Wednesday, August 19, 2009

Homes pollute the water

Via PhysOrg:
They say there's no place like home. But scientists are reporting some unsettling news about homes in the residential areas of California. The typical house there — and probably elsewhere in the country — is an alarming and probably underestimated source of water pollution, according to a new study reported today at the 238th National Meeting of the American Chemical Society.
In the study, Lorence Oki, Darren Haver and colleagues explain that runoff results from rainfall and watering of lawns and gardens, which winds up in municipal storm drains. The runoff washes fertilizers, pesticides and other contaminants into storm drains, and they eventually appear in rivers, lakes and other bodies of water.
"Results from our sampling and monitoring study revealed high detection frequencies of pollutants such as pesticides and pathogen indicators at all sites," Oki says of their study of eight residential areas in Sacramento and Orange Counties in California.
Preliminary results of the study suggest that current models may underestimate the amount of pollution contributed by homes by up to 50 percent. That's because past estimates focused on rain-based runoff during the wet season. "Use of pesticides, however, increases noticeably during the dry season due to gardening, and our data contains greater resolution than previous studies," Oki says.
Pollutants detected in outdoor runoff included ant-control pesticide products. Previous surveys have shown that the majority of purchased by homeowners are used to control ants. To encourage pollutant reduction, the researchers initiated community outreach programs centered on improving both irrigation control and pest management.
I wonder if this will be something that will be studied by urban planners, architects, and landscape architects. I mean, if you ever watched a sewer system being repaired, you know that there are leaks. If you ever had power cut off water distribution to your house, you have probably heard the public announcements warning residents to not drink the water for a few days -- indicating that water distribution systems leak (but that the normal positive pressure keeps the contaminants found in the ground out of the drinking water).

You also know that people use pesticides, herbicides, and fertilizers in their gardens and their lawns. True, not all places are subject to the same cycles of a Californian wet and dry season, nor do all places have the same surficial geology as found in the research area. However, irrigation (i.e., watering your lawn) continues throughout the summer months, and the desire for verdant lawns means that there is a market for fertilizer and pesticide use, and these get into the groundwater.

Now, this article also makes it seem like there are problems with the previous models, and that may well have been the case. However, I don't know that the problem was in the model, but in the groundtruthing of the model, as it was applied to a region outside where it was developed, and why not? Well, I'm assuming that the model was developed a couple (or more) decades ago -- before companies like ChemLawn came into the forefront of "lawncare". They were also probably made before the production of suburbs with massive lawns were included in the "city". In the time when the models were made, therefore, the only major source groundwater recharge came from rain, since people didn't water their lawns (so much) and (might even) have left it to go brown (or grown climate-adapted grass). In this condition, the addition of home-scale lawn chemicals wasn't at all significant, and was therefore left out of the equation.

Skip forward to today, where we live with a California with large ChemGreen lawns (nothing against ChemGreen, but it seems to be the major "lawncare" company in the Ann Arbor region.) that need constant watering (since the lawns aren't made up of climate-adapted grasses) as well as doses of pesticide and herbicide. (Thus, you have warnings of not allowing children or pets on the grass after an application by ChemLawn.) It's not surprising that this new reality in which we live needs to be considered in a different light than the reality in which the model was developed: the physical conditions have changed, and the models representing those physical conditions should also change.

... especially if we will be living in a world in which we want to use science and engineering to make policy and management choices about physical world issues. Especially, too, as we learn the various ways in which we cumulatively impact our surroundings, including those regions that we cannot directly see (e.g., groundwater). Especially, further, if we wish to have predictive capabilities for future management action and being able to incorporate the changes we will see not only form an altered climate, but also from increased population demands on the land, air, and (in this case) water.

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