chapter 3 Hydrology.ppt

Chapter 3 Hydrology
Some fundamental hydrologic concepts
The Presence and Quantity of Water in China
Some fundamental hydrologic concepts:
The Hydrologic Cycle
Rainfall
Surface Water
Droughts
Reservoirs
Groundwater
The Presence and Quantity of Water in China
Definition: Hydrology is a branch of earth science that is concerned with the distribution and movement of water on and under Earth’s surface.
Contents :
Droughts/floods/the presence and quantity of water
In this chapter: measuring present conditions and estimating future variations in water availability
Hydrologic Concepts
Hydrological cycle: Figure
Precipitation
Evaporation
Transpiration
Infiltration and Percolation
Base Flow—p. 71 in Figure
Overland flow and surface runoff
Groundwater Recharge
(1) Precipitation---Water Droplet
Intercepted by vegetation or small surface depressions; temporarily stuck on the surfaces on leaves or grass or it is retained in puddles
Infiltrate through the earth’s surface and seep downward into the ground
Flow over the ground’s surface
(2) Intercepted water—
evaporates+transpiration=evapotranspiration(>50%of the precipitation) /absorbed
(3) Precipitation exceeds bined rates of infiltration and evaportranspiration---overland flow and surface runoff---stream channels, rivers, and lakes, and finally the oceans (the final sink)
(4) Infiltrates the ground surface---percolate into saturated soil and porous rock layers---forming vast groundwater reservoirs---aquifer/seep out onto the ground surface in springs or into streams (base flow)---ocean---evaporation---water vapor in the atmosphere is replenished ---winds---hydrologic cycle
(5) Urban Hydrologic Cycle
Withdrawn from surface water or groundwater---pumped through treatment and distribution systems---used---wastewater is collected in sewer systems---treated---finally disposed or back into surface water or groundwater
Maintenance of this urban water cycle---to protect public heal