Tuesday, February 10, 2009

water, water everywhere

There are some memories that are impossible to properly conjure up without the right setting. It’s tough, for instance, to accurately remember the sound of falling snow in August when it’s 100 degrees outside. Likewise the winters where I live are usually unsuitable for thinking correctly about drought; case in point this winter, during which it seems to have rained every four days for the last three months. You won’t hear me complain because we’ve had unusually dry weather for during the past few years, but I need a truck load of soil delivered to finish up a series of raised bed planters I built last autumn. The person who is supposed to bring me my soil hasn’t had dry enough weather this winter to bring me my soil without getting his truck stuck in my yard. It's good thing I’m not in a hurry.

So it’s been hard this winter to think about how it might be too dry this summer and how hard those conditions make growing food, especially in poor soil. The agricultural extension officer in my county made an interesting comment the other day. He said that if the soil is in great shape, irrigation is unnecessary. He’d be right of course in all but the most extreme drought conditions but then again we’ve had such conditions several times here in the Southeast during the last decade.

Several years ago I was gardening in a neighbor’s backyard in soil that was not yet in prime condition. I all but abandoned the garden in August when we had 10 weeks without a single rain event. As Benjamin Franklin once said, “When the well runs dry, we know the worth of water.” If you’re starting a garden you’ll want to consider how you plan to provide it with the water necessary to be successful if it doesn’t fall from the sky.

I’ll talk more about soil in a future post but it’s worth mentioning here that the health of the soil and its makeup are important when considering how important irrigation will be to the success of your garden. Healthy topsoil will have plenty of organic material in it that will help hold water after it rains. If you’re gardening in the dirt that was left behind in the wake of most new home construction projects it’s likely to dry out much quicker. So it’s important to consider your soil and think about ways to improve it or even ways to import better soil from elsewhere to get your garden going.

Water for irrigation is available from four sources: ground water, municipal water, grey water and rain water.

Ground water is available from springs or by drilling a well. Many parts of the country can support moderate amounts of water being drawn from underground and recharged naturally.

Some parts of the country however are already pumping water out of the ground a rate much faster than can be naturally recharged. These regions are endangering their futures. It’s difficult to gauge how much ground water is left because it’s out of sight. It is also possible that ground water can be contaminated by natural occurring high concentrates of compounds that are poisonous to humans. Have your ground water tested to be sure it’s safe. It’s also worth mentioning that in many parts of the country, drilling a well can be expensive. Contact a local well drill for more information.

Municipal water includes water that is provided by city or county governments. Often this water is pumped from lakes and rivers before being filtered and purified. The chemicals used to clean this water are harmful to soil life and often raise the pH making it less than ideal for irrigation (and arguably less than ideal for human consumption). Given a choice between letting your garden croak or irrigating with municipal water, it’s probably practical to use city/county water. One of the positives about municipal water is that in many places it is easily accessible with good pressure and is relatively inexpensive. It may also have pharmaceuticals and the residues from other chemicals used upstream but hey, nothing’s perfect.

Grey water is water that has been used in sinks, showers and tubs in households. Recycling it entails diverting it to the landscape instead of directing it into the sewer or septic system. It is not water from toilets which is called black water so as to distinguish it from grey water. Using grey water in your garden can be as simple as saving water in a dish pan and pouring it on plants.

Remember that this water can have soaps or oils in it so be careful what you’re using to clean your dishes if you plan to redistribute that water into the landscape. Food or skin particles could be a source of foul smells or even disease if left to build up but for the most part, grey water is a safe way to use water more wisely. Some parts of the country promote grey water recycling while it is illegal in others. Those places where water is scarce have long recycled their gray water. In such parts of the country, grey water systems have developed that are more advanced and direct water and sometimes filter it as part of the plumbing of the house. Art Ludwig’s Create an Oasis with Greywater is the classic text on the subject. Here’s a good website as well.


Humans have been harvest rain water for thousands of years. If you’ve taken a vacation to a tropical island nation you’ve likely seen the systems used there for capturing rain. The water falling from the sky is likely your cleanest source depending on the quality of air in your area. It won’t have harmful chemicals in it and the pH will be very close to neutral.

The sky is the source of water that will naturally irrigated your garden as it has rained on the surface of our planet for millions of years. The catch of course is that it won’t always rain in the amounts desired to keep your garden healthy or at the times when you most need the water. Here in central NC we get more rain in the winter than in the summer and much of our summer rain comes in the form of thunderstorms that might drop 1 or 2 inches of rain within an hour. So while we get more rain annually here in Charlotte, NC than in Seattle, WA or Albany, NY (check your average annual rainfall here) we don’t always get the amount we want when we want it; and that’s without the recent drought periods factored in or droughts of the future aggravated by climate change. Harvesting and storing rainwater is an excellent way to irrigate gardens.

There are three basic types of water storage: above ground, in ground and below ground.

Above ground storage happens in tanks or other containers that hold water collected from impervious surfaces, mainly roofs. Containers range in size from 42 gallon rain barrels to tanks that hold many thousands of gallons. These containers can use pumps to push the water to where it’s needed but because they are above ground they often just use gravity to move water from storage to the garden.

It’s relatively easy to see how much water is available and set up and maintenance of such tanks is relatively simple. The down side is that the aesthetics of a series of rain barrels or a giant tank might not blend in the landscape ornaments in your neighborhood. By the way these storage systems are relatively cheap compared to the in ground or below ground storage systems.

In ground systems refers basically to ponds or lakes. If you have an existing pond on your property consider yourself blessed. This type of natural water storage system has been used for millennia as a way to store irrigation water.
It can also serve as an ecosystem capable of providing you with fish and other sources of protein as well as providing a home for nutritious aquatic plants like cattails. Ponds also serve as a necessary resource for the other animals that will call your property home. Construction of ponds can be expensive depending on size and the type that is right for you based on the soils in your area. In short a pond or lake can is an excellent resource and one that an entire class could be devoted to in terms of construction and utilization. Personally I’ve always wanted to try fresh water pawn production.

Below ground storage refers to tanks used to store water in tanks, well, below ground. The excavation necessary for installation and maintenance and the reinforced tanks necessary for such storage options make this a more expensive choice. It does get the tank out of your yard though and for people for whom space is tight this might be the only option available. A pump will be necessary to get the water back up above ground. Filtration of ingoing water will be even more important as in ground systems are much harder to clean. Brea rainwater harvesting systems is a local company I’ve dealt with in the past in researching and pricing such systems.


The Texas Manual on Rainwater Harvest (a free PDF) is an excellent resource. I printed out a copy and it lives in my bookshelf and is regularly referenced.

Brad Lancaster has written two great books on the subject

Rainwater Harvesting for Drylands and Beyond Volumes One & Two

Here’s an article and a video of Brad.

Abundant Skies: 8 Principles for Successful Rainwater Harvesting

This alternative also looks very interesting. It fights in the crawl space beneath your house.

I’ve heard of similar systems used in Australia and would love to hear from any of my Aussie readers as to how well they work.

I should mention that there is another problem having to do with water that I haven’t mentioned here at all, flooding. Sharon has more experience with this than I do but it’s entirely possible to site your garden and get it completely ready this winter only to see it flooded this spring. Be sure that your garden is outside of all flood zones that fall within your property. Pay attention after (or during) heavy rains to see where the water on your property goes. This will help you not only to be able to avoid areas prone to flooding but also to know what areas might work well as places to store water.

Another aspect of water outside my area of expertise is the spring melt. For many of you living further north, snow and ice will melt in the spring and provide you with a great deal of water. This might mean flooding or it could be an opportunity to harvest water for use later in the year.

Like all other natural systems, understanding the hydrology of your particular site will require careful observation and harnessing the water available to you will take thought and improvisation.


Anonymous said...

nice tip of the cap to coleridge...

Anonymous said...

What do you do if you live in the north -- dry summers, snow in the winter. How do you harvest snow/rain in tanks without the tanks cracking due to freezing?