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Image: Coyote Gulch archives
Collecting rainwater has been in the news lately. Freshman State Senator, Chris Romer, introduced legislation in the session this spring (SB 08-119, Allow Domestic Exempt Cisterns) -- to allow 10 pilot projects statewide -- only to see it watered down into a study request. Governor Ritter signed it into law on May 29th. Central to the issue is the doctrine of prior appropriation. Colorado's rivers and streams are pretty much over-appropriated so senior rights holders zealously defend their place in line. They're all for you taking as much water as you like from any stream as long as they get their water first.
Add to that the difficulty in measuring the consumptive use by homeowners utilizing rainwater catchments and you start to see the problem.
It's very hard to argue that all of the rain that falls on your roof will eventually end up in a stream. Most homeowners direct rainwater to their lawn or garden where it percolates into the soil. Some does end up in the stormwater system, for example, rainwater directed from your garage roof to the alley.
The Colorado Supreme Court has ruled that groundwater in many cases is tributary to streams. A proper understanding of the relationship between groundwater and surface water supports this. In other words they have science behind them.
But that's just in a perfect world. It ignores differences in soils and subsurface geology which may prevent the water that falls on your roof from ever reaching a stream. It also ignores transpiration (water consumed by vegetation that is released to the atmosphere) and some evaporation directly from soils. Proving that your rainwater catchment is only utilizing water that will never get to the stream would be prohibitively expensive for an individual homeowners. The senior rights holders do not have to prove that it does, it is presumed to be tributary.
There is a benefit to collecting rainwater that should be part of the discussion. Stormwater that flows into municipal collection systems picks up pollutants, biosolids, bacteria and chemicals. The silting up of streams is also a problem. Therefore there may be a good argument for keeping more of this water out of the system. Rainwater that percolates into the soil is filtered by natural processes, prior to joining surface water, so the same logic does not apply.
Another benefit would be rainwater used as "grey water" for domestic uses such as clothes washing and toilet flushing. This would cut down the need for treated water significantly. Most health departments oppose the use of grey water for health reasons. It would be hard to keep nasty bugs out of that type of system.
Don't hold your breath waiting for the big water suppliers to get on board the rainwater catchment bandwagon. In most cases they don't want the first use of water in their area of operation to be free. They would rather sell you the right to use water, have you use it once, and buy more for your next use. That's the water market for you.
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