Reduced river flows and warmer water due to climate change will lead to power supply disruptions in Europe, researchers said this week.

A European Commission-funded study conducted in part by the Wageningen University and Research Center in the Netherlands predicted thermoelectric power generating capacity from 2031-60 will decrease 6-19 percent in Europe because of a lack of cooling water.

The study, released Monday, also predicted the likelihood of extreme reductions in thermoelectric power generation will, on average, jump by a factor of three during the period.

Thermoelectric power plants -- those that burn fossil fuels or use nuclear fuel -- rely on consistent volumes of water at particular temperatures to prevent overheating. Thermoelectric plants supply 78 percent of the electricity in Europe and account for 43 percent of the continent's surface water use.

Because of that, reduced water availability and higher water temperatures caused by rising ambient air temperatures triggered by climate change will present significant potential problems for electricity supplies, the authors warned.

The study looked at 61 power plants in central and eastern United States and 35 power plants in Europe -- both nuclear and coal-fired -- outfitted with different kinds of cooling systems.

Warmer water and reduced river flows in the United States and Europe have led to temporary shutdowns of several thermoelectric power plants in recent years, including the Browns Ferry Nuclear Plant in Alabama, which was shuttered during a 2007 drought and again last summer because Tennessee River water was too warm to use for cooling.

During the acute southeastern U.S. drought of August 2007, nuclear and coal-fired plants, including the Browns Ferry facility, within the Tennessee Valley Authority's system were forced to shut down, while a similar drought a year earlier forced shutdowns along the Mississippi River, the U.S. Department of Energy reported.

The phenomenon has also presented problems in Europe. During a serious drought in 2003, France was forced to reduce operations at many of its nuclear power plants.

Regulators also prohibit the discharge of too-warm water from power plants into rivers, citing "downstream thermal pollution." For example, the TVA's Gallatin Fossil Plant in Tennessee isn't permitted to discharge water used for cooling into the Cumberland River that is higher than 90 degrees Fahrenheit.

"Higher electricity prices and disruption to supply are significant concerns for the energy sector and consumers but another growing concern is the environmental impact of increasing water temperatures on river ecosystems, affecting, for example, life cycles of aquatic organisms," co-author Michelle van Vliet of Wageningen University said.

While plants with cooling towers will be affected, the study also found older plants using "once-through cooling" are the most vulnerable. These plants pump water directly from rivers or lakes to cool the turbines before returning the water to its source and require high flow volumes.

Study co-author Pavel Kabat, director of the International Institute for Applied Systems Analysis in Laxenburg, Austria, said one way to cope with future shortages would be to site power plants near saltwater sources.

"Another option is to switch to new gas-fired power plants that are both more efficient than nuclear- or fossil fuel-power plants and that also use less water," he said.