Rainwater Harvesting Warnings
Homeowners should heed a few warnings before building a rainwater barrel. Avoid clear containers to prevent algae growth, and cover the top and all other openings to keep debris and mosquitoes out of the barrel. Mosquitoes can carry the West Nile virus and will turn a rain barrel into a breeding pond.
There also is a patchwork of rainwater harvesting laws in the arid western United States, where the practice is most useful. In every state west of the Rocky Mountains, water law is dauntingly complex. Every drop of rainfall is subject to water rights often stretching back 100 years.
It is illegal in Colorado and Utah to harvest rainwater in barrels (though constructing small depressions and berms is approved) because homeowners typically do not own water rights. On the other hand, cities in Arizona and New Mexico require rainwater harvesting for some new construction projects. Texas offers business tax rebates for large-scale collection systems.