Freshwater systems - lakes, wetlands, rivers, and streams - have been critical to the establishment of civilizations throughout human history. From ancient times, civilizations have been built based on their proximity to water: ancient Mesopotamia thrived because of the ample water provided by the Tigris and Euphrates rivers; ancient Egypt grew up along the Nile; the Romans expended vast resources in building elaborate networks of aqueducts to supply water to their cities. Water bodies are essential to humans not only for drinking but also for transportation, agriculture, energy production, industry, and waste disposal.
Despite the reliance of societies on freshwater systems, only in this century has the importance of protecting the quality of these systems become widely recognized. In the United States, the passage of the Clean Water Act in 1972 reflected widespread awakening to the deteriorating status of the nation's surface waters. The Clean Water Act set a goal of restoring all U.S. lakes and rivers to a "fishable and swimmable" condition.
The Clean Water Act focused on reducing municipal and industrial wastewater discharges to water bodies. But despite all efforts, 40 percent of U.S. surface waters remain too degraded Bottom of Formfor fishing and swimming. Contaminated runoff from expanding urban and agricultural areas, airborne pollutants, and hydrologic modifications such as drainage of wetlands are just a few of the many factors that continue to degrade U.S. surface waters despite reductions in sewage and industrial waste discharges.
Determining which of these factors has the most significant influence on the quality of a water body, requires knowledge about how the water body interacts with its watershed and air-shed and how the various inputs affect its physical, chemical, and biological characteristics.
One of the critical sciences required to understand these freshwater interactions is limnology (from the Greek
, meaning pool or marshy lake). As defined by specialists, limnology includes the study of lakes, reservoirs, rivers, and freshwater wetlands. It is a multidisciplinary science that draws from all the basic sciences relevant to understanding the physical, chemical, and biological behavior of freshwater bodies . In this unit, students will learn few basic concepts of hydrology, like the hydrological cycle, water budget of a river and chemistry of carbon in freshwater.