WEEK 4: Physiology of Streams and Lakes

Question 1

Define Stream

Answer 1

• is a body of flowing water in a defined channel
• Longest:nile
  -largest discharge and dranage : Amazon
  no clear definition between stream and river, streams slightly smaller (but not official)

Question 2

How are streams formed

Answer 2

Thermodynamics: precip brings in water into river system gravity: adds energy that forms channel

Question 3

Drainage area

Answer 3

the area on land where the water comes from

-Watershed area defines is the border of the basin

Question 4

Define Discharge

Answer 4

• volume passing through river per unit time

- if +’ve then related to the drainage area, variably by climate and geology

Question 5

Stream order

Answer 5

supposed to help figure out where the various sources of rivers that stream into the main one

• order 1 is
• streams order must add up to the tributary
• issue: really doesn’t help with any defining

Question 6

Different river patterns

Answer 6

• variably driven by geology
  (dentric - fingers coming into one) (radial&ammlus - formed on volcano/mountains) (trellis parallel ridges) (rectangular - formed by faults)

Question 7

what do Hydrographs measure

Answer 7

measure the continues water discharge over time

• the shape of graph depended on rain/storm events
• effected by urbanization } causes river to get to normal faster, as there is less influtration into soil

Question 8

Name and describe the three ways water gets to a stream

Answer 8

• Overland } above surface flow
• subsurface flow } infiltration, but above water table
• ground water} from bellow water table, aquafire
  factors include incline, solid, moisture of soil, height of water table

Question 9

Types of flow permanence

Answer 9

Perennial } Constant stream, gw
Intermitten} Seasonal (dry vs wet season)
Ephemeral } Stream flows from a storm event, no GW

Question 10

Pool ruffle features

Answer 10

regular river pattern involves, shallow and fast (riffles) alternated with deep slow areas (pools)

• caused by high sloped, most common in areas that gradient, gravel bed
• less effective at higher flows

Question 11

What type of Channel flows

Answer 11

• Meander: Bendy rivers. caused by erosion, then dropping sediment
• Braided: Common in high slopes, non-cohesive sediment and many possible channels
• Confined } Narrow confined stream due to unerodable exterior

Question 12

Flood plain

Answer 12

is a flat area often flooded by overflow, common with low lying meandering streams

Question 13

Define bed material

Answer 13

• this contains river flow

- more e needed to move larger sediments,,, and ones that are more cohesive

Question 14

On river erosions:

Answer 14

Naturally, this occurs to lead to lead to equilibrium as river volume changes,
- bank-erosion involves making it steep, then dropping sediments
- Threshold of bed movement: Shear stress
-

Question 15

On sediment loading

Answer 15

defined about amount passing through a point/time

• dissolved load: Minerals, wont fall out
• suspended load: helping normal flow, lower [] at the bottom more near top
• bed loads: large particles at the bottom, moves at a different rate then water

Question 16

What is a lake?

Answer 16

slow/non-moving body of water in a depression & not connected to the ocean

• can be fresh or saline (esp if high evaporation is a thing)
• includes pools in river, ponds

Question 17

Where are most lakes distributed?

Answer 17

a lot in areas where glaciers left depressions (esp in the north)

• and in the very north (low evaporation, and high precipitation) ( emphasis on the low precipitation)
• intermittent lakes are a thing, but not very common, mainly only in arid areas that fill in during the wet season

Question 18

What is a reservoir?

Answer 18

a man-made lake, often created via damning rivers

• often shallow and it inc productivity
• changes species dynamics of the river
• changes river speed suddenly, causes large segment drops

Question 19

What are the local impacts of Reservoirs

Answer 19

• ## done to stop flooding, but often increases the water level fluctuations } impacts littoral community

Question 20

Global impacts of the reservoir?

Answer 20

• ## due to large sediment deposit, its stoping nutrients and minerals from going into the ocean

Question 21

3 main ways lakes are formed

Answer 21

• Tectonic: moves earths, make deep lakes
• – (Graben lakes: full crust falling) (Horst lakes: crust tilts, one side gets really deep)
• Damning: Natural from lava flows, bevers, etc. Smaller &shallow
• Glacial formation: MOst common esp in the north
• —scour: digs out the earth (cirque) –glacial till: Huge ice deposit, then melts (kettle lakes)

Question 22

Non-main lake formations

Answer 22

• Volcanic, karst (bedrock disovles, sinkhole)

- Fluval (a meandering river that gets cut off, oxbow lake)

Question 23

Subhabitats in lake

Answer 23

1) Pelagic } surface, open water 2) Profundal } open h2o, deep 3)littoral }edge of lake , most productive

Question 24

Lake properties. how they affect productivity?

Answer 24

SA: changes, light exposure
Depth: How far light can get
Volume: combines SA and D
Retention: How long a single molecule of h2o stays in the lake, controlled by in/out of water
Shoreline development: hoe mutch edge of the lake is there, changes amount of nutrence gets into lake

Question 25

What is stratification, how does that happen?

Answer 25

Formation of distinct layers in water due to density changes and temp (or salinity, less common)
(1) Epilimnion (2) Metamnion} sudden change in temp (3) Hypoliminon } lowest o2 levels

Question 26

What are the types of stratification?

Answer 26

Monomimic: Stratifies 1/year, in the summer, warm climates w/o freezing
Dimitic} 2/year, overturns in spring and fall
Poly}many times, done by storm forcing mixing

Question 27

What are the effects of stratification?

Answer 27

mixes nutrients and gases

Question 28

How does water move

Answer 28

• Wind } main cause of movement, , and erodes shore
• —Lake fetch: wind travels over the long side of lake and inc energy build up
• Wave types: (1) small: Circular motion, mixing (1) Large: seich waves, cause by stratification and long fetches