After years of dry winters, 2015/16 wasn’t bad. But nothing like this winter. In almost all of California, we receive the overwhelming majority of our annual precipitation in the winter months of December and January, with good amounts still possible in February.
This year’s above-average amounts so far, combined with saturated soils and warm storms that melt snow and send it downstream to join the rain, means that many of us have standing and running water on our properties. Moving water increases erosion, meaning topsoil leaves the property. Not the best thing for our landscapes and infrastructure like driveways, structures and underground utilities.
So, how can we at least slow the movement of water, keep our topsoil in place, and provide benefit to our landscapes?
Creating swales, catch basins, raingardens and bioswales is something that every property owner can do. Large catch basins are often called ponds in the country. They are often temporary, seasonal water storage systems. A catch basin may be as small as a few feet in diameter. It depends on your property and how much water you need or want to temporarily store on-site. Don’t line the catch basin with dolomite or plastic. The point is for water to stop moving long enough for it to percolate between storms. You can line your catch basin with rock to improve the appearance and make maintenance easier. Catch basins, even small ones, can be used by wildlife, increasing habitat. Habitat loss is the number one cause of species loss, so it’s nice to be able to do some things to try to mitigate the loss from our general tendency towards urbanization. We’ve lost the great Tulare Lake, but we can create thousands of mini lakes and streams that can help return our valley to the seasonal wetlands that helped attract people here in the first place.
Add plants around and in the catch basin and you have created a rain garden. Rain garden plants are those that don’t require a lot (if any) irrigation during the summer. So don’t plant turf or hybrid tea roses. Instead, look for great California plants like native sedge (Carex), California fuscia (Epilobium), purple needle grass (Nassella purpurea), rush (Juncus), deer grass (Muhlenbergia rigens), California wild grape (Vitis californica), mule fat (Baccharis salicifolia), native iris (Iris douglasii or ‘Pacific Coast Hybird’), creeping rye (Elymus triticoides) and yarrow (Achillea millefolium.) Higher up you can plant with any other native tree, shrub or perennial.
Water that percolates underground will also move horizontally and may find storage pockets deep down that the plants can use long into the spring or even summer.
A swale is similar to a catch basin, but is usually more of a ditch shape and often is used to slowly move water away from structures or to a catch basin or pond. French drains can be a type of swale, by removing soil and replacing it with rock, usually to a depth of several feet below grade. Planted up, a swale becomes a “bioswale.” You can make it look like a seasonal seep or creek with boulders, rocks and native plants.
California rose (Rosa californica), native current (Ribes spp), or any of the plants listed above can be used. Bioswales and rain gardens help purify groundwater since the plants act as a filter. So even water that makes if off your property and to the river is better quality for both wildlife and water users. If you have a well, this can also benefit your household water.
Don’t get rid of that storm water, at least not all of it. Keep what you can onsite with these landscape features. Water, even in a wet year, is a precious resource.