Extreme highs and lows: Climate change and the Missouri River : Stltoday

Extreme highs and lows: Climate change and the Missouri River : Stltoday

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We know the Missouri has always gone up and down. But what is different about the river now is that it is jumping up higher and dropping down lower than ever before. We have had the highest monthly flow rate and the lowest September flow rate in recorded history in just the past 16 months. This is a very disturbing trend. It means the Missouri is becoming a wilder, less predictable, and more dangerous river. The Corps has long tried to keep the Missouri caged behind riprap. (By the way, the Corps loves rock. It believes nearly every hydrological problem can be solved with more rock). But this new, erratic river is going to increasingly defy the Corps’ efforts to not only manage it, but to contain it.

In April 2011, the Bureau of Reclamation released a report that examined the future effects of climate change on the Missouri’s hydrology. The Bureau concluded that increases in annual precipitation across the northern plains would result in a corresponding increase in the river’s mean annual runoff at Omaha of 9.7% by the 2050s and 12.6% by the 2070s. Remember, the mean is only an average. The river’s maximum runoff for any given year in the 2050s and 2070s could be far higher. Additionally, warmer temperatures in the winter months will cause a jump in the river’s wintertime discharge rates. Finally, the Bureau stated that the Missouri’s flow regime in the 21st century would be more haphazard, with greater oscillations in volume. The report stated, “… stream flow variability over the basin is expected to continue under climate change conditions … future hydro climate conditions may produce weekly acute runoff events.” The term “weekly acute runoff events” is a benign way of saying the Missouri is going to flood on short notice.