Spring Rains

Even though it is still spring on the calendar, temperatures are soaring, bringing big changes to the atmosphere and the air and water cycles.  Water, mainly from our oceans, constantly evaporates into the air that is moving over the surface.  Denser air fills the lower levels of the atmosphere and is able to absorb more water vapor and more heat.  As an air mass warms, it rises and spreads out in higher levels of the atmosphere.  Air becomes less dense, loses some of its heat, and allows water vapor to condense and form clouds.  Most clouds do not have rainfall because the updraft of warm air is fast enough to keep the small water droplets forming the clouds from falling.  Rain happens when enough water condenses to form a heavy enough droplet to fall.

 As this process of rising and falling air and water droplets continue, a storm develops.  Loss of heat also releases small electrical charges, which will eventually combine into a chain called lightening.  Worldwide, about 2,000 thunderstorms are happening at any given moment.  There are 100,000 annually in the U.S., and about 10% reach a severe level with hail, winds exceeding 57 mph, or spawning tornados.  Rains can be heavy, putting down vast quantities of water on the landscape in a short period of time.  How much water?  One inch of rain on an acre equals 27,154 gallons of water.  At Benedictine’s campus in Lisle, one inch of rainfall equals about 3 million gallons.  On average, rainfall in the continental U.S. would cover every acre with 30″ of water annually.

In the last century, worldwide average temperatures have risen 1.4˚F, and are expected to rise 3˚F to 5˚F in the coming 100 years.  We are experiencing more rainstorms annually, and they are of greater intensities due to warmer air holding more water vapor and rising temperatures sucking more moisture from both land and ocean.  When clouds condense enough to form rain, there is a greater quantity of water vapor, so rainfall is heavier from greater amounts of water falling back to earth.

Heavier rainfalls may be absorbed in some areas, if they do not happen too often.  However, most watersheds have been heavily affected by human activities including deforestation, dams, irrigation activities, depletion of groundwater, and draining of wetlands.  More rainfall running off the surface leads to less moisture in the soil and allows soil to get hotter and drier.  As rains ease toward midsummer, vegetative areas are harder hit by these dry effects.

Rain gardens are a simple and inexpensive way to alleviate some of these problems.  They can be created in any area where the soil is slightly depressed.  Runoff is directed into the area where it can soak into the ground.  Many are planted with grasses or flowering native perennials providing a beautiful garden while reducing runoff.  It is an easy solution you can create in your own backyard.  For more ideas, click this link: for Rain Garden Requirements & Plant Lists from the Illinois Department of Natural Resources.