What state TMDL reports sweep under the carpet: rainfall increases

(“Warmup has cities rethinking waterways” article published by Star Tribune)

Communities across the metro area and beyond are putting their heads together to figure out how to handle the increases in storm water that a warmer climate is expected to bring.

Public works officials, hydrologists, water quality monitors and others have embarked on a study to find where vulnerabilities exist and devise new solutions in the face of increasing — and increasingly intense — rainfall that has been both documented and projected by climate analysts.

The work is funded in part by $300,000 from the National Oceanic and Atmospheric Administration and coordinated by the Minnehaha Creek Watershed District. It will continue into the summer of 2013.

…annual precipitation in parts of south central and southeast Minnesota has increased up to 15 percent in recent years; normal annual rainfall for the Twin Cities is 4.25 inches greater than it was in the 1980s. Statewide, Minnesota’s average rainfall topped 34 inches in 2011 for the first time in 121 years of record-keeping. The Upper Midwest saw a 31 percent increase in “intense” rainfalls — the statistical 1 percent events — from 1958 to 2007, over previous decades, according to the National Climactic Data Center. An increase in intense rainfall is regarded as one of the signature trends of a warming climate, due to warm air’s ability to hold more water.

Our Take:
It’s not just future increases–this Star Tribune article documents the incredible increase in precipitation Minnesota is already experiencing. Certain state agencies and special interests are so busy pointing the finger at farm drainage tile systems that they fail to mention the most significant source for increased volume and energy in our waterways (leading to greater stream bank erosion and cloudiness in the Mississippi River and Lake Pepin). 

It is raining more than in the recent past, and not just a smidgeon. The Cities have seen an increase of 4.25 inches in annual rainfall–at 34 inches average, that’s an increase of 14 percent since the 1980s. And multiply that by all the residential and commercial development in the seven county metro area–more than a third of its land area is now impermeable or semi-permeable–and so you’ve got an incredible increase in the volume of water racing into our rivers. Then there’s that pesky figure about the increased intensity of rainfalls–a third of our rainstorms are not just gentle, soaking rains, but the kind of rains that for instance dumped 6-inches plus of rain in a matter of hours in southwest Minnesota in early May.

Farmers want to work together with all stakeholders to solve our state’s water planning challenges. The next important step will be recognizing the significant change in our climate and what that means for plans to try to control what happens to rainwater.  Finger pointing and unrealistic expectations won’t get us where we want to go.

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