Mt Rose/Galena Fan Groundwater Drawdown Maps

To assess the effects of groundwater production (by both municipal wells and domestic
wells), DWR directed Eco:Logic Engineering, Inc. to perform a computer simulation of
the aquifer in the Mt. Rose Fan area as part of the 2009-2028 Water Facility Plan
Update. The computer simulation started out using the 2008 pumping rate (3,660 afy).
The production rate was increased each year to the buildout demand (5,660 afy) in 2038
to mimic the gradual increase in growth. The results of the groundwater computer
simulation are provided in Figures 3, 4, and 5.
Figure 3 shows the anticipated drawdown of the water table at 2028 (about two thirds of
the way to the buildout demand) in comparison to 2008 levels. In the figure, changes in
water levels are depicted using different colors, with each color representing a 10-foot
range of groundwater declines. Figure 3 indicates that the greatest anticipated decline
in groundwater levels in 2028 is less than 50 feet.
Figure 4 shows the anticipated declines in groundwater levels in 2038 (buildout) in
comparison to 2008 levels. According to the simulation model, the declines in
groundwater levels predicated for 2038 for the most of the Callahan Ranch area range
between 40 and 60 feet. However, declines of up to 80 feet from 2008 levels are
anticipated in a few small areas adjacent to municipal production wells. .
Figure 5 shows the anticipated declines in groundwater levels in 2069 in comparison to
2008 levels. The anticipated declines for the vast majority of the Callahan Ranch Area
are between 40 and 80 feet. The results suggest that there may be a small area
(adjacent to a municipal production well and about ½ mile away from the nearest known
domestic well) that could have a decline of up to 100 feet.

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