Landscape and Irrigation Introduction

The Water Needs of Plants

How much water does it take to grow an attractive and healthy landscape? There really is no “right” answer to this question, it all depends factors such as local climate, type of plants, soil conditions, shading, maintenance practices, and so on.  Some healthy landscapes require no supplemental irrigation beyond what falls from the sky, others rely on substantial amounts of water.  In a perfect world, everyone would put exactly the right amount of water on their landscape to keep it healthy and attractive without any excess runoff or water waste.  We are a long way from a perfect world.

Research has shown that on average about half of the water used in a single-family American home during the course of a year will be put onto the landscape. In a wet climate such as the Pacific Northwest less water is required for irrigating a turf landscape compared with a hot dry climate like Arizona. But even in a wet climate, the landscape area is often the single highest user of water.

“Conventional notions of what affects water use on landscaped areas are changing as more daring communities, water suppliers, and individuals make commitments to stop wasting water.  Historically, the amount of water used for landscape irrigation and other factors that drive peak water demands were assumed to be immutable givens necessitating the construction of large water supply and treatment facilities.  Now, water supply systems…are challenging such assumptions with innovative conservation strategies.”

-Amy Vickers, Handbook of Water Use and Conservation, Water Plow Press, 2001.

The web pages and research reports on the Alliance for Water Efficiency site offer some basic information of landscape design, installation, and maintenance as well as irrigation practices that can help maximize water efficiency.  Improving efficiency in outdoor water use and reducing outdoor water demand are fundamental challenges facing conservation professionals for the foreseeable future.

The following research reports on landscape and water use provide important information on the subject:

Inland Empire Landscape Alliance (2009) Chino Basin Water Efficient Landscape Ordinance 

Aquacraft (2000) Impacts of Xeriscape on Outdoor Water Use

Aquacraft (2009) Evaluation of California Weather-Based “Smart” Irrigation Controller Programs 

Thornhill, S. (2007) Landscape Sector Analysis - Southern California

Various (2006) Florida Waterwise Landscapes - Landscaping to Promote Water Conservation

Various (2006) Standards for Landscape Irrigation In Florida 

Sovocool (2005) Xeriscape Conversion Study Final Report

Various (2005) WaterWise - Residential Landscape and Irrigation Guide for Western Colorado

Chesnutt, T et al (2004) Evaluation of Landscape Performance Certification Program

MWDOC, IRWD (2004) The Residential Runoff Reduction Study

Irvine Ranch Water District (2003) Landscape Sizing in Santa Ana Heights – A Model to Efficiently Size Landscape Area for any Community 

ASCE (2000) Standardized Reference Evapotranspiration Equation