The word hydrography comes from the ancient Greek ὕδωρ (hydor), "water" and γράφω (graphō), "to write."

To formulate socioeconomic development projects for a hydrographic basin, its study must first be undertaken considering it as a natural region. That is why an association of the flows must first be made because in order to study hydrography it is necessary to study the slopes and basins.

A river or water flow is a natural current of water that flows continuously through a channel on the earth's surface. It has a certain flow, it is rarely constant throughout the year, and it flows into the sea, a lake or another river, in which case it is called a tributary. The final part of a river is its mouth. Sometimes they end up in desert areas where their water is lost through infiltration and evaporation.[1]​.

Rivers can be classified from various points of view, among which the following stand out:[1]​.

Depending on the period of activity, in perennial, seasonal, transient, or allochthonous rivers.

According to its geometry or morphology, a river or a certain stretch can be classified into the following categories: rectilinear, sinuous, meandering, anastomosing, with islands, in estuaries, in swamps or mangroves, in deltas.

Depending on their age, they are classified as: young, mature or old rivers.

Depending on its stability condition, a channel section can be considered with static, dynamic stability, with dynamic instability, or with morphological stability.

Its sections can be classified as: high mountain, mountain, mountain slope, intermediate, and plain.

Depending on its degrees of freedom, it can be classified as having one, two or three degrees of freedom.

Depending on the material of the margins and the bottom, they can be considered as cohesive, non-cohesive, armored materials, well graded or with extended grain size, poorly graded or with uniform grain size.

Depending on the conditions of solid transport, three types of channels can be considered: stable, erodible and depositional.

In many countries there are national hydrographic services. Likewise, there is international coordination of hydrographic information, carried out by the International Hydrographic Organization (IHO), an intergovernmental entity founded in 1921, with headquarters in Monaco; which fundamentally regulates marine hydrography.

Hydromorphometry: Dedicated to the study of hydrographic basins, especially their shape, dimensions, composition, response time, etc.

Marine hydrography (nautical cartography): It is dedicated to the measurement, compilation and representation of data related to the ocean floor, seas and coasts, tides and currents, so that they can be captured on a nautical chart.

Large-scale hydrography is usually carried out by national or international organizations that sponsor the collection of data through precise surveys and publish charts and descriptive material for navigation purposes. The science of oceanography is, in part, a consequence of classical hydrography. In many respects the data are interchangeable, but marine hydrographic data will be particularly oriented towards marine navigation and navigation safety. The exploration and exploitation of marine resources is an important application of hydrography, focused mainly on the search for hydrocarbons.

Hydrographic measurements include tidal, current, and wave information from physical oceanography. They include measurements of the bottom, with special emphasis on marine features that pose a danger to navigation, such as rocks, shallows, reefs and other features that obstruct the passage of ships. Bottom measurements also include gathering the nature of the bottom as it relates to effective anchorage. Unlike oceanography, hydrography will include coastal features, natural and man-made, that aid navigation. Therefore, a hydrographic survey can include the precise positions and representations of hills, mountains and even lights and towers that help fix the position of a ship, as well as the physical aspects of the sea and seabed.

Hydrography, especially for safety reasons, adopted a series of conventions that have affected the representation of data on nautical charts. For example, hydrographic charts are designed to represent what is safe for navigation and therefore typically tend to maintain the shallowest depth and occasionally downplay the actual underwater topography that would be represented on bathymetric charts. The first are the sailor's tools to avoid accidents. The latter are the best representations of the actual seafloor, as on a topographic map, for scientific and other purposes. Trends in hydrographic practice since c. 2003-2005 have led to a reduction in this difference, with many more hydrographic offices maintaining "better observed" databases, and then making "safe" products for navigation, as necessary. This has been coupled with a preference for multi-use surveys, so that the same data collected for nautical mapping purposes can also be used for bathymetric representation.

Although, in some places, hydrographic survey data can be collected in sufficient detail to represent the bottom topography in some areas, hydrographic charts or nautical charts only show depth information relevant to the safety of navigation and should not be considered as a product that accurately represents the true shape of the bottom. Soundings selected from the raw source depth data for placement on the nautical chart are selected for safe navigation and are biased to predominantly show the shallower depths that relate to safe navigation. For example, if there is a deep area that cannot be reached because it is surrounded by shallow water, the deep area may not be displayed. Color-filled areas showing different ranges of shallow water are not the equivalent of contour lines on a topographic map, as they are often drawn seaward of the actual minimum depth represented. A bathymetric chart accurately shows marine topology. Details covering the above limitations can be found in Part 1 of Bowditch's American Practical Navigator. Another concept affecting navigation safety is the scarcity of detailed depth data from high-resolution sonar systems. In more remote areas, the only depth information available has been collected with lead lines. This collection method drops a weighted line to the bottom at intervals and records the depth, often from a rowboat or sailboat. There is no data between surveys or between survey lines to guarantee that there is not a hazard, such as a shipwreck or a coral head, waiting there to ruin the boater's day. Harvest vessel navigation often does not match today's GPS navigation accuracies. The hydrographic chart will use the best data available and will warn of its nature in a cautionary note or in the chart legend.

A hydrographic survey is quite different from a bathymetric survey in some important respects, particularly in a bias toward shallower depths due to the safety requirements of the former and the descriptive geomorphological requirements of the latter. Historically, this might include echo-sounding" in a context of preferences for minimum depths, but in modern practice, hydrographic surveys.

• - Strahler, Arthur (1952) important person.

• - International Hydrographic Organization: Hydrographic Dictionary 2nd Part. Special Publication No. 32. Spanish version of the fifth edition of Part 1, Volume I.

• - Wiktionary has definitions and other information about hydrography.

The word hydrography comes from the ancient Greek ὕδωρ (hydor), "water" and γράφω (graphō), "to write."

To formulate socioeconomic development projects for a hydrographic basin, its study must first be undertaken considering it as a natural region. That is why an association of the flows must first be made because in order to study hydrography it is necessary to study the slopes and basins.

A river or water flow is a natural current of water that flows continuously through a channel on the earth's surface. It has a certain flow, it is rarely constant throughout the year, and it flows into the sea, a lake or another river, in which case it is called a tributary. The final part of a river is its mouth. Sometimes they end up in desert areas where their water is lost through infiltration and evaporation.[1]​.

Rivers can be classified from various points of view, among which the following stand out:[1]​.

Depending on the period of activity, in perennial, seasonal, transient, or allochthonous rivers.

According to its geometry or morphology, a river or a certain stretch can be classified into the following categories: rectilinear, sinuous, meandering, anastomosing, with islands, in estuaries, in swamps or mangroves, in deltas.

Depending on their age, they are classified as: young, mature or old rivers.

Depending on its stability condition, a channel section can be considered with static, dynamic stability, with dynamic instability, or with morphological stability.

Its sections can be classified as: high mountain, mountain, mountain slope, intermediate, and plain.

Depending on its degrees of freedom, it can be classified as having one, two or three degrees of freedom.

Depending on the material of the margins and the bottom, they can be considered as cohesive, non-cohesive, armored materials, well graded or with extended grain size, poorly graded or with uniform grain size.

Depending on the conditions of solid transport, three types of channels can be considered: stable, erodible and depositional.

In many countries there are national hydrographic services. Likewise, there is international coordination of hydrographic information, carried out by the International Hydrographic Organization (IHO), an intergovernmental entity founded in 1921, with headquarters in Monaco; which fundamentally regulates marine hydrography.

Hydromorphometry: Dedicated to the study of hydrographic basins, especially their shape, dimensions, composition, response time, etc.

Marine hydrography (nautical cartography): It is dedicated to the measurement, compilation and representation of data related to the ocean floor, seas and coasts, tides and currents, so that they can be captured on a nautical chart.

Large-scale hydrography is usually carried out by national or international organizations that sponsor the collection of data through precise surveys and publish charts and descriptive material for navigation purposes. The science of oceanography is, in part, a consequence of classical hydrography. In many respects the data are interchangeable, but marine hydrographic data will be particularly oriented towards marine navigation and navigation safety. The exploration and exploitation of marine resources is an important application of hydrography, focused mainly on the search for hydrocarbons.

Hydrographic measurements include tidal, current, and wave information from physical oceanography. They include measurements of the bottom, with special emphasis on marine features that pose a danger to navigation, such as rocks, shallows, reefs and other features that obstruct the passage of ships. Bottom measurements also include gathering the nature of the bottom as it relates to effective anchorage. Unlike oceanography, hydrography will include coastal features, natural and man-made, that aid navigation. Therefore, a hydrographic survey can include the precise positions and representations of hills, mountains and even lights and towers that help fix the position of a ship, as well as the physical aspects of the sea and seabed.

Hydrography, especially for safety reasons, adopted a series of conventions that have affected the representation of data on nautical charts. For example, hydrographic charts are designed to represent what is safe for navigation and therefore typically tend to maintain the shallowest depth and occasionally downplay the actual underwater topography that would be represented on bathymetric charts. The first are the sailor's tools to avoid accidents. The latter are the best representations of the actual seafloor, as on a topographic map, for scientific and other purposes. Trends in hydrographic practice since c. 2003-2005 have led to a reduction in this difference, with many more hydrographic offices maintaining "better observed" databases, and then making "safe" products for navigation, as necessary. This has been coupled with a preference for multi-use surveys, so that the same data collected for nautical mapping purposes can also be used for bathymetric representation.

Although, in some places, hydrographic survey data can be collected in sufficient detail to represent the bottom topography in some areas, hydrographic charts or nautical charts only show depth information relevant to the safety of navigation and should not be considered as a product that accurately represents the true shape of the bottom. Soundings selected from the raw source depth data for placement on the nautical chart are selected for safe navigation and are biased to predominantly show the shallower depths that relate to safe navigation. For example, if there is a deep area that cannot be reached because it is surrounded by shallow water, the deep area may not be displayed. Color-filled areas showing different ranges of shallow water are not the equivalent of contour lines on a topographic map, as they are often drawn seaward of the actual minimum depth represented. A bathymetric chart accurately shows marine topology. Details covering the above limitations can be found in Part 1 of Bowditch's American Practical Navigator. Another concept affecting navigation safety is the scarcity of detailed depth data from high-resolution sonar systems. In more remote areas, the only depth information available has been collected with lead lines. This collection method drops a weighted line to the bottom at intervals and records the depth, often from a rowboat or sailboat. There is no data between surveys or between survey lines to guarantee that there is not a hazard, such as a shipwreck or a coral head, waiting there to ruin the boater's day. Harvest vessel navigation often does not match today's GPS navigation accuracies. The hydrographic chart will use the best data available and will warn of its nature in a cautionary note or in the chart legend.

A hydrographic survey is quite different from a bathymetric survey in some important respects, particularly in a bias toward shallower depths due to the safety requirements of the former and the descriptive geomorphological requirements of the latter. Historically, this might include echo-sounding" in a context of preferences for minimum depths, but in modern practice, hydrographic surveys.

• - Strahler, Arthur (1952) important person.

• - International Hydrographic Organization: Hydrographic Dictionary 2nd Part. Special Publication No. 32. Spanish version of the fifth edition of Part 1, Volume I.

• - Wiktionary has definitions and other information about hydrography.