Helix Water District named Tim and Brianna Montgomery of La Mesa as the winner of its 2020 WaterSmart Landscape Contest, an annual competition that recognizes outstanding water-wise residential landscapes based on overall attractiveness, design, efficient irrigation and appropriate plant selection and maintenance.
When planning your landscape, look first at the terrain you’re working with. You can use the contours of your existing land – depressions and slopes – for guidance when planning your landscape grading. If your yard is flat, you’ll need to move soil and features around to create more rain-holding contour areas.
A soil percolation test can be very helpful in preparing your soil. You want to make it as much of a water-retaining sponge as possible before getting to work on rainwater capture plans.
NOTE: If you have existing hillsides, it’s best to get professional advice before grading or other significant changes. Before any digging, call Dig Alert 8-1-1 or visit digalert.org to be sure you won’t hit any underground utility lines.
Move water with gravity
Basins and swales are shallow depressions or channels no more than 24 inches deep on gently sloped or nearly flat landscapes. Basins and swales move water over short distances. With these contours, gravity will move water around to where you want it.
Small, shallow depressions work best in clay soil areas, while sandy soils may accommodate deeper depressions up to two feet. Channels can be planted or lined with rocks and small boulders to resemble natural creek beds.
Use rainwater to your advantage
By planning your landscape so that you don’t have low spots with no plants, you prevent wasting rainwater through runoff. You can also avoid fungus and rot from standing water. Plants in and around the depressions capture and sink small volumes of surface water so that all the rainwater you capture can be used.
Berms are mounds of raised soil, usually planted, that can border basins and swales or be used alone. They help contain and move water around, increasing the holding capacity of basins and swales.
Boulders can add points of interest and slow down water runoff in your landscaping. Boulders also are useful to retain small berms or the edges of swales.
The San Diego County Water Authority and its partners also offer other great resources for landscaping upgrades, including free WaterSmart classes at WaterSmartSD.org.
After a dry spell, the first rainfall is the most important water to capture for your landscape. This is called the “first flush.”
In arid regions like San Diego County, this happens every year because there is a long stretch of dry weather in between rainy seasons.
Why is the first rainfall so important?
It washes away pollutants that have collected since the last rain. This water needs to be filtered as much as possible by landscaping before it goes anywhere else. Usually the next stop for this water is storm drains that empty into oceans. So your landscape can be a very important tool in preventing the buildup of pollutants in local water supplies.
In addition, the first rain in the fall is very important for your plants. New or established plants will want to grow deep roots in the fall and winter, and the additional water is essential. Capturing the rain with your landscape reduces the need for increasing irrigation.
How much water comes off your roof?
Measure the size of your roof to determine how much water will come off it. The shape of your roof doesn’t matter in this instance. The same amount of water falls on the roof whether it is sloped or flat. You can measure a sloped roof either using an aerial view or from the ground without worrying about the slope itself. Just measure the outside edges the same way you would if it was flat and calculate the square footage.
Flat roofs covering a building in one contiguous shape are easier to measure. Some roofs are more complicated. You can divide this type of roof into individual squares or triangles. Then, measure each one at a time and add the figures together for your total roof area.
Calculate your potential water capture
Once you know the total roof area, you can determine the amount of rainfall it generates in gallons, then use the following formula to convert square feet to gallons.
Formula: Rainfall in Inches x Total Square Feet x 0.62 = Gallons of Rainwater from the Roof
Here’s an example using a 1,000 square foot roof: 1 inch of rain x 1000 x 0.62 = 620 gallons.
Even in a dry climate, this rainfall adds up to a lot of water runoff. It’s easy to see how important it is to save as much of this water as possible in a landscape designed to be a sponge instead of a brick. Take the watershed approach to designing your landscape, and you can use the first flush of rain to your advantage.
The San Diego County Water Authority and its partners also offer other resources for landscaping upgrades, including free WaterSmart classes at WaterSmartSD.org.