Rain Harvesting Part 1 – How much and why the State cares
In my last post about water, Kristine pointed out that storing rainwater is illegal in some places. While this fact gets on my last nerve – I guess it is the libertarian rancher blood in me – this is a real concern. Much of this stuff is regulated because of (1) health, (2) safety, and (3) environmental (water table and management) concerns. I will cover the health/safety concerns of dealing with rain water on site in the next couple of posts, but let me explain the water table legality mess since it recently changed in Utah.
Generally speaking, the state owns and decides how to manage water but pushes enforcement through municipalities often in the form of codes. Many of these regulations are antiquated; further, enforcement is generally uneven at best. In the arid SW, the assumption is that the water table needs to be closely managed. For years, Colorado and Utah held that every drop of rain belonged to the water table and thus to the state. To capture rain without a water right was essentially theft and illegal.
It is my understanding that in 2009, Colorado relaxed to their stance to say if you are on a well, you have long-term water rights to the water table below your land and therefore may harvest rain. If you have city water, no rain capturing for you.
Utah, in 2010, also changed their rules. As long as you register your system here, you may harvest and store up to 200 gals above ground. I don’t know what the deal is with specifying 2 each of 100 gal containers – maybe someone following this more closely can help explain.
Utah also now allows you to put in a significantly bigger underground cistern. Besides seeing a significant increase in installation cost, many more states regulate large systems and most municipalities (no matter what the state) are going to want to have some say about anything underground. Check with your city before doing anything that big and permanent. Unless you have a barn, you really don’t need a cistern. Your roof would do just fine.
How much can you get from your roof and what does that buy you in terms of landscaping/gardening (the most common resuse)? 1 inch of rain on 1000 sq ft of surface equates to 623 gal. In SLC, summer months see about .75 inches of rain per month. (Go to weather.com, tab to month, click on averages to see how much your specific location can expect.) In other words, in a 1000 sq ft main level house on the Wasatch front probably would generate about 468 gallons per month during the summer. No wonder the state is concerned about managing this!
Realistically, how much can you capture? Since Utah limits a household to 200 gal in above ground storage, you would have to assume the rain comes in at least 2 storms a month (preferably evenly spaced) to reuse almost every last drop.
How much do you need? Most veggie gardens need between 3/4 and 1 inch of water per week. Thus, a 10×10 ft bed requires about 62 gal per week or 250 gal per month. A quarter of those needs are met with rainfall. By my calculations, you can realistically and legally capture enough rain in SLC to water a 200 sq ft plot. In Southern Utah, Southern Nevada, and AZ – due to the monsoons – you could probably cover the needs of a 100 sq ft plot in July and August (Vegas averages .4 inches these months) if you supplement with city water in spring.
Up next – how to safely install and use a rain barrel.