Rainwater Harvesting During California Drought Periods

Rainwater harvesting may prove a vital solution in drought-prone areas like California. More and more, people are looking at ways to capture, collect and store rainwater for later use as drinking water or for crops. In California, this includes not just stormwater collected during rainy seasons, but also the diversion and collection of snowmelt in the northern part of the state, too.

Can Rainwater be Collected in California?

To get started, this is the most pressing question to answer because there is quite a bit of confusion over the legality of harvesting rainwater in California. Prior to 2012, it was illegal for anyone to collect rainwater within the state. This wasn’t a complete and total ban, however. Rather, it meant that in order to collect rainwater (or to appropriate water from any source, including rain), public and private entities needed to apply for a permit from the State Water Resources Control Board (SWRCB) for permission to capture and use rainwater. The reasoning behind this was that in harvesting large amounts of rainwater, large-scale operations could damage delicate ecosystems that rely on yearly rainfall to thrive.

In 2012, regulations changed with the Rainwater Capture Act. This act eases restrictions on rainwater collection. Residential homeowners are authorized to maintain and operate rain barrel systems for their own use, and commercial and governmental operations can use rainwater capture systems so long as those systems are in line with requirements set forth by the RCA. In effect, the RCA removed SWRCB control over rainwater and how it is used.

What are the Benefits of Rainwater Harvesting?

There are numerous benefits to be had with rainwater harvesting, not the least of which are additional water supplies that drought-prone areas like California can use for crops and drinking water.

Other benefits include flood control. In California, flood waters are often lost to the Pacific Ocean as water naturally diverts and drains into the sea. However, it is possible to protect low-lying areas from flooding by diverting that water elsewhere—and storing it in reservoir for later use. This has the added advantage of reducing pollution in existing freshwater bodies since stormwater runoff often contains toxins, pesticides, sediments and fertilizer that can disrupt freshwater ecosystems. By diverting and containing this water, it also provides for an opportunity to treat it and make it safe for use.

Rainwater collection also helps sustain groundwater levels because these additional water supplies reduce the demand on wells. Because rainwater is mostly free of salts, it is easily treatable as a source of potable water.

Benefits for Residential Areas

For residential homeowners, there are a few major benefits to be aware of. To start, rainwater harvesting is a great way to build overall ecological awareness because it promotes higher consciousness of water usage, water conservation, and environmental concerns. It also lowers municipal water bills—often drastically since things like lawn and garden irrigation can make up a huge portion of your water bill.

Because it reduces the amount of pumping that needs to be done (many rainwater collection and rain barrel systems require no electricity at all), homeowners also stand to save energy, too. In the case of severe droughts or wildfires, these water stores can be used as a backup resource to protect your home or provide a supply of drinking water—if you treat and sterilize the water before drinking it.

Considerations to Make When Harvesting Rainwater

Whether you’re a residential homeowner or a large-scale commercial operation, there are a few things that should be accounted for when harvesting rainwater. As touched upon already, pollution is one of those considerations. Evaporation and natural water loss are others.

For Homeowners

In California, many homeowners make use of rain barrels and other capture systems to collect rainwater from rooftops and driveways. This can result in an excellent reservoir of water to irrigate your yard or to even provide potable drinking water. Before using this water, however, think about what toxins may be in it.

Rainwater itself is largely free of salts, but driveway runoff can contain sediments and automotive pollutants that make the water unsuitable for vegetables or for drinking. Similarly, runoff from rooftops can contain toxins, too. Before using this water as drinking water, water for sanitation, or water for edible crops and plants, it’s wise to treat and filter it.

As far as evaporation goes, this can result in water loss—but most homeowners use barrel systems or tanks, both of which are easily covered to eliminate water loss through evaporation. In the rare case that a small reservoir or backyard pond is used, the evaporation rate can be reduced by focusing on minimizing surface area. Deeper ponds with less surface area will evaporate more slowly.

Preventing water loss through soil or through liners will require you to use an impermeable liner of some kind. Your best option will be an RPE geomembrane that is fish and plant safe, which will ensure that your water stays safe for irrigation use. BTL Liner’s AquaArmor is perfect for this use.

For Commercial Rainwater Collection

On the commercial end of things, you’ll need to think about the same considerations—but in different ways. For instance, pollution is still a concern, but not necessarily in regard to drinking water or the contaminants you’d find on the surface of a typical driveway. Rather, when capturing rainwater runoff from cropland, it will be things like sediments, fertilizers and pesticides that will be your chief concern. If you intend to recapture this water for use with livestock, it will need to be treated to ensure that it is potable first.

More often, however, the bigger concern will be storage for later use with crops—and preventing environmental issues while storing that water. Crop runoff can prove extremely damaging to local freshwater bodies, so you’ll need to make sure your reservoir and channel systems are secure against leaks. Both AquaArmor and ArmorPro are good options to use as reservoir and channel liners to help prevent leaks and environmental contamination.

To combat water loss and evaporation, depth and liner permeability are the two critical components to think about. As with residential ponds, minimizing surface area minimizes evaporation. Water loss through seepage will be the larger concern—but using a geomembrane rather than a clay or concrete liner drastically reduces this type of water loss.

Rainwater Collection: A Potential Solution

For both residential and commercial applications, rainwater harvesting holds a lot of potential. In California, it can go a long way towards maintaining water stability and groundwater levels, even during extreme droughts.


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