Water & Carbon Pack 3

annual changes to river discharge

Seasons have a different temp due to that part of the Earth facing towards or away from the Sun. More or less water is therefore stored in ice and the oceans

changes over a few years to river discharge - sunspots

Number of sunspots changes in an 11 year cycle causing warmer or cooler years.

changes over a few years to river discharg - volcanoes

Infrequent volcanic eruptions can cause cooling or sometimes greenhouse gases. Ash blocks sunlight entering, SO2 reflects sunlight and CO2 is greenhouse gas

changes over centuries caused by humans

Climactic warming means more of the frozen water returns to the seas.

changes over geological time - milankovitch cycle

1. Earth's tilt: 21.8 -24.4 degrees tilt, greater tilt = greater difference between summer and winter. Hotter summers = more melting of ice

2. Orbit/eccentricity: Earth's orbit changes from being more elliptical to more circular over 100,000 year cycle. Elliptical = warmer times which melts ice

3. Precession: Changes the time of year the Earth is closest to the Sun on 21,000 year cycle. Affects when seasons are and therefore radiation received.

tectonic activity

Uplift mountains e.g. Himalayas, increase in cryosphere storage in glaciers.

Pangea separating

As the land mass of Pangea separated a large area moved south and became       Antarctica.                                                                                                                            Increasing ice cover now that land exists at Antarctica will mean ice reflects more heat. Therefore the Earth cools further. Leading to formation of more ice. POSITIVE FEEDBACK CYCLE.

One off storm events causing changes in water transfer (4)

Cyclone Nargis in Myanmar in 2008. Category 1 on Saffir-Simpson scale.

Rainfall was 600mm

Flooding was 14,000km

Storm surge was 3.5 to 4m

Seasonal changes to water transfer - monsoons (4)

Monsoon is th especially wet season triggered by a periodic alternation of wind direction and velocity affecting some tropical regions of the world.

Strongest monsoon effects of heavy rainfall are felt in India, Pakistan and China.

2024 Monsoon India.

90cm of rainfall between June and September.

year to year changes to water transfer - el nino (2)

El Nino is the warming of the ocean surface or above average surface temperatures. Leading to more likely extreme weather events such as typhoons and cyclones. During an event, cool water found along coast of Peru is replaced by warm water. Warm water near Australia and Indonesia becomes cooler. Very dry conditions arrive in parts  of SE Asia, India, eastern Australia and SE USA and Central America.

2014 & 2016: Central and Eastern tropical pacific experienced flooding and droughts. SA, Peru and East Africa experienced flooding

Long term changes to water transfer (3)

Climate change is causing more evaporation, which leads to more precipitation in some areas and less precipitation in others.

• Aridity increases in desert fringes in Australia, China, the USA and the Sahel region (rainfall here has been lower in recent decades than during earlier decades of 20th century)                        

• Rainfall patterns likely to change in the UK. Warmer, wetter winters and longer hotter summers.

flashy flood hydrograph

 steep rising limb, short lag time, high peak discharge, steep falling limb

slow response hydrograph

long lag time, gently inclined rising limb, low peak discharge, gently inclined falling limb.

 

Precipitation affecting river regime

Intense rain, even if for a short period, leads to infiltration excess overland flow. Drizzle has time to infiltrate, however rain for a long period will eventually saturate the soil leading to saturation excess overland flow.

prior weather conditions

Rainfall in previous days will have caused a few pore spaces left in the soil saturation producing flashy hydrograph.

Slope angle

Steep slopes mean water has little time to infiltrate and will lead to a river rising quickly and a potential flood around the river, flashy hydrograph.

temperature

High temperatures lead to high rates of evaporation, less water in river and low peak discharge, producing slow response hydrograph

soil

Deep soil allows a lot of water to be stored. Permeable soil allows water to enter. Slow response hydrograph

land use

Forested area has higher evapotranspiration rates, infiltration, interception and absorption rates. Slow response                                                                                   

Bare/urban area has faster rates of surface run off. Flashy

rock type

Impermeable rock doesn’t let water enter and leads to flashy response. Slate, marble and granite are impermeable.

drainage density

Lots of streams bring water to the given point quickly, increasing likelihood of flooding. Flashy

shape of basin

If drainage basin is shaped so that the tributaries generally reach the measuring point at one time then there will be a high discharge

area of basin

Small basin = short time for tributaries to take water to given point.                 

Large basin = more water falling in it so the peak discharge is higher.

why is soil type important

1. Controls the rate and volume of infiltration

2. Controls the amount of soil moisture storage

3. The rate of throughflow

clay soils

Heavy, high in nutrients, wet and cold in winter and baked dry in summer. Small pore spaces (reduced infiltration and throughflow = more surface runoff), once water enters can stay there. 0-4mm/h infiltration rate.

sandy soils

 Light, dry, warm, low in nutrients and often acidic. Large pore spaces = rapid infiltration, fast throughflow and drainage, less flooding. 3-12mm/h infiltration rate

Silt soils

Fertile, light but moisture retentive and easily compacted. 2-8mm/h infiltration rate.

what causes temporal variations in river discharge (5)

• River regime = annual variation in the discharge of a river measured at a given point.

• Rivers get their water from precipitation, runoff and groundwater.

• Factors affecting river's regime:

Physical: climate, seasons, vegetation, underlying soil, temperature, evaporation and precipitation

Human: dams and reservoirs, irrigation, water transfer schemes and land use

river yukon flow patterns (4)

High flow: Spring and summer (caused by snowmelt)

Low/no flow: Winter (precipitation is frozen)

Seasonable variability: Very large

Human influences: Few. Some HEP use for mining industries

river yukon major influences (2)

Tundra climate

Higher summer temperatures, rainfall and snowmelt coincide.

Amazon river flow patterns (4)

High flow: Wetter season

Low/no flow: Drier season

Seasonable variability: Moderate variability - fed by Andean rivers outside rainforest region

Human influences: Large dams used by Brazil's major cities for irrigation and HEP

Amazon river infuences (3)

Rainforest climate

Seasonal precipitation

Evapotranspiration levels very high

murray-darling australia, flow pattern

High flow: Wet season

Low/no flow: Dry season

Seasonal variability: High

Human influences: Waters are drawn by Australia's major cities and farms for irrigation

murray darling australia influences (2)

Seasonal sub-tropical climate - monsoon climate in northern tributaries of Queensland, which feeds the Darling, temperate climate in the South, which feeds the Murray.                                                  

Most of the basin lies in a rain shadow and undergoes long periods of drought.

water cycle over space - temperate grasslands (8)

Grasses are the dominant vegetation, trees and large shrubs are absent.

Hot summers and cold winters, rainfall is moderate.

Precipitation usually occurs in the late spring and early summer with an annual average of 50 to 90cm.

Large temperature range. Summer = well over 36 degrees and winter =  as low as -40 degrees

Taller grasses in wetter regions

Seasonal drought and occasional fires occur

Soil is nutrient rich

E.g. Prairies of N. America

water cycle over space - tropical rainforest (12)

High rainfall - over 2000mm per year

No dry season

Constantly high temps between 25 and 30 degrees

Convectional rainfall

High evaporation and transpiration rates

Dense vegetation = high interception rates

Rapid cycling of water

High humidity as warm air holds lots of water

AMAZON - impermeable rocks increase runoff

Steep areas increase runoff

Palm oil plantations decrease interception, increase surface runoff, increase soil erosion

Also means less water in area as less evapotranspiration, less rain, forest dieback and therefore less water.

water cycle over space - tundra (8)

Very cold.   

8-9 months it is below 0 degrees.               

Low  annual precipitation between 50 and 350mm per year                                            Permafrost acts as barrier to infiltration and percolation of water.                                                 

Limited precipitation falls as snow, low temps= limited moisture stored in atmosphere, limited transpiration due to limited vegetation                                    

  Igneous rock increases impermeability leading to standing pools of water in summer periods.        

Low relief means little infiltration.                    

Climate change increases temps so more vegetation grows.