When it rains and all the raindrops fall on our roof, have you thought about where the rainwater go to? Well, most of it just go down the sewage, into the creek and river, and evertually out to the ocean. In the past, stormwater was viewed as a something akin to a waste, something we’d get rid of as soon as possible. Not any more. After the historic drought in the last 5 years, everyone realize how valuable water – in any soruce or form – is. When it comes to rainwater, in addtion to rain barrel, there is another great, more direct way to capture it and use it. Better yet, it can be turned into beauty in your garden.
When it rains, we enjoy hearing the sound of raindrops on our roof. After a drought of so long in California, those drops sound more like music to our ears. While enjoying the music, have you thought about where the stormwater goes to? Well, most of it just goes down the sewer, into the creeks and rivers, and eventually out to the ocean. What if that water is not sent away, but reused, such as, turned into beauty in your garden?
Storm water: waste or asset
In the past, stormwater has been treated as something akin to waste in cities, something that is collected and sent out to waterways in nature as soon possible. As people realize now, there are several issues of this. First, a big chunk of water is lost. Rainwater is freshwater that is basically clean in most circumstances. It falls right on our roof so no transportation is required to receive that water. However, in the current infrastructure, that much freshwater is sent right away. “Stormwater could be a significant addition to California’s water supply. Los Angeles estimates that rainfall could provide nearly half a million acre-feet (620 million cubic meters) per year. Steven Moore, a member of the State Water Resources Control Board, said, ‘Stormwater could make a difference, it could see us through seven years of drought instead of five.’” Another issue is pollution. 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. One more issue is the loss of deep water infiltration. As the water that falls on impervious surfaces such as roof and concrete is sent right away, water that would otherwise have gone into soil, percolated and recharged the ground water is lost. As you can see, in cities where impervious cover is common, runoff can be as high as 55%, versus 10% with natural ground cover. It has become clear that rainwater is not a waste, but an asset, a valuable resource of water supply, something that we should capture and reuse. While a common way to do so is using a rain barrel, there is another more direct way – build a rain garden.
What is a rain garden?
According to Wikipedia, “a rain garden is a planted depression or a hole that allows rainwater runoff from impervious urban areas, like roofs, driveways, walkways, parking lots, and compacted lawn areas, the opportunity to be absorbed. This reduces rain runoff by allowing stormwater to soak into the ground (as opposed to flowing into storm drains and surface waters which causes erosion, water pollution, flooding, and diminished groundwater).” “The purpose of a rain garden is to improve water quality in nearby bodies of water and to ensure that rainwater becomes available for plants as groundwater rather than being sent through stormwater drains straight out to sea. Rain gardens can cut down on the amount of pollution reaching creeks and streams by up to 30%.” So exactly what is a rain garden? To understand, we just need to turn our eyes to nature.
Imitate the nature
In spring time, when we go to a nature reserve or park, chances are we can see fields and fields of wild flowers. No one ever installs an irrigation system or waters these plants; they just live and keep turning out splendid blossom, year after year. How do they do it? The answer is, after tens of thousands years, the native plants have adapted to the environment. In California where it rains in winter and gets dry in summer, another area in the world that has Mediterranean climate, plants take in all the water they can get in winter, grow rapidly, and bloom in spring. When summer comes and it becomes dry, they slow their growth or simply go dormant. They stay this way until winter, when the rains come again. As the raindrops come down, they “wake up” from the dormancy, drink up all that water and start to grow and bloom again. They don’t need any additional watering; they just take all the water there is and live throughout a year. This is what plants in a rain garden will do. At a rain garden, the depression or ditch will collect the rainwater runoff from a roof. When it rains, water will be collected there. The plants in the garden will absorb the rain water, and grow; When the rain season ends, they can just live on their own. Very little or no additional watering is needed for these plants in most cases. Just like their brothers and sisters in the nature, they can live with just the rainwater. Compared with water supplied to each household, which is treated with chemicals to comply with the sanitary standards, guess which water the plants like better? Plants watered with rain water can usually grow faster, bigger, and have brighter blossom.
Designing a rain garden
Like so many lawns in California, Larry’s (not his real name) lawn turned brown during the historic drought. Though the drought ended and last winter was one of the wettest on record, the lawn did not come back . The brown lawn had been bothering Larry for a long time, but he was not sure what to do about it, until he heard that his lawn can be built into a beautiful garden; not just any new garden, but a rain garden! One of the downspouts (the one on the left) is right next to the front yard. When it rains, the rainwater will just flow into the garden. The lawn is on a very slight slope from the house to the sidewalk, so the runoff will go outwards naturally. If a shallow basin is built close to the side of sidewalk, the rainwater can reach there and be stored in it. That is exactly the design proposed to Larry. A small winding ditch will take the rainwater from downspout, and send it to this shallow basin. Some plants will be planted. After they absorb the rainwater in winter, they may only need a little watering in the remainder of the year, saving a remarkable amount of water. In addition, since the garden would meet all the requirements of Santa Clara Water District’s Landscape Conversion Rebates program, the garden can apply for the rebate. Larry liked the proposal. It was a “Go” for the rain garden!
Installing a rain garden
- First, the shape of the garden needs to be defined.
For the safety of the foundation, the rain garden should be some distance away. Usually it is advised that at least 10 feet of space should be left between the basin and the house.
- Next, the shape of the rain garden is outlined.
How big should the garden be? It depends on how much runoff the roof can produce, and design an area that can take much of that runoff. Suppose the area of the roof is 1000 square feet, with one inch of rain, it can produce about 600 gallons of runoff. If the rain garden is 1 foot deep, to absorb this much water, it needs an area of about 80 square feet. If the roof area is bigger, the rain garden should be larger too. What shape can a rain garden be? It can be of anything – a circle, a bean, or a peanut. The smooth, curvy lines of these shape not only look appealing, but also reduce the force of runoff and effect of erosion.
- Soil preparation
The bottom of a rain garden needs to be covered with a special type of soil, to help with water infiltration. It is a mixture of organic materials and coarse sand. The bottom of the whole area that water flows by and stays should be covered with the mix.
- Plant selection
Plants in a rain garden should be able to stand both conditions well: wet and dry. Their roots should be able to take moisture for a long time, yet also survive in hot dry summer. One plant that fits this very well is the Douglas Iris. A tough California native, it can be found close to beaches along the west coast. Hardy, drought tolerant, yet tolerant of wet soil, this is great choice for a rain garden.
The beauty of a rain garden
The garden is done! This is before and after The rain garden When it rains, with a garden like this, the rainwater will be captured, and reused. Something that was sent away before can be turned into so much beauty in our own garden!
When it rains and all the raindrops fall on our roofs, have you thought about where the stormwater go to? Well, most of it just goes down the sewer, into the creeks and rivers, and eventually out to the ocean.
Stormwater – a waste?
Stormwater has been treated as something akin to waste in cities, something that is collected and sent out as soon as possible. A complete infrastructure is in place to get this done: gutters and downspouts to collect rains that fall on the rooftops, drains and catchbasins to gather runoffs from downspouts, streets and parking lots, underground storm sewers will then convey all the runoffs and discharge them to a natural water system such as a creek, river and ocean. There are a couple issues with this. First, a big chunk of rainwater is lost to runoff. Rainwater is freshwater that is basically clean in most circumstances, which can be used directly for outdoor purposes, as well as indoor with proper filtering and cleaning. It falls right on our roof so no transportation is required to receive that water. However, in the current infrastructure, that much freshwater is sent right away, requiring another huge set of infrastructure to deliver the water we need. Another issue is pollution. 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 nature untreated, it pollutes the water system discharged into. Toxic substances from cars and pesticides can harm birds, fishes and other aquatic life. Nutrients from the fertilizers can cause the overgrowth of algae, depleting oxygen in waterways and aquatic habitats. The third issue is insufficient water infiltration for the soil under the impervious cover and in general. As we can see in the illustration below, in a natural environment (left), 25% of water is infiltrated in shallow surface, and another 25% will percolate deep into the soil. In a city environment (right), those figures drop down to 10% and 5% respectively, so the water that goes into soil reduces from 50% of total to a mere 15%, a 70% reduction. The lack of deep infiltration is a big problem. Without proper recharge, the groundwater is seriously depleted in many places. As we rely on ground water as part of our water supply, this has a big impact for our water safety. Lastly, waterway erosion and threat of flood. As a huge amount of water is gathered and discharged into waterway, the volume and speed it packs can erode the banks of the stream or river; when the volume is too heavy, it can flood surrounding areas.
Benefits of capturing and reusing rainwater
People’s thinking about rainwater has completely changed. Now, rain water is no longer thought as waste; instead, it is viewed as an asset, something we need to capture and reuse.
- A source of water supply
From 2013-2017, California experienced a historic drought. At its worst point, the water content in the snowpack was only 5% of normal. The drought was so severe, it was one of the worst in the state’s history. After the drought, everyone realized we could no longer take the water supply as we knew it for granted. With climate change, drought might become more frequent and serious; on another hand, with economic expansion and population growth, our demand for water will just grow. How can we build the reliable water supply that can meet our needs? “Stormwater could be a significant addition to California’s water supply. While the potential is still unknown in the Bay Area, Los Angeles estimates that rainfall could provide nearly half a million acre-feet (620 million cubic meters) per year, said Steven Moore, a member of the State Water Resources Control Board. This may sound trivial compared to the 33 million acre-feet people use statewide each year, but it’s not. “Stormwater could make a difference,” Moore said. “It could see us through seven years of drought instead of five.” From a cost perspective, local stormwater capture is one of the cheapest methods for water supply. It is only more costly than urban water conservation, but much cheaper than others like recycling and ocean water desalination.
- Reducing pollution and recharging groundwater
As the importance of rainwater is more thoroughly understood, people have been taking all kinds of steps to keep rainwater instead of letting it flow away. In the cities, permeable surfaces are replacing the impervious ones, and more and more rain gardens have been built, in the streets, around offices and in our gardens. When it rains, the rainwater can infiltrate the soil from the permeable surfaces and rain gardens. In the process, harmful pollutants in the water can be filtered out; the cleaned water can percolate deep in the soil, replenishing groundwater. Here is a storm drain at a street corner. The catch basin around it was built into a rain garden, allowing the rain water to sink into the soil.
- Reducing the threat of erosion and flood
Since water is directed away from the runoff, the total runoff volume will reduce, and the speed and energy that it packs up will lessen. As a result, the force to erode will be smaller, and threat of flood lower.
Building a rain garden
So if you want to build a rain garden now, where can you start? Check out this post “Turn Rain Into Beauty In Your Garden” for some information.
On Oct 6 2017, SB231 was signed into law in California, making it much easier to fund and build rainwater capture projects. The key is the clarification about whether stormwater projects are subject to the exemption of prop 218: Excerpts from SB231: The Legislature finds and declares all of the following: (a) The ongoing, historic drought has made clear that California must invest in a 21st century water management system capable of effectively meeting the economic, social, and environmental needs of the state. (b) Sufficient and reliable funding to pay for local water projects is necessary to improve the state’s water infrastructure. (c) Proposition 218 was approved by the voters at the November 5, 1996, statewide general election. Some court interpretations of the law have constrained important tools that local governments need to manage storm water and drainage runoff. (d) Storm waters are carried off in storm sewers, and careful management is necessary to ensure adequate state water supplies, especially during drought, and to reduce pollution. But a court decision has found storm water subject to the voter-approval provisions of Proposition 218 that apply to property-related fees, preventing many important projects from being built. …. (h) Proposition 218 exempts sewer and water services from the voter-approval requirement. Sewer and water services are commonly considered to have a broad reach, encompassing the provision of clean water and then addressing the conveyance and treatment of dirty water, whether that water is rendered unclean by coming into contact with sewage or by flowing over the built-out human environment and becoming urban runoff. … (l) The Legislature reaffirms and reiterates that the definition found in Section 230.5 of the Public Utilities Code is the definition of “sewer” or “sewer service” that should be used in the Proposition 218 Omnibus Implementation Act. With SB231, it is clear that rainwater capture projects do qualify for the Prop 218 exempts, making them much easier to fund and build. To summarize, facing the ever increasing demand for water and a future with possibly longer and more frequent drought, we now look at stormwater with a completely new perspective. Gone are the days when we think of it as a waste; instead we know it is a great asset, and will try to capture and reuse it in a way that will benefit us, and the environment the best.
As the leaves on the trees have started to turn yellow, we know that fall is here. Here in the Silicon Valley in California, quite some lawns are also brown. Though California’s historic drought already ended in spring, many people keep the habit of water conservation and continue to let the lawns go brown. While this shows we have all been doing our part to conserve water which we can be proud of, the lawn, well, can look a little bit nicer……here comes the good news: fall is a very good time to remove the lawn, plant water efficient plants and have a beautiful garden! Not only is the time great for plants, thanks to landscape conversion rebate programs such as the one offered by Santa Clara Water District, by doing it now, you may also receive some rebates.
Fall is one of the best times for planting
Fall is one of the best times in the year for planting. There are several reasons for this.
- Temperature. Very cold winter and very hot summer days can be harsh for young plants. Fall offers the optimal temperature.
- In time for the rainy season. After plants are placed in soil, to establish and grow in the new place, they need the soil to be wet enough so the roots can stabilize and grow. With California’s Mediterranean climate, the rainy season comes in winter and early spring. When planted in fall, the plants have the right amount of time to settle in the new environment, and take the full advantage of rains when they come in winter.
- Great for spring bloomers. A lot of plants bloom in spring. If they are planted in fall, by next spring some of them may grow enough to bloom. Blossom in spring – what a lovely view!
- Good for pollinators. Most of the plants in a water efficient garden can provide food for bees, butterflies and other pollinators, which are so important for us. However, their population have been on a decline. Bees need more plants that they can feed on. By growing plants in fall, come spring time bees will have much more places to go to have their meal.
Many beautiful plants to choose from
There are a large collection of plants that are both water efficient and beautiful. If the lawn is replaced with plants that are on the Qualifying Plant List of Santa Clara Water District Landscape Rebate Program, it is eligible to receive the rebate of $1 per square feet. Browse some of these water efficient plants here.
Planted in fall, bloom in spring
These two gardens were planted in last fall, after just a winter, they all grew phenomenally and bloomed in spring this year. Last winter was one of the wettest on record, which definitely helped. This California native garden was installed last October. How long did it take to bloom? Less than half year! And it lasted all the way through summer.
This garden was installed in late last fall. It also bloomed in early spring, just several months after the installation.
Conserve water, enjoy the garden
A beautiful garden is not only something you can enjoy everyday, but will also go a long way to conserve water. Although California’s drought already ended, as Gov. Jerry Brown said in a statement, “This drought emergency is over, but the next drought could be around the corner. Conservation must remain a way of life.” Outdoor watering for a lawn typically accounts for half or more of an household’s total water use; to convert a lawn to a water efficient garden, the water consumption for outdoor watering can be reduced by 30 to 60%, for total household 15 -40%. You may receive rebate by removing the lawn and putting in water efficient plants now ($1 per square feet if all requirements are met). Find out more about the Santa Clara Landscape Conversion Rebate Program here. Why wait? Now is the great time to plan and build that lovely water efficient garden! Find out more information at WaterEfficientGarden.com.