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Rain, Rain, Store Away, Use Again Another Day

June 19, 2009

Rainwater harvesting seems like a common sense way to both stretch existing water supplies and reduce stormwater runoff. But state water laws, as well as practical problems associated with water storage and reuse, have made the practice more difficult to implement than one might expect.

In Washington, as an example, rainwater (and other precipitation) is considered a water of the state and a public resource, and therefore its use requires a water right permit.[2] However, the Washington water codes apply specifically to beneficial use of groundwater or surface water, and rainwater has not yet been defined as either one. The Washington State Department of Ecology (Ecology), which has regulatory authority over water rights and appropriations,[3] has not required a water right permit for “de minimis” use of rainwater.[4] Ecology has taken the position that a rain barrel or small ornamental pond with capacity of a few hundred gallons is exempt from water right permitting,[5] but the term “de minimis” is not defined in the regulations or rules.

Bills have been introduced in every session of the Washington State legislature since 2001 to try to address rainwater as a potential water supply. Proposals have ranged from allowing up to 300 gallons of capacity from rooftop collection for use only on the same property[6] to essentially allowing all such collection of precipitation from hard surfaces provided it complies with area-specific rules to be developed by Ecology.[7] Every one of these bills has died in committee.

Debate over what volume of water constitutes a “de minimis” use continues unresolved because the cumulative effect of many rainwater collection systems could impact both surface water and groundwater that is recharged by infiltration of stormwater, and Washington water right law follows the doctrine of “first in time is first in right.”[8] This means that a more recently developed rainwater collection system could be required to cease operation if a party with a previously existing water right can demonstrate that the rainwater system’s use impairs that senior water right.

Given the difficult task of administering this portion of the waters of the state without any regulatory tools to do so, Ecology has come up with some ad hoc solutions.

Seattle Regional Water Right Permit

Ecology has granted Seattle Public Utilities a water right permit that allows collection and non-potable use of rainwater from rooftops of certain properties within its service area.[9] Only properties served by sewer systems that combine stormwater with sanitary flows are eligible; those served by separate stormwater and sanitary systems do not qualify.[10] Justification for this appropriation was twofold: it was intended to augment the city’s water supply as well as to relieve pressure on regional wastewater treatment plants by removing stormwater flow from the system.[11]

Seattle is located in a watershed that has been closed to new surface water appropriations,[12] yet for the purposes of this permit, rainwater has been classified as a surface water source. The combined sewer system created a special circumstance that has allowed the city and Ecology to work around that complication. If not diverted by rooftop catchment systems, water collected under this permit would otherwise be conveyed by the combined storm/sanitary sewer system to a regional wastewater treatment plant and released to a deep marine outfall; thus it would never reach local fresh water bodies. Diverting this water for beneficial use creates no impacts to existing surface water rights or instream flows.[13] Ecology has, therefore, considered this a “new” water source separate from the surface water bodies closed to appropriation.[14]

In order to address potential health concerns arising from use of this untreated water source, all such systems must:

  • Be restricted to non-potable use.
  • Fully conform to the Uniform Plumbing Code.
  • Comply with the policies and procedures outlined in the Seattle-King County Department of Public Health’s Rainwater Harvesting and Connection to Plumbing Fixtures.[15]

Among the requirements imposed by these restrictions are a separate piping system for rainwater, labeling of the rainwater system to avoid confusion with the potable water system, supplementation from a potable water source in the event the rainwater system fails, and cross-connection protections to prevent rainwater from entering the potable water supply.

The Northgate Civic Center is one of several projects developed under this new rainwater harvesting permit. This project redeveloped an asphalt parking lot to include a 10,000 square-foot library, a 20,000 square-foot community center, and a green space park area. The onsite rainwater collection system includes a 267,000-gallon concrete vault located under the lawn, which is adequate to collect runoff from roofs and paved surfaces from a 100-year, 23-hour storm event. A portion of this water is used for irrigating the landscaped areas of the project, and the remainder is released gradually to Thornton Creek to help restore a more natural hydrology pattern.[16]

King County’s King Street Center, which houses office space for more than 1,400 county employees, also uses a rainwater harvesting system under a rainwater harvesting permit. The King Street Center system replaces over one million gallons of potable water a year with collected rainwater. This water supplies more than 50 percent of the building’s needs for flushing toilets.[17]

San Juan County Island-Wide Permits

Ecology is also granting rainwater harvesting water rights in San Juan County. The county is comprised of numerous small islands located in the northern part of Puget Sound. The geology of these islands is not conducive to groundwater recharge and, therefore, precipitation is the primary water resource in the county.[18] The combination of island geology and local weather patterns means that streams often dry up in summer, and wells can go dry or experience saltwater incursion, making them unusable. The local watershed planning unit requested that rainwater harvesting permits be allowed as part of a regional watershed management plan.[19] Ecology has chosen to issue permits for each island independently, again based on the premise that the majority of precipitation runs off to Puget Sound, and would therefore not impact existing surface water rights if impounded for beneficial use.[20] The first of these permits, for Shaw Island and Lopez Island, are anticipated to be issued summer 2009.

While review drafts have not yet been released to the public, Ecology information indicates that the following provisions are likely to be included:[21]

  • Rooftop collection will be allowed only for domestic water use with minor outdoor gardening. Irrigation uses will still require a separate water right.
  • Domestic rooftop collection from properties on a septic system and outside a public water system service area will be allowed with no limit on tank size.
  • Domestic rooftop collection from properties within a public water system service area will be allowed only with permission from the water purveyor.
  • San Juan County will track rainwater collection systems through building code requirements, and report to Ecology annually. [22]

The major difference between the island permits under development for San Juan County and the Seattle Public Utilities permit is that the island permits allow rainwater as a potable water source, and in some cases, the sole source of water supply. San Juan County water systems are anticipated to be subject to more stringent treatment requirements.

Possible Regional Permit for Jefferson County

Water supply in Jefferson County presents a unique set of challenges. Located in the northeast portion of Washington, it lies in a temperate rain forest, with geology much like the San Juan Islands, and limited municipal infrastructure. This combination means that most of the local water supply comes from surface water sources recharged by precipitation. An additional complication is that Jefferson County’s political delineation does not match area geography. The county is comprised of portions of five separate drainage basins, known as Water Resource Inventory Areas (WRIAs), each of which is treated as a separate entity for the state’s required[23] watershed planning process.[24] Rainwater collection has been a topic of discussion during this planning process for most of these areas, usually as part of an instream flow rule designed to protect water quantity for salmon-bearing streams:

  • There currently is no instream flow rule under development for WRIA 16 (Skokomish-Dosewallips). The Implementation Plan for this unit recommends allowing rainwater capture without a water right permit below a specific quantity threshold to be determined by Ecology. There is no discussion of what uses would be allowed for this water.[25]
  • A preliminary draft of an instream flow rule for WRIA 17 (Quilcene-Snow) would allow rooftop rainwater collection from a structure that serves another purpose, such as a house or barn, as long as it is collected in such a manner that is does not mix with water from other sources, and is used entirely onsite. Such water collection must not impair instream flows or existing water rights, but there is no language specifically addressing whether a separate water right permit would be required for use of this water.[26]
  • An instream flow rule is currently under development for WRIA 18 (Elwha-Dungeness). A public review draft has not been released as of May, 2009; however, a summary document explaining the effects of the proposed rule indicates that rainwater collection from rooftops would be allowed for onsite use. Again, there is no language specific to a requirement for a water right permit.[27]
  • There currently is no instream flow rulemaking in progress for WRIA 20 (Sol Duc-Hoh). The Watershed Management Plan for this basin makes no mention of rainwater collection.[28]
  • WRIA 21 (Queets-Quinault) is not currently planning under RCW 90.82.[29]

Certainly, a county-wide water right permit specifying conditions under which rainwater collection would be allowed in this area would simplify planning and permitting for development projects. We understand that Ecology is considering such a permit, but no further information is available at this time.

Other Key Issues and Options

There is another approach to rainwater collection gaining popularity with developers of small commercial and industrial projects throughout the state. It involves keeping storage capacity of the system under 5,000 gallons. The argument for this approach necessitates drawing a parallel between an exempt groundwater well with an allowable withdrawal of up to 5,000 gallons per day[30] and a rainwater collection system with a capacity that makes it impossible to capture more than 5,000 gallons per day. Thus the onsite rainwater collection system would have no greater impact to existing water rights than would an onsite well drilled under the exemption provision and should therefore be allowed without requirement for a water right permit. Many of the developers of these projects are applying for a water right anyway, citing an “unnamed source” of water, to protect themselves against potential civil penalties assessed for non-permitted appropriation of public water.[31] If, however, rainwater is to be classified as surface water as in the Seattle permit, and such a system is to be located in a closed basin, no new appropriation would be allowed, and operation of a rainwater collection system would be prohibited.

A variation on this theme involves the very lack of classification of rainwater. This argument revolves around the fact that rainwater is not defined as either surface water or groundwater, and the rules and regulations as they currently exist are specific to one or the other. Thus, if rainwater is neither, there is no regulatory basis for requiring a water right permit for its use. This approach is untested in the courts, but it is unlikely to be successful based on the definition of water resources as “all waters above, upon, or beneath the earth, located within the state and over which the state has sole or concurrent jurisdiction.”[32] (Emphasis added.)


Washington and some other states have started to manage precipitation and stormwater runoff as a beneficial resource, rather than treating it as a waste stream. There are many ramifications to be considered in utilizing precipitation as a water source, including impacts to groundwater, impacts to surface water to which such runoff may be tributary, health concerns associated with a private water source, and regulatory compliance. Additional guidance from the Washington State Legislature and/or Ecology is needed to address the complications inherent in the current rule and regulations. At this time, rainwater collection in Washington makes sense for:

  • Projects in waterfront or island locations where diverted stormwater flows would not impact existing surface water rights.
  • Projects in areas where stormwater conveyance systems are combined with sanitary sewer systems in such a way that precipitation water diverted from the system would not otherwise impact nearby surface water flows.
  • Projects where current water sources are insufficient due to local weather patterns, geological conditions, and infrastructure restrictions, and where it can be demonstrated that rainwater harvest will not impact existing water rights.
  • Small, independent systems where the quantity of water used can arguably be considered negligible.

For more information on the legal aspects of rainwater harvesting, please contact Jeff Kray at Marten Law Group. For technical aspects, please contact Mandie MacDonald at Landau Associates, Inc.

[1] Mandie McDonald is Environmental Specialist with Landau Associates, Inc., in their Colfax, Washington location. Her work focuses on water resources and water rights throughout Washington and northern Idaho, with particular emphasis on ways that sustainable development affects the interests of existing and potential future water right stakeholders. She has over twenty years of experience performing research and technical support services in various engineering and scientific disciplines.

[2] RCW 43.27A.020.

[3] RCW 43.21A.064.

[4] Ecology Publication Number 07-11-018 Focus on Rainwater Collection and Water Right Permitting, June 2007

[5] Ecology Publication Number 08-11-023 Focus on Proposed Rainwater Rule, June 2008.

[6] House Bill 1423: An act relating to small rainwater collection facilities, 60th Leg. (Referred to Committee on Agriculture and Natural Resources, Jan. 18, 2007; died in Committee).

[7] House Bill 2097: An act relating to rainwater collection facilities, 61st Leg. (Referred to Committee on Agriculture and Natural Resources, Feb. 10, 2009; died in Committee).

[8] See RCW 90.03.010.

[9] Permit to Appropriate Public Waters of the State of Washington. Certificate Number S1-28477P; issued 27 December 2007.

[10] Ecology Report of Examination (ROE), File Number S1-28477, dated 30 January, 2007, pages 1, 2, 5, and 10.

[11] ROE pages 3, 9, and 10.

[12] WACs 173-508 and 173-509.

[13] ROE pages 5 and 10.

[14] ROE page 8.

[15] S1-28477P page 2.

[16] http://www.seattle.gov/dpd/static/NorthgateCivic%20web_LatestReleased_DPDP016095.pdf.

[17] A virtual tour of King Street Center, including a simplified representation of the rainwater collection and distribution system, will soon be available online at http://your.kingcounty.gov/solidwaste/greenbuilding/commercial/king-street-tour.asp.

[18] Golder Associates. 2007. Technical memorandum regarding Analysis Impacts on Water Resources of Rainwater Harvesting on San Juan Islands from Chris V. Pitre and Elizabeth Shea to Roma Call, Washington State Department of Ecology. July 9.

[19] San Juan County. 2004. San Juan County Water Resource Management Plan: WRIA 2. San Juan County Resource Management Committee, Friday Harbor, WA.

[20] http://www.ecy.wa.gov/programs/wr/nwro/sjc_rwc.html.

[21] http://www.ecy.wa.gov/programs/wr/nwro/sjc_rwc.html.

[22] http://www.ecy.wa.gov/programs/wr/nwro/sjc_rwc.html.

[23] RCW 90.82.

[24] http://www.ecy.wa.gov/watershed/pdf/rcw9082-0209.pdf.

[25] WRIA 16 Planning Unit, Sound Resolutions, and Cascadia Consulting Group. 2008. Detailed Implementation Plan: Skokomish-Dosewallips Watershed – WRIAs 16 and 14b. Mason County Planning Department, Shelton, WA. June 19.

[26] Ecology. 2009. PreliminaryDraft Rule. Chapter 173-517 WAC: Water Resources Management Program – Quilcene-Snow Water Resources Inventory Area (WRIA) 17. January 21.

[27] Ecology. 2009. Publication #09-11-004. Water for People, Farms and Fish: Overview of the Dungeness Water Resources Management Program (WAC 173-518). Water Resources Program, Washington State Department of Ecology, Lacey, WA. February.

[28] WRIA 20 Watershed Planning Unit. 2008. Watershed Resource Inventory Area (WRIA) 20 Watershed Management Plan. Washington State Department of Ecology (Lead Agency), Lacey, WA. August 20.

[29] http://www.ecy.wa.gov/watershed/pdf/rcw9082-0209.pdf.

[30] RCW 90.44.050.

[31] Ecology. 2009. Guidance Document #GUID-2005. Water Resources Program Guidance – Levying Civil Penalties. Effective May 13, 2009.

[32] RCW 43.27A.020.

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