repairs. Maintenance staff has also been ordered to set irrigation systems to water landscaping only at night whenever possible to reduce moisture loss.
  • Alternative plantings - Increased efforts to identify plants that require little or no water to survive, and include these in landscaping plans. For example, Caltrans has studied the use of native grass sod and found it to require less watering once established, in addition to providing better control of surface erosion and allowing less sediment loss.
  • Recycled water use--Directed staff to reduce potable water use by 50% and to use recycled water whenever possible.
  • Updated guidance and manuals - Issued new guidance memos related to project development, construction, and maintenance, and updated the Highway Design Manual. Guidance memos have specified additional requirements such as ceasing irrigation in “severe water shortage areas” (as determined by the California Department of Public Health). Caltrans’ May 2014 Water Conservation Guidance details action required and design guidance for specified water conservation categories, which are based upon the level of water restrictions set by Caltrans, statewide requirements, and/or local water agency requirements.

Caltrans updated its Drought Action Plan in spring 2015, building on the action plan developed out of the 2014 workshop, and issued a new memoranda on drought response in October 2015 and July 2016. The 2015 Drought Action Plan identifies additional strategies to help the agency achieve a statewide 50% reduction compared to Caltrans’ 2013 water use. Caltrans is delaying projects that would use potable water, and is implementing other conservation requirements such as requiring proposed new planting and landscaping projects to comply with the California Model Water Efficient Landscape Ordinance, which was updated by the Department of Water Resources in 2015 to increase water efficiency standards. Caltrans has set a goal of 50 percent water use reduction (compared to 2013 usage) and a goal of 100 percent conversion of irrigation systems to using non-potable water sources by 2036.

In addition to roadside landscaping projects, Caltrans applies water conservation strategies in the design, construction, operation, and maintenance of all other transportation facilities. Caltrans has developed a spreadsheet tool that estimates the amount of water needed for project construction, and can be used in conjunction with the department’s latest Water Conservation Guidance.

While Caltrans has had water conservation policies in place for many years, recent severe drought conditions led to new requirements at a statewide and Department-wide level. A 2012 Executive Order issued by then-Governor Brown required that state agencies reduce overall water use at their facilities by 10% by 2015 and 20% by 2020, measured against a 2010 baseline. In January 2014, Governor Brown proclaimed a state of emergency in California due to extreme drought conditions, and directed state agencies to implement water use reduction plans for all state facilities. The proclamation also instituted a moratorium on all new, non-essential landscaping projects on state highways and roads. Continued drought conditions led Governor Brown to issue additional Executive Orders in April 2015, November 2015, and May 2016, requiring the State Water Resources Control Board to set new statewide water restrictions and directing other actions by state agencies to improve drought response.


This Adaptation Clearinghouse entry was prepared with support from the Federal Highway Administration. This entry was last updated on May 5, 2020.

Publication Date: 2014

Related Organizations:

  • California Department of Transportation (Caltrans)


Resource Category:

Resource Types:

  • Agency guidance/policy
  • Best practice
  • Case study

States Affected:


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