The most effective rain water catchment is hands-down, the swale. Swales are trenches dug parallel to slope contour lines that act like water breaks in the landscape. They catch overland flow and re-infiltrate it into the soil. Reversing erosion, improving soil quality and soaking water deep into your landscape.
If you're getting a turf replacement rebate it's an easy sustainability feature with BIG benefits. All you need is a modest slope, a shovel and some wood chips.
Install plants on the down hill or berm-ed side of a swale.
Swales are highly effective at reversing erosion and capturing rain water in the landscape. They can be as short as 5' or as long as your entire property is wide! Typically you want to dig them approximately 1 foot wide and 1 foot deep. Again ensuring the bottom is nice and level or as near level as possible. So the water slows and spreads to the full width of the feature.
Swales are not a Stream. They Slow Down Water and Percolate it Deeper into your Landscape. Think of them like a skinny, temporary pond. That only forms when it rains.
The swale's role is more about infiltration and reducing flow than creating any. It is constructed with a relatively level bottom meaning it does not behave like a stream whatsoever but slows down any water that would otherwise be flowing over the surface of your slope. Collecting it long enough for the plants on its banks to soak up that collection and channeling any excess from extreme weather events to a more strategic point.
It's important to install a spillway for overflow instances in case of extreme weather events. This is a lip in the berm that is 1/2 to 2/3 the height of the berm itself, that will allow any excess water to overflow in a direction you're comfortable with it moving.
Swales are also a wonderful DIY feature for dispersing grey water into your landscape. Their flat bottoms slow and spread water quickly and effectively. Acting as absorption channels like those shown in the image above (ideal for laundry2landscapes grey water systems!)
Laundry to Landscape grey water systems are passive (no electricity) irrigation systems where your laundry water is used to irrigate your landscape. They require no permit to install in the state of California as long as they are within setback requirements from property lines and the water is distributed beneath 4-6" of mulch.
Swales need a Level Bottom to Work Properly
Swales need to be dug with level bottom or near level bottoms to allow water to accumulate. Then filled with either gravel or wood chip to a level surface that primarily stays dry and can also act as a pathway. The wood media or gravel mulch provide natural filtration of the water. At California Wild Gardens, we prefer filling swales with wood chip because it sponges up the moisture and composts over time, giving you a rich mulch to shovel out onto your garden beds and replace every 3-5 years.
Adding Mycelium is a Simple Way to Rapidly Build Soil in Your Garden Swale
You can inoculate your swale wood chip with mushroom mycelium too if you want to help it compost faster. Wine Cap or King strofaria is a great mushroom mycelium to inoculate with because its big, easy and delicious (if you like growing your own culinary mushrooms).
King strofaria are also beneficial partners for your garden plants - helping improve soil and nutrient cycles while fruiting in a symbiotic relationship. Fostering these fungal pathways is also central to natural soil improvement, helping cultivate resilient earth that delivers organic nutrients and moisture directly to plant root zones. Just order a bag of mycelium and spread anywhere there's woodchip. They'll fruit most reliably in spring and fall when there's available moisture and shade.