The Lower Portneuf River Valley Aquifer.
Portneuf Narrows to Chubbuck.
About 350 million square feet (8000 acres).
Volume of Stored Water
About 30 billion cubic feet (220 billion gallons/year).
Natural Throughflow (natural volume of water
flowing through aquifer)
More than 0.7 billion cubic feet/year (more than 5 billion gallons/year).
0.75 billion cubic feet/year (5.5 billion gallons/year).
Average Residence Time (time spent in aquifer
by a water molecule)
About 40 years.
Sources of Groundwater Recharge
Mountain snowpack in the Bannock Range south of Kinport Peak, and in the upper Portneuf River watershed.
The upper layers of the aquifer are the most permeable (water flows through most easily), and are formed from gravels deposited during and after the catastrophic Bonneville Flood at the end of the last Ice Age (about 13,000 years ago). The deeper layers of the aquifer are formed of sediment layers with occasional layers of basalt lava, and were deposited over the previous 8 million years. Thin layers of clay and silt in the aquifer form natural barriers against groundwater flow (they form impermeable barriers). Although the aquifer itself is old the water in it is fairly young. A water molecule resides in the aquifer for an average of about 40 years. Water that the city does not pump for municipal use eventually flows into the Snake River Plain Aquifer.
Pocatello and Chubbuck's Dependence on Groundwater
Pocatello and Chubbuck are totally dependent upon the groundwater resources of our aquifer for ALL of our fresh water supplies. Our municipal wells range from 65 to 450 feet deep. Pumps deliver the water to the surface and into the city's distribution systems. This municipal water is treated with chlorine in order kill disease-causing bacteria. The water at each well is constantly monitored and tested for a wide variety of pollutants.The water in the Pocatello aquifer is the only source of fresh drinking water available to us in the forseeable future. It is truly an irreplaceable resource that needs our care!