WC 2.1.3- river regimes & hydrographs

Question 1

define river regimes

Answer 1

river regime is the annual variation in the discharge of a river, the amount of water that travels through a river.

This means that it is looking at the difference of discharge in a river throughout the year

Question 2

define a river system

Answer 2

a river system is looking at the entire drainage system including the tributaries that connect to it.

Question 3

define a storm hydrograph

Answer 3

storm hydrographs are used to measure a river’s flow and show the change in river discharge over a short amount of time after the storm

Question 4

what is river discharge

Answer 4

river discharge is determined by
the cross-sectional area x mean velocity of the river

discharge= AREA X VELOCITY

this is in a particular part of the course (of the river)

Question 5

define the soil moisture budget

Answer 5

this refers tot he balance of the
inputs, outputs and storage of water within the soil over a period of time.

Question 6

name the inputs of the soil moisture budget

Answer 6

1. precipitation
2. irrigation

Question 7

name the outputs of the soil moisture budget

Answer 7

1. evapotranspiration
2. runoff
3. percolation/ drainage

Question 8

name the storage of the soil moisture budget

Answer 8

1. soil moisture- the water is retained in the soil for plant uptake but the amount of storage depends of the soil type, structure and porosity

Question 9

name and explain the 4 phases of the soil moisture budget

Answer 9

(‘soil moisture’ comes before each phase)

Phase 1. Recharge: occurs when Precipitation exceeds Evapotranspiration, so then it replenishes the soil moisture reserve
Phase 2. Surplus: occurs when soil is fully saturated and any additional rain contributes to percolation/ runoff
Phase 3. Utilization: occurs in dry periods where the plants use the soil moisture and evaporation depletes the water levels
Phase 4: Deficit: occurs when their is not enough moisture in the soil to meet the needs of the plants and evaporation

Question 10

name the three things that soil moisture is important for

Answer 10

1. Agriculture = it is critical for crop growth as it determines the availability of water to plants
2. Hydrology = water resource management= to understand the drought conditions and manage irrigation
3. Environment monitoring = influences vegetation patterns and soil erosion

Question 11

define Evapotranspiration

Answer 11

Evapotranspiration is when water is transferred from the land to the atmosphere by evaporation from the soil and the transpiration from plants

Question 12

define Soil Moisture Budget

Answer 12

an accounting scheme used to predict the soil-water storage
evaporation
water surplus

Question 13

what are the 4 factors affecting a
river regime and flood Hydrographs

Answer 13

1. climate
   2.geology
2. land use
3. seasons (only river regimes)
4. vegetation

Question 14

what are the other influences that apply to Flood Hydrographs and not river regimes

Answer 14

1. Antecedent conditions
2. intensity and duration of the storm
3. slope angle
4. size and shape of drainage basin
5. snow
6. temperature

Question 15

name a few featues that creates a flashy hydrograph

Answer 15

• urbanisation
• deforestation
• steep sloped valley
• prolonged periods of rainfall
• clay soil= impermeable

Question 16

name a few features that create a flat hydrograph

Answer 16

• fields so no urbanisation
  -afforestation
• gentle sloped valleys
• dam/ reservoir upstream
• low rainfall

Question 17

name the 3 factors of a ‘simple river regime’

Answer 17

1. one main ‘flow peak’
2. dependent of seasons
3. steady base flow

Question 18

name the 2 factors of a ‘complex river regime’

Answer 18

1. has multiple ‘peak flows’
2. high base flow

Question 19

list the 5 factors influencing river discharge

Answer 19

1. evaporation
2. geology
3. human factors
4. seasons and precipitation
5. spring maximum

Question 20

name and explain the 6 labels of a hydrograph

Answer 20

1. peak rainfall- the hour that had the greatest rainfall
2. peak discharge- the time where it was maximum discharge by the river
3. normal flow- the average (base flow) of the river
4. Lag time- The period of time between peak rainfall and peak discharge
5. rising limb- the period of time where there’s a Rising discharge following a period of rainfall
6. falling limb- the period of time when the rivers discharge is falling

Question 21

name the 10 river catchment characteristics that influence storm hydrographs (6 have already been mentioned in influences of hydrgographs)

Answer 21

1. rock type
2. soil (infiltration rate)
3. relief (slope steepness)
4. drainage density
5. climate/ weather
6. basin size
7. basin shape
8. vegetation
9. antecedent conditions
10. human activity