Penn State NASA

Module 8: Water Resources and Climate Change


Module 8: Water Resources and Climate Change

Video: Earth 103 Water Module (2:04)

Earth 103 Water Module
Click here for a transcript of the Eart 103 Water Module video.

Today, there are more than a billion people living without access to clean drinking water and that's really hard for us to imagine on the east coast of the United States, where there is water everywhere. Today, I'm standing in a stream near Lemont, Pennsylvania. And if I were here a hundred years ago, I would have readily taken a sample of this water and drunk it. But I’m not quite so sure about that today. There are factories around, there's farms around, and this water is probably not quite good enough to drink. This stream behind me is a tributary to the Chesapeake, and ultimately this water ends up in the Chesapeake Bay, and if I can't drink this water here in rural Pennsylvania, can you imagine what it's like by the time this water gets to the Chesapeake? It would definitely be a bad decision to drink the water flowing into the Chesapeake Bay today.

The other part about being on the east coast of the United States is we're in a lush region, and climate change here is forecasted to make this region maybe a little bit more lush and a little bit higher rainfall in the future. We'll never have a problem with access to drinking water in this part of the world. But if we go out to the western part of the U.S., climate change forecasts predict that the region will become a lot drier, and communities out west in the U.S. are going to have to make really tough decisions as to how they manage their water resources. Such tough decisions have already been made in places around the world such as Australia, where devastating droughts over the last two decades have led rivers to virtually reverse course, and communities have had to make very tough decisions about how they manage their water resources.

So, in this module, we'll learn a lot about how water behaves on the surface of the planet, what is going to happen in the future with climate change, and the choices communities are going to face with dwindling water resources. Now, enjoy it, and please get started.


There is a new generation of super-rich, highly influential people who are starting to invest massive amounts of money and influence in truly important causes. Bill and Melinda Gates in global health, Warren Buffett in reproductive health and food, the Jolie-Pitts in community development, and the Katrina recovery effort. Now, enter Matt Damon and Gary White who have co-founded, an organization dedicated to developing and delivering solutions to the global water crisis. Visit and you will find an impressive array of information and programs. Here are direct facts from that site that convey the magnitude of the current global water emergency.

  • Nearly 1 billion people are living without accessible water
  • 2.5 billion without adequate sanitation
  • 440 million school days lost
  • 220 million hours each day are spent collecting water
  • 3.7 miles walked each day by women and children
  • 4100 children under five die each day from a preventable water-related illness
  • 3.4 million people die each year from a preventable water-related disease

More than any other resource, with the exception of food, water is crucial for human survival. Ancient civilizations were repeatedly forced to deal with the threat of diminishing water supply. Now, climate change presents a new threat by causing the supply and distribution of water to change over the coming decades and centuries. This situation will be made significantly more dire by explosive population growth in parts of the world where water is scarce and by pollution that will continually limit the supply of clean drinking water. The IPCC (2007) stated the situation very clearly: “Water and its availability and quality, will be the main pressures on, and issues for, societies and the environment under climate change.”  The latest 2022 report stresses the need for adaptation.  This will be much easier in the developed world than in developing countries where resources are limited.

Because groundwater systems recover very slowly from human impacts, remediation can be extremely difficult and expensive. In this module, we begin by examining the distribution and behavior of water close to the Earth’s surface; next, we consider how climate change will alter the supply of water and how population growth will change the demand; finally, we present management strategies that will hopefully preserve the supply of water for humans around the globe.

Ancient civilizations developed in some of the driest realms of the planet. Populations in Egypt and Mesopotamia (an area that includes parts of modern Iran, Iraq, Syria, and Turkey) learned how to survive in an arid environment. For example, ancient Egyptians and Mesopotamians constructed an extensive network of canals to transport water away from the Nile River for irrigation. Shadufs, which are contraptions consisting of buckets at the end of a boom which could be lowered with a rope, were used to haul water out of the canals and onto the fields. These civilizations routinely had to live with highly irregular precipitation consisting of periods when large amounts of rainfall flowed through the canals and flooded large areas, alternating with times of almost no rainfall.

Examples of Ancient Civilizations

As the population has increased, and especially with the rise of industry in developed nations, so has demand for water soared. Moreover, industry has increased competition often for the cleanest drinking water supplies.

Nowhere has the interplay between the increasing demand and limited supply of water been more complicated than in the desert southwest of the US. The city of Los Angeles receives a meager 38 cm (15 in) of rain a year. Yet, the city has the highest water usage in California and some of the highest use rates in the country. You would never know by looking at the number of golf courses and car washes and the abundance of lush, green lawns that the city is located in a desert. The same is true for Las Vegas, which receives significantly lower rainfall and is one of the fastest growing cities in the US.

Los Angeles uses much more water than it receives from precipitation and, thus, it imports water from the northern part of California and from states to the east via the Colorado River. In fact, much of the development of Los Angeles was fueled by this supply of water from the Owens Valley in the Sierra Nevada and the Colorado River to the east. Water from the Colorado River began to flow into Los Angeles in the 1920s and 1930s and included the construction of Parker Dam and the Colorado River Aqueduct.

Water Supply and Demand

The growth of other cities that lie in arid locations closer to the Colorado River, including Denver and Phoenix, will likely lead to bitter litigation over water rights in the southwest in the coming decades.  Water supply to the Colorado River is declining markedly as a result of climate change and this is clashing with booming growth of these soutwestern cities. In Spring 2023, the US government brokered a deal with the southwestern states that includes a 13 percent decrease in water supply from the river. This will mandate major consrvation efforts and slower growth. Overseas, countries in arid parts of the globe, for example, Turkey, Iraq, and Syria have also had major disputes about water rights and management. Turkey, which lies at the source of the Tigris and Euphrates rivers, has constructed dams on both rivers for irrigation purposes as well as for hydroelectricity, and this has led to long conflicts with countries downriver including Syria and Iraq.

With projections for the increasingly rapid growth of world population and coupled demand for water for drinking and agriculture, as well as for industry, maintaining a clean water supply looks to be one of the grand challenges of the 21st century. The goals of this module are to learn about how water is cycled on the Earth’s surface and how climate change coupled with the growth of the population will accentuate the global water crisis.