Page 21 - Efficient Irrigation and Landscape Design Standards

Adapted Plant: Adapted plants are not native and not invasive but are able to thrive in the local climate and soil conditions. These plants may be native to other regions of the United States, or have been imported from other continents.
Backflow Prevention Device: A backflow prevention device is used to protect potable water supplies from contamination or pollution due to backflow conditions. In water supply systems, water is normally maintained at a significant pressure to enable water to flow from the meter to the sprinkler head. In a backflow condition, higher pressure on the sprinkler side can push contaminated water into the potable water system.
Distribution Uniformity (D.U.): The measure of the uniformity of irrigation applied across a defined area.
Drip Emitter/Drip Irrigation: Drip irrigation fittings that deliver water slowly at the root zone of the plant, usually measured in gallons per hour.
Drought Tolerant Plant: Plants that have relatively low water requirements, or plants that are well adapted to an arid climate are often described as drought resistant or drought tolerant. Drought tolerant plants are considered adapted or native and able to survive on a region’s natural rainfall with very little supplemental irrigation.
Evapotranspiration (ET): The quantity of water evaporated from adjacent soil surfaces and transpired by plants during a specific time, expressed in inches per day, month or year.
Hydrozone: A portion of the landscaped area having plants with similar water needs, areas with similar microclimate (i.e. slope, exposure, wind, etc.) and soil conditions, and areas that will be similarly irrigated. A landscape hydrozone can be served by
one irrigation valve, or a set of valves with the same schedule. A landscape plan prepared with water efficient landscaping in mind should group plantings by hydrozone to minimize irrigation needs. Landscape design plans should prioritize the use of native plant species, and minimize site disturbance where appropriate.
Infiltration Rate: The infiltration rate is the speed at which water enters into the soil. It is usually measured by the depth (in inches) of the water layer that can enter the soil in one hour. An infiltration rate of 1.0 in/hour means that a water layer 1 inch deep on the soil surface will take one hour to infiltrate.
Irrigation Efficiency: The measurement of the amount of water beneficially applied, divided by the total amount of water applied. Irrigation efficiency is derived from measurements and estimates of irrigation system hardware characteristics and management practices.
Irrigation Contractor: A person who has been certified by the Irrigation Association (IA) to install irrigation systems.
Irrigation Designer: A person who has been certified by the IA to prepare irrigation system designs, and/or a Landscape Architect.
DEFINITIONS 7
Landscape Architect: A person who holds a certificate to practice landscape architecture in the state of Washington/Idaho.
Landscape Irrigation Auditor: A person who has been certified by the IA to conduct a landscape irrigation audit.
Matched Precipitation Rate (MPR): A term used to indicate that the amount of precipitation from sprinklers with MPR in a given area is uniform. MPR sprinklers allow water conservation by limiting dry spots.
Microclimate: The climate of a very small or restricted area, especially when this significantly differs from the climate of the surrounding area. Shaded north sides of buildings have a microclimate compared to areas further from the building that receive more sunlight.
Native Plant: Native plants are defined as the species that exist in a region without human introduction. Native plants in the Spokane region range from desert to alpine environments.
Precipitation Rate: The depth of water applied to a given area, usually measured in inches per hour.
Plant Water Requirement: The depth (or amount) of water needed to meet a plant’s water loss through evapotranspiration. In other words, it is the amount of water needed by the various plants to grow optimally.
Rain Shut-Off Device: A device wired to the automatic controller that shuts off the irrigation system when it rains.
Reference Evapotranspiration Rate or ETO: A standard measurement of environmental parameters that affect the water use of plants. ETO is expressed in inches per day, month or year and is an estimate of the evapotranspiration of a large field of cool season grass, 4-7” tall, that is well watered.
Runtime: The length of time an irrigation zone needs to water a given area.
Root Zone: In irrigation terms, the depth and spread of a plant’s root system.
Soils Report: A report by a soils laboratory indicating soil type(s), soil depth, uniformity, composition, bulk density, infiltration rates, and pH for the topsoil and subsoil for a given site. The soils report also includes recommendations for soil amendments.
Soil Water Holding Capacity: The amount of water that a given soil can hold for plant use. Excess water will infiltrate below the plant root zone and become unusable.
Water Budget Allowance: A water budget is a water management tool used to estimate the amount of water a landscape will require. The water budget takes into account reference evapotranspiration data, plant type(s), purpose and functionality of the landscape, irrigated landscape area, irrigation efficiency, water quality, and rainfall.
EFFICIENT IRRIGATION & LANDSCAPE DESIGN STANDARDS 21