Hydrology - Hydrology:1 Hydrology Hydrologic Cycle Soil...

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Hydrology:1 Hydrology Hydrologic Cycle Soil Moisture Groundwater Runoff Now we turn our attention again to water in all of its various forms. We have looked at water in the atmosphere, so now we will emphasize water near the surface. Water is another substance on Earth with a relatively set total amount, so we can talk about a water cycle and budget. There is new water created in volcanic eruptions and some arriving in comets from space, but those are fairly minor addition and we ll consider the amount of water on the planet fixed. On Earth, oceans store almost all the water, over 97% of the total. Almost all of the rest (over 2%) is held in ice sheets in Antarctica and Greenland. The remaining fraction of one percent is all the water in lakes, streams, groundwater, soils and the atmosphere. But don't forget that water is constantly changing from one category to another. The hydrologic cycle diagrams the locations and paths of water on the earth. This is a simplified version: Concentrating on the near-surface part, we find that several things can happen to falling rain (or snow or any type of precipitation). It may be caught on vegetation, what we call interception . From there, it can remain on leaves and evaporate back into the atmosphere or it can get to the ground. If it isn t intercepted, rain falls directly to the surface and once it gets there, a couple things can happen to it. It can infiltrate or seep below the surface. What doesn t infiltrate either gets stored in puddles or flows over the surface and becomes runoff . You already know a lot about evaporation , but here is a bit more. The temperature of the evaporating water and the relative humidity of the air determine the amount of evaporation. Warmer water evaporates faster than cooler water. In terms of humidity, what is most important is the relative humidity
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Hydrology:2 of the air right at the ground surface. If air at the surface is dry, then there is plenty of room for more water vapor and evaporation is rapid. If air is saturated with water vapor, then evaporation is slow, because there is less room for the evaporating water. Without wind , the air near the surface becomes saturated relatively quickly and evaporation ceases. Wind increases the amount of evaporation by replacing humid air near the surface with drier air from above. So, evaporation will be high in hot, windy places, like West Texas. When plants take up water through roots, they use the water and then it is evaporated from the surface of the plant's leaves. This is known as transpiration. For an area, the water loss from evaporation and transpiration is often combined and called evapotranspiration . Infiltration
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This document was uploaded on 10/27/2011 for the course GEOG 1401 at Texas Tech.

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Hydrology - Hydrology:1 Hydrology Hydrologic Cycle Soil...

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