Variations in Runoff and The Water Cycle

Question 1

What is river discharge?

Answer 1

Its the volume of water that flows in a river per second. Its measured in cubic metres per second

Question 2

What is runoff?

Answer 2

Water flowing on the surface of the land

Question 3

What happens when there is high levels of runoff?

Answer 3

It increases the discharge of a river because more water makes it into the river, increasing its volume

Question 4

What are hydrographs?

Answer 4

Graphs of river discharge over time. Showing how the volume of water flows at a certain point in a river changes over time

Question 5

What does a flood / storm hydrograph show?

Answer 5

River discharge around the type of a storm event. They only cover a relatively short time period (hours or days)

Question 6

What is peak discharge?

Answer 6

The highest point on the graph, when the river discharge is at its greatest

Question 7

What is lag time?

Answer 7

The delay between peak rainfall and peak discharge. This delay happens because it takes time for rainwater to flow in the river. A shorter lag time increases peak discharge because more water reaches the river during a shorter period of time

Question 8

What is rising limb?

Answer 8

The part of the graph up to peak discharge. The river discharge increases as rainwater flows into the river

Question 9

What is falling limb?

Answer 9

The part of the graph after peak discharge. Discharge is decreasing Bec cause less water is flowing into the river. A shallow falling limb shows water is flowing from stores long after its stopping raining

Question 10

What is a flashy hydrograph?

Answer 10

A basin with rapid runoff and not much storage capacity gives a hydrograph with a short. lag time and high peak discharge - It’s steep, roughly symmetrical rising and falling limbs

Question 11

What 4 factors affect the amount of runoff and shape of the hydrograph

Answer 11

Size of drainage basin, Shape of drainage basin, Ground steepness and Rock and Soil Type

Question 12

Explain Size of Drainage Basin

Answer 12

Larger drainage basins catch more precipitation, so. they have a higher peak discharge than. smaller basins. Smaller basins have shorter lag time because precipitation has less distance to travel, so it reaches the main channel more quickly

Question 13

Explain shape of Drainage Basin

Answer 13

Circular basins are more likely to have a flashy hydrograph than long, narrow basins. This is because all points on the watershed are roughly the same distance from the point of discharge measurement. Meaning lots of water will reach the measuring point at the same time

Question 14

Explain ground steepness

Answer 14

Water flows more quickly downhill in steep-sided drainage Bains, shortening. lag time. This means that water has less time to. infiltrate the soil so run off is higher

Question 15

Explain Rock and Soil type

Answer 15

Impermeable rocks and soils don’t store water or let water infiltrate. Increasing surface run off, peak discharge increases as more water reaches the river in a shorter period

Question 16

What 2 natural processes affect Hydrographs, runoff and the water cycle?

Answer 16

Seasonal changes and vegetation and storms and precipitation

Question 17

Explain storms and precipitation

Answer 17

Intense storms generate more precipitation and greater peak discharges than light rain showers. The larger input of water causes flows, like runoff and stores.

Question 18

Why can’t some flows occur

Answer 18

flows - infiltration can’t occur rapidly enough for the size of the input, increasing runoff

Question 19

Explain seasonal changes

Answer 19

the size of inputs, flows and stores vary with seasons

Question 20

What happens in the winter

Answer 20

Temperatures may. drop below 0, causing water to freeze, reducing the size of flows through drainage basins, while the store of frozen water grows. When temperature increases again flows through drainage basins and outputs can bee much larger as ice melts

Question 21

How do plants show seasonal vegetation?

Answer 21

Vegetation intercepts precipitation and slows its movement to the river channel. Interception is highest when there’s lots of vegetation and deciduous trees have their leaves

Question 22

What happens if there is more vegetation in a drainage basin?

Answer 22

The more vegetation the more water is lost through transpiration and evaporation before it reaches the river channel, reducing runoff and peak discharge

Question 23

What 3 human activities affect the size of stores in water cycles

Answer 23

Farming Practices, Land use Change and water abstraction

Question 24

Explain infiltration in the water cycle

Answer 24

When rain hits the surface, what can’t infiltrate runs off instead

Question 25

What 4 ways does farming affect infiltration

Answer 25

• Ploughing breaks up the surface so more water can infiltrate, reducing runoff
• Crops increase infiltration and interception compared to bare ground reducing runoff. Evapotranspiration increases rainfall
• Livestock trample and compact the soil, decreasing infiltration and increasing runoff
• Irrigation can increase runoff if some of the water can’t infiltrate. Groundwater on river levels can fall if water is extracted for irrigation

Question 26

What is irrigation

Answer 26

Artificially watering land

Question 27

What does deforestation do?

Answer 27

It reduces the amount of water that’s intercepted by vegetation increasing the amount that reaches the surface. In forested areas , dead plant material on. the forest floor helps to hold the water, allowing it to infiltrate the soil rather than runoff. When forest cover is removed the amount of infiltration. that can take place decreases

Question 28

What does construction of building and roads do?

Answer 28

Create an impermeable layer over the land preventing infiltration. This increases runoff, resulting in water passing through the system much more rapidly and making flooding more likely

Question 29

What happens at water abstraction

Answer 29

More water is abstracted to meet demand in densely populated areas. This reduces the amount of water in. stores like lakes, rivers, reservoirs and groundwater

Question 30

What happens to water abstraction during dry seasons?

Answer 30

More water is abstracted from stores for consumption and irrigation, so stores are depleted further