1. Surface Water

2. Surface Water Movement
Water Cycle
Earth’s water supply is recycled in a continuous process called the water cycle
Water molecules evaporate from a body of water or the surface of Earth
Condense into cloud droplets
Fall as precipitation back to Earth’s surface
Infiltrate the ground
**The cycle repeats

3. Runoff Runoff: water flowing downslope along Earth’s surface
Runoff might reach a stream, river or lake, it might evaporate, or accumulate as puddles and infiltrate the ground
For water to enter the ground, there must be large enough pores in the soil and rock

4. Streams
Stream: a body of water, confined to a channel, that runs downhill under the influence of gravity
3 functions of streams:
Erode
Transport
Deposit
Goal of a stream is to get water to BASE LEVEL
Lowest erodible point (sea level, resistant rock level)

5. Stream Systems Tributaries: rivers that flow into other streams
Example: The Ohio River is a tributary of the Mississippi River
Watersheds and divides
Watershed: all of the land area whose water drains into a stream system
Can be large or small
Divide: a high land area that separates one watershed from another
In a watershed, the water flows away from the divide, as this is the high point of the watershed

6. Stream Load Stream Load: the material that a stream carries
Materials in suspension
Sediment light enough to be carried by the turbulence of a stream’s moving water
Silt, clay, & sand size particles
Rapidly moving water carries larger particles in suspension than slowly moving water
Bed load
Large, heavy particles that travel on the streambed
The faster the water moves, the larger the particles it can carry
Materials in solution
Materials are dissolved in a stream’s water

7. Stream Carrying Capacity
Carrying Capacity: the ability of a stream to transport material
Depends on VELOCITY and AMOUNT OF WATER
Slope, depth, and width all affect the speed and direction the water moves
Discharge: the measure of the volume of stream water that flows past a particular location within a given period of time
Usually expressed in cubic meters per second (m3/s)
Discharge = average width x average depth x average velocity
As a stream’s discharge increases, it capacity also increases

8. Floods
Flood: when water spills over the sides of a stream’s banks onto the adjacent land
Floodplain: the flat area that extends out from a stream’s bank and is covered by excess water during times of flooding
Floodwater carries along a great amount of sediment eroded from the stream channel
As floodwater recedes, the sediment is deposited and over time accumulates and creates natural levees

9. Formation of Levees

10. Stream Development Stream Channels
Headwater: the region where water first
accumulates to supply a stream
Usually high in the mountain
Stream Channel: narrow pathway carved into the sediment or rock by moving water
Channel widens and deepens as more water accumulates
Stream Bank: Sides of channel, holds water within channel
Mouth: the area of the stream that leads into the ocean or another large body of water

11. Formation of Stream Valleys
The driving force of a stream is gravity
Energy of a stream comes from the movements of water downslope
Stream gradient: downhill slope of the streambed
Steep gradient = rapid moving stream
Gradient gradually decreases downstream
Gradient depends of base level
Base level: the elevation at which a stream enters another stream or body of water
Lowest base level possible is sea level

12. Stream Development Supply of Water
Precipitation (rain)
Underground deposits
As a stream develops, it changes in width and size and shapes the land over which it flows
Young steams actively erode a path towards base level
As a stream approaches base level, it has less energy, so it tends to erode at the sides of the stream (broad valleys with gentle slopes)

13. Stream Erosion
Streams are actively eroding a path through the sediment, and forming a V-shaped valley
Steep sides
Example: Colorado River & the Grand Canyon
Channel shape and roughness
Anywhere the water touches the channel,
there is friction
Wide or bumpy (more friction) = slower
Steeper or smooth = faster

14. Types of Streams
1) Straight: narrow channel, high velocity, high erosion, not much deposition
Seen in mountains
Moves large boulders

15. Types of Streams
2) Braided: wide, shallow channel with bars (deposits of sediment) in center of stream
Occur in deserts and mountain regions with snow

16. Types of streams
3) Meandering: narrow, deep channels with pronounced sinuous curves
Bending and curving in stream channel
Max velocity is in the deepest sections
(located on outside of bend)
Outside of the curve erodes, inside
deposits sediment
Creates cut banks (erodes) and point bars
(deposits)

18. Meandering Rivers
Meaner cutoff: after enough winding, it is common for a stream to cut off a meander and flow along a straighter path
Oxbow lake: the “blocked-off” meander

19. Stream Deposition
The velocity of a stream determines how much sediment it can transport
Rapid flowing streams have more energy  transport larger sediment
Slow flowing streams have low energy  minimal transport, more deposition
Depositional Features:
Bars
Alluvial Fans
Deltas

20. Bars
An elevated region of sediment (such as sand or gravel) that has been deposited by the flow
Bars are typically found in the slowest moving, shallowest parts of rivers and streams, and are often parallel to the shore 

21. Alluvial Fans
A triangle-shaped deposit of gravel, sand, and even smaller pieces of sediment, such as silt
Usually created as flowing water interacts with mountains, hills, or the steep walls of canyons.

22. Deltas
The triangular deposit that forms where a stream enters a large body of water
Water and sediment leave the river mouth and enter slower- moving or standing water

23. Lakes Lake: body of water surrounded by land
Lakes form in different ways in surface depression and in low areas
Cut-off meanders
Sediment blocks from landslides or other sources
Glacial lakes (glaciers carved out the land during the ice age)
Moraine dammed lakes
Kettles – melted blocks of ice in an outwash plain

24. Wetlands
An area of land that is covered with water for part of the year
Bogs:
Not stream fed, receive water from precipitation
Waterlogged, acidic soils
Marshes:
Form along the mouths of streams
Lush growth of marsh grasses
Swamps:
Low-laying areas located near streams
Can develop from marshes that are now filled with shrubs and trees

25. Wetlands and Water Quality
Wetlands play a vital role in improving water quality
Serve as a filtering system that traps pollutants, sediments, and bacteria contained in water sources
Vital habitat for wildlife
From the late 1700-mid 1980, the US lost about 50% of its wetlands