Tom Myers (no relation to the interviewer) is a hydrologist who closely watches the impact of mining on water in the Great Basin. We spoke with him after a presentation on his latest paper in Reno for the Progressive Leadership Alliance of Nevada, a presentation that was repeated in Elko on June 8 and Lovelock on June 9. Further info is available from ECastro@PLANevada.org.
What does your paper say?
I presented results from two papers, actually. PLAN had supported work a year ago where I did a big summary of dewatering deficits created. … The new paper that I’m submitting to a journal talks about how much water is being lost to a specific part of the Humboldt River due to the [now closed] Lone Tree Mine filling up with water. … Because, when it was pumping it created a huge deficit, and where does the water come from to fill that deficit? That’s was the question we were asking for the last 25 years—“You’re creating a deficit. Where is it going to come from?” This is the first time we’ve had data to actually assess that. And we’ve had gauging stations here operating for decades, but we had to have enough gauging stations data as the mines filled with water to actually analyze.
Once the pumping stops—
Well, the Lone Tree Mine lies between Battle Mountain and Winnemucca. And there are several other mines upstream from Battle Mountain. But it’s the only big one in the reach between Battle Mountain and Winnemucca. And it’s been dewatering since 1991. Most of the water it pumps from the ground it dumps into the river. Thus while it was actually mining it may have been pulling water from the river into the groundwater and then pumping it, but you couldn’t analyze that because they were dumping it back into the river. So the gauges didn’t show—I mean, it was impossible to figure out what was what. Once they stopped pumping and the pit starts to fill, where does that water come from? It comes from water that’s left in groundwater storage, flowing into it, but that also creates a suction from the river, pulling water from the river into the groundwater and then into the pit. I did some fancy statistical analysis to compare the period from 2007-to-the-present to earlier periods. It showed that approximately 180,000 acre-feet of water—in addition to what normally would have been lost to the region—was lost. Normally the river reach through there loses about 18 to 20 percent of the water that naturally flows into it. Because of dry conditions, it’s a losing river. The period since 2007, it lost far more than it has at any time since 1946, way before dewatering started. It lost about 39 percent of the water that comes in, so the difference between 39 percent and 21 percent, is 18 percent. That give me the 180,000 acre-feet that’s been lost.
Why should people care?
Well, if you’re a farmer along the river and you rely on water in the river to irrigate with, there’s that much less. That’s 180,000 acre-feet less water that you can divert from the river during base flow periods, and base flow is later summer and fall. So it’s your last crop of alfalfa. It’s also water that supports the levels in Rye Patch [Reservoir]. … It’s a loss to the system. … And ultimately there are six more mines out there that are in different stages of operating, and they’re creating these deficits. The total amount of water pumped in the Humboldt River from mine dewatering is 3.9 million acre-feet. The current estimates of pit lakes—water that will go in and ultimately be a pit lake—is a million acre-feet and evaporation from those in the long term will be about 10,000 acre-feet per year. All that water has to come from somewhere to be made up. The average recharge in the Humboldt River Basin is 233,000 acre-feet per year.