Temporal Variations in River Discharge & Storm Hydrographs Flashcards
What is base flow?
Water entering a river from groundwater creates a natural minimum which is the baseflow.
What is storm flow?
Water entering by overland flow and through flow after precipitation creates storm flow.
What is a simple river regime?
One high and one low discharge corresponding to seasonal temperature and precipitation changes.
What is a complex river regime?
Several high and low discharges in a year.
What are the physical factors influencing river regimes?
Climate: seasonal variation in temp and precipitation and evaporation rates.
Vegetation
Soil
Lithology
What are the human factors influencing river regimes?
Land use
Irrigation and water use
Dam construction - reservoirs can be constructed to store water and even out the flow over time.
What does a storm hydrograph show?
A rivers response to a precipitation event.
What are the 5 features of a storm hydrograph?
Peak discharge
Peak rainfall
Lag time
Rising limb
Recessional limb
What is the peak discharge on a storm hydrograph?
Maximum rate of flow
What is the peak rainfall on a storm hydrograph?
The time of maximum rainfall
What is lag time on a storm hydrograph?
The period between peak rainfall and peak discharge
What is the rising limb on a storm hydrograph?
The part of the graph showing increasing discharge.
What is the recessional limb on a storm hydrograph?
Shows the decreasing discharge
What are the characteristics of a flashy hydrograph?
A short lag time, high peak discharge, and steep rising and falling limbs.
How is rainfall intensity and duration an influence on storm hydrographs?
Heavy or prolonged rain increases overland flow, resulting in a flashy hydrograph
How are antecedent weather conditions an influence on storm hydrographs?
Previous rainfall may saturate the ground, so overland flow occurs quickly
How is temperature an influence on storm hydrographs?
Influences evapotranspiration, affecting the amount of water that can reach the channel; frozen ground prevents infiltration, shortening lag times.
How does basin size and shape influence storm hydrographs?
Larger drainage basins have a longer time lag, circular basins drain quicker due to a shorter distance to a drainage channel.
How does drainage density influence storm hydrogaphs?
Higher densities have shorter time lags and higher peak discharge.
What does drainage density mean?
Concentration of rivers or drainage elements in a drainage basin.
how does geology and soils influence storm hydrographs?
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.
How does slope angle influence storm hydrographs?
Steeper slopes reduce infiltration, increase overland flow and shorten lag times.
How does type and amount of vegetation influence storm hydrographs?
Influences interception, vegetation store & transpiration rate, affecting overland flow and lag times.
How does land use influence storm hydrographs?
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.
