5.3

Question 1

What is the formula for precipitation?

Answer 1

P=Q+E+/-S

Precipitation = Channel discharge + Evapotranspiration +/- Change in store

Question 2

What is field capacity?

Answer 2

The normal volume of water that can be held in he soil.

Question 3

What is potential evapotranspiration?

Answer 3

The amount of water that could be lost by evapotranspiration if there was sufficient moisture available.

Question 4

What is Actual evapotranspiration?

Answer 4

The amount of water that is lost through transpiration (release from leaves) and evaporation (heating of water on surfaces) to the atmosphere

Question 5

What is soil moisture surplus?

Answer 5

Occurs when the soil moisture store is full and there is excess water available for plants, runoff and recharge. (Prec>E/T)

Question 6

What is soil moisture utilisation?

Answer 6

Occurs when moisture from the soil stores is being used by vegetation/humans as the precipitation rate is less than E/T. (E/T > Prec)

Question 7

What is soil moisture recharge?

Answer 7

Occurs when moisture from precipitation infiltrates and percolates in the stores to repay the soil moisture utilisation/deficit. (Prec>E/T)

Question 8

What is Soil moisture deficit?

Answer 8

There is not enough water left in the soil to match potential e/t. Rivers run dry and drought ensues. (P E/T > Prec for a prolonged period)

Question 9

What is a river regime?

Answer 9

The annual variation in discharge or flow of a river at a particular point (usually measured in cumecs).

Question 10

What does European oceanic river regime look like?

Answer 10

There is a drop in the levels of surface run-off/discharge during the summer.

Question 11

What does a glacial melt’s river regime look like?

Answer 11

High levels of surface run off/discharge during summer months, due to melting.

Question 12

What does a tropical seasonal’s river regime look like?

Answer 12

Tropical areas have high levels (stable) of evapotranspiration, leading to low surface run-off/discharge, however summer rain causes a peak.

Question 13

What does snowmelt’s river regime look like?

Answer 13

Melting of snow in early summer/spring leads to high levels of surface run-off/discharge around April till July.

Question 14

What are factors affecting a river’ regime?

Answer 14

Humans - Dam building

Vegetation - vegetation can hold water and release it slowly

Geology of the soil - Permeability and porosity, as water is stored as groundwater

Size of the river - Large rivers may have very complex regimes

Temperature - Evaporation increases during the summer, as the temperature is warmer.

Precipitation (volume,intensity and pattern)
- Regime often reflects rainfall seasonal, or when snow fields or glaciers melt

Question 15

What is a storm hydrograph?

Answer 15

A storm hydrograph shows the variation in discharge (volume) of water at a given point over a short period of time, normally an individual storm (few days).

Question 16

What physical factors cause variation in a storm hydrograph?

Answer 16

Rock permeability - Less permeable rock is going to prevent infiltration. As a result, there will be an increase in surface run-off. This will decrease lag time, as transportation of water via surface run-off is faster than via soil/groundwater flow.

Interception - A high number of vegetation or buildings consequently lead to high levels of interception. This leads to water being returned to the atmosphere via evapotranspiration, before it reaches the surface. This will lead to a reduced peak discharge.

Relief - Areas with a steep relief will have high levels of surface run-off, as the gradient of the land doesn’t allow the water to have time to infiltrate. As a result the lag time will be shorter, as surface run-off is faster than soil/groundwater throughflow.