Rivers

Question 1

Major components in River

Answer 1

• Suspended inorganic matter: Al, Fe, Si, Ca, K, Mg, Na, P
• Dissolved: HCO3, SO4, H4SiO4,

Question 2

Regions of high river runoff

Answer 2

Where precipitation exceeds evaporation
- near equator (10degrees n and s) causing amazon and Zaire
- 30-60 degrees N and S (adequate rainfall, low evaporation)

Question 3

How is global change predicted to affect river runoff and the hydrologic cycle

Answer 3

Increased temp, increased evap, decrease runoff

Question 4

Runoff Ratio

Answer 4

ratio of average river runoff to average rainfall
- world average of 0.46

Question 5

Streamflow

Answer 5

the measured volume of water transported by a river per unit time

Question 6

Discharge

Question 7

What is the average continental denudation rate and how is it determined?

Answer 7

5.85cm of reduction in 1000 years

Question 8

Factors determining the suspended load of a yield?

Answer 8

• geologic and human factors
• water discharge
• river basin area
  -maximum basin relief
  -basin average temp

Question 9

How do reservoirs affect the suspended load of a river

Answer 9

increases suspended load by decreasing water flow
- traps sedimen

Question 10

How do human activities affect the suspended sediment load?

Answer 10

Increases suspended load:
- deforestation and cultivation of the land
- overgrazing
-construction

Decreases in suspended sediment load by:
- building dams and reservoirs
bank stabilization of rivers
-soil conservation

Question 11

Difference between erosion rate and stream transport rate

Answer 11

• Erosion rate is the speed at which soil is removed
• stream transport rate: speed at which sediment is transported via rivers to oceans

Question 12

How is GNP and sediment load related to human population density in the drainage basin of a river system?

Answer 12

high population density and low GNP correlated with increased sediment load

Question 13

What is the importance of reservoirs in the global carbon cycle?

Answer 13

increases carbon burial on land by 0.6-1.5GtC/yr

Question 14

How does the composition of suspended river sediment compare to the average continental crust?

Answer 14

river suspended matter is enriched in the less soluble elements relative tot he parent rock, due to chemical weathering and dissolution of soluble elements.
- rivers are strongly depleted in the most soluble elements such as Na

Question 15

What are the reasons and reactions behind the differing compositions of suspended load and dissolved load in rivers?

Question 16

Why are the compositions of suspended and dissolved materials different in arctic and equatorial rivers?

Answer 16

arctic: lower concentrations of Al and Fe in the suspended matter relative to soluble elements, since smaller amounts of soluble elements have been removed

Question 17

What factors can result in a river displaying a high value of TDS?

Answer 17

high evaporation rates
- anthropogenic inputs
- weathering of rock salt

Question 18

What rock types appear to dominate river water compositions?

Answer 18

silicates, carbonates, evaporites

Question 19

cyclic salt

Answer 19

sea salt carried inland in the atm and deposited in rain or snow

Question 20

What role does relief play in affecting river compositions?

Answer 20

• increased silicate weathering in areas of high relief, but decreased carbonate concentrations

Question 21

what is the source and what controls the flux of DOC

Answer 21

fluxes controlled by drainage intensity, basin slope and amount of carbon stored in the soil. Fluxes increase with increased discharge/area, flatter slopes, and greater soil C.

Question 22

Why doe the fraction of POC in the total suspended load (Or sediment) decrease with increasing TDS?

Question 23

Explain the significant chemical differences between normal, organic-poor, and organic-rich rivers?