How to Harvest Rainwater and Build a Beautiful Landscape

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.

Snow on Mt Humuhum
Snow on Mt Umumhum in Santa Cruz mountain range

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.

water from downspout

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?

rainwater runoff

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 the water present beneath Earth‘s surface in soil pore spaces and in the fractures of rock formations. (Wikepedia)

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.

rainwater runoff on a road

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.

flood prevention

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.

Photo credit: Dave Lastovskiy

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.

front yard

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.

front yard rain garden

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.

front yard rain garden

front yard rain garden

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.

California native plant

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:

front yard 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.

backyard

 

backyard rain garden

 

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.

rain garden

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:

rain garden

With all the storms this year, the garden comes out to look great.  This is how it looks after a strong storm:

rain garden after rain

 

rain garden after rain

rain garden after rain

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.

 

 

 

 

How to Completely Change a Weedy Lawn

This weedy lawn had been bothering the homeowners for a long time.  It was a nice lawn when it was first put in, but needed to be maintained often.   As busy professionals, they really did not have the time.  On the other hand, they wanted to be friendly for the environment and have a small footprint.  The lawn, they felt, used too much water.  When they heard of Santa Clara Water District’s Landscape Conversion Program, that after a turf was converted to water efficient landscaping a rebate would be given to them, they felt the program was just for them.  They could ditch the lawn that took too much work  and used too much water, have brand new landscaping that would use much less, and receive money for doing all this.  They happily got on board.

weedy lawn

Outdoor Lawn Watering: Heavy Water Use

Lawns use a lot of water. According to Ben Erickson,  “While the amount of water needed will vary depending on your climate, the weather, and the time of year; the general rule of thumb is to make sure your lawn receives 1″ of water to your lawn per week during dry conditions.”  So, for a 1000 square feet of lawn, in every week of dry conditions it needs 623 gallons of water, or, 89 gallons a day!

water use for lawn

Imagine 89 gallon water jugs, that is how much water the lawns needs to drink every day.  According to USGS, “Each Californian uses an average of 181 GALLONS of water each day. ”  If we use the number (89 gallons) from the example above, outdoor water use accounts for almost 50% of the overall use.  That is very close to the actual case.  Per “STATE WATER RESOURCES CONTROL BOARD RESOLUTION NO. 2015-0032″, “In many areas, 50 percent or more of daily water use is for lawns and outdoor landscaping.”  In other words, half or more of our water (in the city) is used on outdoor landscaping.  That is a lot of water when you think about it.

Two California Water Bills – SB 606, AB 1668

On May 31,2018, California Gov. Jerry Brown signed into effect two water use efficiency bills, SB 606 and AB 1668.   “In preparation for the next drought and our changing environment, we must use our precious resources wisely. We have efficiency goals for energy and cars – and now we have them for water”.

Historical California drought from 2012-2016
Historical California drought from 2012-2016

In the bill, a goal is set for indoor use   “Establishing an indoor, per person water use goal of 55 gallons per day until 2025, 52.5 gallons from 2025 to 2030 and 50 gallons beginning in 2030.”  If we use 90 gallons as the baseline for today, by 2030, we need to use 44.4% less water than today to meet the goal.

A goal for outdoor will be announced in the near future.  Though we don’t know the actual number yet, we can guess it won’t be  just 1% or 2%.  To achieve that kind of water saving, one of the most effective ways is to replace the lawn with landscaping of drought tolerant plants, which usually can save water by 30-60%.

In addition to the big water saving benefit, there are two advantages that come with it.  After the lawn is gone, the need for mowing is gone too.  While the water wise landscaping still needs to be maintained, the effort required is generally much less than that for lawns.  For busy professionals like the homeowners of this house, it definitely is a great plus.

Another big benefit is the choice of the plants.  Instead of the mono color of green, the drought tolerant plants come in many shapes, colors and textures.  You can choose the ones that sport blossom of red, pink, yellow, purple, white or others of your favorite colors.  That is exactly what the homeowners did for this garden.  They loved flowers and wanted to fill the garden with many of them.

Apply for the Landscape Conversion Rebate

Before the project started, an application was submitted to Santa Clara Water District’s Landscape Conversion Program.  After they received the application, the water district did an on-site inspection and measured the sizes of the lawns that qualify for conversion and the rebate.  After the visit, they sent out the “Notice to Proceed”, which indicated that project could kick off.

Install the Water Efficient Garden

The project started!  First, all the grasses were removed.

Lawn transformation

Then, a small rain garden was built.

Take full use of rain

Rain water is a valuable source of water.  When it rains, water that falls on the roof and flows from downspouts onto impermeable surfaces like driveways will just run off.  This is a waste of water. A better use is to let it soak into the ground and recharge the ground water.  In the process,  harmful particles can be filtered out before the water go back to the ground water, versus being discharged directly into waterways, harming birds and other aquatic animals there.

This downspout comes directly into the garden, which provides a good opportunity to catch the rain and let it soak down in the garden.

Lawn transformation

A small ditch and depression was dug.   When it rains, rain water from the downspout  will flow to this small depression, and soak into the soil.  The plants in the depresson were picked to stand both wet and dry conditions.

Rain garden

One key component for drought tolerant garden is the drip irrigation.  Compared with overhead spray, it can save water by 15 gallon each time you water.  Since water slowly drips down, there will be much less runoff, and thus, much less water waste.

Rain garden

drip irrigation

To save water, another important equipment to install is the rain sensor.  When it rains, it can detect and send the signal to a smart controller, which will delay the scheduled watering.  In many cities, it is now the law that “no watering 48 hours after measurable rainfall (1/8”)” .  With the rain sensor, this can be done automatically, saving so much time and effort.

Rain sensor

Keep the “good old” plants

When an old garden was to be cleared up, not all the old plants need to go.  The ones that still look good, especially if they are drought tolerant, can possibly be keepers.

This flower bed was full of lavender.  The lavenders were lovely bushes, just that they  were obstructed by the weeds.  Lavender are wonderful low water use plants, bloom for a long time, and attract pollinators like bees.  It was decided to be kept as part of the new garden.

Once the weeds were removed, the flower bed looked beautiful:

Bees love to visit and feed on the blossom:

Receive Landscape Conversion Rebate

The garden is done!  This was before

Weedy lawn

The new garden

Garden

Water Efficient Garden

The water district conducted a post inspection.  The lawn was converted successfully, and qualified for the rebate.  A couple weeks later, the rebate check was received.

With the transformation of the lawn, a significant amount of water will be saved.  Instead of a weedy pad that would need so much care, the owner got this beautiful front yard with her favorite flowers, greeting her every day when she leaves for and comes back from work.  When it rains, the rain water from the roof will flow out to feed the plants and go back to nature.  On top of all these, she received a check.  Why wait?  Start today and plan for a water efficient garden.

 

 

 

 

 

 

 

Great Makeover Story: From Barren to Beauty (1)

This story is about an amazing transformation from barren to beauty.

When the owners moved into the house, the first thing they wanted to change was the front and back yards.  It was barren, utterly unattractive.  The main part of the front yard was this hard surface covered with sand.  It had been used as a parking space for years.  The backyard had the similar hard sandy surface as the path, with a big bush of catti plants in the middle.  When it was windy, the sands from the surfaces would be blown up and hit everything around: people, dogs, kids.  It could be messy.

Barren old front yard

Old Back Yard

The owner wanted beautiful landscapes for their yards; meanwhile, they also wanted something that is environmentally friendly, that would not use a lot of water.  To be “good” to the environment was important for them.  They wanted to be efficient for all natural resources, keeping the footprint on environment as small as possible.

Addressing the challenges of building a garden

When one looked at the front yard, the challenges for building a garden was obvious.  A big lot.  Hard surface. No top soil.  And, on a slope.  For plants to grow well, at the minimum, they would need water and soil.  How would these be addressed?

Capture and reuse rain Water

When one checked on the site, they would see two downspouts, one on each side of the house, come right down to the lot.   They pointed to hard surface, which would just let the rainwater runoff.   That is quite a waste.   Rainwater is an excellent resource of water, which can be used to water plants.   To capture and reuse rain water, one can use a rain barrel, or build a rain garden.  As the the front yard is on a slope where rain water would flow down naturally, a rain garden built close to the bottom of the slope could capture the rain water and reuse it well.

Downspout 1
Downspout 1
Downspout 2
Downspout 2

When it doesn’t rain, plants still need water to establish and grow.  For irrigation of a water efficient garden, drip irrigation is the way to go.  It can point to the root area for each plant precisely, so water can get to where it is needed exactly, without mass runoff.  Compared with a sprinkler system, drip can save water by 30-60%.

Select hardy and drought tolerant plants

As the soil under the surface is very hard from years of being used as a parking lot, it was not the best soil for many plants.  Ideally, the soil could be improved with materials such as compost and organic matters over a longer period of time; however, the option was not  available due to the time limit of the project.  This made the selection of plants especially important.

Many native  and other plants are adapted to California’s soil system and can thrive in all kinds of soils.  They can be hardy for tough environments, and need little water once established.  They also have other benefits.  A lot of them produce blossom that are good food for pollinators like bees, butterflies and birds, supporting a vibrant Eco system.

California Native Plant

Repurpose of the existing plants

For the design of the back yard, it was decided that the bush of cactus plants would go; the space would be emptied for other uses.  The catti plants thrived well in the micro system around the house, making them a a good bet for the soil conditions in the front yard.  Instead of discarding them, the catti would be reused for front yard.

Catti Bush

Building the garden

After the design of the garden was finished, the project entered installment.

Installing a rain garden

There are several parts to this.  First, proper discharge of rain water from the down spout.  Instead of letting the rainwater just go down to the ground and run off, the water would be drained into the garden.  Ditches were dug, pipes were connected.   Two  channels were also dug from the end of the pipes to the rain garden.  When it rains, rain water would be discharged out of the pipes, into the channel, then flow into the rain garden.

Pipe 1

Pipe 2

Stream 1

Stream 2

Then an area was dug for the rain garden.   The shape of the rain garden usually is round or curvy, to reduce the force of runoff and effect of erosion.

After that, plants were put into the rain garden.  There are some special requirements for such plants.  Specifically, they should be able to stand both wet and dry conditions well.  Better yet, they can add color and texture to the garden, making the garden look even more attractive.

Lastly, the whole area of the channels and rain garden were filled with pebble stones.  Once the stones were added, two “streams” and a “pond” came into life.  When it rains, all the roof’s rain water would flow into the stream,  out to the pond, seep through the pebbles, water the plants, then percolate deep down and recharge ground water, an act badly needed for our environment.

Rain Garden 1

Rain Garden 2

In big cities where surfaces like concrete is prevalent, only 5% of rain water can infiltrate deep into the soil, depriving groundwater the opportunity of being recharged.  Areas like rain garden can change that and let as much as 25% of rain water go deep under.  Recharging groundwater  is very important for keeping a healthy water system and providing backup when drought hits.

Impervious Cover

A lovely catti Area

Catti plants are favorites for many people!  They come in all kinds of shapes, colors and forms, some of them sporting splendid and beautiful flowers.  They are very drought tolerant, needing only very little water once they are established.  Catti plants can fill out a full garden, or can be integrated as part of a bigger garden, just like what was being done here.  Here they fill out the long stripe along the driveway, offering something wonderful to see and enjoy when one comes home.

Catti Plant 1

Catti Plant 2

A magnet for bees  and birds

Plants with splendid blossom provide the food that bees, birds and other pollinators depend on.  As bees’ population has been on a decline,  it is even more important that we provide places where these small creatures can feed on and take a good break.  Compared with a lawn which does not provide any food or shelter, gardens with drought tolerant and native plants can become a paradise for bees and birds.

Here, this plant was planted in a row along the pathway.  When it blooms, it has this bright beautiful blossom that is hard to miss.  It is not just us who love them,  bees and birds crave them too!

Plant for Bee

Bee

Parking Strip not to be ignored

Compared with the main garden, quite often, parking strips are “after thoughts” since they are a bit small.  However, in quite some cases they still have sizable spaces, and are an important part of the front space.  They can also be filled with the drought tolerant plants and native plants, adding to the curb appeal, and food for bees and birds.

Parking Strip 1

Adding Mulch

After the garden is finished, an important step is to cover the whole surface with mulch.  There are several benefits of this.  First, they can significantly slow down water evaporation, keep soil moist longer so reduce water required for the plants.  They can also suppress the growth of weeds, further reducing water usage.  Third, organic mulch like this made from bark can disintegrate into the soil over time, adding to the organic matters in the soil, improving soil quality and water retention capability.  Aesthetically, they provide this backdrop for all the foliage and blossom, making the space look even more appealing.

A brand new garden

Tieing all the elements together…the new garden was born!  The space has dramatically changed.  Here was how it was like:

Old Yard

And the new garden:

A rain garden doing well in rain

Shortly after the garden was finished, several storms hit the area.  How did the garden do in the rain?

All came out to be good!  Water flew into the stream and pond as designed; plants enjoyed the rain and grew well.

Off the garden, water that came down from impervious surfaces like driveway pooled into runoff, which would flow out to a sewer and empty into the streams and rivers.  There were lots of pollutants in the runoff which would hurt the animals living in the waters, and pollute the broader water system.  That is why we should limit the areas with impervious cover and try to build more rain gardens, like the one shown here.

With a design of native and drought tolerant plants, the front space of this residence has been completely transformed.  Not only has it gone from utterly unattractive to beautiful, but also become  a wonderful place for bees, birds and butterflies.   As the plants are drought tolerant, only a little water will be needed after the plants are established.  Low water use, beautiful, great for the bees – water efficient gardens can add so much charm for your space!

Rain Garden – Turn Rain 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?

  beauty in 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.

Rainwater Runoff

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.

Distance

  • 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

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!