27-11-2012, 05:40 PM
Hydrologic Cycle
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What is the Hydrologic Cycle?
The water that humans use today has been around
for hundreds of millions of years, and the amount
available probably has not changed very much
Water moves around the world, changes forms, is
taken in by plants and animals, but never really
disappears
Hydrology – Fall 2007 – [1] Hydrologic Cycle Mohammad N. Almasri, PhD An-Najah National University
It travels in a large continuous cycle called the
hydrological cycle
The Sequence of the Hydrologic Cycle
Water evaporates from the oceans and the surface
Water vapor is transported and lifted in the atmosphere until
it condenses and precipitates
Precipitated water may be intercepted by vegetation
It becomes overland flow
I filt t i t th d d l t l t d h
Hydrology – Fall 2007 – [1] Hydrologic Cycle 5 Mohammad N. Almasri, PhD An-Najah National University
Infiltrates into the ground and later percolates and recharge
groundwater
Flows through the soil as subsurface flow
Discharges into streams as surface runoff
The Hydrologic Cycle
Vegetation cover, for example, can reduce the rate
of direct evaporation of water from the soil, but at
the same time will result in the loss of water to the
atmosphere by transpiration
Land cover and soil type will largely affect the
runoff. So, as we have more impervious surfaces
then we will have more runoff and less infiltration
8 Hydrology – Fall 2007 – [1] Hydrologic Cycle Mohammad N. Almasri, PhD An-Najah National University
and indeed less recharge to groundwater resources