Minnesotans are paying increasing attention to the potential that climate change could have on everything from asthma and allergies to lake temperatures to crop production.
The latest effort to generate that conversation came Sunday night when the Minnesota Department of Health and Twin Cities Public Television combined to produce “Health and Climate,” a documentary encouraging better understanding of what a changing climate might mean.
One topic not touched on by the film was groundwater, something that could be dramatically affected by climate change. Three-quarters of the state gets its drinking water from wells and how much we can take without taking too much depends on how fast precipitation recharges the water underground.
And the speed of recharging can vary dramatically, depending on how much, how hard and when rain falls, according to the ninth installment in our groundwater Q&A series.
FROM THE PUBLIC INTEREST NETWORK: What impact will climate change have on groundwater?
For the past seven years, I have been leading the team that has developed the three-dimensional groundwater flow model of the Twin Cities metro area (as a consultant for Met Council), upon which most of the current planning is based. As part of that project, we developed a model of groundwater recharge for the period 1995-2010 for the metro area. What we are finding is that precipitation patterns seem to be more focused in local areas (i.e. do not cover the entire metro area as much as in the early parts of the simulations) and precipitation tends to be more in the growing season.
This has several ramifications. (1) more high intensity storms cause the formation of a “boundary effect” at the ground surface, which promotes more runoff and less infiltration (2) precipitation in the growing season is mostly used by plants and does not migrate below the root zone and become recharge and (3) regional precipitation values may not be useful indicators of how a particular community is fairing with regard to recharge. Most importantly, skewing precipitation from the Feb – April period to the June, July, August period means that less recharge is occurring for the same amount of annual precipitation. Nearly all of the metro areas groundwater recharge occurs in March, April, and May – that water reaches the water table in June, July and August. But if there is less precipitation in March, April, and May, we may have similar annual rates as years past but less recharge.
Recently, we used the metro model to perform some 100-year future simulations, based on a well-recognized climate model. Simulating one scenario of temperature and precipitation predictions, we predicted groundwater level reductions in groundwater recharge over the metro area of between 1 and 3 inches per year (compared to the current annual rate of 7 inches per year). During this period, precipitation is predicted to actually increase but an average temperature increase of about 8 degrees F causes longer growing seasons and more evapotranspiration, resulting in less total recharge to the groundwater system.
So, if you believe in such things as climate change, impacts to future groundwater supplies could be very dramatic. What is happening with White Bear Lake (which I do believe is the result of increased groundwater use in that part of the Twin Cities) will be nothing compared to what we will experience if climate changes as some predict. Therefore, it will be even more important to begin to think about how to augment groundwater storage with flood water.