- Slides: 17
Stream Load • Stream Load – everything carried by stream water, both living and non-living – Living – bacteria, algae, fish, etc. – Non-living – Sediment, dissolved gases (like oxygen), etc.
Stream Load • Biotic Index – a scale for showing a stream’s quality based on the types of organisms living in it • Measured from 1 (excellent) to 10 (poor)
Stream Load • How is biotic index calculated? • The tester collects macro (visible to the naked eye) invertebrates from portions of the stream and then groups them and counts them • Some organisms are more sensitive to pollution than others, so if they are present in the water, the scientist can assume the water is fairly clean Mayfly nymph – very sensitive to pollution, so the water must be clean!
Stream Load • Homogeneous mixture (solution) – mixture where you cannot see the individual parts – Example: sugar water – Ex: dissolved minerals in stream water • The amount of particles dissolved in a solution is measured in parts per million (ppm)
Stream Load • Heterogeneous mixture – a mixture where you CAN see the individual parts • Suspension – particles are visible, but small enough to stay mixed in the moving water – Example: sediments in a stream
Carrying Capacity • Carrying capacity – how much a stream can hold – The greater the stream’s volume, the more it can carry – The faster the stream’s speed, the more it can carry
Carrying Capacity • Fast-moving water can carry heavier particles than slow-moving water • As the water slows down, the heavy particles settle to the bottom Fast-moving water All sediments moving Slow-moving water Heavy sediments sink
Check for Understanding Stream Load -- WHAT a stream carries • _______ • Carrying ________ Capacity -- HOW MUCH a stream carries Stream Load Bed Load
Bed Load • Bed Load – sediment rolled or pushed along the bed (bottom) of a stream • Creep – rolling motion • Saltation – bouncing motion
Bed Load • Abrasion – when moving particles bump into each other and scrape each other • Causes the particles to be physically ____ weathered, which makes them rounder and smoother than before
Depositional Features • As a stream slows down, more and more sediments are deposited • Over time, stream deposition can create landforms
Depositional Features • Delta – a triangular deposit of sediment located where a fast-moving stream flows into a larger body of slow-moving water • Named after the Greek letter delta -- ∆ Nile River Delta
Depositional Features • Example: Nile River Delta, where the Nile River empties into the Mediterranean Sea • About 39 million people live in the Nile River Delta, which is well-known for its agriculture • Why? Nile River Delta
Depositional Features • Alluvial Fan – a fan-shaped deposit of sediment at the flat base of a mountain • Water flows down the mountain and then slows down and deposits sediment at the base