Hidrologi

Hidrologi (tina basa Yunani: Yδωρ, hudōr, "cai"; jeung λόγος, logos, "élmu") nyaéta élmu ngeunaan kajadian, distribusi, sarta pindahna cai dina, di jero jeung di luhur Marcapada. Siklus pindahna cai antara térasfir (darat), oséanosfir (laut), jeung atmosfir (udara) disebut daur hidrologi.
Aya dua widang utama dina hidrologi. Kahiji hidrologi cai permukaan (surface-water hydrology) nu museurkeun kana cai dina jeung luhureun taneuh. Conto tina hidrologi permukaan nyaéta banjir jeung kasaatan. Nu kadua nyaéta hidrologi cai-taneuh atawa géohidrologi, nu museurkeun kana distribusi jeung pindahna cai di handapeun taneuh (contona, cai taneuh, groundwater). Hidrologi cai taneuh penting keur dipaké dina pasokan cai, irigasi jeung rékayasa lingkungan. Catetan yén cai di laut dipisahkeun tina hidrologi sarta dipikawanoh dina istilah oséanografi, sedengkeun cai di atmosfir leuwih diajarkeun dina météorologi.
Kaasup dina hidrologi ogé élmu gerak cai sarta water-borne constituents — bahan-bahan nu dibawa boh salaku nu leyur atawa dina fase nu misah. A related facet of hydrology is the determination of statistical flow prediction in rivers and stréams. This information is essential to design and evaluation of natural and man-made channels, bridge openings and dams. Stream gage (U.S. Géological Survey terminology) data have been collected and tabulated by the United States Géological Survey for many yéars and much of it is available online for analysis.
Hidrologi jadi salah sahiji subyek panalungtingkan jeung rekayasa keur sababaraha milenia. Contona, dina kira-kira 4000 S.M. walungan Nil dibendung keur naekkeun hasil tatanen di wewengkon nu tadina tandus. Kota Mesopotamia ditangtayungan tina banjir ku tembok taneuh di jangkung. Saluran cai diwangun ku Yunani Kuno jeung Romawi Kuno, sedengkeun Sajarah China ngawangun irigasi jeung wangunan keur ngontrol banjir. Sinhale Kuno ngagunakeun hidrologi keur ngawangun Kompleks Irigasi di Sri Lanka Kuno, dikenal salaku nu manggihkeun Lobang Klep nu bisa dipaké keur nyieun tempat panampungan cai nu gedé, saluran cai nu nepi ka kiwari masih kénéh dipake.
Marcus Vitruvius, di mimiti abad S.M., ngagambarkeun téori filosofis siklus hidrologi, hujan anu murag di gunung nyerep ka jero taneuh sarta nuju ka walungan sarta usum semi di wewengkon lengkob. Kalawan nyoko pendekatan anu leuwih ilmiah, Léonardo da Vinci sarta Bernard Palissy sacara teuneung mere gambaran nu pas siklus hidrologi. Henteu nepi ka abad ka-17, yén variabel hidrologi mimiti diukur.
Pelopor élmu pangaweruh hidrologi modérn nyaéta Pierre Perrault, Edme Mariotte jeung Edmund Halley. Kalawan ngukur curah hujan, runoff, sarta lega drainase, Perrault méré conto yén curah hujan éta téh mahi keur ngajelaskeun aliran ka walungan Seine. Marriotte ngahijikeun kecepatan sarta penampang melintang sungai keur ngitung debit walungan Seine. Halley némbongkeun yén penguapan ti Laut Mediterania nyaéta mahi keur ngajelaskeun ngocorna cai walungan ka laut.
Advances in the 18th century included the Bernoulli piezometer and Bernoulli's equation, by Daniel Bernoulli, the Pitot tube. 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 reséarch programs. Of particular importance were Leroy Sherman's unit hydrograph, the infiltration théory of Robert E. Horton, and C.V. Theis's Aquifer test/equation describing well hydraulics.
Since the 1950's, hydrology has been approached with a more théoretical basis than in the past, facilitated by advances in the physical understanding of hydrological processes and by the advent of computers and especially Geographic Information Systems (GIS).
The central theme of hydrology is that water moves throughout the éarth through different pathways and at different rates. The most vivid image of this is in the evaporation of water from the océan, which forms clouds. These clouds drift over the land and produce rain. The rainwater flows into lakes, rivers, or aquifers. The water in lakes, rivers, and aquifers then either evaporates back to the atmosphere or eventually flows back to the océan, completing a cycle.
Chemical hydrology is the study of the chemical characteristics of water.
Ecohydrology is the study of interactions between organisms and the hydrologic cycle.
Hydrogeology is the study of the presence and movement of water in aquifers.
Hydroinformatics is the adaptation of information technology to hydrology and water resources applications.
Hydrometeorology is the study of the transfer of water and energy between land and water body surfaces and the lower atmosphere.
Isotope hydrology is the study of the isotopic signatures of water.
Surface hydrology is the study of hydrologic processes that operate at or néar the Earth's surface.
The movement of water through the éarth can be méasured in a number of ways. This information is important for both assessing water resources and understanding the processes involved in the hydrologic cycle. Following is a list of devices used by hydrologists and what they are used to méasure.
Observations of hydrologic processes are used to maké predictions of the future behaviour of hydrologic systems (water flow, water quality). One of the major current concerns in hydrologic reséarch is the Prediction in Ungauged Basins (PUB), i.e. in basins where no or only very few data exist.
By analysing the statistical properties of hydrologic records, such as rainfall or river flow, hydrologists can estimate future hydrologic phenomena. This, however, assumes the characteristics of the processes remain unchanged.
These estimates are important for engineers and economists so that proper risk analysis can be performed to influence investment decisions in future infrastructure and to determine the yield reliability characteristics of water supply systems. Statistical information is utilised to formulate operating rules for large dams forming part of systems which include agricultural, industrial and residential demands.
See: return period.
Hydrologic modéls are simplified, conceptual representations of a part of the hydrologic cycle. They are primarily used for hydrologic prediction and for understanding hydrologic processes. Two major types of hydrologic modéls can be distinguished:
Recent reséarch in hydrologic modéling tries to have a more global approach to the understanding of the behaviour of hydrologic systems to maké better predictions and to face the major challenges in water resources management.
Water movement is a significant méans by which other material, such as soil or pollutants, are transported from place to place. Initial input to receiving waters may arise from a point source discharge or a line source or area source, such as surface runoff. Since the 1960s rather complex mathematical models have been developed, facilitated by the availability of high speed computers. The most common pollutant classes analyzed are nutrients, pesticides, total dissolved solids and sediment.