1	Groundwater and Surface Water
2	Hydrologic Cycle Circulation of Earth’s water supply Processes involved in the cycle Precipitation Evaporation Infiltration Runoff Transpiration Balanced cycle
3	Distribution of Water
4	Facts about water use 2/3 of the human body is water Can survive about a month without food, only a week without water Each American uses, on average, 168 gallons of water each day Flushing the toilet - 2 to 7 gallons Brushing teeth - 2 gallons Shower - 25 to 50 gallons Water covers nearly 80 percent of the Earth's surface, yet less than 1 percent can easily be used for drinking Tap water is cheap for most Americans. Each pays, on average, about 27 cents per day. About half of our water comes from groundwater and half comes from surface-water sources.
5	Running Water Stream-a flowing body of water confined in a channel that flows downslope under the influence of gravity River-major branches of a stream
6	Variables that control streams Discharge-amount of water that passes through a cross-section of the stream in a given amount of time Velocity-the speed of the water as it moves down the channel Gradient-downhill slope of the bed Sediment load-rock carried by the stream Channel size and shape
7	Stream Erosion Removal of rock and mineral matter from the bed of a river Influenced by 3 factors: Hydraulic action-the ability of the water to pick up and transport rocks Solution-rocks that are dissolved by the water Abrasion-erosion of the channel due to collision and grinding away from the stream load Coarse material more effective Potholes: smooth, round cavities eroded by the abrasive action of the sediment load
8	Sediments Transported by Stream Transported material is called the stream’s load Bed load-large, heavy sediments that travel on the streambed Suspended load-light sediments that are lifted and carried in the water Dissolved load-dissolved minerals or rocks (ions in solution) Capacity Maximum load a stream can transport Competence maximum particle size a stream can support Determined by the stream’s velocity
9	Erosion and Deposition by Streams
10	Stream Deposition Caused by a decrease in velocity Competence is reduced Sediment begins to settle out Stream and river sediments Usually well-sorted, called alluvium Floodplain deposits Natural levees Back swamps Alluvial Fans Develop where a steep stream leaves a narrow valley Deltas Forms when a stream enters an ocean or lake
11	Floodplains, Natural Levees, and Swamps
12	Deltas
13	Alluvial Fan
14	Channel Patterns Once a stream reaches the lowest point it will flow to, the stream’s energy is directed from side-to-side
15	Drainage Patterns A map view of a river and its tributaries is a drainage pattern Can reveal structure and rocks beneath tributaries form a V or Y shape (points downstream) when joining the main stream
16	Groundwater Only about 0.6% of the world’s water is found underground, but is still a significant natural resource Groundwater is water found in the pores of soil and sediment, plus narrow fractures in bedrock Groundwater is the largest reservoir of fresh water that is readily available to humans USGS estimates groundwater in the first 0.5 mile in the crust is 3000X greater than the volume of water in all rivers at any point, and about 20X greater than the volume in all the lakes and rivers
17	Distribution of Groundwater Zone of aeration Area above the water table Open spaces primarily air Zone of saturation All open spaces in sediment and rock are completely filled with water Water within the pores called groundwater Water table – the upper limit of the zone of saturation
18	Factors Influencing Groundwater Storage and Movement Porosity Amount of open space within sediment or rock Volume of voids/Total volume Permeability Ability to transmit fluid Depends on connectedness and size of pores Mud and clay have high porosity but low permeability Hydraulic conductivity Describes rate at which water flows through rock
19	Groundwater Wells Wells Most groundwater removed by wells is for agriculture Water usually flows into wells at depth, then pumped to surface Drawdown Lowering of watertable near a well by pumping Results in formation of a cone of depression Artesian well Wells where water rises to the surface itself, without having to be pumped
20	Groundwater Drawdown by Pumping
21	Artesian Wells
22	Groundwater at the Surface Springs Occur where the water table intersects the surface Relationship to streams Most flow in streams and rivers supported by groundwater discharge Gaining streams Water table intersects stream Losing streams Water table is below stream
23	Gaining and Losing Streams
24	Groundwater Contamination Pesticides and herbicides from agriculture Water or irrigation leaches into ground water City landfills Septic tanks Radioactive waste Gas (leaks from gas station storage tanks) Naturally occurring minerals Pumping wells can make contamination worse Drawdown can reverse flow contaminating wells that were pure before pumping started saltwater