Animas River groundwater level monitoring after the Gold ... · the Animas River, New Mexico, after...

Ethan MamerTalon Newton

Stacy TimmonsNM Bureau of Geology and Mineral Resources

A Division of NM Tech

With funding from

NM Environment Department

GROUNDWATER LEVEL MONITORING along the Animas River, New Mexico, after the Gold King

Mine 2015 mine-water release

Gold King Mine Spill• August 5, 2015• ~3 million gallons of mine-

waste water, and 540 tons of mine-waste sediment were released into the Animas near Silverton, CO

Figure from EPA, 2017

– Dissolved contaminants flowed past Farmington within a week of the spill

– Contaminated sediments were deposited and left behind

Gold King Mine Spill

Figure from EPA, 2017

• EPA findings (2017)– 90% of sediments were deposited along the

Animas River upstream of Farmington after spill– Remaining sediments were transported out of the

system during 2015 fall storms and 2016 snow melt

Gold King Mine Spill

Figure from EPA, 2017

• Goals:– Evaluate groundwater-surface

water interaction– Describe annual and seasonal

fluctuations– Determine any “at risk”

locations along the river

Study Area

Groundwater Monitoring Network: Manual measurements

• Between 59 and 74 wells measured during each seasonal transition.

• USGS WL steel tape protocol

• 8 measurement periods• August ‘15 –June

’17• ~ 640 WL

measurements

Animas River stage:Manual measurement periods

• Network measured 4 times a year• Measurement timing intended to capture hydraulically

significant periods in the groundwater/ surface water system

Winter Baseflow in river (late January)

•Pre-irrigation season (late March)

•Peak river flow (early June)

•End of irrigation season (October)

Groundwater Monitoring Network: Continuous data loggers

• 24 wells instrumented with pressure transducers• 2 installed September ‘15• 2 installed January ’16• 1 installed in June ‘16• 19 installed late ’16/ early ‘17

• Monitor water levels and temperature every hour

• 13 also monitor the specific conductance

• 5 barometer loggers installed along Animas reach for barometric corrections

June High

October High

Winter High

Summer Low

• Little can be determined from manual measurements alone

Winter High

Summer Low

June High

October High

• Combining pressure transducer record with manual measurements we can extrapolate trends to wells without complete records

• Very close to river: median 320 ft

• Median water table is 9.4 ft bgs

• Small seasonal fluctuation: median 3.5 ft

River Stage Controlled (22 of 70)

• Water levels are hydraulically linked to the river and closely follow the fluctuations in stage

Irrigation controlled (38 of 70)

• Much farther from river: median 1,810 ft

• Deeper water table: median 14.7 ft

• Large seasonal fluctuation: median 5.7 ft

• Aquifer is recharged during the irrigation season, during which water levels recover, before dropping when ditches are shut off

Winter-recharge/ Summer evapotranspiration (10 of 70)

• Farther from river: median 1,160 ft

• Small seasonal fluctuation: median 2.1 ft

• Very shallow WT: median 2.5ft

• Summer decline is related to vegetation drawing from the aquifer

Gaining stream

Losing stream

• Water table is LOWER than the river, and water infiltrates into the aquifer from the river.

• Water table is HIGHER than the river, and water flows into the river from the surrounding aquifer.

Reaches where water table gradient has been found to be flat or slightly losing during winter.

Water table in October

Water table in March

How close is too close?• Using the water table

maps to calculate the gradient in losing reaches

• Approximating the conductivity of the alluvial aquifer and its porosity

• We can calculate the distance river water can travel during the winter.

• ~2 feet/day • ~130ft in 9 weeks

Still a GAINING RIVER overall

• During Winter, when no water is being diverted into the Ditches, water is moving from the alluvial aquifer into the river.

• Most of Animas River has gaining conditions.• Seasonal fluctuations in river stage and water levels are

enough to reverse groundwater/ surface water flow direction.• Potential for future contamination from lingering sediments, and

reversals in groundwater flow

• The river and the groundwater in the valley are hydrologically connected.

• The irrigation ditch water is feeding the shallow water table, recharging groundwater during the irrigation season.– Potential pathway for contamination to enter aquifer

Acknowledgments• Very kind landowners• NM Environment Department - Dennis

McQuillan, Diane Agnew, Patrick Longmire, Kris Pintado

• U.S. EPA – Funding to NMED• USGS - Jesse Driscoll, Lauren Sherson,

Nicole Thomas, Amy Gallanter• NMOSE – Doug Rappuhn, Rob Pine,

Shawn Williams• NMBGMR/NMT - Trevor Kludt, Scott

Christenson, Kitty Pokorny, Brigitte Felix, Sara Chudnoff, Bonnie Frey, Dustin Baca, Geoff Rawling, Mark Mansell, KylianRobinson

NM Bureau of Geology and Mineral Resources NM Bureau of Geology and Mineral Resources