question: Why is the water in our drinking glass clear and colorless but all the water in Earth’s rivers /lakes/oceans blue?
comment: Normal white light is made up of a mixture of colours. Water absorbs the red light a bit. Only a tiny amount of red light gets absorbed by a 2 inch wide glass of water. But when you look across even a few meters, like a swimming pool or even bigger, almost all the red light is gone, and it looks blue. This absorbing behaviour is called 'attenuation' and lots of water means lots more distance for the light to travel through, and so lots more distance for the colour red to 'attenuate'.
passages: Absorption intensity decreases markedly with each successive overtone, resulting in very weak absorption for the third overtone. For this reason, the pipe needs to have a length of a meter or more and the water must be purified by microfiltration to remove any particles that could produce Mie scattering.
  
  Section::::Color of lakes and oceans.
  
  Lakes and oceans appear blue for several reasons. One is that the surface of the water reflects the color of the sky. While this reflection contributes to the observed color, it is not the sole reason.
   Section::::Composition.
   The "color" of the ocean is determined by the interactions of incident light with substances or particles present in the water. White light from the sun is made up of a combination of colors that are broken apart by water droplets in a "rainbow" spectrum. Large quantities of water, even in a swimming pool, would appear blue as well. When light hits the water surface, the different colors are absorbed, transmitted, scattered, or reflected in differing intensities by water molecules and other so-called optically-active constituents in suspension in the upper layer of the ocean. The reason that open ocean waters often appear blue is due to the absorption and scattering of light. The blue wavelengths of light are scattered, similar to the scattering of blue light in the sky but absorption is a much larger factor than scattering for the clear ocean water. In water, absorption is strong in the red and weak in the blue and so red light is absorbed quickly in the ocean leaving blue. Almost all sunlight that enters the ocean is absorbed, except very close to the coast. The red, yellow, and green wavelengths of sunlight are absorbed by water molecules in the ocean. When sunlight hits the ocean, some of the light is reflected back directly, but most of it penetrates the ocean surface and interacts with the water molecules that it encounters. The red, orange, yellow, and green wavelengths of light are absorbed and so the remaining light we see is composed of the shorter wavelength blues and violets.
   Scattering from suspended particles also plays an important role in the color of lakes and oceans. A few tens of meters of water will absorb all light, so without scattering, all bodies of water would appear black. Because most lakes and oceans contain suspended living matter and mineral particles, known as colored dissolved organic matter (CDOM), light from above is reflected upwards. Scattering from suspended particles would normally give a white color, as with snow, but because the light first passes through many meters of blue-colored liquid, the scattered light appears blue. In extremely pure water—as is found in mountain lakes, where scattering from white-colored particles is missing—the scattering from water molecules themselves also contributes a blue color.
   BULLET::::- Particles and solutes can absorb light, as in tea or coffee. Green algae in rivers and streams often lend a blue-green color. The Red Sea has occasional blooms of red "Trichodesmium erythraeum" algae.
   Some constituents of sea water can influence the shade of blue of the ocean. This is why it can look greener or bluer in different areas. Water in swimming pools (which may also contain various chemicals) with white-painted sides and bottom will appear as a turquoise blue.
  
  Clean or uncontaminated water appears blue in white-tiled swimming pools as well as in indoor pools where there is no blue sky to be reflected. The deeper the pool, the bluer the water.
   Water distribution on Earth
  
  Water is distributed across earth. Most water in the Earth's atmosphere and crust comes from the world ocean's saline seawater, while freshwater accounts for only 2.5% of the total. Because the oceans that cover roughly 71% of the area of the Earth reflect blue light, the Earth appears blue from space, and is often referred to as the "blue planet" and the "Pale Blue Dot". An estimated 1.5 to 11 times the amount of water in the oceans may be found hundreds of miles deep within the Earth's interior, although not in liquid form.
   Section::::Sedimentation and blue carbon burial.:Spatial variability in sedimentation.:Submarine Canyons.
   Color of water
  
  The color of water varies with the ambient conditions in which that water is present. While relatively small quantities of water appear to be colorless, pure water has a slight blue color that becomes a deeper blue as the thickness of the observed sample increases. The blue hue of water is an intrinsic property and is caused by selective absorption and scattering of white light. Dissolved elements or suspended impurities may give water a different color.
  
  Section::::Intrinsic colour.
   Section::::Dye.
  
  Bromophenol blue is also used as a dye. At neutral pH, the dye absorbs red light most strongly and transmits blue light. Solutions of the dye, therefore, are blue. At low pH, the dye absorbs ultraviolet and blue light most strongly and appears yellow in solution. 
   The sea is seen as blue for largely the same reason: the water absorbs the longer wavelengths of red and reflects and scatters the blue, which comes to the eye of the viewer. The colour of the sea is also affected by the colour of the sky, reflected by particles in the water; and by algae and plant life in the water, which can make it look green; or by sediment, which can make it look brown.
  
  Section::::Science and nature.:Atmospheric perspective.
   BULLET::::- Particles in water can scatter light. The Colorado River is often muddy red because of suspended reddish silt in the water. Some mountain lakes and streams with finely ground rock, such as glacial flour, are turquoise. Light scattering by suspended matter is required in order that the blue light produced by water's absorption can return to the surface and be observed. Such scattering can also shift the spectrum of the emerging photons toward the green, a color often seen when water laden with suspended particles is observed.
  
  Section::::Color names.
   Section::::Types of blue carbon ecosystems.:Mangrove.
   Sedimentation is the rate at which floating or suspended particulate matter sinks and accumulates on the ocean floor. The faster (more energetic) the current, the more sediment it can pick up. As sediment laden currents slow, the particles fall out of suspension and come to rest on the sea floor. In other words, a fast current can pick up lots of heavy grains, where as a slow current can pick up only tiny pieces. As one can imagine, different places in the ocean vary drastically when it comes to the amount of suspended sediment and rate of deposition.
   The most important light-absorbing substance in the oceans is chlorophyll, which phytoplankton use to produce carbon by photosynthesis. Chlorophyll, a green pigment, makes phytoplankton preferentially absorb the red and blue portions of the light spectrum and reflect green light. Ocean regions with high concentrations of phytoplankton have shades of blue-green depending upon the type and density of the phytoplankton population there. The basic principle behind the remote sensing of ocean color from space is that the more phytoplankton is in the water, the greener it is.
   Section::::Types of blue carbon ecosystems.:Algae.
   Blue carbon
  
  Blue carbon is the carbon captured by the world's coastal ocean ecosystems, mostly mangroves, salt marshes, seagrasses and potentially macroalgae.
   Section::::Recordings by other artists.
   The intrinsic colour of liquid water may be demonstrated by looking at a white light source through a long pipe that is filled with purified water and closed at both ends with a transparent window. The light turquoise blue colour is caused by weak absorption in the red part of the visible spectrum.
   Dr. Roger Bachman, another nationally recognized limnologist, agrees and says the Society denies it ever made such a ranking. “While the term ‘blue water lake’ is not a scientific term, it is a fact that lakes and oceans with exceptionally pure waters like Lake Tahoe, Crater Lake, Lake Superior and the Sargasso Sea appear blue to the eye. When sunlight penetrates these waters the wavelengths (colors) of light are absorbed more strongly than blue, so that more of the blue remains to be scattered back out of the water surface.” 
   Section::::Sedimentation and blue carbon burial.:Spatial variability in sedimentation.
   The concepts of green and blue water were first introduced by Falkenmark in 1995, and defined green water as "the rainwater that infiltrates into the root zone and is used for biomass production", and blue water as "the water that either runs off from the soil surface or percolates beyond the root zone do form groundwater"
   Section::::Mechanisms.
  
  Self-association is correlated with the anthocyanin concentration. When concentration is higher we can observe change in the absorbance maximum and increase of colour intensity. Molecules of anthocyanins associate together what results in stronger and darker colour.
   Water preferentially absorbs red light, and to a lesser extent, yellow, green and violet light, so the color that is least absorbed by water is blue light. Particulates and dissolved materials may absorb different frequencies, and this will affect the color at depth, with results such as the typically green color in many coastal waters, and the dark red-brown color of many freshwater rivers and lakes due to dissolved organic matter.
   In solution at pH 3.6 (in the middle of the transition range of this pH indicator) obtained by dissolution in water without any pH adjustment, bromophenol blue has a characteristic green red color, where the apparent color shifts depending on the concentration and/or path length through which the solution is observed. This phenomenon is called dichromatic color. Bromophenol blue is the substance with the highest known value of Kreft's dichromaticity index. This means it has the largest change in color hue, when the thickness or concentration of observed sample increases or decreases.
  
  Section::::External links.
  
  BULLET::::- Bromophenol blue at OpenWetWare
  
presuppositions: If water contained in a drinking glass is clear, then the water in the oceans, lakes and rivers of the Earth should not be blue.
corrections: The color of the water changes based on the amount of light the water absorbs, water in a glass of water doesn't absorb nearly as much water as the ocean, therefore the ocean is blue and the cup of water is not. 
raw_presuppositions: If water contained in a drinking glass is clear, then the water in the oceans, lakes and rivers of the Earth should not be blue. The water in a drinking glass is clear and the water in Earth's rivers, lakes and oceans is blue.
raw_corrections: The color of the water changes based on the amount of light the water absorbs, water in a glass of water doesn't absorb nearly as much water as the ocean, therefore the ocean is blue and the cup of water is not.  The water in a drinking glass only looks clear based on light absorption and the water in Earth's rivers, lakes and oceans only looks blue.