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Weather modification’s effect studied downstream

by Wyoming Livestock Roundup

Laramie – While the Wyoming Water Development Commission’s ongoing weather modification project continues, the University of Wyoming’s Glenn Tootle has begun a project to enhance predictions of the modifications’ effect on streamflow.
    “Streamflow is strongly driven by the amount of snowfall in the mountains, so if we can improve forecasting from snowpack we can show how current weather modifications will result in increased streamflow down below,” explains Tootle, a civil engineering assistant professor at UW.
    In addition, the project is working on long lead-time forecasting, which looks at climate signals three to nine months ahead, versus the current zero- to three-month forecasting.
    Tootle and his team rely on current stream gauge instrumentation from the U.S. Geological Survey and the WWDC, but this year marks the third and final of current funding and Tootle says the final step is to develop a physical model of the North Platte.
    “In the physical model we could enter in how much more snow we’re getting as a result of weather modification, and we could see how much the model says we’ll get in additional streamflow as a result,” he says.
    “Ultimately the stakeholders are interested in how much more water they’re getting from weather modification,” says Tootle, calling himself the “bottom line” person. “If the weather modification folks come to me and say they’ve increased snowpack from 16 to 18 inches, I’ll be able to tell them how much more streamflow they’ll see as a result.”
    Weather modification project lead Barry Lawrence of the WWDC says with weather modification they’re looking for 10 to 15 percent additional snowpack in the mountains. “We want to be able to translate that into additional streamflow in the basin, then we need to enter project costs and figure out how much we’re paying per additional acre-foot of water at the bottom line – that’s a critical piece of the project,” he says.
    “Better forecasts will create less risk for water managers, and hopefully the Natural Resources Conservation Service (NRCS) and the National Weather Service (NWS) will incorporate our methods,” says lead Graduate Research Assistant Cody Moser, who works on the project with fellow lead Graduate Research Assistant Ty Soukup.
    Moser hopes the NRCS and NWS will incorporate the antecedent soil moisture and climate methods after their research papers are published.
    “We’re working to give water managers and planners a quantitative measurement of how much more water they’ll get from weather modification,” he says. “It’s a good educated guess, and it’s as good as we can do with the uncertainties we have.”
    “My scientists are looking at increasing snowpack levels, but we want the next link in the chain and what that means for additional flow in the North Platte,” says Lawrence.
    “This project has a lot of implications for Wyoming, because our stakeholders are asking for proof of additional snowpack due to weather modification, and what that will provide in runoff,” notes Lawrence. “Hopefully this project can answer those questions, because a lot of programs stop with the measurement of snowpack.”
    Two challenges to the research have been its dependence on history repeating itself and land use changes. “Forecast models rely on the principle that history, or the climate, repeats itself,” says Moser. “However, with climate change the models may create a forecast based on previous climate norms.” He says the forecast models also don’t take into account land development or the amount of cover on the land, which creates different watershed characteristics.
    Tootle hopes in the next few years the project will move from forecasting into physical representation of the North Platte area. A map of the North Platte would contain grid cells representing land area. “We’d be able to specify grid cells in the mountains with increased snowpack and then run the model to find the resulting increase in cubic feet of water at Pathfinder Dam,” explains Tootle.
    General circulation models (GCM’s) showing precipitation and temperature estimates for the rest of the century have become associated with the study of climate change around the world, and Tootle is interested in applying them to Wyoming.
    “We could take our North Platte model and combine it with information from the GCM’s to forecast what the North Platte will look like for the next 50 years,” he says. “The question becomes, will weather modification ‘off-set’ the impacts of climate change? That’s the next big focus.”
    Tootle’s work will continue to focus on sustainable engineering as it relates to water resources sustainability, working on the question of what can be done to counteract what’s happening with the climate.
    The research proposal was accepted and funded by the University of Wyoming Water Research Program (located on the UW campus in the College of Engineering and Applied Science), which works directly with the WWDC.
    “The most important result from our research is increased forecast accuracy compared to current forecasting methods,” says Moser. “The objective of streamflow forecasting is creating the most accurate streamflow forecasts.”
    Christy Hemken is assistant editor of the Wyoming Livestock Roundup and can be reached at

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