<p>[[{"fid":"105","view_mode":"default","type":"media","attributes":{"style":"float:right;margin:0 0 5px 5px;","alt":"Evapotranspiration diagram","title":"Evapotranspiration diagram","class":"adaptive-image media-element file-default"}}]]Understanding the way your plants function helps provide the right amount of water to ensure a healthy landscape and maximizes the efficiency of water applied to your landscape.&nbsp;</p><p>One way to do this is by using local weather conditions to help determine how much water your lawn and plants need to maintain healthy growing conditions.</p><h2>The Basics Of How Plants Function</h2><p>Just as you release water vapor when you breathe, plants do too! It&rsquo;s called <strong>transpiration</strong>.&nbsp; When plants transpire faster than water is being replaced, they can wilt or die.&nbsp; Similarly, soils also lose moisture through <strong>evaporation</strong>.</p><p>Combine the two and you&rsquo;ve got <strong>Evapotranspiration</strong>, or ET, which is the combination of water lost from the soil through evaporation and from plants through transpiration.&nbsp; The amount of water lost through ET is equal to the amount of water that must be replaced to maintain healthy growing conditions.</p><p>Just remember:</p><ul><li>ET values are calculated from local weather conditions to help you determine how much water is needed for your landscape.</li><li>ET changes with local weather conditions.</li><li>ET is affected by amount of sun, wind and air temperatures.</li><li>ET varies for different types of plants.</li></ul><h2>So, Why Are We Talking About It?</h2><p>Here in the Portland metro area, water use can more than double in the summer months. Unfortunately, our usage increases at a time when there is less water available to us.</p><p>By making a few simple changes to your <a href="http://www.conserveh2o.org/measure-your-sprinklers-water-use-watering-gauges">watering routine</a>&nbsp;you can make a big difference for your plants and your pocketbook.</p><h2>How Are Evapotranspiration and The Weekly Watering Number Related?</h2><p>The Consortium contracts with a weather forecasting service to provide a free weather forecast and <a href="http://www.conserveh2o.org/weekly-watering-number">Weekly Watering Number</a> each Thursday.&nbsp; The Weekly Watering number is derived that week&rsquo;s evapotranspiration number.</p>