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By Bob Valen 

Let's hear it for evapotranspiration!

Weather Watcher


We just witnessed an event that is part of the Water Cycle on our home planet — snow melt. Though the quick disappearance of snow is not fully attributed to melt-off. There are other events going on as the snow gradually disappears. Yes, there were waterfalls on the Grand Coulee walls, lots of runoff water dumped into Banks Lake. Those waterfalls were a part, albeit a good part, of the snow disappearance. Let’s also take a look at evapotranspiration (e·vap·o·tran·spi·ra·tion), generally the sum of water evaporation and transpiration.

Here’s what’s going on when evapotranspiration occurs. According to the U.S. Geological Survey, water is “lost to the atmosphere from the ground surface, evaporation from the capillary fringe of the groundwater table, and the transpiration of groundwater by plants whose roots tap the capillary fringe of the groundwater table.”

Likely, only a small part of snow water cycling is via plant or tree transpiration. This process is not visible to us. Interesting fact: a large oak tree can transpire 40,000 gallons of water per year. Those sunny, warm days, coupled with a breeze or good wind, greatly helped with the evaporation of a good amount of snow and snow water.

The Water Cycle incorporates many things — storage in ice and snow, precipitation, snowmelt runoff to streams and lakes, infiltration, groundwater discharge, groundwater storage, water storage in oceans, evaporation, condensation, water storage in the atmosphere, evapotranspiration, surface runoff, streamflow, springs, freshwater storage and sublimation. Now you have some additional subjects to research further; enjoy!

Total snowfall for the Winter of 2018-19 as measured at the home weather station (note: I missed some measuring days) was 28.2 inches with a Snow Water Equivalency (SWE) of 2.81 inches. Our official weather station measured 11.6 inches. For February, we had 16.4 inches of snowfall, and the all-time record is 17.1, set back in 1959. Moses Mountain, as of this writing, has 31 inches from a seasonal high of 41.

Weather data for the month of March 2019 at the home weather station is as follows: a high temperature of 65.8˚F (record: 74˚F, 1942) on the 31st and a low of 0.3˚F (record: 0˚F, 1955) on the 3rd. Big spread in temperatures, I’d say! Snowfall was 4.2 inches (record: 9.8”, 1951) and total precipitation was 0.83 inches (record: 4.13, 2012) including Snow Water Equivalency (SWE).

A quote about spring from Edward Giobbi, American artist and cookbook author: “I think that no matter how old or infirm I may become, I will always plant a large garden in the spring. Who can resist the feelings of hope and joy that one gets from participating in nature’s rebirth?”


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