If you live in a dry area such as the western United States, you have probably heard about the drought crisis that we, along with many other nations around the world, are facing. Many municipalities throughout California have implemented restrictions on outdoor watering. Lake Mead and Lake Powell, which provide drinking water for more than 40 million people in the southwestern United States, are reaching record-low water levels. This summer, my husband and I stayed in Big Bear, California while our home was fumigated. When we walked by Big Bear Lake, we were shocked at the low water levels. Boat docks were completely exposed, and the water level was so low that you would have to walk several hundred feet of the dry lake bed to access the water.
In the following blog post, I will discuss the megadrought in California and why it is important to improve both drought and flood resilience throughout California. Finally, I will discuss some solutions that individuals and communities could implement to adapt to the changing climate in California.
What is a Megadrought?
An area is experiencing drought when it experiences a prolonged period of time with abnormally low precipitation. Droughts can be as short as 15 days or last decades. A megadrought is a prolonged drought that lasts for two decades or longer. The current megadrought (22 years) that the Western United States is facing is associated with the driest conditions that the region has seen in thousands of years. At least 95% of the region is facing abnormally dry or drought conditions. Researchers from the University of California, Los Angeles (UCLA) and the Lamont-Doherty Earth Observatory of Columbia University in New York analyzed growth ring patterns in trees across Arizona, California, and Nevada to record soil moisture levels. The results of this study indicate that the current megadrought is the worst megadrought California has seen in more than 1,200 years.
A shift in hydrology
According to a report published by the California Department of Water Resources (DWR), Water Year 2021 (October 1, 2020, to September 30, 2021) was the second driest year in California history with state emergency proclamations covering 50 counties. This came after a five-year drought, which lasted from 2012 to 2016, that ended after Water Year 2017 (the second wettest year in history). It appears that the hydrology in California is shifting to mimic conditions seen in the Colorado River Basin, where several dry years are followed by an occasional wet year.
I recently attended the California Stormwater Quality Association (CASQA) conference in Palm Springs, California. At the conference, one of the speakers discussed how rainfall patterns have shifted in the last several years. An analysis that looked at long-term precipitation data in San Diego, California found that annual precipitation had not changed significantly in the last 100 years. However, there are longer periods of drought between more intense rainfall events. These new precipitation patterns indicate that drought and flooding will continue to be an issue in the future. Another speaker from 2ND NATURE presented the results of a similar analysis performed for several major cities throughout the United States. The analysis indicated that due to extreme events, cities that receive less annual rainfall are expected to see an increase in total runoff.
Hot Drought
Hot drought is another term I have heard recently to describe what is going on in California. This is because the current drought conditions can, in part, be attributed to warmer temperatures. When it is hotter, the atmosphere becomes “thirstier” meaning that it has a higher demand for moisture. In other words, there is a greater vapor pressure deficit, which is the difference between the moisture in the air and how much moisture the air can hold. This means that more water evaporates into the atmosphere. In this way, warm temperatures can make drought worse because plants and wildlife actually need more water even though there is less water available.
Solutions
It is unlikely that freshwater supplies will be able to keep up with global demand by 2040. This means that water is a global issue. Unfortunately, this inability to keep up with the increasing global demand for water has the potential to cause political instability, stifled economic growth, and food shortages. Some places, such as Cape Town, South Africa have already experienced ‘Day Zero,’ which describes a situation where municipal water supplies are largely switched off. This means that people would have to stand in line to receive their daily ration of water rather than turning on the tap. Will this happen in the United States? I hope not, but the fact that ‘Day Zero’ is even a remote possibility is frightening.
Fortunately, there are many ways communities and individuals can increase drought resilience. However, many of these solutions will require changing people’s perceptions, which takes time. For this reason, it is important to begin implementing such solutions now rather than waiting for things to get even worse. As the demand for fresh, clean water increases and supply becomes more limited due to drought and pollution, people will increasingly rely on alternative sources of water and creative waste management solutions. The following sections describe some of the strategies for building drought resilience in your community.
Rainwater Harvesting
Rainwater harvesting can be categorized as active or passive. Passive rainwater harvesting involves capturing runoff and allowing water to soak into the ground. This hydrates the soil and minimizes the amount of runoff that enters storm drains. Active rainwater harvesting is what most people think of when they hear the term rainwater harvesting. Active rainwater harvesting involves collecting runoff from an impervious surface (typically a rooftop) and storing the runoff in a tank. The water stored in these tanks can be used for irrigating landscape plants, flushing toilets, or even drinking as long as the water is treated properly. Using water collected on-site reduces the amount of potable water required for nonpotable water needs. In this way, you can think of rainwater harvesting as an insurance policy of sorts. Finally, rainwater harvesting reduces the strain on stormwater infrastructure at a time when rainfall events are becoming more intense. The following video shows a demonstration that depicts the benefits of rainwater harvesting.
Stormwater Capture and Reuse
Stormwater capture and reuse are very similar to rainwater harvesting in that it involves collecting stormwater runoff and storing that water in a cistern. However, the cistern is typically a large underground tank that collects runoff from a larger drainage area.
This article describes a regional stormwater capture and reuse project in the San Francisco Bay Area.
Greywater
Greywater is gently used water from bathroom sinks, showers, baths, and washing machines. A greywater system allows you to use water from your shower or washing machine to irrigate landscaping. However, greywater is not safe to drink and should not be used to irrigate a vegetable garden. The simplest greywater systems are laundry-to-landscape and branched drain systems. Homeowners can expect to pay a couple of thousand dollars for a professionally installed system of this type. In some places throughout California, greywater systems are being installed in new construction!
Desalination
Desalination is the removal of dissolved minerals within seawater. Desalination provides a significant amount of water supply in the Middle East. More than half of the world’s desalination occurs in the Middle East. In the United States, roughly 400 desalination plants have been constructed since the early 1970s. California has the largest desalination plant in the western hemisphere, the Claude “Bud” Lewis Carlsbad Desalination Plant in San Diego County, California. It cost roughly one billion dollars to construct the Carlsbad Desalination Plant, which was completed in 2015. It produces about 50 million gallons per day (mgd) which accounts for about 10% of San Diego County’s water supply. The cost of desalination is around $2,500 per acre-foot, which means that it is still quite a bit more expensive than imported water ($1,400 per acre-foot). However, as water becomes more scarce, the cost of imported water is expected to increase significantly. For this reason, municipalities are making investments in desalination to increase drought resilience.
Cloud Seeding
Cloud seeding is a weather modification technology. It involves sowing clouds with small particles to make them rain or snow. Scientists have been seeding clouds since the 1940s, and Utah has been cloud seeding since the early 1950s. Basically, seeders shoot silver iodide into winter clouds where it helps form ice crystals. The results of over 70 years of cloud seeding research are mixed. Cloud seeding can also be expensive.
Sustainable Landscapes
According to the Public Policy Institute of California (PPIC) Water Center, outdoor water accounts for roughly half of statewide urban water use. This means that the largest water-saving potential in an urban setting lies in making landscapes more water-efficient or “drought-tolerant.” Recently, I took over the Ocean Friendly Gardens (OFG) program for the North Orange County Surfrider Chapter. As a result, I have started learning a lot more about sustainable landscaping. I have learned that if properly designed, sustainable landscapes are more beautiful and less maintenance than conventional lawns. A sustainable/drought-tolerant landscape is comprised of the following elements:
- Climate-appropriate plants that have adapted to local weather conditions.
- Efficient irrigation practices (e.g., drip irrigation, using smart controllers).
- Applying mulch to promote healthy soil.
Many water districts throughout California offer rebates or other incentives to encourage residents to convert lawns to more drought-tolerant landscaping.
Blackwater Recycling
Blackwater is a term that describes water from toilets and kitchen sinks. It requires more treatment than greywater because blackwater contains bacteria and pathogens from food particles, feces, and other human body fluids that are hazardous. The simplest blackwater recycling system involves using water from a common septic tank, where waste is settled and lightly filtered, for subsurface irrigation for landscaping. More elaborate systems can make blackwater clean enough to drink. However, these systems are very expensive and require complex, specialized maintenance. It can also be difficult for people to overcome the mental hurdle of drinking treated toilet water. There are also regulatory challenges associated with installing blackwater systems in California. However, the potential water savings associated with blackwater recycling are enormous. Aquacell, an Australian company that specializes in water recycling, investigated the payback for various water recycling methods. The table below summarizes the results of their findings.
| Water Recycling Method | % Reduction in water use at a commercial building | % Reduction in water use at a student housing development |
| Low flow fixtures | 8% | 3% |
| Rainwater Harvesting | 20% | n/a |
| Greywater Recycling | 50% | 44% |
| Blackwater Recycling | 90% | 54% |
The numbers in the table above show that blackwater recycling systems can potentially have a higher return on investment despite the high initial cost. However, these systems can have costly repairs when something goes wrong. It is also worth noting that these systems can have an unpleasant smell (sewage) associated with them.
An example of blackwater recycling in the United States is a plant located in north Orange County, California. The $143 million facility was discussed in an article published by the Orange County Register in 2015. The Orange County Water District (OCWD) facility treats treated water from the Orange County Sanitation District that would have otherwise gone to the Pacific Ocean. This recycled water, which is referred to as “toilet-to-tap,” minimizes the strain put on the groundwater basins that Orange County residents rely on for drinking water. Successful projects such as this one show that wastewater should be viewed as a resource rather than a liability, especially during a drought.
As this technology continues to improve, the benefits of blackwater recycling will become more apparent, and these types of systems will become more widespread. This decentralized approach to wastewater management will reduce the need for expensive upgrades at municipal wastewater treatment plants.
Air Conditioning (HVAC) Condensate Recovery
Air conditioning and refrigeration are widely used in California for creating comfortable indoor environments and for food preservation. As the water in an air conditioning system is being cooled, it is dehumidified, which causes water to be removed as condensate. This condensate, which is called heating, ventilation, and air conditioning (HVAC) condensate, can be used for subsurface irrigation or process makeup (such as a cooling tower) rather than allowing it “go down the drain” into the sanitary sewer system. By reusing this high-quality HVAC condensate rather than municipal water to meet onsite nonpotable water needs, the strain on the local water infrastructure is reduced.
It is important to note that HVAC condensate can amplify Legionella and other airborne pathogens. Such pathogens can make people sick, especially when an amplifying device that creates aerosols, like an air conditioner or spa, is present. This means that untreated HVAC condensate should be handled in such a way that aerosols will not be inhaled by humans. HVAC condensate should be treated for biological contamination even when used for subsurface irrigation or process makeup.
The following table, which was obtained from Boulware (2013) lists the estimated amount of condensate that can be recovered from a five-ton air conditioning system in an office building.
| Cities | Estimate Amount of Condensate Recovered (gal/yr) |
| Atlanta, Georgia | 1,186 |
| Boston, Massachusetts | 575 |
| Dallas, Texas | 1,068 |
| Indianapolis, Indiana | 806 |
| Minneapolis, Minnesota | 339 |
| Los Angeles, California | 119 |
| Miami, Florida | 2,886 |
Solar Water Distillation
Solar distillation is a desalination method that converts saline (salt) water into purified water using solar energy. The seawater or brackish water, which is known as feedwater, is heated by the sun until it evaporates. The condensation of the evaporated water can then be harvested for use. A simple solar still can be constructed from a plastic sheet in a survival situation. The video below describes how.
Solar distillation is a technique that dates back as early as the fourth century. In his writings, Aristotle describes a method of evaporating impure water and condensing it to generate drinking water. The first modern solar still was built in Las Salinas, Chile in 1872. It was comprised of 64 water basins made of blackened wood with sloping glass covers. This system was used to supply water about 5,000 gallons of water per day for the animals working in the mines. During the 1950s, interest in solar distillation was revived, and people sought to develop large centralized distillation plants. In California, the goal was to build plants that could produce one million gallons of water per day. However, after about a decade, researchers concluded that such plants would be too expensive in comparison to fuel-fired plants. Although solar distillation is still not considered to be a cost-effective means of supplying water on a large scale, it does make sense in areas where poor-quality water can be treated in large enough quantities to meet the demand for potable water.
Fog Water Harvesting
Fog water harvesting is a technology that has been used around the world for a very long time. In some areas, whole communities depend on fog water to supply potable water for their daily drinking water and washing. It probably goes without saying that fog water harvesting works best in areas where there is a lot of fog. For this reason, fog water harvesting is probably most appropriate for areas along the central coast of California that get a significant amount of fog.
A fog collector system is comprised of a square of vertically mounted mesh, typically made of nylon, polyethylene, or polypropylene, that can capture several gallons of water in a single day under the right conditions. The mesh part of a fog water collection system mimics the way the surface and ridges of a leaf collect dew along its stem.
Collected fog water can be used for irrigation or even potable water. Hangar 1, a distillery in the San Francisco Bay area, even makes vodka out of fog water. It should be noted that fog has been found to convey mercury from ocean upwelling. However, researchers have stated that the levels of mercury found in fog (to date) are not dangerous to humans. Peter Weiss-Penzias, an environmental toxicologist and researcher at the University of California Santa Cruz, conducted a study that found that although the mercury content in fog is not dangerous to humans, it can pose a threat to other terrestrial mammals (the study looked at mountain lions specifically). This is because mercury concentrations can increase by at least 1,000 times with each step up the food chain.
To learn more about fog water harvesting, check out this blog article that I wrote:
I would also recommend checking out the research conducted by Dr. Daniel Fernandez, who is a professor at California State University Monterey Bay. He also founded Bayside Fog Collectors, which is based out of Marina, California.
The video below shows some of the fog collection systems installed by Dr. Daniel Fernandez.
Dew Water Harvesting
Dew is water droplets that form on exposed objects in the morning or evening. As the surfaces of exposed objects cool by radiating heat, atmospheric moisture forms water droplets on the surface. The following conditions are optimal for dew water harvesting: clear night skies, little water vapor in the higher atmosphere, and sufficient humidity in the air. Unlike fog water harvesting, where the wind is desirable, the turbulence created by wind can prevent dew from forming.
While fog water harvesting systems involve a vertical collection surface, a dew harvesting system requires a horizontal collection surface. An efficient dew-condensing surface should be thin and lightweight. In addition, it should also be insulated underneath and be sloped sufficiently to drain condensate via gravity. Research has shown that a well-designed dew water harvesting system can collect 0.002 – 0.012 gal/ft2 of dew each night. However, the collection rate depends on the quality of the collection surface and the local weather conditions.
The quality of the collection surface has a significant impact on the amount of dew that can be collected. A study conducted by Dr. Sharan of the Indian Institute of Management found that dew production was 2.5 times greater when collected from new roofs versus existing roofs. This is because new roofing material has a higher emissivity. Dr. Sharan’s work also found that 35% more water was collected from rooftops with a western exposure due to longer time in the morning shade after sunrise.
The video below describes a dew harvesting system that was successfully installed in India. The reporter indicates that similar systems could collect 2.6 gallons per night from a residential rooftop.
Although dew harvesting systems will probably not collect as much water as some of the other technologies described in this article, they could be viable in areas where there are very limited options or serve as supplemental sources of water. As more research related to dew collection is conducted, more sophisticated collection surface coatings will develop. This will result in dew harvesting systems that perform better.
Imported Water Supply
Imported water from the Colorado River has allowed California to become what it is today. Southern California would not be what it is today without water imported from the Colorado River via the Colorado River Aqueduct. Recently, the feasibility of exporting water from the Mississippi River to the western United States has been discussed in the news. From a technical standpoint, it is probably possible to build a pipeline that would convey water from the Mississippi River to California. However, it would be very expensive and there would be significant environmental consequences. Furthermore, the Mississippi River has dropped to record low-levels. This indicates that it is probably not a good idea to take water out of the Mississippi River, especially since it is such an important aspect of the economy in the United States.