surface runoff

Examples of surface runoff in the following topics:

• The Phosphorus Cycle

  • In addition to phosphate runoff as a result of human activity, natural surface runoff occurs when it is leached from phosphate-containing rock by weathering, thus sending phosphates into rivers, lakes, and the ocean.
  • This sediment then is moved to land over geologic time by the uplifting of areas of the earth's surface .
  • One of the worst dead zones is off the coast of the United States in the Gulf of Mexico, where fertilizer runoff from the Mississippi River basin has created a dead zone of over 8,463 square miles.
  • Phosphate and nitrate runoff from fertilizers also negatively affect several lake and bay ecosystems, including the Chesapeake Bay in the eastern United States, which was one of the first ecosystems to have identified dead zones.
  • Phosphate enters the oceans via surface runoff, groundwater flow, and river flow.

• The Water (Hydrologic) Cycle

  • Rain eventually percolates into the ground, where it may evaporate again (if it is near the surface), flow beneath the surface, or be stored for long periods.
  • More easily observed is surface runoff: the flow of fresh water either from rain or melting ice.
  • Runoff can then make its way through streams and lakes to the oceans or flow directly to the oceans themselves.
  • Rain and surface runoff are major ways in which minerals, including carbon, nitrogen, phosphorus, and sulfur, are cycled from land to water.
  • The cycle is complete when surface or groundwater reenters the ocean.

• The Nitrogen Cycle

  • Human activity can release nitrogen into the environment by two primary means: the combustion of fossil fuels, which releases different nitrogen oxides, and the use of artificial fertilizers in agriculture, which are then washed into lakes, streams, and rivers by surface runoff.
  • A major effect from fertilizer runoff is saltwater and freshwater eutrophication: a process whereby nutrient runoff causes the excess growth of microorganisms, depleting dissolved oxygen levels and killing ecosystem fauna.
  • Some of this nitrogen falls to the ocean floor as sediment, which can then be moved to land in geologic time by uplift of the earth's surface, becoming incorporated into terrestrial rock.

• The Carbon Cycle

  • This carbon can be leached into the water reservoirs by surface runoff.

• When building new, think before doing

  • Cover parking areas with light-coloured cement or other light-coloured surfacing rather than asphalt.
  • Dark colours absorb sunlight (and heat) and textured surfaces tend to be more heat-absorbing.
  • Channelling rainwater runoff from a building into tanks (for later use) or swales lined with indigenous vegetation is not only eco-friendly it's also cost-effective when compared to an expensive network of underground pipes and treatment plants.

• Soil Formation

  • Regional surface features (familiarly called "the lay of the land") can have a major influence on the characteristics and fertility of a soil.
  • Topography affects water runoff, which strips away parent material and affects plant growth.
  • Materials are deposited over time, decompose, and transform into other materials that can be used by living organisms or deposited onto the surface of the soil.

• Parametric Surfaces and Surface Integrals

  • A parametric surface is a surface in the Euclidean space $R^3$ which is defined by a parametric equation.
  • A parametric surface is a surface in the Euclidean space $R^3$ which is defined by a parametric equation with two parameters: $\vec r: \Bbb{R}^2 \rightarrow \Bbb{R}^3$.
  • Parametric representation is the most general way to specify a surface.
  • The same surface admits many different parametrizations.
  • A surface integral is a definite integral taken over a surface .

• Surfaces in Space

  • A surface is a two-dimensional, topological manifold.
  • For example, the surface of the Earth is (ideally) a two-dimensional surface, and latitude and longitude provide two-dimensional coordinates on it (except at the poles and along the 180th meridian).
  • The concept of surface finds application in physics, engineering, computer graphics, and many other disciplines, primarily in representing the surfaces of physical objects.
  • Historically, surfaces were initially defined as subspaces of Euclidean spaces.
  • In spherical coordinates, the surface can be expressed simply by $r=R$.

• What's Next?

  • The agency pressed auto-makers and electric utilities to reduce small particles of soot that their operations spewed into the air, and it worked to control water-polluting storm and farm-fertilizer runoffs.

• Surface Tension

  • Surface tension is a contractive tendency of the surface of a liquid that allows it to resist an external force.
  • If no force acts normal (perpendicular) to a tensioned surface, the surface must remain flat.
  • In order for the surface tension forces to cancel out this force due to pressure, the surface must be curved.
  • Again, since the energy at the surface is due in large part to the intermolecular attractive forces between particles on the surface and those in the interior, the surface tension is an indicator of the extent of those forces.
  • The surface tensions of a few common liquids and solutions are as follows, in dyne/cm (note the particularly high surface tension of water):