Midweek Post...Evaporation Project

Since my local climate is working on a 13th consecutive day of no measurable rainfall, I decided on Tuesday, the 18th, to arbitrarily fill my rain gauge with stored rainwater from the barrel. This was an ideal time to perform a detailed evaporation project. Hot temperatures, plenty of sunshine, no rainfall, varying dewpoints.

My goal is to demonstrate that the period of time during the day that produces the most evaporation is the middle of the day through the afternoon, a time that I will often see residents and businesses 'wasting' water, bringing little benefit to the soil and wasting precious natural resources, incurring, I hope for them, a hefty water bill for the billing cycle.

I started my project at noon on the 18th with 3.33" rainfall in the gauge.

By 11:00 a.m. this morning, nearly 47 hours later, the gauge registered 2.68", a loss of 0.65" in just those 47 hours.

My hypothesis was that the period of observation between 12:00 p.m. and 5:00 p.m. would yield a higher percentage of the total evaporation within an undetermined time period (I have to make sure it's not going to rain...that's why it's not a determined period of time).

Although my results are not final, preliminary readings show that of the 0.65" that evaporated from the gauge during the 47-hour period, 0.37" occurred during the 2 - five hour periods listed above for the 18th and the 19th.

This represents 57 percent of the total evaporation occurred in just this 10-hour period of time. Nearly 0.04" per hour on average evaporated during this peak time of noon to 5 for both days.

On the other hand, the other 37 hours produced an average evaporation rate of only 0.008" per hour. When we compare the two evaporation rates (0.04"/hr versus 0.008"/hr), do the math yourself. The rate during peak evaporation was 5x greater than the other hours.

Therefore, my preliminary conclusion is watering the lawn is not beneficial to the root system during the middle of the day as much is evaporated. In addition, disease generation is promoted. I'm not the only one suggesting this, but 'professionals' will tell you that watering the lawn early in the morning is more beneficial as the ground can soak up the water more efficiently with a less likely introduction of disease that can actually harm the lawn.

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Briefly, switching gears, I looked at the U.S. Drought Monitor report due this morning....

Kentucky still does not show any drought, or even abnormal dryness (which I was expecting for a couple of counties in northwest Kentucky).

MS