What Does a Hydrologist Do?

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A hydrologist takes a water sample from a creek.

According to NASA’s Earth Data project, only 3% of the world’s water is freshwater, and only about 1% can be readily used. This tiny fraction is what’s immediately available for irrigation, power, industrial practice, and drinking. Water availability and quality remain fundamental challenges in most parts of the world.

As the world population continues to grow, so does the need for potable, usable water. Consider the following projections as stated in the 2021 version of the WHO/UNICEF Joint Monitoring Programme report titled: “Progress Drinking Water, Sanitation and Hygiene.”

By 2030:

  • 6 billion people will lack access to safe drinking water
  • 9 billion people will lack basic hand washing facilities
  • 8 billion people will lack safe sanitation services

These statistics underscore the urgent need for hydrologists, who study the quality, quantity, and availability of water. Their work finding alternative water sources and building water treatment systems aims to sustainably improve the world’s readily available water supply and lower the number of people who lack access to water for drinking, washing, and sanitation.

Hydrologist Job Description

Today’s hydrologists play pivotal roles in improving both the availability and quality of water supplies around the globe. What a hydrologist does on a daily basis includes key tasks such as evaluating major water projects such as dams and irrigation systems; forecasting water supply levels; and understanding the impacts of pollution, erosion, and flooding.

Hydrologists apply scientific knowledge of how water moves throughout the earth’s crust to practical issues of sustainability. They analyze precipitation such as rain and snow, observing their impact on groundwater levels, river flow, and evaporation cycles. This analysis enables hydrologists to make informed conclusions about how environmental changes influence water sources.

To conduct these studies, hydrologists use equipment like remote sensors and sophisticated computer programs to gather and analyze vital data. The nature of this analytical work may bring hydrologists into contact with environmental and civil engineers, scientists, and public officials of various levels.

Types of Hydrologists

While there are many types of hydrologists, two main categories cover a wide range of the common issues addressed by the profession.

Groundwater Hydrologists

Groundwater is a vital source of fresh water and an alternative to surface water sources, making it a staple of municipal water supplies. It is often less expensive and more convenient to tap into groundwater via an aquifer than it is to extract water from a river or lake. Plus, groundwater is usually less contaminated with runoff than these other sources.

Hydrologists who specialize in groundwater assist with the assessment of related projects, as well as with cleanup efforts. Some of their tasks may include:

  • Overseeing the drilling of test wells into water-bearing rock and sediment, before a full-sized well is cleared for development
  • Estimating the volume of water in a potential underground source by analyzing geologic records and documentation of any past drilling results
  • Determining the ideal pumping rate for a groundwater well, so it does not go dry or become prone to saltwater intrusion
  • Collecting water and soil samples from wells near landfills, anaerobic lagoons, and oil fields to evaluate current contamination and consult on cleanup
  • Advising on the locations of waste disposal sites to minimize the chances of major future contamination

Surface Water Hydrologists

Surface water hydrologists focus on water from lakes, rivers, and reservoirs, which collectively accounted for two-thirds (67%) of public supply withdrawals in 2021, according to the data aggregate site Statista.

Surface water hydrologists address some similar supply-related and environmental issues as groundwater hydrologists, but they do so within the context of the unique complexities of managing these more heavily utilized water sources.

Flooding mitigation is a key task for surface water hydrologists. With that in mind, they may gather historical records of rainfall and snowpack, analyze river flows, and calculate the necessary boundaries and depth of a reservoir. This information is useful in deciding how much water to release, and determining what areas, if any, might flood under severe conditions. For example, the extreme rainfall on Philadelphia and its surrounding suburbs from 2021’s Hurricane Ida demonstrated the risks of reservoir overflows as well as the need to gauge existing infrastructure.

Surface water hydrologists also evaluate pollution levels and utilization. Unlike groundwater, surface water sources may be used for swimming and hydroelectric power generation, creating additional safety and sustainability requirements for hydrologists to consider.

Hydrologist Salary and Career Outlook

The median 2020 salary for a U.S.-based hydrologist was $84,040, according to the BLS. That number is well above the median salary the BLS lists for all occupations. Factors like education level, years of experience, and job location can influence the precise salary amount an individual may receive in the role.

Due to continued population growth and growing attention to environmental concerns, hydrologists should see steady employment growth in the near future. The U.S. Bureau of Labor Statistics (BLS) has projected a 6% increase in employment from 2020 to 2030.

Hydrologists must have at least a bachelor’s degree, although a master’s or doctorate degree is necessary for advanced positions in leadership and research. Some employers may set a master’s degree as a prerequisite for any open hydrologist positions. Undergraduate degrees in hydrology are rare, meaning many hydrologists instead attain a BS in engineering or earth science. Similarly, graduate degree programs may include hydrology courses under the umbrella of environmental science.

Beyond educational credentials, some hydrologists opt for voluntary professional certifications from bodies such as the American Institute of Hydrology (AIH). The AIH offers certifications for both groundwater and surface water hydrology and also for water quality.

Build a Future in Environmental Engineering

A hydrologist’s work goes beyond studying water. They help improve communities, and solve urgent crises by finding solutions that give people access to an essential resource. As the demand for clean water grows, hydrologists will continue to be called upon to help maintain safe sources.

The online Master of Science in Engineering program at the University of California, Riverside can be a key step toward a career as a hydrologist. The program offers an Environmental Engineering specialization, which includes a specific focus on water resources, plus the freedom and flexibility that comes from a 100% online format.

Learn how we can help you gain the skills and expertise to become a leader in the hydrology field.

Recommended Reading:

The Growing Need for Advanced Water Treatment

Roes for Engineers in the Marine Industry

Use Your Environmental Engineering Degree in Water Systems


American Institute of Hydrology, About

NASA Earth Data, Freshwater Availability

NPR, “Former Michigan Gov. Rick Snyder Charged in Flint Water Crisis”

The Philadelphia Inquirer, “Hurricane Ida Wrecked a Major Water Plant and Nearly Caused a Drinking-Water Catastrophe for Philly’s Suburbs”

Statista, Distribution of American Water’s Water Supply in Financial Year 2021, By Source

United States Environmental Protection Agency, Combined Sewer Overflows (CSOs)

United States Environmental Protection Agency, Flint Drinking Water Response

United States Environmental Protection Agency, Smart Growth and Water

United States Geological Survey, What Is Hydrology?

U.S. Bureau of Labor Statistics, Hydrologists

WHO/UNICEF Joint Monitoring Program for Water Supply, Sanitation and Hygiene (JMP) – Progress on Household Drinking Water, Sanitation and Hygiene 2000–2020