California’s drought woes have garnered a consistent flow of media attention, but the Golden State isn’t the only place with dismal rainfall, a low snowpack or month-long dry spells. Many growers throughout the country are starting to feel the effects of climate change in the form of hotter summers and dryer winters.
There are a number of tools that can help growers capture and conserve water during thermometer-busting heat waves, ranging from old-school agricultural solutions to futuristic methods.
- Drip Irrigation
Description: This water-saving irrigation system directs water at or near the plant’s root zone. While growers can purchase drip irrigation systems with automatic controls, one can also be created cheaply using a garden hose and some additional tubing.
How it works: The system is designed to slowly and steadily deliver water to the plants. A feeder hose connects the drip irrigation system to the water source. When the system is turned on, the water flows out of drip emitters, typically quarter-sized devices that are aligned in rows on the ground. These emitters ensure water flows directly into the ground, maximizing root zone absorption while minimizing surface moisture and water loss due to evaporation.
Water saved: This depends on a variety of factors, including the number of plants and the inputs used. Fully automated systems have a higher capacity to conserve water than low-tech do-it-yourself versions. Pros: Reduces weeds by keeping soil surface dry; works in conjunction with recycled water, mulch, ollas and other aids.
Cons: Can be costly; can’t be used to harvest or store water; unless growers have an automatic system, they will need to monitor the process.
- Rain Barrels
Description: As the name suggests, rain barrels are large containers that collect and store rain.
How they work: These plastic, wood and metal barrels capture runoff from a roof. The barrels collect and store water, which would typically go through gutters and downspouts.
Water harvested: A typical residential rain barrel holds 55 to 90 gallons of water. Depending on the rainfall in the region, barrels can be filled multiple times during one storm and hundreds of times throughout the rainy season.
Pros: Passive collection process; low cost (there are do-it-yourself or ready-made options); can easily be connected to drip irrigation systems or used in conjunction with ollas.
Cons: Dependent upon weather conditions; storing rain for the dry season can be a hassle; minimal cost savings; rainwater collection laws vary by city and state.
Description: An ancient irrigation method that has regained popularity with today’s gardeners, ollas are bottle-necked unglazed clay or terracotta pots that are buried in the ground. They irrigate the plants below the surface of the soil.
How they work: When an olla is buried — be it in the ground of the garden or in the same container as a potted plant — the neck (top) of the olla remains exposed but capped. This is where growers add water. Because of the porous nature of clay/terracotta, the water slowly seeps through the walls of the olla toward the plant’s roots. The water flows in this direction due to a suction that is created when the roots grow around the olla. The plants only pull as much moisture as necessary, ensuring the grower won’t waste resources or stress the plant by overwatering.
Water saved: Water savings vary depending on the size of the olla, the amount of plants and other factors related to production methods. Some estimates indicate that 50-70% water savings can be realized, particularly for vegetable crops. Growers are likely to not only use less water, but to water less frequently.
Pros: Low cost; reduces weeds by keeping soil surface dry; works with recycled water; reduces crop inputs (some estimates say up to 50% less fertilizer is required); can be used in conjunction with other water-saving equipment.
Cons: Not generally viable for commercial-scale operations; active watering process requires growers to fill the pots; can’t be used to harvest or store water.
- Fog-Harvesting Systems
Description: Originally developed to capture airborne water droplets in regions with severely limited annual rainfall, fog-harvesting systems are composed of vertical woven mesh (typically polyethylene or polypropylene), two posts and a bucket, tank or other water-capturing vessels.
How they work: The systems harvest water droplets from dense fog with light to moderate winds. Water droplets form on the mesh screen and gravity pulls them down the screen into a bucket. Because the water in fog is clean, as long as the collection process is carefully handled, the water remains clean and ready to be used on crops. FogQuest, a Canadian nonprofit that tackles fog and water collection projects in developing countries, suggests erecting single collectors spaced about 15 feet apart. Double collectors, which have three posts, can also be used, but the system shouldn’t join two double collectors together. This would obstruct the wind, limiting the amount of water collected.
Water harvested: FogQuest estimates each cubic meter of fog contains anywhere from .05 to .5 grams of water per cubic meter of fog. The organization’s large capture systems (with a 40-square-meter collecting surface) harvest an average of 50 gallons per day throughout the year. Research conducted at MIT, however, indicates that there may be a way to capture even more water. Most systems can get 2% of the water during a mild fog condition, but researchers predict that finer mesh harvesting systems could collect as much as 10% of the water.
San Francisco-based Hangar 1 recently introduced a vodka that is made primarily of Bay Area fog captured using a FogQuest system. According to a story by Fast Company, Hangar 1’s Fog Point is 60% fog.
Pros: Passive collection process; relatively low cost (FogQuest sells small- to mid-sized pieces of mesh for small-scale collection projects); water doesn’t require a filtration system; can easily be used with other water-saving systems; also collects rain.
Cons: Requires the grower to build the system; dependent upon specific weather conditions; needs to be erected in an area without obstructions such as trees or buildings.
Description: Growers are familiar with mulch, but when it comes to keeping cannabis crops moist during dry times, not all components are created equal. Coarse organic options, such as bark, wood chips, compost or sawdust, tend to be the best at absorbing rainwater, limiting evaporation and reducing soil temperatures.
How it works: Mulch absorbs and reflects sunlight to prevent moisture from evaporating, and it is known to increase soil water retention by decreasing runoff.
Mulch is most effective at conserving water when it’s applied in the spring, particularly after a wet winter, or in the autumn before the first frost. If growers wait until the summer, the soil is likely dry enough that the water-saving properties won’t make much of a difference.
Water saved: The water savings vary, but to conserve as much as possible, the Oregon State Extension Service recommends growers layer the mulch three to four inches deep and replenish it every one to two years for bark, or every two to four years for wood chips.
Pros: Relatively low cost; reduces weeds by keeping soil surface dry; works with recycled water, ollas, drip irrigation and other equipment; long-lasting.
Cons: Can’t be used to harvest or store water; generally most effective when applied early in the growing season.