ARCHIVE ACCESS

Use the archive below to review an expanding selection of hot, new information about groundwater and related subjects. Select a topic from the list below and then CLICK to access.

WATER CAPACITY

Complete 2000 Draft Report
Figure 1
Figure 2
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Figure 4
Table 1

SOURCE WATER ASSESSMENT PROGRAM

What is the Source Water Assessment Program?

Pocatello SWA
Download the Full Report (PDF)

RUNOFF & EROSION

What is Runoff & Erosion?
What are the Effects?
Is the LPRV Aquifer at Risk?
What Can You Do to Help?
S. Grant/N. Fore Rd. Project
Take a Look at Some Photos:
    * Drainage
    * Erosion 1
    * Erosion 2
    * Flooded Drains 1
    * Flooded Drains 2
    * Flooded Drains 3
   

You can also learn more
about Runoff & Erosion in
Storm Drain Stenciling!

Some archive entries
are in PDF format.

IN THE HOT SPOT!

Water Balance and Total Pumping Capacity
of the Lower Portneuf River Valley Aquifer
By, John Welhan, Idaho Geological Survey.
Geology Department, Idaho State University.
January, 2000. DRAFT

Summary

A detailed water balance of the upper part of the lower Portneuf River valley (LPRV) aquifer has been completed, in order to provide a best current estimate of available water capacity for build-out analysis. The LPRV aquifer relies on recharge form snowpack and precipitation in the southern Bannock Range for more than 70% of the total recharge required to sustain its water balance; less than 15% is derived from the upper Portneuf River basin through the Portneuf Gap and about 5% is estimated to derive from other drainages, principally the Pocatello Creek watershed. Current pumping withdrawals by the Cities of Pocatello and Chubbuck account for 80-85% of this recharge, leaving approximately 1.1 to 1.5 billion gallons of annual capacity remaining, or approximately 14 - 17% for future development.

Best available information indicates that the aquifer is already supplying 80% of its maximum capacity in normal water years, and may be overpumped during drought periods. Because the municipal aquifer is relatively narrow, it does not contain a lot of water in storage. Therefore, only slight overpumping can lower the water table significantly. For example, during the 2000 water year, the combination of additional withdrawal by Pocatello's newest supply well, #44, and below normal recharge from the Bannock Range, the water table in the southern valley dropped to its lowest level in 30 years; most of this decline can be attributed to the demand which Well 44 placed on the aquifer. Clearly, future management of this water supply will have to be closely tied to future development planning.

Because we know very little of the water-bearing potential of the deeper part of the aquifer system not tapped by wells, we can only surmise that the impact on future capacity will depend on the depth and permeability at which deeper aquifers can be found, the quality of their ground water, and the rate at which they are recharged.

The potential to develop surface water runoff in the southern Bannock Range is limited. Even if as much as half the total surface runoff in southern Bannock Range watersheds could be diverted, it would increase total capacity by less than 5%.

Use the links in the archive at left to learn more
about the water capacity of the LPRV Aquifer,
in addition to other topics of interest!