Groundwater Depletion

What is Groundwater?
To understand more about what groundwater is and how it works, check out this YouTube video:

Aquifers in the Helena Area:
There are three main aquifers that we pull from for water in the Helena area:

  • Tertiary Aquifers: limited yields and recharge. Water quality is generally poor, with high levels of dissolved solids
  • Bedrock Aquifers: generally good but variable yields, with primary recharge from snow melt infiltration. Water quality varies, but generally is good with low dissolved solids.
  • The Helena Valley Aquifer: high yields, and shallow depths to ground water, with recharge from streams and irrigation waters. Generally good water quality.

  • To view more details on the Geology and Hydrology of the Helena area, you can click here to view this Story Map.

    Groundwater Monitoring
    The Lewis and Clark County Water Quality Protection District monitors over 130 wells monthly, and has been collecting this data for over a decade. All of the information collected by the District is uploaded to the Montana Bureau of Mines and Geology’s Groundwater Information Center (GWIC). Each well has a corresponding “GWIC ID” that you can use to search for and download data from that well.

    The monthly groundwater level measurements have allowed us to track trends over time, and identify areas that are experiencing signs of depletion.

    To view all monitoring wells and their GWIC ID’s, you can click here to view this Story Map.

    Groundwater Depletion
    Aquifers that receive little to no recharge from surface waters or groundwater are vulnerable to groundwater depletion. When the amount of water being pumped out of the aquifer exceeds that coming in, the water level will continue to drop, causing yield deficiencies for wells that are no longer deep enough to reach the water level (wells are at a higher risk to “go dry”). Below is a map that highlights the areas where there are signs of groundwater depletion. It is important to note that these hydro-geologic systems are complex, and local scientists still do not yet fully understand why we are seeing depletion in some areas.

    Map 1: Groundwater depletion in the Helena area. Each circle represents an individual well. The minimum value of the groundwater level (when the water was at its highest point) was extracted for each year, for each well. The “trend” was determined based on the percentage of years where the highest groundwater level point is lower than the year before. Groundwater level data were extracted from the Montana Bureau of Mines and Geology’s Groundwater Information Center, from as early as 1995 until the most recent data collected in 2018. The number of measurements per well varies.

    In the case below, 100% of the maximum height values per year were lower than the year before. This well would be colored red on the map, and indicative of signs of groundwater depletion. You can find this well on the “North of Lincoln Road” map below. GWIC ID: 64755

    Now let’s zoom in closer to the areas where multiple wells are showing groundwater levels declining each year.

    NOTE: The trends do not incorporate the magnitude of depletion. For example, a well may be represented as a red circle (or decreasing trend), but is losing 1/2 foot per year, while others that are also decreasing may be losing much more than that. Keep a close eye on the scale of the hydrographs to understand the magnitude in which the well is depleting.

    Hover your mouse on the image below, and you can view the GWIC ID and the hydrograph for each well. Click on the “Read More” link and you will arrive at the GWIC’s website where you can investigate the hydrograph more closely and download the data.

    1) North of Lincoln Road

    2) Emerald Ridge

    To view more information on the Emerald Ridge investigation, you can click here to view this Story Map.

    3) Southeast Helena

    NOTE : Because of these wells’ proximity to the irrigation canal and its connectivity to the Helena Valley Aquifer (see “Aquifers in the Helena Area” section above for reference), the Water Quality Protection District is not concerned about water supply here, despite some of the decreasing trends we see. The other two areas (North of Lincoln Road and Emerald Ridge), for example, are drilling from bedrock aquifers that are disconnected from the Helena Valley Aquifer and, generally, receive little recharge from surface water and precipitation.

    So what is the solution?
    In order to balance recharge with withdrawals, strategies to enhance recharge and/or reduce withdrawals can be employed. We typically rely on nature to supply groundwater for aquifer recharge, however there are methods to provide groundwater recharge through artificial means.

    Managed Aquifer Recharge (MAR)
    MAR refers to the intentional recharge of water into an aquifer for later recovery and use. MAR may employ a variety of techniques that include:

  • infiltration ponds
  • injection wells
  • surface water diversions

  • Water from a variety of sources including surface watercourses (streams, ditches, canals), stormwater runoff, and even wastewater or graywater can be used in the recharge process.

    Where methods to enhance recharge are not feasible, or do not provide sufficient volumes to maintain water levels, water conservation measures and methods to reduce withdrawals can be used.

    Groundwater Conservation

  • Reduce groundwater use through:
  • catchment systems (greywater, runoff capture)
  • xeriscaping
  • HOA agreements

  • Other Methods

  • Drill a deeper well ($$, groundwater withdrawal, impacts to neighbors)
  • Establish public water supply/community well ($$, water rights, regulations)
  • Water hauling/cistern ($$, no local water hauling in Helena)

  • Drilling deeper wells that tap into a deeper aquifer may solve this issue for the current generation. However, aquifers that receive no recharge will eventually no longer be there as extraction continues. You can think about extracting groundwater similarly to extracting any other natural resource, such as oil. There is a limited supply, and although the time when our largest groundwater aquifers are no longer able to support our communities seems far away, it is important to think about our actions now that will impact future generations and the sustainability of our communities.

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