27. Landscape Sustainability - Irrigation Efficiency
In the few months since I wrote about water efficiency and irrigation water use, California has gone from a dry year to a very dry year, with drought restrictions looking likely for most of us Californians. So it is more important than ever to make sure you are watering your garden as efficiently as possible. Beyond the use of plants that don’t need much extra water, and grouping plants with similar water needs, there are also a lot of ways to get water to your plants more efficiently, whether you already have an irrigation system or not.
First of all, do you need an irrigation system? That depends on many things, but mainly the size of your garden, the amount of time you want to spend watering it, and the climate you’re in. For most of California the long dry season means that you have to do some watering and using a hose starts to get time consuming, even for the average little yard in Berkeley. Plugging your hose into one of the old fashioned sprinkler attachments saves you time, but will almost always be wasting water. So the majority of gardens are going to benefit in a lot of ways from an automatic irrigation system.
Spray versus Drip Irrigation
I’m not going to attempt to describe everything about irrigation systems here, but I want to talk about one of the big choices you have: overhead spray or drip irrigation. Overhead spray irrigation uses the more traditional sprinkler heads that are meant to uniformly spray water over the tops of the plants. Drip irrigation uses tubing with emitters that deliver water at the ground level to specific points.
Generally drip irrigation is much more efficient for all types of landscapes. Lawn areas are perhaps the one place that spray irrigation works well, but there are recent developments in drip tubing with in-line emitters that are able to evenly water a lawn with a lot less water. (You should be keeping your lawn size to a minimum anyway!) Because drip irrigation is delivering water at specific points, you have a great degree of control and can get the water directly to the root systems of your plants, applied at a slow rate so that it all sinks down into the soil right there. Drip irrigation also avoids two other big efficiency losses for spray irrigation: evaporation as that fine mist travels through the air, and wasted overspray onto paved areas.
Varieties of Drip Irrigation
When thinking about what sort of drip irrigation system will be most efficient for your yard, you should consider variables such as plant type, plant spacing, soil type, and the slope of the ground. In most home gardens, with shrubs spaced a foot or more apart, drip tubing is probably the best system to go with. This consists of the spaghetti-like 1/8” tubing snaking around to deliver water to the root balls of the plants. This tubing generally sits on top of the soil for ease of access, but is concealed from view below a bark mulch layer. The emitters plug into the end of a tube and are placed at the edge of the plant’s root ball. For a more densely planted area with groundcover or lawn, in-line drip tubing is better. This consists of a tube with emitters set within it at regular intervals which can be placed in parallel rows to evenly distribute water throughout the area. Micro-sprays and bubblers are other efficient alternatives to overhead spray that can deliver water to a root zone area that is larger than can be served by a few drip emitters.
Smart Irrigation Controllers
Another important aspect of irrigation system efficiency is the controller you use to operate it. For a small yard you may just have a single zone that all gets watered at once, which only requires a simple time clock. However, if you have more than one watering zone and a number of different valves, then you need a more sophisticated controller. Once you get to that point, Smart Controllers (also referred to as Weather Based or Self-Adjusting) are the best option. Some manufacturers claim that you can reduce your water use by 30%-70% with these controllers – quite significant!
A smart controller factors in different variables to calculate available soil moisture. Based on this calculation, it adjusts the amount of water your garden receives on any given day for big improvements in efficiency. The variables that can be included are: current temperature, rainfall, humidity, solar radiation, soil moisture, evapotranspiration, historic weather data and prevailing weather conditions. This data comes from on-site sensors installed with the system, as well as local weather data obtained from a connection to the internet. For example, a rain gauge attached to your roof eave will tell the system not to run the irrigation when it is raining, and the more advanced ones can adjust the amount of irrigation water according to the amount of recent rainfall. It is impressive how intricate the calculations are with these smart controllers, and certainly worth a little more expense for the water that you will save over the years. There are also some rebates available from local water providers; for example, the East Bay Municipal Utility District offers a $75 rebate for the installation of an approved “Self- Adjusting Controller”.
Irrigation Elation
I’ve just touched on a few aspects of efficient irrigation systems to give you an idea of the many great benefits of an efficient automatic irrigation system. Maintenance of your irrigation system is also critical to keeping things efficient, and with drip tubing you do have to be careful not to accidently cut something and create a hidden leak. Having a dedicated irrigation water meter will help to warn you of leaks and improve your awareness of the water used. You can also have an Irrigation Audit done by either your water supplier, or by a professional. For example, EBMUD offers a free Residential On-Site Water Survey that can get you going in the right direction.
Installing a small drip irrigation system can be done on your own and the Urban Farmer store is a good place for do-it-yourselfers to start. However, there really is a lot to a maximally efficient irrigation system design, and when in doubt, consult with a professional Irrigation designer and/or Landscape Architect. Drip irrigation not only saves you water, it also decreases the chances of plant diseases, and it even reduces weed growth since the water only goes to the plants you want to grow. Happy dripping!
References:
The Urban Farmer Store: http://www.urbanfarmerstore.com/
Bay Area Water Supply and Conservation Agency: http://bawsca.org/
Stop Waste.org Lose Your Lawn page: http://www.stopwaste.org/at-home/home-gardening/go-from-lawn-to-garden
East Bay Municipal Utility District: https://www.ebmud.com/water-and-wastewater/water-conservation/residential-services-and-rebates