Sunday, February 22, 2009
I woke up this morning to a beautiful interplay of trees and fog. We are in the middle of a rain storm this weekend, bringing desperately needed rain to the California watershed. These days, although we have well-water from an aquifer shared with only 2 other families, we take water preservation and conservation very seriously.
As you can see from the photo (at right), we have fog and rain on this mountain. The trees are of the type which capture airborne moisture and turn it into fog drip and we typically receive a respectable number of drenching storms between November 1 and mid-April.
Swales are sculpted from the land, depressions where rain water can collect and then slowly be absorbed by the ground. The complementary structure to a swale is a berm, a raised lip of land around the swale that keeps the water exactly where desired. The only tool you need to construct a swale is a shovel, although large amounts of land are better worked using a backhoe. We have 3 - 5 acres (out of a forested 10) that we'll be working swales on. If you want to construct a swale, check if it is an unpermitted activity in your county. Building swales does not require a permit in San Mateo County.
An alternative to swales would be flat land that has built up a thick duff layer. Alongside our steep driveway, we have encouraged the duff to such an extent that water uphill will not show up downhill, being completely held and absorbed by the soil and duff. I don't know the word for this technique.
Desert Water Catchment Strategies, including Swales