Managing microclimates

From shade and sun to slopes and soils, microclimates deserve some serious attention so we asked three irrigation experts for their tips.

How do you determine a microclimate?

You can do some sun/shade exposure studies and models for understanding that aspect of the microclimate.  A lot of times we use historic weather, weather patterns and evapotranspiration [information] and a lot of the municipalities these days have that information available. We can use that to evaluate what an anticipated water requirement would be for a turfgrass area or a shrub and groundcover area or whatever. So we use historic modeling for an initial planning.

Then depending on the client’s budget and their motivation and sophistication, we might specify a weather station or an onsite means of collecting data in the future as the project moves forward, and interface that with a control system.

-        Doug Macdonald, principal of Aqua Engineering in Fort Collins, Colo. and consultant with the American Society of Irrigation Consultants
 
How do you look at water movement?

A good example of that is consideration of slopes. Water, via rainfall or irrigation, migrates from top to toe via gravity.  In our experiences, the water requirements of the lower portions of the slope can be reduced by 30 percent.

Prior to planting or designing a sloped landscape, a zoning plan is created to group plant material with similar water requirements. This allows any supplemental irrigation to be designed in zones to better manage duration and frequency of water application tailored for plants of common water needs. One example of a successful slope zoning concept is to group low water-use plants at the top two-thirds of a slope and zone the lower one-third for more moderate water using material. It provides an advantage using this water migration from rainfall or irrigation to better accommodate the natural water requirement of the plant material. 

The plant health at the top of slope improves due to naturally drier conditions as well as the plant health at the toe of slope.  We’re using natural migration of water to sustain an intended zoning concept while minimizing any supplemental application of water. 

-        Steve Hohl, principal at Water Concern and past president of the ASIC

 
How can a microclimate change?

When a newly planted landscape has, let’s say it has 3-inch caliper trees, and over a 10- or 20-year period, they’ll grow and change the microclimate. How often does an irrigation system get changed to adapt to that microclimate? Not very often.

Windbreaks are another good example. A windbreak that matures over the course of 10 or 20 years, and the microclimate that’s downwind of that windbreak, is going to change for the benefit. But if your irrigation system is designed such that you’ve got differing microclimates mixed on single laterals, then you don’t have a whole lot of choice other than adapting the irrigation system to that future change.

-        Stephen Smith of Regenesis Management and past president of the ASIC