While Rich is enjoying the weather and allure of the Rocky Mountains this week, I have sought refuge from today’s predicted 95° heat index. This post (from an air-conditioned Wi-Fi hot spot in Chatfield, MN) is a brief accounting of the flow regime in the South Branch of the Root River over the past few weeks.
The National Weather Service (NOAA) has assured us that the frequency and intensity of thunderstorm events will increase as global temperatures rise. Calling these “mega-precipitation” events, we have observed several of these storms across Minnesota and Wisconsin during the summer of 2016. Localized flooding has occurred throughout the Driftless Area in watersheds from the Upper Iowa River, north to the St. Croix in Minnesota and Wisconsin.
In the Root River watershed, the flow regime strongly reflects the almost weekly thunderstorm events (see graph) with discharge increasing within 24 hours of the precipitation, and abating to fishable levels (less than 300 cfs) in 3-4 days. The good news is that smaller streams whose watersheds happen to dodge the thunderstorms (or, vice versa) have been flowing clear even when the Root and Whitewater Rivers are unfishable. Hydrographs of the March to mid-July period, and a discussion of the precipitation spike on May 19 are available here.