1. Water

2. Hydrologic Cycle
The hydrologic cycle is a model that describes the movement of water through the reservoirs of the Earth
Processes involved in the hydrologic cycle
Precipitation
Evaporation
Infiltration
Runoff
Transpiration

3. Hydrologic Cycle
Evaporation: Water changes from liquid to vapor Transpiration: Water taken up by plants passes into the atmosphere Condensation: Water changes from vapor to liquid Precipitation: Water returns to the surface of the earth as rain or snow.

4. Hydrologic Cycle
Surface Runoff: precipitation that drains over the land or in streams Infiltration: Water works its way into the ground through small openings in the soil.

5. The Hydrologic Cycle

6. Sources of Earth’s water

7. Streamflow
Surface Runoff begins as overland or sheet flow as precipitation moves downhill
Sheet flow eventually becomes a stream - water that flows downslope along a clearly-defined natural pathway.

8. Streamflow Characteristics
Stream gradient - steepness of the slope. The gradient is highest near the stream’s headwaters (source) and decreases as it moves downslope toward the ocean.
Stream discharge - the amount of water passing any point during a unit of time (example: ft3/sec).
Stream load – suspended and dissolved sediment carried by the stream.

9. Types of Stream Channels - Straight
Straight Channel
Usually occur only in short stretches
Generally have a high gradient (near headwaters)
Classic V-shaped valley (as opposed to glacial U-shaped valley)

10. Types of Stream Channels- Braided
Braided Channel
Low gradient
Large, variable sediment load that varies seasonally (e.g. snowmelt, storm activity)

11. Types of Stream Channels- Meandering
Meandering Channel
Usually occur downstream, near the mouth
Low gradient
Cut bank erosion and point bar deposition
May eventually form an oxbow lake

12. Oxbow Lake Form when the meanders get too close together.
River cuts a new, direct channel between the meanders. Meandering Channel
Oxbow lake will eventually become a swamp and dry up.
Oxbow Lake

13. Stream Deposits
Floodplain – Flat valley floor adjacent to the stream, which is inundated when the stream overflows its banks Alluvium – unconsolidated sediment deposited by the stream

14. Stream Deposits – Alluvial Fans
Rapid change from high gradient to low gradient environment causes stream to slow down and drop its sediment load.
Fan-shaped deposit as water escapes its channel.
Often found in arid to semiarid environments with infrequent rainfall/flash flood conditions.

15. Stream Deposits – Delta
Similar to an alluvial fan, but found at the mouth of the stream
Fan-shaped deposit as stream flows into ocean and slows down, dropping its sediment load.
Distinctive fan-shape looks like the Greek letter delta: Δ

16. Drainage Basins
Drainage Basin: The total land area that contributes water to a stream. Also called a watershed, or catchment basin.
The drainage pattern consists of the interconnected network of streams in an area
A drainage basin of one stream is separated from the drainage basin of another by an imaginary line called a divide.

17. Successive drainage basins: The Yellowstone, Missouri, and Mississippi

18. Mississippi River Drainage Basin

19. Surface water resources
Fresh water supply
Many populations around the world lack access to clean drinking water
Essential for
Cause of socio-political conflicts
Direct human consumption
Crop and livestock
Industry
Scarcity of water resources

20. Water-related conflicts in California
Colorado River
Colorado River Compact among 7 states
Dispute between Imperial County and San Diego.
Effect of Los Angeles Aqueduct on Mono Lake, Owens Lake, Owens River Gorge

21. Groundwater - Subsurface water contained in pore spaces in sediment and rock
Zone of aeration (vadose zone): pore space mainly filled with air
Saturated zone (phreatic zone): pore space filled with water
Water Table: Top surface of the saturated zone

22. Groundwater
Groundwater moves through the interconnected pore spaces of rock and sediment from areas of higher pressure to areas of lower pressure
Rock porosity
Relative amount of space in underground rock
Rock permeability
Ease of flow through rock

23. Groundwater Water table tends to mimic topography
The water table comes up to the surface at streams, springs, and lakes

24. Discharge and Recharge
Water percolation - Process of water seepage through rocks and sediment
Recharge - Replenishment of groundwater
Discharge – process of water moving from the subsurface to the surface.

25. Aquifers and Aquicludes
Saturated rock or sediment that is porous and permeable, so able to be accessed by well.
Aquiclude
Layer of impermeable rock or sediment from which water cannot be drawn

26. Types of Aquifers Unconfined aquifer Confined aquifer
Water table not protected from surface recharge
Vulnerable to surface and near surface contamination
Well water rises to water table and must be pumped to surface
Confined aquifer
Protected from surface by aquiclude,
Recharge area is often distant
Water under pressure and rises above water table in well

27. Artesian Well Well which accesses water from a confined aquifer
Water rises in artesian wells without pumps due to release of confining pressure
Less likely to be contaminated by surface runoff, but otherwise the same H2O.