Hydrology Scientific study of the properties, distribution and effects of water on the Earth's surface, in the soil and underlying rocks, and in the atmosphere. 70% of the Earth is covered in water. History of Hydrology
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70% of the Earth is covered in water
History of Hydrology
Hydrology has been a subject of investigation and engineering for millennia. For example, in about 4000 B.C. the Nile was dammed to improve agricultural productivity of previously barren lands. Mesopotamian towns were protected from flooding with high earthen walls. Aquaducts (1) were built by the Greeks and Romans, while the Chinese built irrigation and flood control works.
Marcus Vitruvius, in the first century B.C., described a philosophical theory of the hydrologic cycle, in which precipitation falling in the mountains infiltrated the earth's surface and led to streams and springs in the lowlands. With adoption of a more scientific approach, Leonardo da Vinci and Bernard Palissy independantly reached an accurate representation of the hydrologic cycle. It was not until the 17th century that hydrologic variables began to be quantified.
Pioneers of the modern science of hydrology include Pierre Perrault, Edme Mariotte, and Edmund Halley. By measuring rainfall, runoff, and drainage area, Perrault showed that rainfall was sufficient to account for flow of the Seine. Marriotte combined velocity and river cross-section measurements to obtain discharge, again in the Seine. Halley showed that the evaporation from the Mediterranean Sea was sufficient to account for the outflow of rivers flowing into the sea.
Advances in the 18th century included the Bernoulli piezometer and Bernoulli's equation, by Daniel Bernoulli, the Pitot tube, and the Chezy formula. The 19th century saw development in groundwater hydrology, including Darcy's law, the Dupuit-Thiem well formula, and Hagen-Poiseuille's capillary flow equation.
Rational analyses began to replace empiricism in the 20th century, while governmental agencies began their own hydrological research programs. Of particular importance were Leroy Sherman's unit hydrograph, the infiltration theory of Robert E. Horton, and C.V. Theis's equation describing well hydraulics.
Since the 1950s, hydrology has been approached with a more theoretical basis than in the past, facilitated by advances in the physical understanding of hydrological processes and by the advent of computers.
1. A pipe or channel designed to transport water from a remote source, usually by gravity.
For more detailed information:
Stream gauge - stream flow
Sling psychrometer – humidity
Radar - cloud properties
Piezometer - groundwater pressure and, by inferrence, groundwater depth
Tensiometer - soil moisture
Infiltrometer - infiltration
Disdrometer - precipitation characteristics
Time domain reflectometer - soil moisture
light blue zones are aquifers,
darker blue hatched zone is an aquitard,
light brown (tan) section is the vadose zone (unsaturated zone), and
dark brown area is "impermeable" bedrock (an aquiclude).
Aquitard-is a geological formation of layers comprised either of clay, with tiny connected pores, or on non-porous rock that restrict water flow from one aquifer to another.
Vadose zone (unsaturated zone)- is part of the ground that is between the water table and the surface that is not considered groundwater.
Aquiclude-An impermeable body of rock that may absorb water slowly but does nottransmit it.
Watershed- The region draining into a river, river system, or other body of water - They are very important because they provide habitats for animals, lessen flooding, and prevent erosion. -Pollution anywhere within the watershed can potentially affect life anywhere downstream from it. - We all live in watershed
Information about your watershed
The flow of a river is quite irregular when considered over long time periods.It is characterized by rises from rainfall and snowmelt followed by gradually receding flow.The most elementary river and flood forecasts are concerned with predicting the time and height of stages caused by peak flows