Auburn, Feb. 13--If you think heavy rainfall this winter has replenished Alabama’s water table, think again.

For starters, much of the rain that fell across Alabama this winter ended up being washed into lakes, rivers and streams instead of seeping into the soil and eventually reaching underground water reservoirs (or aquifers).

"People see these streams and reservoirs filling up after significant rainfall over several months and think our water tables are recharged and ready to go," says Dr. Jim Hairston, a water quality scientist Alabama Cooperative Extension System.

"No, they’re not."

"What they don’t know is that a lot of this water, especially during heavy rainfall, ran off the ground surface into rivers and streams faster than it could be absorbed into soil and carried farther down to underground water supplies."

Coupled with this problem is the stress on aquifers stemming from private and municipal water use from wells and agricultural irrigation drawn from deep wells. In some cases, water is pumped out of the aquifers faster than it can be replenished from rainfall, a factor complicated by last summer’s drought.

"People often think there is a never-ending supply of groundwater," Hairston says. "However, if you’re drilling more wells to provide this water to municipal drinking water and irrigation systems, you’ve got to think about the long-term effects – especially if it appears the groundwater isn’t being recharged fast enough to replace what’s being taken out."

In some cases, the distance from the water recharge area (the point at which water is absorbed into and pumped from the ground) and the aquifer is as far as 50, and even 100, miles. Since water may flow only a few inches an hour, it may take months, even years in some cases, before it reaches its final destination.

As a result, there often is a significant time delay from the point at which rainfall soaks into the soil to the point from which it is pumped from an aquifer.

Groundwater depletion is a far bigger concern in south Alabama, where greater use is made of groundwater than in north Alabama, which still depends primarily on surface water for most of its industrial and municipal drinking water needs.

The good news is that with the exception of Louisiana and Florida, Alabama receives more annual rainfall than any other state – roughly 55 inches. Also, compared with other states,

Alabama enjoys substantial groundwater supplies, despite the stress caused from last summer’s drought.

As long as towns and cities continue enacting measures to conserve these resources, Hairston believes there will be plenty of groundwater available for future needs.

A major focus of these measures undoubtedly will involve limiting commercial and industrial development in areas where primary aquifer recharge occurs.

"Whenever you’re removing natural vegetation from recharge areas and replacing it with asphalt and concrete, you’re potentially limiting the amount of rainwater that otherwise would soak into the aquifer," Hairston says.

If groundwater isn’t a big enough concern, expanding population growth, coupled with severe drought periods in some regions of the state, is placing an ever bigger strain on surface water supplies throughout most of the state.

Last year in Birmingham, for example, the almost complete withdrawal of water from Lake Purdy and Inland Lake, due to extended summer drought, left municipal planners scrambling to find alternative drinking water resources.

One solution would have involved building a pipeline to the Coosa River more than 30 miles away.

However, this proposal enraged Coosa area residents because the water diverted from the river would have been emptied into the Cahaba River after waste treatment and never returned to the Coosa River.

The decision to divert water permanently out of the Coosa River into another river would have amounted to what is known as an "interbasin transfer," which has become one of the most hotly debated water management issues in the world.

Birmingham’s water shortages underscores a major conservation challenge many Alabamians and other people throughout the world will face throughout the 21^st century, he says.

More and more city planners will be forced to adopt stringent conservation provisions in order to safeguard existing surface water and groundwater resources.

One effective and relatively inexpensive solution will be to build off-stream reservoirs near major rivers in order to trap water during high-flow periods, Hairston says.

Once used, the water then can be treated and returned to the stream for future use.

Source: Dr. James Hairston, Extension water quality scientist (334) 844-5686.