Rivers Flashcards
Major components in River
- Suspended inorganic matter: Al, Fe, Si, Ca, K, Mg, Na, P
- Dissolved: HCO3, SO4, H4SiO4,
Regions of high river runoff
Where precipitation exceeds evaporation
- near equator (10degrees n and s) causing amazon and Zaire
- 30-60 degrees N and S (adequate rainfall, low evaporation)
How is global change predicted to affect river runoff and the hydrologic cycle
Increased temp, increased evap, decrease runoff
Runoff Ratio
ratio of average river runoff to average rainfall
- world average of 0.46
Streamflow
the measured volume of water transported by a river per unit time
Discharge
What is the average continental denudation rate and how is it determined?
5.85cm of reduction in 1000 years
Factors determining the suspended load of a yield?
- geologic and human factors
- water discharge
- river basin area
-maximum basin relief
-basin average temp
How do reservoirs affect the suspended load of a river
increases suspended load by decreasing water flow
- traps sedimen
How do human activities affect the suspended sediment load?
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
Difference between erosion rate and stream transport rate
- Erosion rate is the speed at which soil is removed
- stream transport rate: speed at which sediment is transported via rivers to oceans
How is GNP and sediment load related to human population density in the drainage basin of a river system?
high population density and low GNP correlated with increased sediment load
What is the importance of reservoirs in the global carbon cycle?
increases carbon burial on land by 0.6-1.5GtC/yr
How does the composition of suspended river sediment compare to the average continental crust?
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
What are the reasons and reactions behind the differing compositions of suspended load and dissolved load in rivers?
Why are the compositions of suspended and dissolved materials different in arctic and equatorial rivers?
arctic: lower concentrations of Al and Fe in the suspended matter relative to soluble elements, since smaller amounts of soluble elements have been removed
What factors can result in a river displaying a high value of TDS?
high evaporation rates
- anthropogenic inputs
- weathering of rock salt
What rock types appear to dominate river water compositions?
silicates, carbonates, evaporites
cyclic salt
sea salt carried inland in the atm and deposited in rain or snow
What role does relief play in affecting river compositions?
- increased silicate weathering in areas of high relief, but decreased carbonate concentrations
what is the source and what controls the flux of DOC
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.
Why doe the fraction of POC in the total suspended load (Or sediment) decrease with increasing TDS?
Explain the significant chemical differences between normal, organic-poor, and organic-rich rivers?
