U.S. environmental scientist Stephen Carpenter has been awarded the 2011 Stockholm Water Prize, the prestigious international award for water conservation.

The professor of zoology and limnology at the University of Wisconsin-Madison's win was announced by nominating committee head Professor Per Arne Malmqvist at a seminar here Tuesday -- World Water Day.

"Professor Carpenter has been nominated for his outstanding leadership in setting the ecological research agenda, integrating it into a socio-ecological context, and in providing guidance for the management of aquatic resources," said Malmqvist, who is also scientific director at the Stockholm International Water Institute.

He said that Carpenter's groundbreaking research showed how lake ecosystems were affected by the surrounding landscape and by human activities and his findings formed the basis for concrete solutions on how to manage lakes.

The 59-year-old Carpenter is recognized as one of the world's most influential environmental scientists in the field of ecology.

"By combining theoretical models and large-scale lake experiments, he has reframed our understanding of freshwater environments and how lake ecosystems are impacted by humans and the surrounding landscape," Malmqvist said.

Carpenter is also recognized for his contribution to understanding how lakes can be affected through nutrient loading, fishing and the introduction of exotic species.

Carpenter is best known for his research on trophic cascades in lakes -- a concept which describes how impacts on any species in an ecosystem will cascade down, or up, the food chain. For example, overfishing of large fish in a lake can result in an increase of small fish, thus decreasing the abundance of zooplankton further down the food chain.

By extension, this would increase the growth of algae and amplify the effects of eutrophication (depletion of oxygen in water bodies due to excessive plant growth caused by excess nutrients). Those findings have influenced concrete strategies for dealing with eutrophication and have provided a practical framework for the management of freshwater resources, resulting for example in the understanding that it might not be enough to reduce the emissions of nutrients to a lake in order to overcome the problems, but that one might need to change the composition of the fish community as well.

Carpenter said in a televised interview he was thrilled by news of the award.

"It is a great honour to be selected. The prize will increase my resolve and sense of obligation to work on emerging issues of freshwater, such as climate change and the connections of food and water security," he said.

He will be presented with the prize by Swedish King Carl XVI Gustaf during the 21st World Water Week in Stockholm on August 25.

The Stockholm Water Prize is presented annually since 1991 and is considered the world's most prestigious award in water-related science. It honors the individual or organization deemed to have done to the most to conserve and protect the earth's water resources.