An Introduction To Hydrology

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An Introduction To Hydrology

Aerial view of green landscape with river

The field of hydrology is a crucial area of scientific study and employment for people interested in protecting the earth’s water resources, in combating water pollution and in providing engineering hydrology. Hydrologists work in conjunction with the work of civil engineers in developing water resources infrastructure. Hydrology is the scientific study of the effects, properties and distribution of water on the earth’s surface in soil, underlying rock structures and in the earth’s atmosphere.

The science of hydrology works to understand the planet’s complex water system to help solve water use problems related to human involvement with the use of water resources. By its finite nature, the water available for human consumption is limited. Although there is plenty of water on earth, it is not necessarily of the right quality, in the right place, and at the right time. Solving water problems is the work of the field of hydrology today.

The Water Cycle

The science of hydrology studies the properties of the earth’s waters and their occurrence, movement and distribution across our planet as well as water’s relationship with the environment during all phases of its hydrologic, or water, cycle. This cycle is a continuous process of water purification through evaporation as water vapor is taken from the earth’s land and ocean surfaces into the atmosphere. It cycles from there back into the oceans and land. During this cycle hydrology studies the chemical, biological and physical processes involving water as it takes various paths into the atmosphere then moves over and beneath the surface of the earth and through its fauna.

Water’s paths in its cycle are many. As it falls as rain, sleet or snow and then later returns to the atmosphere, it spends some time along different paths:

  • It may be captured in polar ice caps and stay there for eons.
  • It may flow into rivers and then to the ocean.
  • The soil may absorb it, the sun returns it to water vapor or plants transpire it.
  • It may percolate through the soil down into the ground and into the aquifer (ground water reservoirs) to be stored.
  • It may flow into springs or wells and even streams by seepage.

The different paths of the water cycle may be as short as a few days or as long as millions of years.

How People Tap the Water Cycle

With the help of the science of hydrology, people tap the water cycle for our own uses in homes, services, businesses and industries; irrigation of farms and parklands; and the production of hydroelectric power. After our usage, the water is returned to another part of the water cycle. A water resource engineer, also known as an engineering hydrologist, works in the planning, design, analysis, construction and operation of projects designed to control, utilize and manage water resources. The job of a hydrologist is to apply math principles and scientific knowledge to solve problems of availability, quantity and quality of water resources for human society.

What Hydrologists Do

A hydrologist provides a range of services from helping a homeowner solve drainage problems in his yard to planning multimillion dollar public water infrastructure projects. Hydrologists work to:

  • design irrigation system for vineyards and farms.
  • find water supplies for towns and cities.
  • control soil erosion.
  • control flooding of streams and rivers.
  • protect the environment by preventing and cleaning up water pollution.

Hydrologists work both in the field and in the office, frequently with computer analysis programs. Specific job responsibilities of hydrologists include to:

  • collect basic data of many different kinds
  • oversee water quality testing
  • direct the work of field crews
  • use various evaluation, monitoring and testing equipment
  • interpret all hydrologic data
  • prepare and conduct modeling studies for predictions of flooding
  • perform analyses for identifying and measuring strength of possible water supplies
  • perform analyses of consequences of water releases from reserves
  • identify risks of pipeline leaks on underground water tables

Precipitation and Runoff

During the water cycle, the air flowing over the oceans and land lifts water vapor into the air mass and up to an ever higher altitude, causing the cooling of the air. As that air cools, condensation converts the water vapor into droplets of water. This droplet formation growth is necessary for the liquid water in clouds to be released (to reach the ground) against the air’s lifting mechanism.

As precipitation falls to the ground as rain, snow or some other form, it is absorbed by the earth or becomes runoff if the soil cannot absorb it all. Land sections natural form areas known as “catchments” that collect runoff and concentrates its path at a downhill or downstream point (a “catchment outlet”). There the runoff joins the watershed through a mouth that allows the water to flow into a stream, creek or pond to head to the nearest river and on to the ocean.

Surface Water and Ground Water

Surface water goes into the nearest rivers, lakes or reservoirs. Some of the runoff goes into underground areas where it is collected as ground water or part of the underground aquifer. Hydrologists measure how much water is available from local supplies of surface water and determine whether it is sufficient presently to meet a city’s needs and to predict if it can be projected to meet future needs. They provide information to all the various reservoir managers along the same river that allows them to work together to make the best water management decisions for all the population involved. Surface water is highly susceptible to pollution and must be constantly monitored, tested and cleaned.

Groundwater actually is the United State’s largest source of usable water storage. These underground reservoirs are less vulnerable to pollution, are more convenient to use and contain a great deal more water than the total of all the surfaces lakes and reservoirs, including our Great Lakes, combined throughout the whole nation. It is frequently cheaper to use and in some locations, is the only source of water. Groundwater is accessed through wells and pumps. Hydrologists are responsible for estimating the maximum and optimum yield of these wells.

Polluted groundwater may be less visible but is more insidious and much harder to clean up. It usually results from contamination resulting from the improper disposal of waste in landfills above it. The major sources of groundwater pollution are:

    • household and industrial chemicals
    • garbage landfills
    • industrial waste sites
    • processed wastewater from mines, oil field pits, and tailings
    • septic tank fields and systems
    • sewage sludge

Industries today recognize that the cost of prevention is far less than the cost of clean-up and work with hydrologists to select appropriate waste disposal facilities sites.

The Importance of Hydrology to Civil Engineers

This collection of knowledge, data, information and observation is used in conjunction with engineering hydrology and civil engineering to design, build and operate reservoirs and dams, including hydroelectric power plants run by water from the reservoirs. Civil engineers learn the expected flood flows over spillways, in a highway system’s culverts, or in an urban area’s storm drainage system and can plan and build accordingly. They are advised what hydrological computer systems need to be in place to accomplish tasks such as flood analysis needed to design hydraulic structures and other types of programs and tasks.

Water is a vital necessity. Without it, there can be no life on earth. The field of hydrology is quite diverse and highly complicated. It also provides extremely valuable information to many other fields of endeavor as they provide their valuable skills and services. Its interconnection with the field of civil engineering is essential.

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