The Flow Rates of Coldwater Spring changes over time.



The primary reason for this is rainfall.

Coldwater aquifer lies solely in the Decorah Shale and Platteville Limestone layer of rock, well above the water table at the river level. Due to this fact, it is fully dependant on rainfall to replenish it.

While it may seem alarming to say that Coldwater Spring has a reduced flow now, compared to say the year 2000, when shown against rainfall data, this makes sense, and is NORMAL.

The 55 yearly average rainfall in this area is 27.3 inches. Compare that over the last few years;

Because monitoring of the flow rate of Coldwater Spring didn’t happen until Highway construction neared in 1998, this period of higher than normal rainfall became the “baseline” data. 

During the redesign of the Highway 55/62 interchange, and the liner placed there specifically to protect the water flows to Coldwater, the Minnesota Department of Transportation agreed to use these figures. Not because it was the historical average, but because it was all that was known for actual figures, and the higher than normal rainfall and flow rates provided an added level of protection to the spring.

If the liner was based in higher than normal flows, then it’s slightly over built!

Consider that in October 2003 for example, Coldwater flowed at as little as 45 gallons per minute. In November 2012, it flows at about 60 gallons per minute (counting the same way as in 2003- both the springhouse and creeklet to the south, plus the seeps, which are unfortunatly no longer measured at all. The spring is measured by the NPS only at the springhouse. But if you go to Coldwater and place your hand over the springhouse outflow, note how much water flows from under the steps...this water flow, plus any other seeps that flow into the resivoir are NOT currently measured or recorded. While MnDOT measured the total outflow, NPS only measures the springhouse and creeklet outflow!). This is then further complicated by some rain events, such as in  May 2012 there was over 9 inches of rain, but the  months of July, August, and September 2012, only recieved 6.6 inches combined. Further, nearby lake levels (which are dammed to keep their levels up) also may play a role in keeping the water table at certin levels.

The hydrology of Coldwater goes well beyond the Hwy55/62 interchange and the liner there - designed to save 30% of the flow to Coldwater Spring.

The 30% figure is a reduction from potentially diverted water, not so much as a source of water.  Coldwater is a gravity fed spring where water simply flows downhill to the river.

The interchange is built physically lower than the outfall of Coldwater Spring.

Therefore, the drainage ditches had the potential to drain water away from the spring. That is where the 30% figure comes from- it could divert 30% of the flow from the spring outlet to the new lower drainage ditch.

So the liner under the 55/62 interchange isolated it from the water- so the water has to continue to flow out of it’s current location at Coldwater Spring.

Below is the section of the Hwy 55/62 interchange where the liner exists. It also details the main fractures that  provide the path of waterflows to Coldwater Spring;

HOWEVER, note that this pattern does not exist only at this area, but rather it flollows a much larger area. This is also evidenced by the fact that when the Watershed District placed dye at the SW Loop Pond, it took 16 days for the dye to move over to Coldwater Spring. When Dye was placed over the main fracture (in green on the drawing above) it showed up at the Spring in 90 minutes. The vast majority of water comes from the north! See the map below.  Also the ENTIRE area consists of the same general formations. The other springs, are not the only springs- shown springs are the other springs that are the approximate size of Coldwater Spring, or larger. (Cohen's spring for example, is considerably larger than Coldwater) The springs at Keewaydin field, and at Bloomington road do flow down storm sewers. The others flow openly. Th e spring at the old fish hatchery has public access just east of 86th st and Old Shakopee road.

Coldwater Spring has had major construction around it, altering not only the land, but the spring itself. Click here for further info!