The water news this year sounds like a lot of recent years. So little rain and snow that the governor has declared a state of emergency. The ground is dry and much of the water that usually comes down from the hills will soak into the ground and never make it to the reservoirs.
It isn’t strange, really. We live in a high mountain desert in the second driest state in the country. That much has not changed. We can plan on chronic water shortages. Exceptionally dry years drive the point home, but we always need to try to conserve water.
Gardens need water and we need gardens and landscapes for a host of reasons, so we must mesh the need for irrigation with efficient water use.
Drip irrigation is an exceptionally good method to apply a minimal amount of water while still giving plants an ample amount to grow on. Drip systems can reduce the amount of water applied by up to 70 percent and still produce excellent garden growth. This alleviates over watering problems, runoff, and erosion if the systems are designed and used properly. There are several other pluses. Since these systems are designed to put the water only where it is wanted, at the base of desirable plants, they don’t water weeds between the rows. You can get out into the garden even during irrigation because the areas between rows remain dry. This cuts down on the work of weeding and other maintenance operations and greatly increases crop yields by not encouraging the competition.
Sprinklers lose a lot of water to evaporation — especially on hot days — but drip systems lose little. Most of the water emitted reaches the plants’ roots. Soaker hoses put water directly on the ground in a thin strip, but drip irrigation is more efficient in precisely regulating water output and placing it in specific spots. Drip hoses disperse water slowly so it has time to soak in instead of running off or puddling. The chances for overwatering are also lessened. Unlike soaker hoses, drip components allow use of a wider range of emitters and they compensate for changes in water pressure and elevation.
If the emitters are spaced far enough apart, there will be an area of dry surface soil between their moist circles. When rain is absent or infrequent, this dry zone means that weeds will not have enough water to germinate.
All drip systems have several basic components. The starting point is a shut-off valve between the main water supply and the drip system. In a simple system this is the standard hose bib or outside faucet. An anti-siphon valve is required by some building codes to prevent irrigation water from siphoning back into drinking water. Without this valve, dirt, fertilizer and other contaminants can be sucked backward into the culinary supply pipes.
Water contaminants are particularly troublesome for drip systems. Sediment plugs openings and makes the watering uneven. Place a 200 mesh or finer filter in the system before the pressure regulator. The pressure regulator reduces the pressures to low levels to prevent the system from blowing apart since the components are not glued together.
Specialized hoses are used as header hoses or submains for drip systems. It is formed from low density polyethylene and is very flexible and will curve into a tight arc without crimping. Elbows are available but are rarely needed. The header hose is inexpensive and durable. Water is delivered to the soil through emitters or through drip tubes that are attached to the header hose. Emitters are varied parts that are punched into the tubing to control the water flow.
Drip tubes have holes or openings built into special tubing. For calcium problems, use large orifice emitters.
Drip irrigation kits usually do not have the optimal garden design. Parts from one kit will not fit other kits, and spare parts are usually sold in packets. When purchasing a system, buy from a dealer who stocks standardized parts and will help design your system.
Use a manual or an automatic valve for each separate bed. Using an automatic timer or controller is a convenient way to regulate the watering time. Timers that run on water pressure and shut off after a certain amount of water passes through are not recommended, because they will not shut off due to the low water pressure and small volume of water used in a drip system. Electric valves control the entire system using an inexpensive timer.
All irrigation systems are designed to replace moisture lost by both evaporation and transpiration. The evaporation/transpiration rate is affected by temperature, humidity, dew point, wind speed and sun. Plants need at least the same amount of water as they lose through these forces.
Tubes can be buried, but leaving them on the surface has many advantages. You will know where they are and can avoid cutting them with hoes and cultivators. Rodents, especially gophers, can cause problems because they can chew through buried lines.
On ground that rises and falls, pressure compensating emitters are required. They deliver the same amount of water regardless of the change in elevation or the length of the line. Without these, more water will flow out at the bottom of dips than at the top of ridges.
Estimate the future needs of the planting when planning the drip irrigation system. Take into account the length of each line and the number of lines needed for the garden. Different plants have different water requirements and people tend to water for the thirstiest plants. Group plants with similar needs and put in a system that will accommodate those needs.
Three basic plant groups can be adapted to drip irrigation. These include fruit trees, vegetables, and ornamental shrubs, trees and flowers. Different emitters accommodate these plants’ different needs.
The flow rate of tubing or drip emitters is measured in gallons per hour, or GPH. The greater the GPH, the faster the water comes out and the broader the area that will be soaked. The GPH is best determined by the difference in soil texture. Sandy soils require a high flow emitter, 2 to 4 GPH, to disperse enough water to spread. In clay soils, use low flow emitters, 1/2 to 2 GPH 18 to 24 inches apart, or higher flow, 2 to 4 GPH, spaced farther apart.
Experimentation is the easiest way to determine the watering pattern. In dry soil, start one emitter dripping at the correct pressure. Check the water spread every hour by poking a rod into the ground alongside the emitter or drip hose at increasing distances away from the starting point. Because each drip emitter applies water to a localized spot, it is easy to check the water level and the spread in a soil profile. When water is applied slowly to sandy soil it soaks a deep and narrow area. The soaked area forms a carrot-shaped profile. When water is applied more quickly it soaks a beet-shaped profile. The profile shape depends on the consistency of the soil because sandy soil will absorb water in a carrot pattern as it quickly penetrates, while in clay soil absorption will be beet shaped.
Drip irrigation is ideal for vegetable beds. Suggested dimensions for vegetable beds are 3 to 4 feet wide. Each 3-foot bed needs two lengths of inline drip hose.
Drip installation is not difficult as long as the system has been well designed. Most components easily slide together. All metal pipe threads should be coated with Teflon tape to make a watertight seal.
Flush the drip system after assembly to keep the lines clean and free from emitter clogging dirt. After all the emitters are punched into the line, open the closures and flush the lines individually. When using an automatic controller, check to determine if the lines are turning on and off as planned. Set the timer and observe it as it goes through several cycles.
Keep the system working well by flushing the filter every two to four weeks. Remove algae build up on the screen with bleach and a stiff brush. Each month flush the drip lines for a minute or two. In severe cases of silting or calcium buildup, clean the emitters by pumping a weak acid solution through the system.
Unburied lines should be rolled up and stored inside in the fall. Drain the lines and cover or plug the ends to keep insects or other unwanted creatures from getting inside and clogging the lines the next season. Lines under heavy mulch can be left if all lines are drained and there won’t be any traffic on the frozen soil over the drip line.