2.3.2a Water Cycle, Surface Water, and Ground Water 1
Water Cycle Water is EVERYWHERE About 97.2 % is in the oceans About 2.15 % is in glaciers and ice sheets About 0.65 % is freshwater in lakes, streams, groundwater, and the atmosphere Water constantly moves among the oceans, the atmosphere, the solid Earth, and the biosphere. This unending circulation of Earth’s water supply is the water cycle. 2
Water Cycle
How much of our planets water is fresh? Water Cycle How much of our planets water is fresh? How does that affect life on our planet? 4
Processes involved in the Water Cycle Not in notes, just know REALIZE: Running water starts as precipitation and either infiltrates the surface to flow under ground, or becomes runoff and creates streams and rivers
Water Beneath the Surface Distribution and Movement of Water Underground
Groundwater Much of the water in soil seeps downward until it reaches the zone of saturation. The zone of saturation is the area where water fills all of the open spaces in sediment and rock. Groundwater is the water within this zone. The water table is the upper level of the saturation zone of groundwater.
Groundwater Movement Groundwater moves by twisting and turning through interconnected small openings. The groundwater moves more slowly when the pore spaces are smaller. http://techalive.mtu.edu/meec/module01/Infil tration2.html
Groundwater The movement of water through the ground depends on 2 factors Porosity: The percentage of pore spaces Determines how much water can be stored Permeability: The ability to transmit water through interconnected pore spaces
Groundwater Impermeable rock Groundwater Surfacewater Recharge Aquifer Precipitation Evaporation Stream Water table Groundwater
Groundwater Wells that are drilled into the zone of saturation are successful Wells drilled into the zone of aeration (aka not deep enough) are not successful Over-pumping a well can create a cone of depression
Groundwater
Aquifers An aquifer is underground soil and/or rock through which water can easily move. Groundwater is stored in aquifers
Aquifers Unconfined aquifer Confined aquifer Has no barrier between its top layer and the surface of the ground Water level rises and drops in response to precipitation infiltrating directly above Confined aquifer Sandwiched between two largely impenetrable layers (clay, shale, etc) Recharges more slowly due to limited number of places through which rainfall can enter
Aquifers of NC
END OF PART I
Path of a drop of water… Remember: A drop of water can either infiltrate into the ground (groundwater) or runoff the surface into a river or stream
Surface Water and Ground Water Groundwater and surface water have a reciprocal relationship, regularly feeding each other. Most streams and rivers get about half their volume from groundwater.
Floods During a flood, surplus surface water helps recharge groundwater.
Flood and Flood Control A flood occurs when the discharge of a stream becomes so great that it exceeds the capacity of its channel and overflows its banks.
Flooding What are some things that cause flooding? Heavy Rain Rapid Spring Snowmelt Why are floods bad?
Flooding There are several methods used to help prevent flooding: Artificial levees Create Dams Sandbags Limit construction around areas known to flood Mississippi Flooding What caused the flood? What caused the most damage during the Flood?
Drainage Basins A drainage basin is the land area that contributes water to a stream. A divide is an imaginary line that separates the drainage basins of one stream from another.
Drainage System Pattern formed by streams, rivers, and lakes Depends on Topography of the land (landforms) Hard or soft rocks Gradient of the land (how steep it is) Divided from each other by topographic barriers (mountains/high points) called a watershed
Rivers Flow of a river or stream is due to GRAVITY. Velocity of a river is due to the geology of the watershed How steep, how narrow, much water, etc Discharge (volume rate of water flow; or how much water is passing by) is measured by: Width x Depth x Velocity