For most young scholars, a visual depiction of the water cycle is one of the earliest – and most memorable – science lessons learned at school. Along with the ozone layer and its shielding of harmful ultraviolet rays, the constant replenishment of our water supply is a fundamentally critical component of life on Planet Earth.
Water Cycle’s Basic Principles
More formally known as the hydrological cycle, the chart of how Mother Nature constantly recycles its finite supply of water is a familiar sight in elementary and secondary classrooms, featuring a 360-degree daisy chain of arrows and annotations. Water stored in the atmosphere falls back down to earth in the form of precipitation (rain, sleet, snow, humidity) and runoff from snow caps. Some of it seeps into the ground, some of it sits in bodies of water and another portion is pumped through living organisms and then expelled.
Evaporation, Evapotranspiration, and Sublimation
The main ways in which water is transferred back up to the atmosphere are evaporation, evapotranspiration and sublimation. Evapotranspiration is the combination of evaporation and transpiration. The latter refers to the way humans (through breath) and plants (through secretion) release absorbed water back into atmosphere and overall water cycle. Sublimation reflects the fact that in some cases, snow and ice turns directly back into a gaseous, vapor state, bypassing the liquid or water form.
Negative Impact on the Water Cycle
In 2010, a great amount of concern has grown over the potential impact on the water cycle of the historic British Petroleum (BP) oil spill in the Gulf of Mexico. Sadly, one study commissioned for the Russian government notes that the fallout effect of toxic rain could come not from the oil itself but from Corexit 9500, an oil dispersant widely used in the wake of the spill by BP. The report, prepared for Russian Prime Minister Vladimir Putin by scientists at the Shirshov Institute of Oceanology, is but one of many attempts to quantify what is expected to be a complex and long-lasting impact of the BP oil spill on the worldwide water cycle.
United States Geological Survey (USGS) – Hydrologic Cycle, Retrieved August 29, 2010 from http://ga.water.usgs.gov/edu/watercycle.html
BPComplaints.com – “Gulf Oil Spill Causing Toxic Rain, Killing Crops???”, July 1, 2010, Retrieved August 29, 2010 from http://www.bpcomplaints.com/2010/07/urgent-gulf-oil-spill-causing-toxic-rain-killing-crops/