This past week, mother nature delivered some much needed precipitation to the Central Arizona Highlands. The parched earth got a much needed drink of water and we enjoyed cooler temperatures, dramatic skies, and rare humidity.
On Friday, July 13, we wandered around the watershed to watch how it shed water. And boy did it shed! See photos of our observations in this image gallery. Impervious cover – hard surfaces like roads, driveways, and roofs – prevent the rain from soaking into the ground where it would be naturally filtered, stored, and slowly released as stream flow.
The image above shows what happens as a watershed is urbanized and natural ground cover is replaced with impervious surfaces. The rain becomes stormwater runoff and is diverted to the nearest water body, increasing flows and flooding, eroding soils, and carrying pollutants like nutrients and bacteria into our creeks and lakes.
Much of the Upper Granite Creek Watershed is developed; it is also a topographically diverse area. Stormwater that runs down our steep slopes picks up velocity and, in turn, carries a greater load of sediment and pollutants with it. You can see this during the storm in the form of turbid (murky) stormwater and after, as sediment and pebbles are deposited on roadways.
While there is a myriad of pollution sources in the watershed, stormwater is the greatest threat to water quality because it can pick up and carry those pollutants great distances, discharged directly into our creeks and lakes. The precipitation events that this monsoon has delivered thus far provide further evidence that stormwater Best Management Practices (BMPs) are needed in our watershed. The Watershed Improvement Council is currently in the process of recommending BMPs, many of which encourage the following basic priniciples: minimize impervious areas, slow stormwater, reduce pollution sources, establish protected areas, and integrate these priniciples into municipal operations and ordinances.
You can do you part to prevent stormwater runoff from your property by collecting your roof runoff in rain barrel or drain your downspouts drain to a depressed vegetated area. Minimizing impervious surfaces around your home or creating vegetated areas around impervious surfaces will allow natural ground cover to do its job of infiltrating and filtering rain. You can find more information about employing these practices around your home and neighborhood.