California, “The Golden State” of the United States, is known for having beautiful weather year-round, sunny skies, and for producing 90% of all of the country’s wine. The state paints a mosaic of diversity, from its culture, climate, and geography to its hot deserts to its snow-covered peaks and foggy shores. The highest and the lowest points in the continental United States sit in California just within 100 miles of one another! Mount Whitney is 14,505, while Badwater Basin in Death Valley is 282 feet below sea level. Death Valley is considered the hottest, dirtiest place in the country, often reaching temperatures greater than 120 degrees Fahrenheit during the summer. Rain is also scarce in Death Valley, which averages only around 2 inches each year. 

California’s vibrant diversity is not without consequences, now bearing only little resemblance to its former beauty. It has been called “the most hydrologically altered landmass” not just on the United States, but on the planet. What used to be deserts and grasslands are now converted to reservoirs. These conversions were brought about by the state’s effort to collect and store water to move to arid lands. California’s varying water needs and resources reflect its efforts to balance its water supply and demand. This has made California a leader in water efficiency and conservation initiatives in the country.

Water Supply

Water resources in California can support 35 million people and irrigate more than 5.68 million acres of farmland. Unsurprisingly, it has emerged as the nation’s leading agricultural producer at the expense of converting the state’s marshes, swamps, and tidal flats to farmlands. Because of California’s natural resources’ drastic changes, it has become one of the country’s major manufacturing centers and has one of the world’s largest economies. To maintain its position as an agricultural state, it relies heavily on three main interconnected water sources – mountain snowpack, reservoirs, and aquifers. 


The Sierra Nevada region consists of 25% of California’s land area and is one of the world’s most diverse watersheds. It receives 60% of the state’s total annual precipitation in the form of rain and snow. Sierra Nevada snowpack, acting as a natural reservoir, holds water until it melts during spring and summer and provides runoff water to rivers and reservoirs. Typically, the snowmelt from the Sierra Nevada can supply 30% of the state’s water supply. Water supply from the region also irrigates farms that produce half of the fruits, nuts, and vegetables in the United States. Most importantly, Sierra Nevada provides water that irrigates dairy manufacturers, making California the largest milk producer in the U.S. 

Due to warm and dry winters, however, the snowpack is now on the decline. In March 2020, the Sierra Nevada range had limited snow covering, which indicates snow droughts in the mountains. These changes have potentially profound, not to mention an expensive impact on California’s water supply and salmon runs ski resorts and fire risk in the region. Also, Sierra snowmelt is a source of drinking water in the Sierra Nevada region. Cities stretching from San Francisco Bay Area to Southern California or around 23 million people also depend on Sierra snowmelt for a portion of their drinking water.


Fear of drought and long summers, and having historically high temperatures, state efforts to store water has become more prevalent in constructing reservoirs. A reservoir is a storage space created to store fluids, especially water. It may either be natural or an artificial lake designed to store water for long-term use. California has over 1,000 major reservoirs strategically situated in its territory. Did you know that 200 out of the thousand have a combined capacity of over 40 million acre-feet? Most of California’s large reservoirs are owned by the Federal Bureau of Reclamation.

California’s largest storage reservoir, Shasta Lake, can store an average of 4.5 million acre-feet water. It is the keystone of the federal Central Valley Project (CVP). CVP is one of the largest water and transport systems in the world. Water is transported through a 450-mile facility and encompasses 18 dams and reservoirs. Being CVP’s keystone facility, it is among the world’s largest dams in terms of capacity. Flooding was taken into consideration when construction began in 1938 and was completed in 1945. 

Its strategic position, located 12 miles north of Redding, Shasta Lake can trap cold waters from the Pit and McCloud rivers and the headwaters of the Sacramento River. During years of normal precipitation, Shasta Dam can store and provide about 20% of California’s developed water or about 7 million acre-feet of water. Through the Central Valley Project, water is transported from Lake Shasta in the Northern part of California down to Bakersfield in the southern San Joaquin Valley. Within the route, CVP can transport water to 250 contractors in 29 state counties. 

The Orville Dam, the centerpiece of the State Water Project, is also the largest water storage facility in California and can hold 3.5 million acre-feet of water. What makes the Orville Dam so important is its role in the State Water Project or California’s aquatic lifeline, the 444-mile long California Aqueduct. It brings water to cities and farms in the entire state. Without Orville Dam, California would have never become the economic powerhouse that it is today. On top of that, it features a fish barrier dam and recreation facilities like boating, camping, and fishing for Californians to enjoy. 

For a list of the largest reservoirs and dams in California, please refer below:

ReservoirVolume (Km^3)OutflowDam
Shasta Lake5.615Sacramento RiverShasta Dam
Lake Oroville4.364Feather RiverOroville Dam
Trinity Lake3.02Trinity RiverTrinity Dam
New Melones Lake2.96Stanislaus RiverNew Melones Dam
San Luis Reservoir2.518San Luis CreekSan Luis Dam
Don Pedro Reservoir2.504Tuolumne RiverNew Don Pedro Dam
Lake Berryessa1.976Monticello Dam
Lake Almanor1.613North Feather RiverCanyon Dam
Folsom Lake1.382American RiverFolsom Dam
Lake McClure1.264Merced RiverNew Exchequer Dam
Pine Flat Lake1.233Kings RiverPine Flat Dam
New Bullards Bar Reservoir1.229North Yuba RiverNew Bullards Bar Dam
Diamond Valley Lake0.999Domenigoni CreekWest Dam
Lake Tahoe0.903Truckee RiverLake Tahoe Dam
Lake Havasu0.797Colorado RiverParker Dam
Lake Isabella0.701Kern RiverIsabella Dam
Lake Don Pedro2.50New Don Pedro
Santa Ana River0.1796 Seven Oaks Dam


California depends on two main sources for its water: surface water and groundwater. Runoff water that goes to lakes, dams, and reservoirs consists of surface water. Groundwater, on the other hand, is found beneath the earth’s surface. It can also be found in the pores and spaces between rocks and soil or aquifers

The majority of the rain and precipitation California gets falls as snow in the Sierra Nevada region or the northern part of the state during winter. When the supply of surface water cannot meet demand, groundwater is then pumped from aquifers to supplement the water supply. Water from aquifers accounts for nearly 60% of the country’s water supply, especially during a dry year. 

Although unseen, aquifers are a critical freshwater resource in California. It is found in 40% of the state’s land area. Water pumped from aquifers supply water to urban areas and supply water for agricultural irrigation. Aquifers are a great equalizer in the state. Unlike surface water, which is concentrated in California’s northern and eastern parts, they can be found throughout the state’s land area. Most importantly, they are found where demand for freshwater is very high, like in the Central Valley and Los Angeles. 

Drought in California

Starting in 2012, California has experienced its driest and highest temperature for three consecutive years. It led to a sharp decline in the Sierra Nevada snowpack. In April 2015, there was no snow covering the Sierra Nevada range when it is typically at its highest. From 2012 to 2016, when California experienced an intense drought, portions of the valley sank as much as 60 centimeters each year. This is a slow-motion disaster whose consequences we are facing now. This can also be attributed to California’s insatiable thirst for groundwater.

Even aquifers are now becoming more and more depleted. 74% of the groundwater well levels have declined by over 2.5 feet in just a matter of three years. California, being the most populous state, does not help the issue. Rather, it contributes to its continued depletion. California has the highest population at 40 million residents. Half of the municipal water use is for landscaping, and 1/3 is for residents’ home use, creating ample conservation opportunities. 

For years, groundwater collection has gone unregulated at the state level. In 2014, any law about how groundwater can be pumped, collected, and used was enacted. The new groundwater management era started on September 17th, 2014, when Governor Jerry Brown signed the Sustainable Groundwater Management Act (SGMA). SGMA took effect in 2015 and has since then changed the way groundwater is collected. 

Mainly, the act empowers local officials to regulate the trend of critically over-pumping water from groundwater resources. Having the end goal to bring groundwater basing into balanced levels before pumping begins anew. This will allow groundwater to recharge, allowing the resource to supply more water and for a longer period. It also mandates that local agencies draft and adopt sustainability plans for both high-priority and medium-priority groundwater basins. SGMA makes it mandatory that basins reach its goal of sustainability within 20 years or in 2040. This will buffer from drought and climate change, eventually contributing to having reliable water supplies, notwithstanding the state’s weather patterns.

Sustainable Groundwater Management Act consists of three legislative bills, namely:

  1. Senate Bill SB 1168 (Pavley)
  2. Assembly Bill AB 1739 (Dickinson), and 
  3. Senate Bill SB 1319 (Pavley).

The legislation provides a framework for the attainment of long-term sustainable groundwater management across California. SGMA recognizes that there is no one-size-fits-all solution to this issue because each groundwater basin is different.

The legislation does not remove the distinction between surface water rights and the personal and private property right to pump groundwater. The act does not attempt to restrict property owners from pumping groundwater within their property or allow the disclosure of how much water one can take from his or her property. The state intervention is proscribed, except in extreme conditions where local officials and control is proved inadequate.

Rainwater Harvesting: Alternative Water Source

California is not a stranger to droughts, arid season, and minimal to zero rainfall. Along with its declining water resources, Californians are looking for ingenious ways to conserve and preserve water for the driest times of the year. Rainwater harvesting is, arguably, one of the easiest ways to do so.  

Rainwater harvesting is considered illegal in California before 2012. You must first obtain a permit for you to collect water in your home. Residents can only collect rainwater provided that they have secured a permit from the State Water Resources Control Board (SWRCB). Therefore, the prevailing law is Section 1200 of the California Water Code, which provides for a penalty for rainwater harvesting without a permit. Resident and businesses who did not secure a permit from SWRCB will be penalized for misusing and illegally harvesting water that technically belongs to California. 

However, with the Rainwater Capture Act through Assembly Bill 1750 (2012), rainwater harvesting has been legalized in the State. Californians are now relieved from the requirement of getting a permit before collecting rainwater.  Capturing rainwater off of rooftops is now completely legal in California. Rainwater Capture Act recognizes the development of California’s infrastructures. This has resulted in increased water volume, mainly rainwater, flow off buildings, roads, parking lots, and other impervious surfaces to flood channels, surface water streams, and sewers. Because of these obstructions, less water is allowed to infiltrate into groundwater aquifers. As a consequence, we face increasing water and pollution that flows to the ocean and surface waters. Also, droughts and shortages in the water supply are a recurring situation in California, making local water supply augmentation and conservation efforts a top priority.

Precipitation patterns in the State have drastically changed, which can be attributed to climate change. This has strong implications for California’s water supply. Instead of depending heavily on snowpack and water from snowmelt, it is predicted that the state’s water will mostly come from rain. Reservoirs will not be able to capture most of the rainwater as it is positioned to catch snowmelt. This said, rainwater and stormwater capturing and harvesting has become an ideal alternative for Californians. 

Rainwater Capture Act emphasizes the following:

  • Rainwater and stormwater, when captured and properly managed, can significantly contribute to the meager local water supplies;
  • Harvesting rainwater can lessen the demand for potable water as it provides an alternative water source for non-potable uses; 
  • Groundwater aquifers can recharge, thereby increasing available water supplies for potable water;
  • Opportunities for rainwater and stormwater capture as a solution to augment water supply requires efforts at all levels, especially from individual landowners to local officials, all the way to state-level legislation; and
  • No existing water rights are impaired or altered by the legislation.

Residential, commercial and even governmental landowners may install a rainwater capture system. The system is a facility that is designed to capture, retain, and store rainwater. This may consist of runoff water from building, parking lot, or any other manmade infrastructure or surfaces. Under the Rainwater Capture Act, the landowner may install any of the following rainwater capture systems:

  1. Rain Barrel System, which is a straightforward set-up. Barrels are placed under the gutter to capture rainwater flowing off the roof and gutter. This is the ideal system if you intend to use rainwater for outdoor, non-potable uses. You must comply with manufacturer instructions before you install the system in your backyard.
  2. Rainwater Capture System for other Outdoor Non-potable uses or infiltration to groundwater. 
  3. Underground Capturing is an underground rainwater capture system that harvests water from gutter downspouts or runoff rainwater that falls on permeable pavers. This is a more elaborate system that includes water filters, and water is collected in underground containers. Water collected by the system can be used for landscaping and in commercial buildings for toilets. 
  4. Rainwater Capture System for Indoor Nonpotable Use requires a stricter guideline before installation. These conditions apply for the approval of a rainwater capture system in any land or building:
    1. The system must comply with the California Building Standards Code;
    2. The catchment system must include supplemental filtration, a disinfection device or its equivalent, as approved by the local agency;
    3. A permit must be issued after inspection and approval of the local agency and local public health department. The landowner must comply with the conditions provided in the permit; and 
    4. Any rainwater captured by the catchment system must only be used for non-potable purposes. These may include heating, toilets, urinals, ventilation, clothes watching machine, air-conditioning systems, or any other use permitted by the California Building Standards Code. 

Rainwater is a resource and asset. It is only right that we do not treat it as a waste product. This reason alone is enough for our law-making agencies to set forth rules and regulations for we must do things. Installation, construction, altercation, and the repair or rainwater harvesting systems intended for non-potable use must be approved by the authority having jurisdiction of the area. There are additional criteria that may differ from city to city or per county. Check your locality’s regulations. Naturally, no permit for the construction of rainwater catchment systems will be released without a complete plumbing plan. Not only that, the plan must prove to be satisfactory to the issuing authority. The catchment system also requires maintenance and regular inspection to ensure that all components are based on the manufacturer’s recommendations. 

Berkeley Rainwater Harvesting Guide

On average, Berkeley, California, receives roughly 20 inches of rain per year. Perfectly good and useful rainwater flows off your roof and into the drains and outflows to the San Francisco Bay. If you endeavor to harvest rainwater, this effort will help conserve water and can potentially lead to a reduction in your water bill. By collecting rainwater and stormwater, you will have an available water supply to water your garden. Harvested water from rain is low in sodium, and chloramine making it a perfect resource for watering your plants. Plus, it is fluoride-free! This will also replenish depleting local aquifers and reduce the amount of rainwater that runoffs into the Bay. 

Local authorities in Berkeley recommends the easiest, most low-tech rainwater catchment system or the rain barrel attachment. By simply attaching a barrel to your downspout, you can collect the runoff water from your roof and gutter. Rain barrels often come with a spigot and hose, so you can easily use the rainwater you have collected in your garden. No water treatment is required in this type of catchment system. Most importantly, you do not need to secure a permit for the rain barrel catchment system.

Here are the guidelines for non-permitted rainwater catchment systems:

  • Harvested rainwater shall be used solely for irrigation;
  • Overflow must be safely disposed to a stormwater drain or garden. It must not be discharged across public right-of-way or to the adjacent property or cause any inconvenience to the public;
  • Landowners must use a food-grade container for water storage;
  • Placement of the catchment system must be secure, leveled, or near gutter downspouts; 
  • Elevation of the catchment system is recommended to ease the flow of irrigation;
  • Scree gutters that serve to filter debris must be located a minimum of 3 feet from the property line;
  • Attach fine mesh to screen rainwater catchment openings with a standard measurement is .05 inch x .05 inch. This will prevent mosquitoes from entering the water storage, making it sanitary and securing public health and safety;
  • The barrel is an attractive nuisance, so owners muse securely fasten large openings to avoid accidental drowning among children and even adults;
  • Label the barrel and pipes with a clear and large enough sign, “NON-POTABLE RAINWATER, DO NOT DRINK”;
  • Clean the rainwater catchment systems and your roof gutters annually; and
  • If you are using harvested rainwater for edible water plants, consider installing a first-flush diverter. This will dispose of the first inch of collected rainwater that often contains the debris not caught by the mesh filter. 

However, more complex catchment systems may involve plumbing works, electrical work, soil excavation, and other structural requirements if you plan to install complex catchment systems in your home or a commercial building. This scale’s rainwater catchment systems typically require professional help to review design, especially for construction and safety considerations. Here are the permits you will need before you can install complex catchment systems:

  • Plumbing permit
  • Electrical permit
  • Building permit

These are required when your catchment system storage capacity is 5,000 gallons or more and when the height to width ratio larger than 2-to-1. You will also need plumbing, electrical, and building permits when the system uses pumps or make-up water supply connections 

  • Zoning review or permit 

However, a  zoning review or permit is unnecessary if the catchment system is installed at least 3 feet from the side property lines. It must not obstruct parking access. 

  • Additional review and permits 

These may be required if the collected rainwater will be used for spray irrigation and other indoor uses.

Los Angeles County Rainwater Harvesting Guide

Los Angeles County gets around 15 inches of rain annually. This is s significant amount of rainwater that is a sure way to conserve a scarce resource when harvested. It is a win-win situation for residents of L.A. County because they get water for non-potable uses, save money while also protecting the environment. 

In September 2011, the Los Angeles County Department of Public Health, Environment Health Division (EHD) released guidelines on enhancing available water resources in the County of Los Angeles. The agency has categorized rainwater and stormwater as alternative non-potable water sources. For an overview of the guidelines, kindly refer to the following:

For Irrigation:

  • Rain barrels must have a screened inflow opening, a spigot, or a hose;
  • Rain barrels must have an overflow pipe or its equivalent;
  • There is no minimum water quality standard; and
  • No treatment process is required.

For Car Washing:

  • Rain barrels must be labeled as non-potable water use only;
  • There is no minimum water quality standard; and
  • No treatment process is required.

Both irrigation and car washing purposes must be connected to indoor or outdoor municipal potable plumbing. However, the catchment system must not be pressurized or sprayed. Most importantly, the rain barrels must comply with the manufacturer’s installation manual and installation requirements set by local agencies. Above ground, rain barrels should satisfy the health and safety requirements of the County Building and Safety plan checkers. Checkers will be checking the following:

  • The barrel or cistern attached to your downspout must be made of UV-resistant heavy-duty plastic a minimum of 3/16 inch thick or of higher quality materials;
  • It must not exceed 5 feet in height, which shall not exceed 1.5 times the width;
  • The barrel must be equipped with screened inflow;
  • There must be a 3-inch gap above the screen and the opening; 
  • Roof drain must not be directly connected to the container;
  • All inflow and outflow must be sealed, plugged, and screened to repel mosquitoes from entering;
  • Openings must not be larger than 6 inches;
  • A gravity flow must be positioned near the bottom of the barrel; and 
  • Every rainwater barrel or cistern must be labeled, “NOT SAFE FOR DRINKING.”

San Diego County Rainwater Harvesting Guide

There are very few local water supplies in San Diego County. Consequently, 85% to 90% of the county’s drinking water comes from the Colorado River and Sacramento Bay-Delta. Several factors also affect water supply across San Diego County. The area experiences intense droughts and regulatory restrictions. This pushed the San Diego community and the local officials to develop conservation plans and policies to ensure that every San Diego resident meets their water demands. Under the City of San Diego Public Utilities Department’s leadership, new policies were placed for water conservation efforts. Among these is the use of rainwater harvesting systems.

As much as we enjoy keeping our lawn green and eating fresh produce from our backyard, 30% to 50% of the total water use often goes to landscape irrigation. This is a big chunk of water consumption that can be easily remedied by a simple solution – rainwater harvesting. Installing a straightforward rainwater collection system can significantly reduce this usage of potable water. Through collecting rainwater and reusing it for lawns and gardens, we can collectively decrease the stress we are causing on our valuable and limited supply of potable water. Also, local aquifers get enough time to replenish before their groundwater is pumped again. 

Over twenty years ago, the City of San Diego’s Water Conservation Program was put in place to address the chronic drought that plagues California. Rainwater harvesting is highly encouraged in San Diego from rain barrels, rain gutters, downspout redirects to greywater systems. Among these, rain gutters are the easiest way to collect rainwater from your roofs. Typically, rain gutters are installed just below the roofing material’s edge and are then connected to a downspout. The downspout serves as the conveyor for the collected water to travel from the rooftop to the ground surface. You can easily divert rainwater into your garden, your landscape, or any green space. Of course, installing a rain barrel below your rain gutters will yield more rainwater.

Considering the amount of rain San Diego gets annually, a 1,000 square feet of roof surface can take 625 gallons of water for every single inch of rain. With this, you can potentially collect 6,250 gallons of rainwater annually. Imagine the resource you can harvest right in your backyard!

If you need more motivation to collect rainwater, San Diego offers rebate programs. You can receive up to $1 for every gallon of rainwater you collect through your rain barrel catchment system. If you install new rain gutters, you can get up to $1.25 for every linear foot of aluminum gutter. You can submit an application for a rebate as long as you satisfy the installation requirements. In addition to your application, a W-9 form must be submitted to the City so you can receive your rebate funds.

Rain Barrel Installation Recommendations:  

  • Install the rain barrel on an elevated foundation to increase gravity flow;
  • Rule of thumb, it should be able to accommodate a watering can;
  • Foundation must be solid and level, like concrete pads, pavers, or brick;
  • Outlet pipe or faucet must be placed six inched from the bottom of the barrel;
  • Secure the barrel with straps to make it earthquake and calamity proof;
  • Follow manufacturer’s recommendations for installation; and
  • Consider limiting the height to width ratio, ideally, 2:1 to prevent stability issues.

What does not qualify for a rain barrel rebate?

  • Barrels purchased before January 1st, 2018;
  • Cost of labor, fuel, or tools;
  • Additional cost associated with fixtures or other components;
  • Homemade rain barrels; and
  • Taxes, fees, or tariffs accrued from the purchase of rebate-related device or work performed.

Rain Gutters Installation Recommendations:  

  • Ensure that the rain gutters are sloped properly for rainwater to drain out easily;
  • Aluminum and galvanized gutters are highly recommended. Consider using these materials as they last longer than PVC;
  • Galvanized gutters are preferred if you live near the ocean;
  • Consider recycling old metal gutters;
  • Use gutter guards to minimize clogging; and
  • Consider using splash blocks or riprap rocks to cover the areas underneath so it can redirect runoff rainwater.

What does not qualify for a rain gutter rebate?

  • Fasteners, hangers, elbows, corner pieces, end caps, downspouts, rain barrels, cisterns, splash rocks, riprap rocks, and leaf guards
  • Old gutter haul-away and disposal fees
  • Gutters obtained before December 1st, 2018
  • Labor, tool, or fuel costs
  • Fixture or component costs for installing or securing gutters
  • Taxes and fees for rebate-related device or work provided

Benefits of Rainwater Harvesting in California 

Tax Credits

Proposition 72 Rainwater Capture Tax Break passes by an overwhelming majority votes. The proposition exempts rainwater catchment systems from property tax assessments. As it does not apply retroactively, it shall only apply to systems constructed on or after January 1st, 2019. It aims to encourage more homeowners to employ water conservation measures at home. Installing rainwater catchment systems will increase your home’s value when it is sold, making it more attractive to a lot of residents. 

There are no known state incentives, but here are local incentives you might want to consider:

  • Calistoga
    • $1,500 Residential 
    • $5,000 Commercial
  • Santa Monica RWH
    • Up to $2,000 rebate for cisterns
    • Up to $5,000 for a Sustainable Landscape
    • Other rebates available

Help Reduce the Stress on Our Scarce Water Resource

California’s infrastructure is aging, and due to the strain it has endured in the past, updating its structure is expensive and not cost-effective. Groundwater resources are now overdrawn, and installing rainwater catchment systems proves to be a simple, affordable alternative to this problem. By catching and collecting rainwater from your roof, you lessen your draw on the stress we collectively cause to our water resources.

Protect Your Local Watershed 

Rainwater and stormwater are often polluted, and unfiltered and excessive runoff may infiltrate our surface waters. When left unmitigated, rainwater will collect contaminants along the way and will most likely runoff to bodies of water. This will endanger aquatic life where we get our food. Installing rainwater catchment systems in your homes and collecting rainwater will reduce polluted runoff.

Reduce Your Carbon Footprint

In California, 20% of per-capita energy use is devoted to treating and transporting water. Water is also a huge component of cleaning as well as cooling energy generation facilities. Having an alternative water resource means less reliance on water coming from treatment facilities. If every landowner installs a rainwater catchment system, we collectively contribute to saving energy.