Hydrology

Hydrology
Name	Hydrology
Etymology	From Greek hydor (water) and logos (study)
Field	Earth science
Subfields	Surface water hydrology, Groundwater hydrology, Hydrogeology
Related	Meteorology, Oceanography, Geology, Civil engineering, Environmental science
Notable scientists	Robert E. Horton, John G. Ferris, Ven Te Chow
Organizations	International Association of Hydrological Sciences, American Geophysical Union, World Meteorological Organization

Hydrology is the scientific study of the movement, distribution, and management of water on Earth and other planets, including the hydrologic cycle, water resources, and environmental watershed sustainability. It is a core component of the Earth sciences and intersects with disciplines such as meteorology, geology, and civil engineering. Practitioners, known as hydrologists, apply their knowledge to solve problems in areas like water supply, flood control, and ecosystem health.

Overview

The field examines all phases of the water cycle, from precipitation over continents like Asia and North America to its flow in river systems such as the Amazon River and the Mississippi River. Historical foundations were laid by figures like Pierre Perrault and Edme Mariotte in the 17th century, with modern systematization advanced by Robert E. Horton. Key institutions driving research include the United States Geological Survey and the World Meteorological Organization. Hydrology is fundamentally concerned with quantifying water fluxes and storages within natural and engineered systems.

Hydrological cycle

The continuous movement of water, known as the hydrologic or water cycle, involves processes like evaporation from the Pacific Ocean, condensation, precipitation, and runoff. Major components include infiltration into soils studied at places like the Hubbard Brook Experimental Forest, transpiration from vegetation, and groundwater recharge into aquifers such as the Ogallala Aquifer. This cycle is powered by solar energy and influenced by climatic patterns monitored by agencies like the National Oceanic and Atmospheric Administration. Understanding this cycle is critical for modeling climate interactions studied by the Intergovernmental Panel on Climate Change.

Sub-disciplines

* Surface water hydrology: Focuses on water above ground, in channels like the Nile River or lakes such as Lake Baikal, analyzing phenomena like flooding and sediment transport. * Groundwater hydrology (Hydrogeology): Studies water beneath the Earth's surface in aquifers, with pioneers like Charles V. Theis developing well hydraulics theories. * Chemical hydrology: Examines water chemistry, including pollution from events like the Love Canal incident, often in collaboration with the Environmental Protection Agency. * Ecohydrology: Investigates interactions between water and ecosystems, such as in the Florida Everglades or the Murray-Darling Basin. * Hydrometeorology: Bridges hydrology and meteorology, focusing on precipitation and storm events like Hurricane Katrina.

Measurement and analysis

Data collection employs instruments like stream gauges deployed by the United States Geological Survey, rain gauges, and piezometers. Remote sensing technologies from satellites like those in NASA's GRACE mission and radar systems such as NEXRAD are vital. Analytical methods include statistical frequency analysis for events like the Great Mississippi Flood of 1927 and computer modeling using systems like the Hydrologic Modeling System developed by the Hydrologic Engineering Center. Fieldwork often occurs at research basins like the Sleepers River Research Watershed.

Applications

Hydrology is essential for designing infrastructure such as the Hoover Dam and the Delta Works in the Netherlands. It informs water supply management for megacities like Los Angeles and Beijing, agricultural irrigation from sources like the Colorado River, and flood warning systems operated by entities like the Federal Emergency Management Agency. It also supports environmental restoration projects in areas like the Chesapeake Bay and legal frameworks such as the Clean Water Act.

Challenges and future directions

Current challenges include addressing impacts of climate change on glacial retreat in the Himalayas, managing droughts in the Sahel region, and mitigating pollution from sources like the Cuyahoga River. Future directions involve integrating big data from projects like the Global Earth Observation System of Systems, advancing predictive models at institutions like the National Center for Atmospheric Research, and promoting sustainable water policies through international agreements like those under the United Nations Educational, Scientific and Cultural Organization. Emerging fields like socio-hydrology examine human-water system interactions in regions like the Aral Sea basin.

Category:Earth sciences Category:Water