Lecture 2 -- Rivers Flashcards
- The stream order classification system is a way to divvy up a watershed into ecologically distinct units. Describe how the biophysical characteristics of a 1st order stream might differ from the characteristics of a 5th order stream.
1st - Headwater streams, high in the mountains, (steep, fast, narrow, shallow), cold water, high oxygen, heavily shaded w/ lots of leaf litter
5th - Large river, (slow, wide, deep, u-shaped), water is warm, low oxygen, lots of direct sunlight, phytoplankton and fine sands
- On a river meandering across a floodplain, will the thalweg of the river be located on the cut bank or the depositional bank of the river? Is there more hydraulic energy in the river along the cut bank or the depositional bank? Why do sand bars form on the depositional bank?
Thalweg: The highest energy part of the river, (blue arrows) usually the middle/deepest part,
Located on the CUT BANK, because it is the waters energy that is pushing at the bank and eroding it.
- Why do river floodplains provide some of the most diverse habitat in a watershed?
Because hyporheic zone have lost of life (bacteria, fungi, invertebrates), lots of biochemical processing (nutrient cycles)
- How do hyporheic zones affect water quality in a river channel?
They increase water quality b/c hyporheic means it runs underground.
- How can humans affect flow through the hyporheic zone?
1
- What’s the difference between ground water and hyporheic water?
1
- What’s the difference between a riffle and a glide?
Riffle is really shallow part of river with pebbles and rocks so it riffles over.
A glide is when the river is even and smooth there is no pool or riffle, the energy is running in the middle.
- Which is more likely to be associated with a meander curve, a pool or a riffle? Is there more likely to be more oxygen at the bottom of a riffle or pool?
A pool! it cuts the bank and creates a pool
More oxygen is in the riffle because lots of turnover to get oxygen in the waters
- Describe three functions of the riparian zone.
- Keep stream bank from eroding
- Generate much of the food that fuels food webs downstream (inorganic matter)
- Keep sediments and pollutants out of stream
- Habitat for animals that live near the stream
- Why are riparian zones important in providing food to young salmon?
They shade the stream, salmon like cold water!!
- Why would a 4th order stream tend to support more phytoplankton than a 1st order stream? Why would a 4th order stream have less dissolved O2, warmer temperatures, slower water, or higher turbidity than a 1st order stream?
Because 4th is larger. More sunlight and fine matter to support phytoplankton. Less O2 because no riffles or water churning, slower meandering river.
- What are the four invertebrate functional feeding groups?
Shredders, Collectors, Scrapers, Predators
- Why are shredders in streams similar to millipedes in forests? What are the two types of Collectors? Which feeding group scrapes algae off of rocks in the stream? Would you be more likely to find shredders in 1st order streams or 6th order streams (why)?
Shredders - Tear up coarse inorganic matter (leaf litter) and turn it into finer pieces
Collectors - filter particles from water column or gather them from an area
Grazers (scrapers) - scrape rocks and wood surfaces for algae or fungi
Shredders is a 1st order stream because more debris to shred
- To which of the four functional groups would a freshwater clam belong?
Collector - most clams are filter feeders!
- Of the four functional groups, which are generally decomposers, which are primary consumers, and which are secondary consumers?
Collectors are generally the decomposers
Primary consumers would be the shredders, secondary be the collectors/grazers
- Would you expect more grazers in 1st order, 4th order, or 10th order streams, and why?
4th order
More grazers in mid order streams, big and slow enough for algae but not too big
- Where would you expect to find the most shredders, and why?
Shredders are in 1st order streams because they are heavily shaded with lots of leaf litter and debris to shred
- In general, how do you think the invertebrate community would differ between a 1st order stream and an 8th order stream, and why?
1st order - mostly shredders and collectors
8th order- slower river, mostly grazers and predators, collectors
- If there was a disturbance in the watershed that resulted in a large input of fine sediment into the river, how do you think the river’s invertebrate community would change (which of the 4 groups would be harmed more than others, are there any that might increase)?
Grazers would be impacted the most but everything would be bad.. less algae and phytoplankton because of the cloudy river.
- If there was a logging operation that removed all of the alder trees from part of the watershed, how do you think this would affect the in-stream invertebrate community in the area?
Shredders in 1st order streams. They are heavily dependent on shady rivers with lost of trees to drop debris in the rivers..
