The Hydrologic Cycle, Residence Time, and Water-Rock Ratio

1 THE HYDROLOGIC CYCLE, RESIDENCE TIME, AND WATER-ROCK RATIO 

The geochemical behavior and chemical and isotopic properties of natural waters are related to their location in the hydrosphere, that is, as precipitation, stream flow, soil water, groundwater, ocean water, etc. A goal of this section is to make the reader aware of the unique and different chemical and isotopic properties of each of these waters and explain why their chemistries differ. 

The hydrologic cycle can be thought of as involving the movement of water liquid and vapor between reservoirs, including the ocean, atmosphere, lakes and streams, soils and groundwater. 

The water has a residence time (tn) in each of these reservoirs, which is defined as 

Water amounts or fluxes can be measured in volumes or weights. In terms of weights, equals the weight of the reservoir divided by the weight rate of flux into (or out oO the reservoir. For the ocean, which contains 94% of Earth s water 

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