Washington, DC Landscaping Rules: Rainwater Harvesting (2026)
Key Facts
- Governing rule
- 11 DCMR Subtitle C, Chapter 6 (Green Area Ratio)
- Water feature threshold
- 50% of annual flow must be harvested rainwater
- Water feature wet duration
- Must hold water 6 of 12 months
- Spray irrigation
- Must meet DOEE Stormwater Guidebook treatment
- Drip irrigation
- No additional stormwater treatment required
- GAR bonus
- 0.1 multiplier for harvested stormwater irrigation
- When required
- Submitted with GAR score sheet at permit application
Summary
DC's Green Area Ratio zoning rules let builders count rainwater harvesting toward the required landscaping score, but only if the system meets exact conditions: water features must run on at least 50% harvested rainwater, and stormwater used for irrigation must meet DOEE treatment standards for spray systems.
603.11 Harvesting stormwater for irrigation shall meet the following conditions: (a) If the irrigation type is spray, applicants shall follow treatment standards set forth in the current District Department of Energy and Environment's Stormwater Management Guidebook; and (b) If the irrigation type is drip, no additional treatment of stormwater is required. ... Water features shall meet the following conditions: (a) Water features must use harvested rainwater for at least fifty percent (50%) of the annual flow; and (b) The water features must be under water for at least six (6) out of twelve (12) months.
Full Breakdown
Title 11 DCMR Subtitle C, Chapter 6 sets the District's Green Area Ratio (GAR), a landscaping score required on building permit applications for most new construction and additions. Rainwater harvesting is one of the credited GAR elements, but Section 603 disqualifies any landscape feature that doesn't meet its specific conditions from counting toward the score. 11, a property using harvested stormwater for irrigation must follow the current DOEE Stormwater Management Guidebook's treatment standards if the system sprays the water; drip irrigation is exempt from that extra treatment step.
Vegetated walls and vegetated roofs that rely on stormwater harvesting for irrigation must also be physically connected to that irrigation system to earn credit, not merely built with the capacity for it. Water features earn a GAR multiplier only when at least 50% of their annual flow comes from harvested rainwater and the feature holds water at least six of twelve months a year. 3), prepared with a landscape plan from a Certified Landscape Expert, such as a DC-licensed Landscape Architect or ISA Certified Arborist, documenting the irrigation and drainage plan for any area irrigated with harvested rainwater. 9 multiplier schedule, on top of any credit for the underlying landscaped area itself.
Violations & Fines
A landscape element that fails its Section 603 conditions, for example a water feature under the 50% rainwater threshold or a vegetated wall lacking the required irrigation connection, simply does not count toward the property's GAR score. Because DOB reviews the GAR score sheet as part of building permit review under Section 604, a shortfall that drops the project below its zone's minimum GAR can hold up or block permit issuance until the landscape plan is revised.
Frequently Asked Questions
Can I count a rain garden toward DC's landscaping requirement?
Does a backyard pond get GAR credit for using rainwater?
Do I need city approval to irrigate landscaping with harvested rainwater?
Sources & Official References
Other rules in Washington
Compare Washington to another location·View the District of Columbia landscaping rules overview
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