Figure 5. Trends in heavy precipitation (daily amounts greater than 1.25 inches per day) across regions of the United States. Figure published in the National Climate Assessment 2014 (https://www.globalchange.gov/nca4).


If we look across all 50 states, there is variation in the precipitation amounts and seasonality of precipitation. One of those changes is the shift between spring and summer precipitation. One way we have looked at this is to assess how much of the annual precipitation occurs during spring (April-June) compared to summer (July-September). As an example, the state-wide changes for Missouri are shown in Figure 4. Although there is variation among the years, the trend is obvious in the shift. When we have done a deeper analysis of the record, we are finding that the variation in the rainfall amounts during the spring and summer have shown more variation in the last decade than over the entire record. Our variability in precipitation amounts is changing and this will continue to challenge us in terms of managing our soil water resources.


Increases in Rainfall Intensity One of the changes that has been detectable in the precipitation record has been the increase in rainfall intensity (Fig. 5). Tis means that more of our storms are coming as intense events and it is not unusual for casual observers to comment on the intensity of storms.


Across the U.S., there has been an increase in heavy precipitation and at the state level there is a clearer trend and a change in the amount of heavy precipitation. As an example, the changes in events with more than 2


TPI Turf News September/October 2019


inches for Virginia is shown in the following diagram (Fig. 6). Since 1990, the number of events has shown significantly more events than in the previous years. Heavy precipitation events present challenges in water management because they can overwhelm the ability of the system to absorb or infiltrate water.


Implications for Turfgrass


Management If we consider that soil water is necessary for turfgrass growth and longevity, then the changes in precipitation amounts, timing, and intensity become important factors to consider. How much soil water that is available to a turfgrass stand will be dependent on the soil’s ability to store water? For example, a sandy soil will have much less water than a clay soil and would require much more frequent precipitation events to ensure continued growth. Understanding the soil resource for a given location will help guide the best management practices to create a positive condition for the growth and maintenance of turfgrass.


Te establishment phase of turfgrass will be subject to potential damage and runoff from intense precipitation events and will require attention to the preparation of the soil and potentially providing cover to absorb the raindrop energy before it hits the soil surface. For example,


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