Definitions for stormwater and rainwater harvest and use/reuse

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• Backwash: Water that is pumped in reverse through filters, removing trapped sediment and other collected material
• Beneficial use of stormwater: Use of stormwater to meet water demands, including but not limited to: irrigation, drinking, washing, bathing, cooling, and flushing. Commonly referred to as “reuse.”
• Cistern: A tank that stores water.
• Collection efficiency: Harvested water volume as a percent of the total rainfall on the source area during a certain period of time.
• Disinfection: Reduction of viable micro-organisms to a level that is deemed suitable for the intended use.
• Dry running protection: System for protecting a water pump against running when no water is present.
• First flush device: A device that diverts runoff generated during the beginning of a rainfall event, which carries higher levels of debris and contaminants from collection surfaces, from entry into storage components. Only suited for warm weather applications. Extreme caution should be observed in cold climates.
• Green Roof: a rooftop treatment practice where a thin planting media is established on roof surfaces and then planted with hardy, low–growing vegetation
• Harvested water: Water that is collected from impermeable surfaces, such as rooftops and parking lots, and stored for future use.
• Make-up water supply: Municipal water or other reliable water source that is used to supply water for beneficial use in the event that harvested water is not available.
• Non-potable water: Water that does not meet drinking water standards.
• Overflow Siphon: Functions as a trap to keep out vermin and also to evacuate floating pollen and debris in the tank during rain events.
• Potable water: Water that meets drinking water standards.
• Pre-storage treatment: Best management practices that are used upstream of the storage unit.
• Pretreatment: Treatment of harvested stormwater prior to entering the storage unit; typically processes that remove trash, gross solids, and particulate matter.
• Post-storage treatment: Practices that are used to remove fine particulates, dissolved pollutants and microorganisms from harvested rainwater.
• Rainwater: A form of stormwater that is collected directly from roof surfaces which can have lower levels of pollutants than other sources of stormwater.
• Recycled Water: Water which, as a result of treatment of waste, is suitable for direct beneficial use or a controlled use that would not otherwise occur and is therefore considered a valuable resource (Current California Water Code 13050-13051)
• Reuse: Use of stormwater, greywater, or blackwater to meet water demands, including but not limited to: irrigation, drinking, washing, cooling, and flushing.
• Runoff: The portion of rainfall or snowmelt not infiltrated, evaporated, or transpired that drains or flows over the land and becomes surface flow.
• Source area: Surface area from which water is harvested (e.g., rooftop, roadway, green space).
• Stormwater: Rainfall or snowmelt that runs off surfaces.
• Sub-surface irrigation: Water that is applied below ground level for plants and is not directly exposed to above ground surface and/or air.
• Surface irrigation: Water that is applied above ground level for plants and is directly exposed to the above ground surface and/or air.
• System pressure: Pressure needed to deliver water to the designated fixtures.
• Treatment: Treatment of harvested stormwater after storage but prior to distribution; typically processes that remove dissolved pollutants and bacteria.
• Wastewater: Used or spent water containing pollutants or solids and discharged from homes, commercial establishments, farms, or industries.
• Water harvesting: The process of capturing and retaining water for beneficial uses at a different time or place than when or where the water was generated.
• Water yield: The volume of harvested water over a certain period of time.