Drought is a climate-related scenario that has been with us since the dawn of recorded history and obviously before recorded history. The National Drought Mitigation Center (NDMC) at the University of Nebraska defines it as follows: "Drought is a protracted period of deficient precipitation resulting in extensive damage to crops, resulting in loss of yield."

NMDC goes on to say that drought is an insidious hazard of nature. "In the most general sense, drought originates from a deficiency of precipitation over an extended period of time……resulting in a water shortage for some activity, group, or environmental sector."

For a water guy, "drought" and "water shortage" are not words you want to hear. Implied but not clearly spelled out in the definitions above are the economic impacts of drought. I think economic consideration should be included in the definition.

Let's examine drought further. California presently is experiencing drought conditions. Say you live in California and the normal precipitation averages 15 inches per year. Assume that you have three years in a row where the average precipitation drops to 8 inches. Is this a drought? Yes.

Where does California's water come from? Its primary surface water bodies (streams and lakes) are fed by rainfall and by snowmelt from the Sierra Nevada. A second source of water for parts of California is the Colorado River. The third source is groundwater.

A major decrease in precipitation means that there is significantly less runoff from snowmelt and from rainfall. Less runoff and snowmelt means less water in the reservoirs that provide drinking water supplies to California's 39+ million residents. After a year or two it means less water for the Central Valley of the state, the source of much of the vegetables supplied to supermarkets in the country.

What about other water sources? If California is in a drought, it is likely that some other western states may also be impacted and flows in the Colorado River may be diminished. This means less water for agricultural areas in Southern California as well as major urban areas.

Groundwater may be impacted in two ways. First, diminished precipitation usually means diminished recharge of aquifers from infiltration of rainfall. Second, growers in the Central Valley may rely more on groundwater pumping as their allocated surface water diminishes. This may lead to declining water levels in the aquifers, or water mining. Protracted drought could even lead to dewatering of aquifers.

Droughts are not limited to arid or semi-arid areas. Virginia has an average rainfall of about 40 inches per year. Suppose that Virginia went three years with an average rainfall of 25 inches. Would we have drought conditions? Yes. Would we have water restrictions? Yes. See why the word insidious is apt? Protracted droughts do have enormous economic impacts, not only on the areas impacted but also on other areas of the country (and the world) that depend on products from the impacted areas.

It has been predicted that climate change due to global warming will bring changes in precipitation patterns with more severe storms but it will also bring more serious and protracted periods of drought. Will the U. S. be able to meet these challenges? I have no idea. I guess we'll have to wait and see.