Saturday, June 30, 2012

Introduction To Drip Irrigation System Design 102


In my previous article, Drip Irrigation System 101, I set forth the basics on how to approach your watering system design by laying out your landscape and determining what the watering requirements will be for your area. Those that have an interest in drip irrigation are individuals interested in water wise gardening and saving money.

Additional interest for drip irrigation is for those odd-shaped and narrow areas where conventional impulse type sprinklers would not be economical as a conservatory water measure. Besides being easy on water supplies and it will be a deciding factor on determining exemption status on water restrictions which may be imposed in a drought area by local authorities.

Drip irrigation exceeds 90 percent efficiency whereas sprinkler systems are 50 to 70 percent efficient. It is so efficient that many water utilities exempt landscapes irrigated with drip from restrictions during drought. Note that any irrigation system is only as efficient as the watering schedule used. If systems are set to water excessively, any system including drip can waste water.

Low volume application of water to plant roots maintains a desirable balance of air and water in the soil. Plants grow better with this favorable air-water balance and even soil moisture. Water is applied frequently at low flow rates with the goal of applying only the water plants need. Sprinkler irrigation results in a greater wet-to-dry fluctuation in the soil and may not produce optimal growth results.

Over the years micro-irrigation systems have evolved in a better design for use in the home gardens. Traditionally it was used in the commercial growing industry. When combined with a controller, drip irrigation system can be managed with ease.

There are a lot of benefits for a drip irrigation system, minimizes water loss due to runoff, wind and evaporation. As seen in Colorado drip irrigation can be operated during the windy periods frequently seen in Colorado.

All in all, drip irrigation system are easy to maintain and change as different scenarios present themselves.

Up to now, all we have done was to praise the virtues of a drip irrigation system; well, there are some disadvantages. For example, if emitters are poorly placed, too far apart or not enough, root development may be restricted. Drip tubing can be a trip hazard especially for dogs and children but is less problematic if covered with mulch and fastened with wire anchor pins every 2 to 3 feet. Drip lines can also be easily cut while undertaking other landscape maintenance activities.

A final word on emitters; there are two types, pressure-sensitive or pressure-compensating. Pressure-sensitive emitters a higher flow at higher water pressure. Pressure-compensating emitters provide the same flow over a wide pressure range.

For those of you who would like to calculate the GPM in your home, follow the below procedure:

To evaluate source flow rate, run water full force from an outside faucet and note the number of seconds it takes to fill a bucket. Calculate the gallons of flow per hour (gph) by dividing the bucket size in gallons by the number of seconds required to fill it, then multiply by 3600 seconds for gallons per hour.