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Surface Water Topics: Surface Water Movement Stream Development

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Presentation on theme: "Surface Water Topics: Surface Water Movement Stream Development"— Presentation transcript:

1 Surface Water Topics: Surface Water Movement Stream Development
Lakes and Freshwater wetlands

2 Surface Water Movement
Where does the water come from? The Water Cycle Water is recycled in a continuous cycle called the water cycle. Water is evaporated from a body of water, then condenses into cloud droplets, then falls back to the Earth’s surface.

3 What powers the water cycle?
The Sun

4 Runoff Water flowing down slope along the Earth’s surface is called runoff. Water that does not seep into the soil is called runoff. Many factors will determine if water will infiltrate (seep into) the soil. Runoff may reach streams, rivers, lakes or oceans .

5 Infiltration Water that seeps into the ground (soil) and becomes groundwater. Runoff vs. Infiltration Relationship: As runoff increases infiltration ___________.

6 Factors that effect runoff…
Vegetation – more vegetation will create less runoff and more infiltration. Rate of Precipitation – Heavy precipitation will create more runoff and light gentle precipitation will create more infiltration. Soil Composition – Humus (organic soil) is less compact and will allow for less runoff and more infiltration. Compact soil such as clay will lead to more runoff. Slope – steeper slopes will allow for greater runoff.

7 Stream Systems The first surface water to runoff will flow in thin sheets. (overland flow) Eventually water will collect in small channels (Rills). As runoff increases the channels widen, deepen, and become longer. (Gullies) If there is enough water supply, water will flow more permanently in a channel and become a stream.

8 Stream Systems All streams flow down in elevation.
Paths of the streams can vary due to: - slope of the land - type of material through which it flows. Streams can join together, forming larger and larger streams, and eventually rivers. Streams flowing into larger streams or rivers are called tributaries.

9 Watersheds and Divides
All of the land area whose water drains into a stream is called a watershed. A divide is the high point or ridge that separates watersheds.

10 Stream Load All of the material that the water carries in a stream is known as the stream load. There are three main ways a stream can carry its load: Solution – material dissolved in the water. Suspension – particles small enough to be held up in the water by the streams movement. (dependent on velocity ESRT p. 6) Bed Load – larger sediments that are too big to be held up by the water. These sediments are rolled or pushed along the bottom of the stream by the water. (sand, pebbles, cobbles) Rounded fragments are formed by this process. (physical weathering)

11 Carrying Capacity The ability of a stream to transport material is called the carrying capacity of the stream. Carrying capacity is dependent of stream velocity and discharge. Discharge is the volume of water that passes a specific point in a given period of time. We can calculate discharge as: Discharge = width x depth x velocity (m3/s) (m) (m) (m/s)

12 Carrying Capacity As the streams velocity increase the streams discharge? Increases As discharge increase the carrying capacity? As carrying capacity increases, erosion?

13 Stream Velocity How do streams reach higher velocities?
- higher slopes - greater depths - smooth channel (less friction)

14 Floodplains Water spills over the streams banks onto the land near the stream, creating a flood. The wide flat area next to a stream that gets covered with water during floods is called the floodplain.. As floodwater recedes its velocity decreases and drops its sediment load onto the floodplain.

15 Stream Development Moving water will carve a path.
The headwaters is where water first starts to accumulate for a stream. As water starts to flow it carves a path, overtime forming a stream channel. The stream channel widens and deepens as more water accumulates and cuts into the Earth’s surface.

16 Headward Erosion Streams grow longer by headward erosion.
Erosion works backwards upstream. Streams are usually small and narrow at this point. Streams can capture the water from other streams if they erode through the high area or divide between the other streams drainage basin (watershed).

17 Stream Erosion

18 Stream Valleys Streams form V-shaped valleys as they cut into the Earth. Gorges and canyons are formed by stream valleys. Streams and rivers will continue to erode into the land until it reaches base level. Base level is the elevation at which the stream enters into another body of water. The ultimate base level is SEA LEVEL.

19 Meandering Streams As a stream ages, slope decreases, which also decreases velocity. As streams approach base level, the stream valley widens. More material is deposited in the stream, sometimes causing the channel to bend or curve….forming a meander. Water will flow at different rates in a meandering stream.

20 Stream Features (p.225)

21 Stream Features to remember…

22 Rejuvenation We learned that streams are cutting down until they reach their base level. What happens if a stream reaches base level, but then the land is uplifted? Rejuvenation An uplift in land or a decrease in base level cause a stream to start cutting down again towards the new base level…”to make young again”.

23 Lakes A lake is a depression in the surface materials of a landscape that collects and holds water. Lakes receive water from: - streams - runoff - precipitation - groundwater

24 How do lakes form? Oxbow lakes Streams get blocked by sediment
Basins are carved out by glaciers, then filled with water. Kettle lakes Cirques are filled with water

25 How do lakes change? Eutrophication – the process by which lakes become rich in nutrients from the surrounding watershed, resulting in a change in the kinds of organisms in the lake.

26 Freshwater Wetland A wetland is a land area that is covered with water for most of the year. Examples of wetlands: - bogs - marshes - swamps Waterlogged soil is rich in peat moss. As peat moss breaks down it produces acids, creating acidic soil.

27 Wetlands

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