A reality based independent journal of observation & analysis, serving the Flathead Valley & Montana since 2006. © James Conner.

12 June 2015

How dry it is

This has been a Dust Bowl week, hot, windy, and almost frighteningly dry. A good week for photovoltaics and wind turbines, but a brutal week for lawns, gardens, and farms. My patio flowerpots needed drinks twice a day, and the dirt in a flowerbed on the west side of my house became hard as stone only a few hours after being watered. Today is cooler, but may be the windiest day of the week; the wind is freshening as I write this.

One measure of drought is the streamflow in rivers that are not dammed. In the Flathead, the North and Middle Forks of the Flathead River, are free-flowing. The sum of their flows is a good indicator of how much surface water is available. Below, I’ve plotted the combined flows for 2015, and the drought year of 2001, over the median for the last 75 years. Severe droughts also occurred in 1977, 1944, and 1941 (and before).

The breaks in the 2015 hydrograph are due to missing values for the North Fork. Usually, the culprit is ice. After the water year is completed, the USGS reconstructs the missing data for the published record. The median in the graph was smoothed using a seven-day window.