Mining the Ogallala

Richard (Rick) Mills

Ahead of the Herd

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As a general rule, the most successful man in life is the man who has the best information

Freshwater aquifers are one of the most important natural resources in the world today but we are pumping the groundwater out so fast nature can’t keep up. Some places we’re literally mining the water – once the water is pumped out its gone forever, it isn’t coming back anymore than the gold in a mined out deposit.

These fast shrinking underground reservoirs are essential to life on this planet. They sustain streams, wetlands, and ecosystems and they resist land subsidence and salt water intrusion into our fresh water supplies.

Many people think of aquifers as underground lakes but that’s not the case – the water is held between rock particles. Water infiltrates into the soil through pores and cracks until it reaches what is called the zone of saturation – all of the spaces between the rocks are filled with water, not air. This zone of saturation occurs because water infiltrating the soil reaches an impermeable layer of rocks it can’t soak through.

There are two types of aquifers: replenishable (a permeable layer of rock above the water table and an impermeable one beneath it) and non-replenishable (also known as fossil aquifers, no recharge) aquifers. Most of the aquifers in India and the shallow aquifer under the North China Plain are replenishable. When these are depleted, the maximum rate of pumping is automatically reduced to the rate of recharge or refill.

For fossil aquifers – such as the vast U.S. Ogallala aquifer, the deep aquifer under the North China Plain, or the Saudi aquifer – depletion brings pumping to an end.

The Ogallala Aquifer (a south to north trend consisting of thick sands and gravels) is the leading geologic formation in what is known as the High Plains Aquifer System. The Ogallala has a total water storage capacity about equal to that of Lake Huron. The entire system underlies about 450,000 square kilometers (174,000 square miles) of eight states – Colorado, Kansas, Nebraska, New Mexico, Oklahoma, South Dakota, Texas, and Wyoming.

On the High Plains there is very little water surplus – evaporation levels are almost the same as precipitation levels meaning there is little recharge of groundwater from precipitation. What little recharge there is for the Ogallala comes from ground water percolating very slowly eastward from Rocky Mountain snowmelt.

The Ogallala waters more than one-quarter of all irrigated acreage in the U.S., provides water for some of world’s largest cattle feedlots and four of five people living above it count on the aquifer for their drinking water.