Water, carbon and nitrogen cycles, all three of them are global biogeochemical cycles and describe the cycling of these nutrients through the various spheres of the Earth. There are a number of differences between these cycles and some of them are listed here:
- In the water cycle, water changes between its various phases (solid, liquid and gas), but always stays water. In the case of the carbon and nitrogen cycles, various chemical forms of carbon (carbon dioxide, carbonates, sugars, etc.) and nitrogen (ammonia, nitrite and nitrate) are cycled through regularly.
- Life is required for the cycling of carbon and nitrogen. Nitrifying and denitrifying bacteria are critical to the nitrogen cycle. Similarly, plants and animals are necessary for the carbon cycle. The water cycle, on the other hand, can continue in the absence of life.
- Evaporation is the only process for returning the water to atmosphere, while carbon can be returned back by combustion, chemical reactions, respiration, etc. Nitrogen can also get back to the atmosphere by denitrification and fossil fuel combustion.
- Fossil fuels are not part of water cycle, unlike the carbon and nitrogen cycles.
Hope this helps.