I was asked a question today about the Cape’s drought status. Ignoring the irony that questions of drought are usually asked on rainy days, I decided to look at the data before answering the question (I know, novel approach these days). What I learned was revealing and worrisome.
The water year, a measure of precipitation from October 1 through September 30, ended in deficit of just below four inches for the year on Cape Cod depending on exactly where you live. Four inches below average doesn’t seem like a big deal and not reflective of the drought conditions we heard a lot about that resulted in low pond levels, stressed local water supplies, outdoor watering restrictions and stressed plantings. And that is where the data becomes revealing.
Of the 12 months in the water year, precipitation was below long-term monthly averages in ten of those months. Even in the months where precipitation was moderate but below normal, much of the rain came in short, intense storms. What this means is that we had extended dry periods that were interrupted by intense storms that put a lot of water on the ground.
If you are still reading you may be thinking, so what? Well, here are some of the issues. Low precipitation in the winter and spring means that the groundwater that provides base flows to our streams and determines the level of our ponds is lower and will be low for much of the rest of the year. Why? Because recharge happens mostly before the trees leaf out. Once the growing season begins, recharge largely stops so dry winters and springs have a long influence over the remainder of the year.
Long dry periods stress plants and cause the soil to harden and shed a greater amount of the water that falls than normal ,resulting in high rates of runoff and lower absorption. The runoff transports sediment, fertilizers and pesticides to nearby waterways and damages those resources. Long dry periods lower streamflow and make the water warmer and less hospitable to fish, and can strand herring migration in and out of ponds.
There are other effects and repercussions that are more subtle and hard to observe, but this all begs the question if this year is an aberration or reflective of a new normal. Partly, we will have to wait and see, but this year reflects a lot of what we have been told to expect from climate change. While that is alarming by itself, the whole exercise has reminded me to look beneath the headlines to see what is really happening and to use that information to inform my own behavior. Lower water tables from changing precipitation patterns increases the importance of water conservation and moving away from thirsty lawns and replacing them with native landscaping practices described at APCC.org.