Environmental News

July 23, 2008

Box of Rain – States Take a Closer Look at Rainwater Harvesting

By Jeff Kray

While water withdrawals from streams and wells are often closely monitored and contentious, regulators have historically tended to look the other way when it comes to water captured as rain. But as water becomes more scarce, regulators have begun to more closely scrutinize the increasingly popular practice of “rainwater harvesting” – collecting rainwater in barrels, buckets, and tanks.

Presently, there is little consistency among states in regulating the harvesting of rainwater. Some states, like Colorado, prohibit rainwater harvesting.[1] Other states, like Washington, are considering requiring a permit only for rainwater capture systems above a threshold amount.[2] In other places – notably Santa Fe, New Mexico – rainwater harvesting is actually required. Systems for rainwater capture must be installed on every new 2,500 square foot or larger residential or commercial building in that city.[3] Arizona, Hawaii, Kentucky, Ohio, Texas, and West Virginia are all either regulating or considering regulating rainwater harvesting.[4]

What is Rainwater Harvesting?

Rainwater harvesting is the collection, storage, and conveyance of rain as a water source. As the nation realizes the limits of its existing freshwater resources attention is returning to rainwater capture to help ensure adequate water supplies. Rainwater harvesting systems range from a barrel placed under a downspout to multiple tanks with pumps and controls. Residential collection systems can range from a 50-gallon rain barrel to cisterns of 30,000 gallons or more. Commercial systems can be much larger. As discussed below, rain water harvesting can provide several environmental benefits.

Catching and storing rain is an age-old practice throughout the world. In China, rainwater harvesting may date as far back as 6,000 years.[5] In India, the practice dates back over 4,000 years and traditionally meant storing water in tanks or reservoirs.[6] “By some estimates, 20,000 villages in India are harvesting their rains.”[7]

In the United States, water resources are primarily governed by state, rather than federal, government. State and local governments have taken opposing approaches to rainwater. As noted above, for example, Colorado assumes that rainwater contributes to streamflows and, therefore, prohibits rainwater capture systems.[8] Similarly, local and state building codes, zoning laws, and other regulations in Colorado and other states may limit rainwater harvesting’s availability.

In contrast, the trend in other states is moving towards encouraging rainwater harvesting. In 2005, for instance, the Texas legislature created a committee to evaluate and recommend minimum water quality guidelines and standards for rainwater use.[9] Texas provides financial incentives for rainwater capture systems and water utilities in Austin and San Antonio encourage rainwater harvesting to conserve water.[10] Under such policies, professional companies have installed more than 400 full-scale rainwater harvesting systems in central Texas and, over the last ten years, homeowners have installed more than 6,000 rain barrels through the City of Austin’s incentive program. Washington appears to be on the verge of adopting an approach to rainwater harvesting regulation similar to that of Texas.

Rainwater Harvesting in Washington State

Washington law broadly defines water resources as “all water above, upon, or beneath the surface of the earth, located within the state.”[11] Rainwater is, therefore, a state water resource the use of which through harvesting may require a permit. In the past seven legislative sessions, the Washington Legislature has unsuccessfully attempted to define how much rainwater capture is exempt from the permit requirement. Despite these efforts, existing law still provides no clear guidelines on the issue.

The Washington Department of Ecology has created a de facto exemption for certain rainwater harvesting and does not require homeowners to obtain water right permits to collect and store small rainwater amounts.[12] At the same time, Ecology has not yet provided guidance as to what it considers an amount of water that might trigger the need to obtain a permit. As a result, homeowners, businesses, non-profits, and other entities have been capturing rainwater from roofs and other suitable services without permits, but also without certainty that they are free from potential enforcement. Ecology has now determined to provide further guidance by rule.

For water quality purposes, capturing rainwater before it becomes stormwater runoff not only decreases the amount of stormwater that may need treatment, but it also decreases the amount of water that quickly runs off urbanized land into local streams, often carrying pollutants from human activities and scouring gravel from their beds, deepening and degrading them in the process.[13] In Washington’s Puget Sound region and in some other urban areas, stormwater and wastewater also sometimes share the same sewer line in what are called combined sewer systems. Large storm events can create so much stormwater that it exceeds the combined sewer system’s capacity and, as a result, the untreated excess flows into local lakes, streams, or the Puget Sound in what are called a combined sewer overflows (CSOs). The cumulative effect of many large scale rainwater collection systems may decrease the frequency of CSOs.

Washington has two distinct climates. East of the Cascades typical rainfall averages 10-20 inches, less for central Washington and more for the Cascade foothills and the northeast and southeast corners. West of the Cascades, typical rainfall averages 30-60 inches in the lowlands and double that for the Cascade foothills and the Olympic Peninsula.[14] Similarly, water is most limited on both sides of the state in summer and early fall, the time at which the demands are highest.

The state’s challenge is to define the permitting requirements for rainwater collection in a manner that differentiates between systems that cause little, if any, hydrologic impact (the vast majority of small systems) and those systems that could impair other water rights, notably in closed basins where Ecology is not issuing new water rights. For example, 50-gallon rain barrels used to gather water for residential urban gardens may provide stormwater management benefits without impairing water resources, whereas rainwater collection for consumptive use, such as irrigation, could potentially impair other water rights by limiting water amounts that would otherwise flow into freshwater streams with their own water rights or streams that supply other water right holders. The problem is that Washington has never defined the threshold for de minimis rainwater harvesting. As a result, Ecology will need to draft its proposed rule cautiously to avoid legal challenges asserting that it has exceeded its legal authority.

Seattle Public Utilities recently received a regional water right permit from Ecology to capture and put to use approximately 23,000 acre-feet of rainwater that falls on rooftops in areas of the city served by CSOs.[15] Similarly, island residents in San Juan County anticipate that they will be able to legally continue using rain for their water supply under island-wide water permits that Ecology is expected to issue in fall 2008.[16] Ecology’s proposed rule would not affect either the regional rainwater permit recently obtained by the City of Seattle, or future island-wide permits in San Juan County.

For many other actual or potential rainwater harvesting systems, obtaining permits is administratively and economically unfeasible. Few homeowners are likely to engage in Washington’s water right permitting process for a rain barrel, nor is Ecology likely prepared to handle a large volume of such applications. For such smaller systems, the solution is for Washington to clearly define which ones are required to obtain permits and which are not.

Washington’s Rainwater Collection Rule

Ecology currently envisions a rule recognizing and clarifying its historical permit exception for capturing, storing, and using small rainwater amounts. Furthermore, Ecology plans to create a distinct permit application for individuals and regional entities that plan to construct rainwater collection systems that do not qualify for the permit exemption, and the rule will authorize priority processing of those applications due to their stormwater management benefits.[17]

The proposed rule could include:

  • Defined threshold limits, below which a water right permit will not be required.
  • A distinct permit application process for individuals and groups that plan to construct rainwater harvesting systems that do not qualify for the permit exemption.
  • Authorization for Ecology to expedite (priority process) rainwater permits due to their stormwater management and other environmental benefits.

Ecology is seeking public comment on where it should set the threshold for requiring a water right for rainwater harvesting. It has not yet set a timetable for its proposed rule or provided a draft for public comment.


Policymakers are beginning to remove hurdles to implementing rainwater capture systems and creating incentives for investing in such systems. Rainwater harvesting has the potential to provide outdoor irrigation and replace other water resources for indoor uses such as toilet flushing. As the legal and technical availability of rainwater expands, Washington and other states have signaled that they will also continue to ensure that the law protects existing water rights.

For more information on rainwater harvesting and Marten Law Group’s water resources and water quality practices please contact Jeff Kray

[1] Colorado’s Division of Water Resources maintains that rain is assumed to ultimately contribute to streamflows and is deemed state property. Rain barrels are, therefore, illegal. M. Subramanian, Rainwater Harvesting Catches the Attention of State and Local Government, Western Water Law (June 2008). Colorado is considering a bill that would permit rainwater harvesting. See proposed Senate Bill (SB) 08-119.

[2] Ecology has conducted several public meetings about its proposal and is preparing, but has yet to release, a draft rule.

[3] Santa Fe County, N.M. Municipal Code § 2.4.1 (2007).

[4] Rainwater Harvesting Catches the Attention of State and Local Government, Western Water Law (June 2008).

[5] M. Subramanian, Rainwater Harvesting Catches the Attention of State and Local Government, Western Water Law (June 2008).

[6] Vijaysree Venkatraman, Thirsty Indian metropolis finds an answer in the rain, Christian Science Monitor (March 20, 2008).

[7] Fred Pearce, When Rivers Run Dry, p. 266 (2006).

[8] Id.

[9] Id., citing Texas’ House Bill (H.B.) 2430 (2005).

[10] Id.

[11] RCW 43.27A.020.

[12] Focus on Proposed Rainwater Rule, Washington Department of Ecology (June 2008).

[13] http://www.ecy.wa.gov/programs/wr/hq/rwh_sw.html.

[14] http://www.ecy.wa.gov/programs/wr/hq/rwh_augm.html.

[15] Water Briefs at p. 24, The Water Report #53 (July 15, 2008).

[16] Id.

[17] http://www.ecy.wa.gov/programs/wr/hq/rwh_rule.html.

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