Temporal Variations in River Discharge & Storm Hydrographs

Question 1

What is base flow?

Answer 1

Water entering a river from groundwater creates a natural minimum which is the baseflow.

Question 2

What is storm flow?

Answer 2

Water entering by overland flow and through flow after precipitation creates storm flow.

Question 3

What is a simple river regime?

Answer 3

One high and one low discharge corresponding to seasonal temperature and precipitation changes.

Question 4

What is a complex river regime?

Answer 4

Several high and low discharges in a year.

Question 5

What are the physical factors influencing river regimes?

Answer 5

Climate: seasonal variation in temp and precipitation and evaporation rates.
Vegetation
Soil
Lithology

Question 6

What are the human factors influencing river regimes?

Answer 6

Land use
Irrigation and water use
Dam construction - reservoirs can be constructed to store water and even out the flow over time.

Question 7

What does a storm hydrograph show?

Answer 7

A rivers response to a precipitation event.

Question 8

What are the 5 features of a storm hydrograph?

Answer 8

Peak discharge
Peak rainfall
Lag time
Rising limb
Recessional limb

Question 9

What is the peak discharge on a storm hydrograph?

Answer 9

Maximum rate of flow

Question 10

What is the peak rainfall on a storm hydrograph?

Answer 10

The time of maximum rainfall

Question 11

What is lag time on a storm hydrograph?

Answer 11

The period between peak rainfall and peak discharge

Question 12

What is the rising limb on a storm hydrograph?

Answer 12

The part of the graph showing increasing discharge.

Question 13

What is the recessional limb on a storm hydrograph?

Answer 13

Shows the decreasing discharge

Question 14

What are the characteristics of a flashy hydrograph?

Answer 14

A short lag time, high peak discharge, and steep rising and falling limbs.

Question 15

How is rainfall intensity and duration an influence on storm hydrographs?

Answer 15

Heavy or prolonged rain increases overland flow, resulting in a flashy hydrograph

Question 16

How are antecedent weather conditions an influence on storm hydrographs?

Answer 16

Previous rainfall may saturate the ground, so overland flow occurs quickly

Question 17

How is temperature an influence on storm hydrographs?

Answer 17

Influences evapotranspiration, affecting the amount of water that can reach the channel; frozen ground prevents infiltration, shortening lag times.

Question 18

How does basin size and shape influence storm hydrographs?

Answer 18

Larger drainage basins have a longer time lag, circular basins drain quicker due to a shorter distance to a drainage channel.

Question 19

How does drainage density influence storm hydrogaphs?

Answer 19

Higher densities have shorter time lags and higher peak discharge.

Question 20

What does drainage density mean?

Answer 20

Concentration of rivers or drainage elements in a drainage basin.

Question 21

how does geology and soils influence storm hydrographs?

Answer 21

Permeable rocks allow more percolation and groundwater, decreasing overland flow and discharge.
Soil type and depth influence infiltration and through flow, affecting overland flow and lag time.

Question 22

How does slope angle influence storm hydrographs?

Answer 22

Steeper slopes reduce infiltration, increase overland flow and shorten lag times.

Question 23

How does type and amount of vegetation influence storm hydrographs?

Answer 23

Influences interception, vegetation store & transpiration rate, affecting overland flow and lag times.

Question 24

How does land use influence storm hydrographs?

Answer 24

Artificial, impermeable surface increase overland flow, reducing lag times.
Agricultural practices, such as compassion of soil by animals or machinery can influence infiltration rates.
Construction of dams and reservoirs reduces peak discharge.