Hydrology

Water occupies 70% of the earth's surface.

Hydrology (from the Greek: ὕδωρ, "hýdōr" "water" and λόγος, "lógos" "study& #34;) is a branch of Earth sciences that studies water, its occurrence, distribution, circulation, and physical, chemical, and mechanical properties in the oceans, atmosphere, and Earth's surface. This includes precipitation, runoff, soil moisture, evapotranspiration, and the balance of glacial masses. On the other hand, the study of groundwater corresponds to hydrogeology.

On the contrary, hydrography is called the study of all the masses of water on Earth and, more strictly, the measurement, collection and representation of data related to the ocean floor, coasts, tides and currents, so that they can be reflected on a hydrographic chart. Notwithstanding this difference, the terms will be used almost as synonyms, since the part of hydrography that is of interest here is that which creates relief, therefore, that which is in contact with the earth's surface, and for this very reason the one that is subject of hydrological analysis.

The circulation of the masses of water on the planet are responsible for the modeling of the earth's crust, as is evident in the geographic cycle. This influence is manifested as a function of the distribution of coherent and fragile rock masses, and the deformations that have affected them, and are fundamental in the definition of the different reliefs.

Let us remember that a river is a water current that flows through a channel from the highlands to the lowlands and discharges into the sea or in an endorheic region (collector river) or into another river (tributary). Rivers are organized in networks. A hydrographic basin is the total area that discharges its runoff waters to a single river, waters that depend on the characteristics of the feeding. A drainage basin is the part of the earth's surface that is drained by a unitary river system. Its perimeter is delimited by the divide or interfluve.

The layouts of the hydrographic elements are characterized by the adaptation or maladaptation to the lithological and tectonic structures, but also the geological structure acts in the domain of the hydrographic networks determining their structure and evolution.

The hydrological study begins with the morphometric analysis of the basin, which includes: the delimitation of the basin, the measurement of the area and length, maximum and minimum height, compactness index, shape factor, hypsometric curve, slope average, characterization of the drainage network and the altimetric profile of the main channel, among others.

Definitions

In the course of its development, hydrology has been defined in various ways, one of the simplest is the one derived from the etymological analysis of the word, therefore, it would be: hydrology is the science of water

At the current level of development of human activities and of science in general, it is not possible to be satisfied with the previous definition, which is too simplistic and incomplete, therefore it is recommended to analyze the following:

Hydrology is the science that deals with the waters of the Earth, its occurrence, circulation and distribution, its physical and chemical properties and its influence on the environment, including its relationship with living beings. The domain of hydrology encompasses the complete history of the existence of water on earth

U.S. Federal Council for Science and Tecnology (1962)

Hydrology is the science that deals with the processes that govern the exhaustion and recovery of water resources in the continental areas of the Earth and in the various phases of the hydrological cycle.

World Meteorological Organization

History of hydrology

Generally, the various authors recognize 8 periods in the historical development of hydrology, these are:

Speculative period

Although the dates are not exact, various authors such as O.E. Meinzer, define this period, from antiquity to 1400. During this period the concept of hydrological cycle was speculated by many philosophers such as Homer, Thales, Plato, and Aristotle, among others in Greece; by Seneca and Pliny in Rome. Most of the concepts developed at this time turned out to be wrong, with the exception of the one proposed by Marco Vitruvio, who established that groundwater came from the infiltration of rainwater and melting snow.

The great hydraulic constructions of antiquity, which required practical hydrological knowledge, belong to this period, among them the wells of Arabia, the Kanats of Persia, the aqueducts of Rome, the canals and irrigation systems, and water control works. floods in China; and irrigation zones in Egypt, Mesopotamia, India, and the Andes.

Observation period

Between 1000 and 1600. In the period known as the Renaissance, there was a gradual shift from the pure philosophical concepts of hydrology to the observational science of that time. For example, based on observations, Leonardo da Vinci and Bernard Palissy achieved a correct understanding of the hydrological cycle, especially regarding the infiltration of rain and return of water through springs.

Period of measurement

Between 1600 and 1700. The beginning of the modern science of hydrology can be considered in the 17th century, with the measurements, for example: those of Pierre Perrault and Edmé Mariotte in the Seine River in Paris and Edmond Halley in the Mediterranean Sea, which reached correct conclusions of the studied hydrological phenomenon. The first studies of artesian wells also correspond to this period.

Period of experimentation

Between 1700 and 1800. During the 18th century, hydraulic experimental studies had a great boom and as a result of They many hydraulic principles were obtained, for example: Bernoulli's theorem and piezometer, Chézy's formula and D'Alembert's principle, Pitot and Borda tubes.

Modernization Period

Between 1800 and 1900. The 19th century was a great era of experimental hydrology that began in the period preceding and more firmly marking the beginning of the science of hydrology. However, most of the contributions were made in geohydrology and in the measurement of surface waters (Hydrometry). For example: the Hagen-Poiseuille equation of capillary flow (1840), Darcy's Law (1856), the Dupuit-Thiem well formula (1863) and the Ghyben-Herzberg principle (1889).

In the field of hydrometry, in relation to the gauging of surface waters, great progress was made, including: the development of various flow formulas and measuring instruments and the beginning of the systematic gauging of currents. Among the main contributions is the discharge formula of Francis' weirs (1855), the determination of the Chézy coefficient proposed by Ganguillet and Kutter (1869) and by Manning (1889) and in the field of evaporation, Dalton's law. (1802), finally, in the field of precipitation, the correlation between rainfall and altitude, determined by Miller (1849).

Empiricism Period

Between 1900 and 1930. Although much modern hydrology work began in the 19th century, the development of quantitative hydrology was still immature and then the science of hydrology was largely empirical, either because the physical basis for various hydrological determinations was not well known, or because much experimental quantitative information was available to be used and processed. During the final part of the 19th century, and the following 30 years, hydrological empiricism was evident, for example: hundreds of formulas empirical were proposed, selecting their coefficients and parameters based on judgment and experience.

Rationalization Period

Between 1930 and 1950. In this period, the great hydrologists began to use rational analysis to solve the hydrological problems raised, such as: Sherman (1932) with the concept of unit hydrograph. Horton (1953) with the theory of rain infiltration, Theis (1935) who introduced the concept of non-equilibrium in well hydraulics, Gumbel (1941) who proposed the probability distribution of extreme values, Hazen (1930) who promoted the use of statistics in hydrology, Bernard (1944) who discusses the role of meteorology and marks the beginning of hydrometeorology and Einstein (1950) who introduces theoretical analysis in sedimentation studies. Another notable development of this period was the establishment of many hydraulic and hydrological laboratories in the world.

Theorization period

From the 1950s to the present. Around the year 1950, theoretical approaches have extensive use in hydrological problems, since many previously proposed rational principles can be subjected to true mathematical analysis. Sophisticated instruments and high-speed computers begin their development, and then delicate measurements of hydrological phenomena can be taken and complicated mathematical equations involved in applying modern hydrological theories can be solved.

Examples of theoretical hydrological studies are: the linear and non-linear analysis of hydrological systems, the adoption of statistical and transient concepts in the hydrodynamics of groundwater and surface water, the application of mass and heat transfer theories to the evaporation analysis, the energetic and dynamic study of soil moisture, the sequential generation of synthetic hydrological data and the use of operations research in the design of water resources systems.

Importance of hydrology

Floods are extreme hydrological events that can be prevented by studying hydrology.

Currently, hydrology plays a very important role in planning the use of Hydraulic Resources, and has become a fundamental part of engineering projects that have to do with water supply, sewage disposal, drainage, protection against the action of rivers and recreation. On the other hand, the integration of hydrology with mathematical geography, especially through geographic information systems, has led to the essential use of the computer in the processing of existing information and in the simulation of the occurrence of future events.

Hydrological studies are essential for:

• The design of hydraulic works, to carry out these studies are frequently used mathematical models that represent the behavior of the entire basin supported by the work under review.
• The optimized operation of the use of water resources in a complex system of hydraulic works, especially if they are of multiple uses. In this case conceptual mathematical models are generally used, and are processed in real time.
• The correct knowledge of the hydrological behavior of such a river, stream, or lake is essential to establish areas vulnerable to extreme weather events.
• Preview a correct road infrastructure design, such as roads, roads, railways, etc.

All this and many more applications make the hydrologist an important character in any multidisciplinary team that faces civil engineering problems in general and problems of an environmental nature.

Division of Hydrology

Hydrology can be categorized, according to the form of analysis, and the use that will be given to the results. It can be classified, even knowing the limitation of any classification in:

Applied Hydrology or Hydrological Engineering

Qualitative hydrology

In qualitative hydrology the emphasis is given to the description of processes. For example, in the determination of the forms and causes that cause the formation of a sand bank in a river, a study associated with the solid transport of water courses; or to the analysis of the occurrence of condensation in certain points of a road, which affect visibility and therefore can advise to change the route of the same.

Hydrometric hydrology

Hydrometric hydrology, or hydrometry, focuses on the measurement of hydrological variables, it is basically field work, where the proper use of measuring instruments, the proper selection of the premises in which the measurements are carried out and the correct interpretation of the results is essential for the quality of the information collected. Helping in its entirety to be able to calculate aspects related to channels and hydrological dependencies.

Quantitative Hydrology

The emphasis of quantitative hydrology is on the study of the temporal distribution of water resources in a given watershed. The most widely used instruments in this branch of hydrology are mathematical instruments, statistical models and conceptual models.

Hydrology in real time

It is the newest branch of hydrology, and it became popular from the 1960s - 70s, with the rise of telemetry networks, where sensors located at various points in a basin transmit data in real time to a operational center where they are immediately analyzed to be used to help make decisions of an operational nature, such as opening or closing gates of a specific hydraulic work.

Branches of Hydrology

The International Association of Scientific Hydrology (IASH) proposes the following division of hydrology:

• Oceanographystudy of oceans and seas.
• Meteorology, water study in the atmosphere.
• Surface hydrology, Study of the continental waters, (in the current language to this branch is frequently referred to as hydrology, without other specification). Surface hydrology is divided in turn into:
  • Agricultural hydrology
  • Forest hydrology
  • Urban hydrology
  • Hydrology of arid and semi-arid regions
  • Pantaneous area hydrology
  • Control hydrology of avenues or growing
• Hydrometeorology, studies the problems common to the fields of Meteorology and Superficial Hydrology.
• Limnology, lake study.
• Potamology, study of the rivers.
• Hydrogeologystudy of groundwater.
• Criology, solid water study (snow and ice).