Next few weeks critical for how soil conditions affect spring runoff
The Jamestown area has not seen much precipitation the last couple of months.
JAMESTOWN – The next few weeks will be critical for how soil conditions will affect spring runoff and the next growing season, according to Allen Schlag, hydrologist with the National Weather Service in Bismarck.
“We are still about four weeks away from having low enough temperatures to really lock our soils up,” he said.
The Jamestown area has not seen much precipitation in the last couple of months. Jamestown received a little more than half inch of precipitation in September and about a quarter inch in October, according to measurements taken at the North Dakota State Hospital. Normal precipitation is about 2.25 inches in September and 1.9 inches in October.
Schlag said the amount of moisture in the ground has a large effect on how water behaves the next spring.
“We are quickly approaching the winter season and meteorologic winter around here is roughly December through at least the end of February, but when we start talking about the winter season, one of the key components of that is that our soil temperatures drop to below freezing,” he said. “So when we have wet soils, the freezing of those soils makes the ground impermeable.”
He said any water that hits the wet soils that have frozen will run off.
The temperature of dry soil will eventually drop below freezing but since it doesn’t have lots of moisture content, it will be permeable, Schlag said.
“Next spring when we have our initial snowmelt there that happens in our historically normal time of the year, roughly mid-March into early April, those soils will still take a fair amount of moisture in,” he said.
Normally, soils start freezing around the end of November to early December, he said. He said that’s the timeframe when soils freeze at greater depths than just a few inches.
The National Oceanic and Atmospheric Administration’s winter outlook is calling for a little chance of a colder winter in North Dakota, Schlag said.
“They really got us for most of the meteorologic winter in equal chances — that means they don’t have a strong inclination as to whether it’s going to be above normal, near normal or below normal — but there is a La Nina in place,” he said. “La Ninas have a distinct tendency to cool us or keep us colder than normal through much of the winter.”
Because temperatures are expected to be a little lower this winter, there won’t be nearly as many warm snaps as before during the winter, which means there will be more moisture on the ground in the form of snow and ice because it hasn’t melted during the winter, he said.
Schlag said sublimation will still happen. Sublimation is when water goes from a solid form, skips the liquid phase and goes straight into the atmosphere, he said.
“We still see sublimation all throughout the winter but those warm periods where we have a tendency to melt our snowpack, they are pretty important because that’s moisture that just won’t be available a lot of times come spring for runoff or infiltration into the soil,” he said.
Schlag said most of the state will be looking at average amounts of snow.
“One of the interesting things about this winter outlook even though we have it being cooler than normal pretty much for the entire winter and again going into early next spring, it’s next spring where the La Ninas have a tendency to give us a little bit of extra moisture,” he said.
He said there were two large blizzards in April when the snow had heavy water content.
“That is a very typical kind of La Nina spring where we get a couple of very large rain and/or snow events in that critical early melt season,” he said. “This year it came after we had melted off most of our snow already and our soils had already thawed and so we dumped 2 feet of snow on large areas where the ground underneath them was thawed and then we slowly melted that snow off and all of the water went into the ground.”