There’s a whole lot of water on Earth! Something like 326,000,000,000,000,000,000 gallons (326 million trillion gallons) of the stuff (roughly 1,260,000,000,000,000,000,000 liters) can be found on our planet. This water is in a constant cycle — it evaporates from the ocean, travels through the air, rains down on the land and then flows back to the ocean.

The oceans are huge. About 70 percent of the planet is covered in ocean, and the average depth of the ocean is several thousand feet (about 1,000 meters). Ninety-eight percent of the water on the planet is in the oceans, and therefore is unusable for drinking because of the salt. About 2 percent of the planet’s water is fresh, but 1.6 percent of the planet’s water is locked up in the polar ice caps and glaciers. Another 0.36 percent is found underground in aquifers and wells. Only about 0.036 percent of the planet’s total water supply is found in lakes and rivers. That’s still thousands of trillions of gallons, but it’s a very small amount compared to all the water available. Read more

The oceans, atmosphere, continents and cryosphere are part of Earth’s tightly connected climate system. The ocean’s role in the climate system involves the transport, sequestration , and exchange of heat, fresh water, and carbon dioxide (CO 2 ) between the other components of the system.

When waters descend below the ocean surface, they carry with them dissolved atmospheric gases. The time-dependent tracers in the oceans provide information on which waters have been in contact with the atmosphere on various timescales. They also give information on the ocean circulation and its variability.

The timescale information is needed to understand and to assess the ocean’s role in climate change, and its capacity to take up human-derived constituents, such as CO 2 from the atmosphere. Thus, the advantage to using tracers for ocean circulation studies is the added dimension of time: their time history is fairly well known; they are an integrating quantity; and they provide an independent test for time integration of models and biogeochemical processes. Read more

Nowadays, the United States is an urbanized country – the vast majority of us live in cities. When you have hundreds of people living in a square mile, it is much more efficient to have the county/city water department deliver water to households than to have everyone drill their own well or build their own water tank. Municipal water systems supply water for a city’s residential, commercial, parkland, schools, and fire-fighting needs. Even industries get some of their water from these public-supply systems.

So just how does your city supply water to you? A great deal of engineering goes into supplying our water needs. Cities have to have a means of storing a tremendous amount of water so it is available when we need it. Probably, somewhere near you (at a higher altitude), a river was dammed to form a reservoir. These reservoirs can be very large or they may cover just a few acres. Sometimes a well is dug to supply ground water to the storage reservoir. Closer to your home might be a water tower, which will always be built on high ground. Read more