Acre-feet: How much water is enough in the desert?

We’re looking at buying a house in Placitas. Houses out here are on their own septic and well systems, and it’s common for houses in this area to share a well with other houses.  This is presumably to save on the cost of drilling.  Wells out here have to be about 600 feet deep (no, that’s not a typo).  600 feet or more, compared to only 90 feet in other parts of the country. So it costs about $25,000 to drill a well out here.

Our current house shares its well with one other house. The permit allows the well to draw 1 acre-foot per year, which is 325,851 gallons.  This is more than enough for the two houses on the well. According to the EPA, the average American household uses about 300 gallons per household per day, which is 109,500 gallons per household per year.  This is about 120 gallons per person per day.  So a two-person household ought to use about 87,600 gallons per year.

We knew the house that we’re looking at buying shares a well with several properties, but we just found out this community well is permitted for only 3 acre-feet per year, and it’s shared with 13 other properties! A 1/14th share of 3 acre-feet isn’t nearly as much as half of 1-acre-foot. Our 1/14th share would come to only 69,825 gallons per year.

Do we actually need the national average of 43,800 gallons per person per year?  Domestic water use in deserts is generally higher than in the rest of the country. Part of that is the use of evaporative coolers for air conditioning.  Evaporative coolers use significantly less power than central air conditioning using a condenser, but they use a lot of water. Also it’s very hard to grow anything in the desert without at least some irrigation, even though most people in our area do not have lawns.

Our real estate agent is assuring us that only about 62% of the water allocated to this community well is currently being used on an annual basis.  I’m wondering why?  Are all our neighbors using vastly less than average? Is it because there’s almost no children in this retirement area? Is it because many people are only here seasonally?

The real question, that we can’t answer, is “Will there be a water shortage in the future?” Or at a more basic level, will we regret buying this house?

UPDATE!  Our real estate agent just found out that the original water rights were expanded to 4.05 acre-feet per year, so now each household is limited to 110,000 gallons per year.  Here’s the new graph, showing the current household limit on this community well to be nearly identical to the average US household usage.  So we still can’t go crazy with gardens and fountains and ponds…but we wouldn’t do that in the desert anyway.