Base flow, drought, and the problems of Maxwell, New Mexico

Maxwell sits next to the Canadian River, which as you can see from the picture is not much of a river right now. It’s not a big river in any year, but right now it’s in particularly bad shape. The nearest USGS stream gauge downstream is showing less than 10 percent of average flow for this time of year.

As Roberto and I will show in a story scheduled to run Sunday, Maxwell’s in a heap of trouble. Its water well field, east of town across the river, is barely producing. Maxwell is one of the most extreme cases of a New Mexico municipality in water trouble, and its problems are intimately connected to low levels of what hydrologists call “base flow”.

At this time of year, absent rain and before the snow starts melting, the only water in our rivers is base flow – the water generated as a river’s bed intercepts the shallow riverside aquifers. When I talk to water managers these days, the discussion often turns to the low base flow. On the Rio Grande at Otowi, for example, the current flow is just a hair above half of of the mean for this time of year.

The low base flows is telling us that the shallow aquifers, parched by two-plus years of drought, are seriously depleted. For Maxwell, which depends on a shallow aquifer for its municipal drinking water, that means a dwindling supply. For the rest of us, it means that once our meager snowpack begins to melt as spring temperatures warm, a big slug of the first water will simply disappear into the parched aquifers.

That’s one reason that, unless March precipitation makes a dramatic turnaround, it’s going to be a seriously dry year on all of New Mexico’s rivers.