WATER WARS: A look at Gallatin Valley Water Controversies

Stop 5:
Day Ranch

Stop 6:
Fish Creek

Stop 7:
Other Considerations



Stop 5: Day Ranch Overview

At this stop we will explore the Day Ranch controversy and try to understand how geology plays into the arguments.


  1. Review the geology of the area.
  2. Make connections between the geology and controversy.
  3. Ask the questions relevant to the controversy.

for Air Photo
Stop 4 topographic portion Modified from Topo II
To better orient yourself, take a look at the trip log page!
contour interval: 40 ft


Looking south along River Road

You have looked at a variety of geologic units, some that provide an abundance of water (the West Gallatin Alluvium) and other that have very little, if any, water available (the Archean Gneiss). Much of the controversy surrounding Day Ranch involves water, so as you can imagine, geology is quite important to the controversy. So to lets take a look at the geology of Day Ranch.

Contact looking west on High Flat Road

Here is another contact between the gneiss and sediments. From the topography you can imagine a thin layer of Tertiary sediments over the Archean gneiss. Hopefully you are thinking : "this bench looks quite similar to the Day Ranch bench...this could be a problem!"

Alternative geologic map?
  • What kind of rock is found at the Day Ranch site?
  • How thick do you think this rock unit might be? How far below is the gneiss?
  • If you were a geologist for the consulting company hired to determine the water potential at Day Ranch, what questions might you be asking yourself? Would you be concerned about the groundwater potential for the Day Ranch bench?
  • Looking again at the well data, how deep of a well do you think you would have to drill to get enough water up on the benches?

The Argument:

So, the benches may or may not be the best place to build a golf course. Interesting enough, the Day Ranch owns land on the valley floor (plots 1 & 2)...

Montana Ranch Plat Map
image courtesy of Montana Homes and Ranch

Location map of Day Ranch with plot size and numbers

  • Using your Topographic Maps and Surficial Geology maps, determine what rock unit the Day Ranch owns on the valley floor.
  • Map interpretation:
    1. Using the other maps provided, assess this rock unit for water bearing capacity.
    2. Is it an aquifer or aquitard?
    3. What is the transmissivity?
    4. Is it a "better" aquifer than the Tertiary sediments found on the bench?
What does transmissivity tell us?
  • Using the well data and the geologic maps, compare and contrast the aquifer on the valley floor and the aquifer on the bench. Which aquifer would you, as a consulting geologist, suggest the Day Ranch use?

If the Day Ranch owns water on the valley floor, it should not be a problem if they cannot find adequate water on the benches. SO, what really is the problem???? Move on to the next page to find out....

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