Secrets of water’s underground treks, revealed

aquatic: An adjective that refers to water.

aquifer: Rock that can hold pools of groundwater. The term can also be applied to those underground pools of water.

catchment: (in hydrology) A term for the land that drains all of the water that falls on it into open waters, which can be rivers and streams or lakes and oceans.

clay: Fine-grained particles of soil that stick together and can be molded when wet. When fired under intense heat, clay can become hard and brittle. That’s why it’s used to fashion pottery and bricks.

climate change: Long-term, significant change in the climate of Earth. It can happen naturally or in response to human activities, including the burning of fossil fuels and clearing of forests.

computer model: A program that runs on a computer that creates a model, or simulation, of a real-world feature, phenomenon or event.

continental United States: Also known as the lower 48 states, these are all U.S. states except Alaska and Hawaii. They all reside below Canada and above Mexico.

crop: (in agriculture) A type of plant grown intentionally grown and nurtured by farmers, such as corn, coffee or tomatoes. Or the term could apply to the part of the plant harvested and sold by farmers.

crust: (in geology) Earth’s outermost surface, usually made from dense, solid rock.

fertilizer: Nitrogen, phosphorus and other plant nutrients added to soil, water or foliage to boost crop growth or to replenish nutrients that were lost earlier as they were used by plant roots or leaves.

groundwater: Water that is held underground in the soil or in pores and crevices in rock.

link: A connection between two people or things.

nitrate: An ion formed by the combination of a nitrogen atom bound to three oxygen atoms. The term is also used as a general name for any of various related compounds formed by the combination of such atoms.

pollutant: A substance that taints something — such as the air, water, our bodies or products. Some pollutants are chemicals, such as pesticides. Others may be radiation, including excess heat or light. Even weeds and other invasive species can be considered a type of biological pollution.

porous: The description of a substance that contains tiny holes, called pores, through which a liquid or gas can pass.

simulation: (v. simulate) An analysis, often made using a computer, of some conditions, functions or appearance of a physical system. A computer program would do this by using mathematical operations that can describe the system and how it might change over time or in response to different anticipated situations.

U.S. Geological Survey: (or USGS) This is the largest nonmilitary U.S. agency charged with mapping water, Earth and biological resources. It collects information to help monitor the health of ecosystems, natural resources and natural hazards. It also studies the impacts of climate and land-use changes. A part of the U.S. Department of the Interior, USGS is headquartered in Reston, Va.

watershed: A high point in the landscape that marks the dividing line away from which any flowing water will head. For instance, a mountain chain may mark where water on one side drains via rivers into one ocean, and water falling on the other side will drain into a different ocean (via rivers).

weather: Conditions in the atmosphere at a localized place and a particular time. It is usually described in terms of particular features, such as air pressure, humidity, moisture, any precipitation (rain, snow or ice), temperature and wind speed. Weather constitutes the actual conditions that occur at any time and place. It’s different from climate, which is a description of the conditions that tend to occur in some general region during a particular month or season.

wetland: As the name implies, this is a low-lying area of land either soaked or covered with water much of the year. It hosts plants and animals adapted to live in, on or near water.