Unused groundwater resources present a bright future for our nation’s water needs.
We have long believed a planet whose surface is covered by water should not be facing water shortages. However, 97 percent of the Earth’s water is too salty for humans and agriculture. Glaciers and ice caps put another significant portion out of reach. Groundwater resources, much of which have long been considered out of human reach, are becoming increasingly available thanks to technological advances driven by increasing water value.
The Hydrologic Cycle
The central concept in the science of hydrology is the hydrologic cycle, a convenient term to denote the circulation of the water from the sea, through the atmosphere, to the land, and thence with numerous delays back to the sea. Water returns to the sea by overland and underground routes and in part through re-evaporation and transpiration from vegetation, lakes, and streams.
Transport within the hydrologic cycle involves movement of water through multiple reservoirs, from a height of 15 km above the ground to a depth of some 5 km beneath it. The reservoirs include atmospheric moisture, oceans, rivers, lakes, icecaps, soil, and groundwater. The transport mechanism from one physical state or aquifer to another is either gravity or solar energy over periods that range from hours to thousands of years.
The pioneer of intensive groundwater investigations was Germany’s Adolph Theim, who around 1900 introduced field methods for making tests of the flow of groundwater and applied the laws of flow in developing water supplies. Under his influence, Germany became the leading country in supplying its cities with groundwater, and it still derives more than 80 percent of its water needs from wells.
Because we can see surface waters and tremendous amounts of money have been spent building visible dams, levees, artificial reservoirs, aqueducts, and irrigation canals involving surface water, it is natural that we tend to think of surface water as the major source of fresh water. However, less than 3 percent of the unfrozen fresh water on planet earth is in streams and lakes. The other 97 percent is underground.
Groundwater is tracked by remote sensing and tracer techniques, but water movement is exceptionally difficult to follow. It is known that groundwater migrates slowly. Sometimes, groundwater moves only a few millimeters a day, although occasionally it moves a few meters per day. Near the water table, the average cycling time of water may be a year or less, whereas in deep aquifers it might be centuries.
Through test wells and controlled pumping, it is not difficult to measure the recharge rate and flow behavior around a particular site. Nevertheless, there is difficulty sensing movement in the aquifer as a whole.
Water can be stored in the pores of rocks, but it can also be stored in cracks and fractures, and sometimes those fissures can provide conduits to allow water to travel quickly and over great distances.
Considerable Unexplored Aquifers
No one knows how many unexplored and unexploited aquifers exist, but the amount of water stored in them is thought to be considerable. This was the focus of my book Modern Groundwater Exploration, published by Wiley in 2005, to help exploration geologists uncover vast stores of water yet undiscovered. Water exploration companies have not yet made a major impact on the stock markets of developed countries, but they would not be a bad bet for adventurous investors.
Technology Increases Supply
Water exploration must be tied to the many great advances made by the petroleum industry, which long ago recognized the value of computer technology. The petroleum industry’s need for data processing power is insatiable, and it has resulted in many computer technology advances. Today, we stand on the launching pad to a journey into high-technology groundwater location and development the foundation of which have been laid through advances in petroleum and other mineral exploration.
The oil industry has been a driving force in the computer industry since Texas Instruments began as a company in 1930 known as Geophysical Service. Seismic imaging now available for groundwater studies led to the development of computer programs to assess sound waves generated in rock to infer the nature and location of rock layers capable of trapping oil. From initial two-dimensional images, computers ultimately were programmed to process gigabytes of data that would result in three-dimensional images.
In 1985, more than a day of computing time was required to analyze a square kilometer of subsurface structure. By 1995, computers could perform the analysis in 10 minutes. Meanwhile, the cost to survey 10 square kilometers dropped from millions of dollars to tens of thousands of dollars.
Concurrently, computer-assisted drilling technology has rapidly advanced, assisting resource recovery efforts. Advances include saw drill bits that have direct sensing tools to help locate resources.
Today, water is growing in value because of its usefulness for recovering natural gas and oil from shale formations through hydraulic fracturing, also known as fracking. The fracking revolution is creating energy abundance that promises to benefit our economy for decades or centuries to come. Water is key to this revolution, which should serve to spur more advances in water resource discovery and production.
Jay Lehr, Ph.D. ([email protected]) is science director of The Heartland Institute and is holder of the world’s first doctorate in groundwater hydrology.