Dunkelheit wrote:
In practice only the topsoil will be polluted and degraded? Now that's a relief.
No, seriously. Beside the yet mostly unknown health risks and unknown chemical reactions of chlorinated water in the landscape there is one aspect that should make you think: When you water your garden with chlorinated water all the negative loaded minerals will be gradually washed out of the soil, e.g. phosphate, sulfur, nitrate. Because chlorid is blocking all the positive loaded anodes with an anion. It is highly reactive. Watering with chlorinated water has a cumulative effect on the soil, too. In the end you have to use mineral oil fertilizer to replace your missing nutrients.
In Europe it is forbidden to water plants with chlorinated water that serve humans directly or indirectly (e.g. cattle, chickens) as a food source. It is also strictly forbidden to empty your swimmming-pool's content in the landscape.
I think you're over-estimating the amount of chlorine, and conflating covalently-bonded chlorine with chloride ions.
I didn't say, or mean, "only topsoil." Tap water usually doesn't have much chlorine in it (pool water is a very different story), and good soil has a lot of buffering capacity. Most soil microbes will survive, unless the soil is extremely poor or the irrigation is idiotically frequent.
Most of the chlorine does eventually become chloride ion, but not enough to dissolve absolutely every cation. In fact, a reasonable amount of irrigation will probably not even put in as many chlorine atoms as healthy soil would have sodium atoms. Also, if stored rainwater is scarce, using it on the lawn doesn't make much sense to me, if it might later mean chlorinated tap water is used in the garden.
I absolutely agree that food production via irrigation with chlorinated water is a bad idea in the long run, I just wanted to state that seldom, deep irrigation of a lawn might be, on balance, a good thing for microbial life, even if the water is chlorinated.
"the qualities of these bacteria, like the heat of the sun, electricity, or the qualities of metals, are part of the storehouse of knowledge of all men. They are manifestations of the laws of nature, free to all men and reserved exclusively to none." SCOTUS, Funk Bros. Seed Co. v. Kale Inoculant Co.