The city of Pocatello is back to the drawing board after voting against buying $6.2 million worth of water rights.  The deal would have been made with Portneuf Marsh Valley Canal Company.  City officials backed out after credible threats of lawsuits from water users “downstream”.

Water is a big issue for Pocatello.  Its main source of water is the Lower Portnuef Valley Aquifer, and it’s running dry.  The Portneuf River flows through Pocatello, but it does not recharge the aquifer, and the city does not take any water from it.

To add to the problem, the city of Pocatello is not the only one using the Aquifer, the city of Chubbuck also gets its water from the same source.

For a long time it was thought that surface water runoff made its way to the ground water (Aquifer), but now its known that most surface water runoff just ends up in rivers heading out to the oceans (although some recharging comes from Mink Creek, and snow).

Geoscientists believe the Lower Portnuef Valley Aquifer was created 17,000 years ago when a natural dam broke, releasing a huge sea into the area (Bonneville Flood).  Part of that sea was trapped in what is now known as Lower Portnuef Valley Aquifer.

Another issue is that while many aquifers are held in small rock formations, even pebbles and sand, the Lower Portnuef Valley Aquifer is trapped by huge boulders, which were part of the natural dam holding back the ancient sea.  You can see huge boulders around the area now.  Every time a housing development goes in they end up spending a lot of time digging out the boulders in order to put in basements.  It has also resulted in lucrative local rock mining businesses.

The water in the Aquifer is almost finite, it does not easily recharge as was once thought.

However, while most rain ends up in rivers, any water from slow melting snow, or used on farms or residential properties can get into the Aquifer.  The problem is that large boulders do not filter the incoming surface water, like sand or pebble aquifers. This means the Lower Portnuef Valley Aquifer is very vulnerable to contamination.

To add to that, the soil is only about 2 to 8 feet thick, before you hit rock.  I can attest to that since I’ve done a lot of landscaping here, and I grow vegetables and fruits.  I can dig the depth of a shovel blade and hit rocks 4 inches in diameter or bigger.  The thin soil means if you dump used motor oil on the ground, or use chemicals on your garden, it’s almost instantly heading for the Aquifer.

There is a three part (boring, basically a college lecture from 2010) video explanation of the Lower Portnuef Valley Aquifer issue, presented by Glenn Thackray of Idaho State University:

 

Thackray explains that the cities, residents, farmers and businesses take out more water from the Lower Portnuef Valley Aquifer, per year, than what flows into the Aquifer.  This has been going on for a long time, and is why we’re running out of water.  Add to that the fact that we’ve had some very dry winters, with less than normal snowfall (a big source of recharge, because it melts into the ground, unlike rain that runs off).  The water level has been dropping since the 1990s.

Pocatello city officials say they are taking this issue seriously, and are being proactive about finding a solution.