by Rick Ellis
Welcome to The Irrigation Series, Part 2, where I explain why we, in the Land of 10,000 Lakes, need to add city/well water to our lawns! Can’t Mother Nature take care of that for us? Although we do have a lot of surface water from the remnants of the last few glacial periods, we don’t get as much rain as you may think. Parts of Minnesota get the same annual precipitation as Ft. Worth, Texas! Huh? Surprisingly true, and in the summer, we can get HOT, as you long-time Minnesotans can attest. Perhaps not the almost–daily 110–degree temps in the Metroplex or Waco last summer, but hot enough. Furthermore, we don’t receive as much precipitation as Chicago or even Kansas City.
Why do we Minnesotans spend our valuable drinking water on a plant not native to our fair state? In the northern regions, we typically plant a cool season variety called Kentucky Bluegrass. This type of grass is native to the cool summer climates of northern Europe. When maintained correctly, Kentucky Bluegass looks great and feels great to our bare feet! But what level of effort goes into that gorgeous (ahem…albeit non-native) yard?
Mowing it, aerating it, seeding it, fertilizing it, weeding it, dethatching it, AND irrigating it.
As I stated above, we do not get a lot of rain in the Twin Cities during the summer months. Do you know how much water your lawn needs in the growing season? The rule of thumb is 1-inch per week, typically 2,500 to 10,000 gallons for normal-sized residential yards. This comes from a combination of rain and irrigation, as well as snow melt during the spring and fall. Those late fall snowstorms, UGH! The cool season grasses we typically plant require 40 to 50% more water than native vegetation, mature trees, and shrubs.
Evapotranspiration
Why do our lawn grasses need so much water to stay healthy and lush? The big scary word I am going to throw out now is EVAPOTRANSPIRATION. What does that word mean? It is the combination of water loss from evaporation (water loss from the soil) and transpiration (water loss from the plant leaves). Soil moisture, air temperature, sunlight reaching the leaves and soil, humidity, and wind all influence this rate. Evapotranspiration is highest when it is hot (over 90 degrees F), with low humidity, some wind, and no shade. Matching the evapotranspiration requirements of your lawn can be achieved in a variety of ways. With suburban watering rules, the best way to achieve this is with a properly designed irrigation system and a smart irrigation controller.
Stay tuned for my final installment of The Irrigation Series, which will address how to best design your lawn irrigation system and use a smart controller for optimal efficiency! And in case you missed it, click here to read my first post of the series!
Rick is a professional hydrogeologist, a Certified Landscape Irrigation Auditor, and operates an irrigation and water conservation company in Woodbury, MN called Save Water Inc. A father of two, Rick loves spending his free time exploring small towns, playing golf, and teaching folks about water-related topics. Please reach out to Rick through his web page to learn more!