The Carson Range looms over Carson Valley in this photo by Katherine Replogle.
An update of a U.S. Geological Survey water study of the Carson Valley will cost Douglas County an estimated $359,500 and take about three years.
That’s the county’s share of the $553,000 project.
Members of the Minden Town Board were scheduled to hear a report on the proposed study and offer input at their regular meeting Wednesday.
The study would evaluate the effects of a variety of groundwater management options on water resources in the Valley.
U.S. Geological Survey Northern Nevada Studies Chief Kip Allander was scheduled to attend the Minden meeting.
The town is one of Carson Valley’s major water purveyors, supplying drinking water to the Johnson Lane area, Indian Hills and Carson City.
The county is required to develop a water resources plan for the state.
Three studies have been produced in the 21st century, including one in 2006, another in 2008 and a third in 2012.
“However previous projections assumed growth rates similar to those experienced in the early 2000s and did not evaluate the more modest growth rate that has since been capped at 2 percent,” according to a draft proposal.
The models prepared in 2012 predicted that more pumping could lower groundwater levels as much as 60 feet on the east side of Carson Valley and decrease downstream flow by 16,500 acre feet a year.
The model included in the 2012 study will be updated to 2020 conditions.
The study will also evaluate changes in the hydrologic system related to moving domestic well use to water systems.
Johnson Lane and Ruhenstroth both have significant nitrate plumes associated with the use of septic tanks.
Moving residents from wells to domestic water systems could reduce the amount of nitrates in the water.
According to the draft, well owners digging deeper for water could result in higher arsenic concentrations in their water.
A scenario where domestic wells could be served by water systems would be determined by county managers and local water districts.
Groundwater is essentially the only source of drinking water in Carson Valley. Irrigation is conducted from the Carson River and streams, in addition to treated effluent. Under Nevada water law, in years when there is insufficient water in the river to meet irrigation requirements, ranchers with supplemental rights may pump water from the aquifer.
Of the roughly 96,000 acre feet of water estimated in the Carson Valley aquifer slightly more than half are designated for supplemental rights, according to a Lumos and Associates study conducted on behalf of the Gardnerville Ranchos.
The State Engineer estimated Douglas County pumped 30,928 acre feet of water in 2017, which was a flood year and required only 9,339 acre feet of pumping for irrigation.
Annual recharge is about 38,000 acre-feet from the mountains, 10,000 acre feet from the river and another 4,500 via irrigation infiltration, according to the study.
Nevada law prohibits mining water, which means taking more than the recharge amount.
