Where’s Your Garden’s Water From?

By Karen Filchak – Extension Educator – Residential Environmental & Water Quality

garden hoseWater for farms and gardens can come from several possible sources, including wells, municipal sources, ponds and rain barrels. Some water sources are more likely than others to be harboring harmful pathogens that might contaminate your garden goodies with salmonella and E. Coli and other creepy things. Public water supplies are monitored and treated for contaminants, so city dwelling gardeners are usually pretty safe. But it’s up to the home gardener to have the garden’s water source tested (private well, rain barrel or pond) before watering the garden’s edibles.

Can You Wash Away Those Garden Worries?

Is your watering hose attached to a well, a pond or your local public water supply? You may think that this is not a question that needs to be asked this year, when we have been deluged with ample water from the sky for months now. Things can change quickly enough, though. I am currently sitting on my sister’s porch in Virginia looking out on a lawn that is golden brown. They had a wet spring too. You may be turning on the spigot soon enough. August could be dry as a bone.

Several foodborne illness outbreaks in recent years have been attributed to irrigation water that is contaminated with a variety of pathogens. In 2003, green onions from Mexico sickened 500 and killed 3 people. Irrigation water was thought to be the source of the hepatitis A virus that caused the illnesses. Remember the E. coli outbreak attributed to spinach a few years ago? While a definitive cause has never been identified, the Centers for Disease Control (CDC) considers contamination of surface/ground water by manure from a nearby ranch as one possible source. And, more recently a salmonella outbreak tied to Serrano peppers may also have been the result of contaminated irrigation water.

Water can be the source of a variety of pathogens or microorganisms that cause food or water borne illness, including E. coli O157:H7, Salmonella spp., Shigella spp., Cryptosporidium parvum, Giardia lamblia, Cyclospora cayetanensis, and the Norwalk and hepatitis A viruses. A lot of research is going on right now to figure out if these microorganisms are simply hanging out on the surface of crops (which means you can wash them off) or if they are actually finding their way INTO the plant from contaminated soil or irrigation water. This is why commercial farmers are being asked to pay attention to the source of their water.

We always think that these outbreaks are only going to happen on big factory farms. But, the bugs that cause foodborne illness are just as likely to be in your compost, your soil, on your hands or in the bird poop that lands on your very own lettuce crop. And, they can also turn up in well water or pond water you use to water your garden. Or, maybe in the rain barrel that is catching the rain off your roof (that same roof where pigeons, squirrels and other wildlife like to frolic and perch).

Just like commercial farmers, home gardeners use water for irrigation (we call it watering), sometimes to apply pesticides and to clean produce of the major dirt before we bring it inside.

Water for farms and gardens can come from three possible sources (not counting rain). Municipal or public water systems are the best source of water for use on fruits and vegetables. They have the lowest risk of contamination. Public water supplies are monitored and treated for contaminants. Private wells that are tested annually and found to be safe are also unlikely to contaminate produce. Ground water is less likely to have microbial contaminants than surface water. Surface water (ponds and streams) is most likely to be affected by watershed activities and season and, therefore, present the greatest risk of contamination from harmful pathogens. Rain barrels have become quite popular, but there is not a lot of research out there addressing the risk of microbiological contamination from this water source. So…If you use a public water supply there is no issue, really.

  • If you have a well, test your well water at least once per year.
    At the same time, it is always a good idea to check the condition of your well, well cap, and the area around your well. If there are any signs of a maintenance problem or indications of access by mice or other wild life, have it professionally evaluated and fixed. Also, if you notice changes in your water quality, such as cloudiness after a storm, this may indicate that surface water is contaminating your well. Have it checked and test the water.
  • If you use surface water, do a baseline test.
    It might not be a bad idea to do a baseline test to determine the quality of that water. Surface water is the source MOST likely to be contaminated with microorganisms that can cause illness. So, water that is heavily contaminated may not be a good choice for watering edible crops.
  • If you use a rain barrel, keep in mind that the jury is still out on this one.
    Some dismiss the notion that there is risk from salmonella from bird or squirrel poop or other microbial contamination. But, if you do have the option, it might be best to save rain barrel water for use on non-edible plants.
  • Where should you test, what does it all mean?
    If you need to test your water source (well or surface), how do you do this and what to the tests mean? Water testing can be useful tool, providing you with information about the quality and safety of your water supply. First, you can go to Connecticut’s Department of Public Health website to find a list of licensed environmental laboratories in Connecticut or contact your local health department.

Standard/conventional water tests will tell you if your water supply contains “fecal coliforms” or “generic” E.coli. The presence of these organisms shows that your well is contaminated with bacteria, but does not tell you about the presence of pathogens (bacteria, viruses or parasites that can make you sick) like E. coli O157:H7. Only a small portion of E. coli strains are pathogenic. If you are concerned about possible contamination by specific bacteria or other pathogens, you should request that your water sample be tested for these.

While standards do exist for drinking or potable water (find them at the EPA website), there are no universally accepted standards for irrigation water used on fruits or vegetables. In California, current recommendations follow a guidance level of 1000 fecal coliform or 126 generic E. coli per 100 ml of water. You might consider using this level to guide your own use of surface water on the home garden.

Paying attention to the source of the water used in your garden is a good idea. And it doesn’t take much time or money. The lucky recipient of your extra zucchini will surely appreciate it. It doesn’t take too much time to do things right.