Climatologist Explains Use of Soil Moisture for State-Level Drought Monitoring | Harvests
In a recent webinar on the practical applications of soil moisture information, South Dakota State climatologist Laura Edwards described how her office uses information about soil moisture levels. soil to monitor drought levels in the state.
This second webinar in the series was hosted by the National Integrated Drought Information System and the National Weather Service and was sponsored by the National Coordinated Soil Moisture Monitoring Network, a multi-agency initiative led by NIDIS to provide an information system National Coordinated High Quality Soil Moisture Report. to support the public good. One of the goals of the series is to raise awareness of soil moisture as a key hydrological indicator.
“I kind of cover everything from floods to droughts and everything in between,” Edwards said.
Last year in eastern South Dakota, according to Edwards, the only green vegetation that showed up was kochia, but “we’ve had a tremendous recovery in that part of the state.”
“But that doesn’t mean we’re off the hook yet,” she said. “And so we continue to monitor drought conditions really year-round around South Dakota.”
It might sound a bit funny to think that a northern climate with snowfall would experience drought during the winter months. But it happens.
“You think the drought might not matter, but it really does,” she said. “Still even in our economy, in our landscape that is so agriculturally driven, even winter drought can make a difference.”
For Edwards, she examines a handful of indicators as they relate to drought monitoring. She starts with the US Drought Monitor, which she checks weekly.
“We monitor this more when we’re in drier drought conditions, but we monitor this all year round,” she said. “And I have a group of people that I work with every week to come up with some sort of consensus recommendation for South Dakota.”
They check different indicators in a few climatic zones in all seasons. This can be difficult to coordinate as there are three National Weather Service offices that cover South Dakota, as well as the state geologist, state fire meteorologist, as well as human rights personnel. state water to the state Department of Agriculture and Natural Resources, but through them. she is able to keep an eye on things.
“So one of the things also about monitoring drought conditions is that we actually got through the side incident in South Dakota in which myself and the state fire department meteorologists are helping to notify the governor’s office each spring of drought conditions,” she said.
Edwards has already started having these communications with the South Dakota Drought Task Force. Usually on or around May 1, they announce whether the task force should be activated or not.
Edwards also works at South Dakota State University Extension, primarily in agriculture, including crops, livestock, and natural resource management. They communicate all year round depending on the season regarding the impacts.
She also collaborates with the US Department of Agriculture and their offices within the state, and regional efforts with climate centers.
Soil moisture is becoming an area of growing importance to Edwards due to the increased amount of data available as well as soil moisture measurements. In South Dakota, the soils are quite diverse, Edwards said. The east side was glacial, while the west was not.
“We have very different soils west of the Missouri River and east of the Missouri River,” she said. “We see some differences in soil moisture and soil response to precipitation in eastern and western landscapes with the different soil types.”
Edwards feels that at the state level, she has an advantage when she can drill down into data when monitoring drought. One of the tools she uses for this is the South Dakota Mesonet which is operated by SDSU. Currently, it is a network of nearly 40 stations.
“They’re in a big period of growth right now where there will be over 150 stations statewide covering almost the entire state here in about five years,” she said. “So in a fairly short time, we’re going to know a lot more about soil moisture, temperature, weather variables, above ground and below ground at a scale of about 25 miles.”
Many residents will be within 25 miles of a mesonet weather station by the time the upgrade is performed. Each will have most of the standard weather variables – wind speed and direction, air temperature, pressure and precipitation.
Other instruments contribute to the understanding of the water balance around the state, in addition to solar radiation, temperature and soil moisture. With this information, the entire water balance can be measured.
“We have this at five different depths, which becomes really, really important,” Edwards said.
There is generally very little change in soil moisture during the winter season when the soils are frozen.
“It often gives us a good picture of our starting points in the spring when we’re in thaw season like we are now,” she said. “Unfortunately, we don’t yet have a record long enough to determine normal, so we’re looking more for incremental week-to-week or month-to-month differences and comparing individual dates within archives to find out which diapers are drying or wetting and that sort of thing.
Overall, Edwards thinks the collection of tools they use for soil moisture, including models sent remotely from in situ data, all serve a purpose.
“These transitional seasons like spring and fall, we’re trying to better understand our soil’s response to precipitation and the snowmelt season,” she said. “This year, we had very little snow with it. So we haven’t tested that much this year, but it’s something we’re looking forward to.
There are great tools with the Mesonet, but Edwards has a wish list, including improved data visualization.
“Getting more differences between times — like say a month, a week, whatever to help inform the Drought Monitor,” she said. “Going beyond that volumetric water content, going towards something like water available to plants and other indicators, that’s where we like to go and we have soil samples.”
Eventually, the soil moisture measurement will be calibrated based on soil type, and Edwards is working with the USDA to do this.
“Which would even be just one step closer to allowing us to better understand our soils here in South Dakota,” she said. “I think we’ve come a very long way over the past few decades. We still have a few steps to go and I think the future is bright for us.