Aquifer: An underground layer of sand, gravel, or permeable rock where water collects.
Ecosystem: A system or area defined by a community of living organisms (plants, animals, bacteria) and their environment working together. A meadow, forest, and wetland are all different types of ecosystems.
Erosion: Wearing away of soil and rock from land by water, wind, ice, or gravity.
Floodplain: A low-lying land area along a stream or river that becomes covered with water when the stream or river spills over its banks. The flood water carries small rocks, gravel, and dirt – known as sediment – that builds up the land and enriches the soil over many years. Floodplains are important to people and wildlife. Flood waters spread out and slow down on a floodplain, protecting nearby communities from flood damage. Plants and trees in floodplains also filter pollutants and sediment.
Groundwater: Water that is stored in pores, cracks, and crevices below the water table and serves as the source of water for wells and springs.
Habitat: The area or environment where an animal finds the food, water, shelter, and space it needs to survive.
Hard Surfaces: When it rains, water runs off hard surfaces such as parking lots or sidewalks and enters storm drains. Many people think that water entering storm drains gets treated, but it does not; it gets dumped directly into streams. Hard surfaces speed the flow of water, causing erosion. In addition, water that runs over hard surfaces can become heated during warm weather and increase the temperature of stream waters, causing problems for fish and macroinvertebrates that need cool, well-oxygenated water.
Invasive Species: A species of plant or animal that is not native to a given ecosystem but whose presence might cause environmental harm to the system or harm to human health. Invasive species often thrive in new habitats because they have no natural predators in the new ecosystem to keep them in check.
Macroinvertebrates: A spineless animal visible without the use of a magnifying glass. Benthic macroinvertebrates, which live in the bottom of streams and wetlands, are good indicators of water quality because they live in the same area most of their lives and differ in their sensitivity to pollution. Which macroinvertebrates you find – or don’t find – in a stream indicates the pollution level of the water. Benthic macroinvertebrates include aquatic insects (such as dragonfly and damselfly larvae) and crustaceans (such as crayfish, snails, and clams). See our “Key to Stream Macroinvertebrates” for more macroinvertebrates and illustrations of each.
Nonpoint-Source Pollution: Pollution that cannot be traced to a single source. Oil, gasoline, brake fluid, trash, fertilizers, pesticides, and animal waste that wash into waterways and damage water quality are considered nonpoint-source pollution. For more information, read “Sources of Pollution: Point and Nonpoint.”
Nutrients: Substances that promote growth. In a stream or other body of water, fertilizers, animal waste, and decaying leaves and grasses can be considered nutrients. In excess amounts, nutrients become pollutants.
Point-Source Pollution: Pollution from a sewage treatment facility or industrial plant is called “point source” pollution because it comes from a single “point” – a pipe, ditch, or other discernible source carrying waste away from these facilities. For more information, read “Sources of Pollution: Point and Nonpoint.”
Pollutant: Any substance that causes harm to human health or the environment.
Riparian Zone (also called a “Green Zone”): This term is used to describe the green ribbon of plants along the side of a stream, where the land and water can overlap. A riparian zone has distinctive plant species, soil types, topography, and wildlife because it is so close to the water. Riparian zones vary in size. For example, vegetation along a desert stream may be small and sparse while the vegetation along a mountain stream may be tall and lush.
Runoff: Rain or snowmelt that flows over ground surfaces. This water can collect nutrients, pollutants, and other materials from air or land and carry them into streams and lakes.
Sediment: Soil, rock fragments, and other material transported and deposited by water, wind, or other forces. For example, it is natural for stream waters to carry sediment. “Sedimentation” occurs when the rocks and dirt carried by the water build up on the bottom and sides of a stream.
Soil: Soil is a mixture of solids (minerals and organic matter), liquid, and gases that occurs on a land surface.
Stream Banks: Areas on either side of a stream that restrict lateral water movement at normal water levels.
Watershed: The land area that drains into a stream or other body of water. Watersheds come in many different sizes; the watershed of a small creek may also be part of the watershed for a larger river. For example, water flows into the Mississippi River from more than one million square miles of land in 33 states and two Canadian provinces. Within that Mississippi River watershed are many smaller watersheds.
Wetland: A wetland is an area of land where the soil holds water all or part of the year. A wetland usually holds a mix of plants – such as trees, shrubs, grasses – and shallow surface waters. They are found in low-lying areas on floodplains and coastal areas. Wetlands are very important natural systems. They provide essential habitat for a wide variety of plant life and many different kinds of amphibians, reptiles, birds, insects, mammals, and fish. Wetlands water filter runoff from the surrounding land, removing pollution and helping to keep water clean. Wetlands also provide natural and highly effective flood control.