New year, new rain. It has been a wet start for California in 2019. Since the start of the year, several strong storms have hit the state, each bringing some serious amount of rainwater. As a result, the majority of the state is no longer in some dryness conditions it was in before. In the year’s first snow survey conducted on Jan 3, the snowpack water content was 67% of average; 4 weeks later, in the second survey conducted on Jan 31, it jumped to 125% thanks to all the storms. In a dry place like California, all these rains spell joy for everyone. With the memory of the last mega drought still fresh on everyone’s mind, it is natural to ask: how can we best deal with all this water? Just let it run away, or harvest it and reuse it, e.g., to build a rain landscape?
much storms Since begin of the year
Since the new year starts, storms kept coming to California. On 1/16, one of the strongest storms pounded northern California for 3 days, bringing in 1-5 inches of rain for many places. The city of San Jose received 1.36 inches.
Just 2 weeks later, another storm pummeled the area for 4 days, with San Jose receiving 1.9 inches. At this point , “Rainfall totals across Northern California continue to creep closer to average for this time of year. Through Sunday at 6 p.m., rainfall totals for the water year which began Oct. 1 include Redding at 21.24 inches (109 percent of normal), Santa Rosa at 19.23 inches (90 percent), San Francisco 12.22 inches (88 percent), Oakland 9.42 inches (81 percent) and San Jose 7.42 inches (87 percent).”
This time, the storm not only brought rain, but also snow to the peaks in the area. “A “very cold air mass” lowered snow levels to only about 1000 feet in the San Francisco bay area, having all the major peaks covered in snow on Feb 5 morning. Last time this happened was 1976. Here, you can see Mt. Umumhum in the Santa Cruz Mountain range covered in snow.
For most of us, while we enjoy the rains, sometimes it can also spell some inconveniences. Some roofs might leak. Water pools under the downspout, which can be damaging for the base of the house. Roads full of water that makes driving hard.
Most of the infrastructures in place are indeed designed to send the rainwater out as soon as possible. Rainwater runoff flows down streets, into storm drains and then right out to the creek and ocean. However, is this the right thing to do?
Rain Water is Critical for Water Supply and the Environment
Rain water is basically clean water that falls right on every household’s roof. Many times, it is not just a trivial amount – can be quite a bit. For a house in San Jose with a roof of 1000 sq ft, the 1.9 inches of rain that it received in last storm translates to 1184 gallons of water. If we use the state’s average water use of 63 gallons per person per day, the water is enough for a person’s use of 19 days. with just one storm’s water on one roof.
If we use the 7.42 inches that San Jose has received since the beginning of the water year (10/1/2018), then the roof has received 4625 gallons, enough for 73 days or about 2 and a half month’s use.
As we can see in the photo above, this much water just went down the drain and was gone. If we add all the roofs’ rainwater together, for the whole city, and the area, the amount of rainwater that goes out this way is a gigantic number. What impact does it have on the environment when so much rain water goes away instantly?
Loss of fresh water
Rain water is fresh water delivered to every household without any transportation. The water can be used for irrigation, or other daily needs if properly treated and meeting certain hygiene standard. In comparison, a big part of the city water we use is delivered to us over mountains, plains and across hundreds of miles, or even longer. A big chunk of tap water in the coastal cities comes from Sierra Navada range in the east of the state. By turning the rainwater away instantly, we lose much water that can otherwise be used. California is a dry place, such a loss of water is a waste we can not afford.
Depletion of underground water
Groundwater is an important source of our water. “Groundwater provides the largest source of usable water storage in the United States, and California annually withdraws the largest amount of groundwater of all the states.” (Wikipedia) In California, “On average, underground aquifers provide nearly 40% of the water used by California’s farms and cities, and significantly more in dry years.” We depend on the ground water for our water supply; unfortunately, due to heavy pumping, some water basins have been “critically overdrafted.”
“Groundwater supplies are replenished, or recharged, by rain and snow melt that seeps down into the cracks and crevices beneath the land’s surface. ” In cities, with the prevalence of impervious surfaces such as rooftops and driveways, rainwater runs off, instead of falling on the soil underneath those surfaces, depriving the soil the recharging.
Just last week, it was reported that due to the overpumping during the historic drought from 2012-2016, a California town sank over 2 feet in 9 years. If we want to secure a future with stable water supply, it is of utmost importance that we recharge the groundwater now.
Pollution to Waterway
As it flows through the surface of the city, stormwater runoff collects all kinds of pollutants such as motor oil, gas, chemicals, fertilizers, pesticides, etc. As the stormwater is discharged into the waterways untreated, the toxic substances can pollute the water and harm birds, fishes and other aquatic life that live there.
Risk of flash flood, mudslide and erosion
During storms, a large amount of stormwater can gather and join force, flow down slopes, fill freeways and roads, and flood lower places. Here, after the storm on Jan 16, a city was working to take water out from its storm water system to prevent flooding.
In the same storm, after heavy rains hit the Santa Cruz mountain area, a mudslide happened on southbound highway 17, forcing the closure of all lanes. In southern California, evacuation orders were issued to communities in LA County and Santa Barbary country for the high risk of flash flood.
2 years ago in May 17, a debris slide at the Monterrey section of Pacific Coast Highway (highway 1) was so massive that it forced the highway to close for more than 1 year, before it finally reopened in June 18. Pacific Coast Highway (PCH) is world famous with its majestic views for the pacific ocean. The long closure had a pretty big impact on the area’s tourism. Here, the Bixby bridge could not be crossed through for a year due to the PCH’s closure.
Harvesting Rain with a Rain Garden
As the rain water is so critical for us, for our water supply and environment, we should harvest it for a good use, instead of letting it runaway.
There are several ways to harvest rainwater. One is to install rain barrels or cistern. The rainwater can be collected and stored in the barrels or cisterns; which can be taken out for irrigation later.
Another way is to build a rain garden. As EPA defines it: “A rain garden is a depressed area in the landscape that collects rain water from a roof, driveway or street and allows it to soak into the ground. Planted with grasses and flowering perennials, rain gardens can be a cost effective and beautiful way to reduce runoff from your property. Rain gardens can also help filter out pollutants in runoff and provide food and shelter for butterflies, song birds and other wildlife.”
Here we are going to use 2 rain gardens that were just finished to illustrate how they were built. When the owners first planned a garden project for their house, they just wanted to build some veggie beds in the backyard so they could grow veggies. However, at the site review, after everyone looked at where the downspouts were and how the rainwater was sent and not used, it became clear that these were good opportunities to capture the rainwater with rain landscapes.
How to build a rain garden
While rain gardens have different looks and shapes and may serve slightly different functions depending on the locations they are in, some basic steps to make them are pretty much the same. Here are the major steps in building a rain garden for a residential house.
First, Find out where the downspout is and where the water flows to, and identify a good location for the rain garden. The soil at the location should absorb water well. If not sure, take a water test: dig a hole of 6 inches, fill in water to full, then see how long it takes for the water to soak down. If it takes more than 12 hours, consider another location.
In the front, the downspout is located right next to the yard. While all the rainwater would go into soil, which was good, it could be further diverted out and flow to a rain garden, allowing soil soaking for a bigger area.
Second, outline the water channel and the rain garden. It can be a circle, an oval, a peanut, or a kidney – shapes of curvy lines. Here is the outline for the rain garden in the front yard.
Lastly, install the rain garden. Dig out the depression along the shape defined, add a layer of soil that is comprised of compost and coarse sand, then put in plants which are rain garden appropriate – can stand both wet and dry conditions well. After all is done, for a nice touch, add some pebbles on top, which help filter out debris in the rainwater, and give the garden a nice look.
Around rain garden, some more plants were added. Most were California native plants. There are several big advantages for planting native versus non-native.. First, it saves water. Native plants only need a fraction of water compared with non-natives after they are established; second, as the native plants have been the food for local insects and pollinators, they provide a far stronger support for the local eco system.
Along the edge, a row of lavenders were planted, adding much charm to the garden. Here is the old front yard, and the new yard with the rain landscape:
In the backyard, a downspout pointed right at the drainage so the rainwater was lost right a away. In the project, a pipe was connected and the water was piped out to a corner away from the house, where it can soak down to the soil.
In this blog post the process is explained in more detail.
You can also take a look at this video.
Rain gardens Examples
Here is another example for rain garden. The downspout comes down to the front yard, with all the rainwater soaking the small area close to the house. After the rain garden was built, water was diverted to this depression, making a nice rain landscape.
This is another project with a rain garden. There are two downspouts one each side. Before the rain garden was built, rainwater just soaked the area or flew down driveway. After the garden, both downspouts’ rain water are captured and diverted further. This was how the garden was built:
With all the storms this year, the garden comes out to look great. This is how it looks after a strong storm:
Santa Clara Water District Rain Harvesting Rebate Program
From 2019, Santa Clara Water District started a “Rainwater Capture Rebate Program“, adding to the original “Landscape Conversion Rebate Program”. On its website, the district says:
“We are pleased to announce our new Rainwater Capture Rebates starting January 1, 2019! Rainwater capture, also know as rainwater harvesting, can be used as an alternative water source, reducing demands on our treated water supply and replenishing our underground aquifers. Keeping rainwater onsite also serves an important role in reducing stormwater runoff that can lead to erosion, flooding, and pollution of our creeks and streams. Through our Landscape Rebate Program online application process, residents and business owners can apply to:
- Receive a rebate up to $35 per qualifying rain barrel installed to collect rainwater from existing downspouts,
- Receive a rebate of $0.50 per gallon for diverting existing downspouts to qualifying cisterns, and
- Receive a rebate of $1 per square foot of roof area diverted (up to $300 per site) into an installed rain garden to collect roof water runoff.
Projects that have been started or projects that have already been completed prior to application approval are not eligible.”
In summary, rainwater is a resource too valuable to lose. We should harvest as much of it as we can. Install a rain barrel, or build a rain garden: it will go a long way to saving water, protecting our environment, as well as giving you beautiful landscapes right around your home.