Land Use and Water Quality

Streams, rivers, and lakes are an important part of the landscape, as they provide water supply, recreation, and transportation for humans, and a place to live for a variety of plants and animals. Groundwater also is an important water resource that serves as a source of drinking water for more than 140 million people in the United States.

Land-Use Planning

Land and water resources are essential for farming, grazing, forestry, wildlife, tourism, urban development, transport infrastructure, and other environmental functions. The increasing demand for land, coupled with a limitation in its supplies, is a major cause for more conflicts over land use throughout the world.

Landfills: Impact on Groundwater

Solid waste landfills are a necessity in modern-day society, because the collection and disposal of waste materials into centralized locations helps minimize risks to public health and safety. Solid waste landfills, which are regulated differently than hazardous waste landfills, may accept a variety of solid, semi-solid, and small quantities of liquid wastes.


Landslides are natural hazards that cause millions of dollars of damage each year and also cause many deaths. They are defined as downslope movements of soil and rock under the influence of gravity.

Law, International Water

Of all the resources that people depend on, only air is more directly vital to sustaining human life than water. Deprive a person of air, and he dies in minutes.

Law of the Sea

The oceans have long been viewed by societies as a wide-open free space—a vast frontier associated with adventure and mystery. In the seventeenth century, nations formalized this viewpoint into the Freedom of the Seas doctrine.

Law, Water

Water law is a system of enforceable rules that controls the human use of water resources. In the United States, these rules are created by statutes, court decisions, and administrative regulations.

Legislation, Federal Water

Federal involvement in water resource legislation initially addressed issues of water use, such as managing the commons (e.g., regulating fisheries) and regulating navigable waterways to support navigation and commerce. As the country grew westward, water legislation was used to fund massive water development projects to increase water supplies for irrigation, hydroelectricity, flood control, and municipal and industrial water supply.

Legislation, State and Local Water

Surface water and groundwater are transboundary resources that often cross political boundaries. Generally, under the United States' federal system of government, no single governmental level has absolute sovereign authority over water.

Leonardo da Vinci

Leonardo da Vinci is history's foremost Renaissance man, a master of both art and science. Da Vinci is best known as the artist who created such masterpieces as the Mona Lisa, Madonna of the Rocks, and The Last Supper.

Leopold, Luna

Luna Bergere Leopold, the son of the famous wildlife ecologist Aldo Leopold (who wrote the environmental classic, A Sand County Almanac) has been described by the American Geological Institute as one of the most distinguished earth scientists of the last half of the twentieth century. He was a leader in the development of a better and more quantitative understanding of streams and the landscapes they form.

Lewis, Meriwether and William Clark

Meriwether Lewis and William Clark are best known for their exploration from 1804 to 1806 of the Louisiana Purchase and the Northwest Territory in what is now part of the United States. Lewis, the personal secretary to president Thomas Jefferson (1743–1826), was appointed by the president to lead the exploration of the 2 million square kilometers (about 800,000 square miles) of land purchased in 1803 by the United States from France, the Louisiana Purchase.

Life in Extreme Water Environments

Beginning in the early 1990s, scientific knowledge of the environmental limits of microbial life on Earth expanded dramatically as microbiologists applied new methods of molecular biology over a broad range of environmental extremes. Microbial species are now known to occupy a vast range of environments that previously were unimagined.

Life in Water

Life is thought to have originated in an aquatic environment—the oceans. Living organisms have since adapted to numerous aquatic habitats, both Sea nettles and jellyfish are pelagic and planktonic, meaning that they live in the water column and primarily float or drift as opposed to swimming.

Light Transmission in the Ocean

Visible radiation, or light, from the Sun is important to the world's ocean systems for several reasons. It provides the energy necessary for ocean currents and wind-driven waves.

Marginal Seas

Marginal seas, which separate coastal zones from open oceans, often exist as large indentations into continental landmasses. Some of the major marginal seas include the Arabian Sea, Baltic Sea, Bay of Bengal, Bering Sea, Beaufort Sea, Black Sea, Gulf of California, Gulf of Mexico, Mediterranean Sea, Red Sea, Ross Sea, Weddell Sea, and all four of the Siberian Seas (Barents, Kara, Laptev, and East Siberian).


Mariculture is the farming of aquatic plants and animals in salt water. Thus, mariculture represents a subset of the larger field of aquaculture, which involves the farming of both fresh-water and marine organisms.

Marine Mammals

What comes to mind when the subject of marine mammals is introduced? Most people probably only think of a few species of dolphins, whales, or Keiko, the killer whale made famous by a Hollywood movie and by efforts to return him to the wild, is shown in 1997 at the Oregon Coast Aquarium in Newport, Oregon.

Markets, Water

Some people think of water as a gift of nature, with profound cultural, spiritual, and aesthetic significance, concluding that such a natural resource should not be bought and sold like fast-food hamburgers, t-shirts, or diamond rings. But water has many uses and immense total value, and if people want to use it to maximum benefit, they must have some mechanism to decide who gets it, when, for what purposes, and at what levels of quality.

Mars, Water on

Water and other easily vaporized molecules become more common as one moves outward from the Sun. Since Earth has a substantial amount of water, one can assume that Mars should as well.

Microbes in Groundwater

Microorganisms found in groundwater can be seen only through a microscope (shown here). Viewing extremely small organisms such as viruses requires a powerful microscope, such as a scanning electron microscope.

Microbes in Lakes and Streams

Many sights and sounds attract people to the water, from the waves lapping at the shore of a lake, to the fish and turtles that break the surface now and again. But other components of the fresh-water ecosystem cannot be seen with the naked eye: the microorganisms, or microbes, that constitute the foundation of the aquatic abundance that people see and enjoy.