WATER CYCLE AND WATER INSECURITY

Global Water Budget

Global Water Budget

The global water cycle is comprised of many stores, the largest being oceans, which contain 97% of global water .

2.5% of stores are freshwater ( 69% is glaciers, ice caps and ice sheets , 30% is groundwater)

Surface and other freshwater only accounts for around 1% of global stores.

Hydrology in Polar Regions (5)

▪ 85% of solar radiation is reflected

▪ Permafrost creates impermeable surfaces

▪ Rapid runoff in spring

▪ Seasonal release of biogenic gases into atmosphere

▪ Orographic and frontal precipitation

Hydrology in Tropical Rainforests (4)

▪ Dense vegetation consuming 75% of precipitation

▪ There is limited infiltration

▪ Deforestation leads to less evapotranspiration and precipitation

▪Convectional rainfall

Drainage basins

A drainage basin is an open subsystem operating within the closed global hydrological cycle. It’s defined as an area of land drained by a river and its tributaries with a boundary (known as the watershed), usually composed of hills and mountains.

Also referred to as catchment areas because they ‘catch’ precipitation falling within the watershed.

Inputs not governed by outputs -can lose more than they gain/ vice versa

Inputs to the Drainage Basin –

Factors affecting volume/condition of precipitation:

(3)

Factors affecting volume/condition of precipitation include:

▪ Seasonality – In some climates (such as monsoon and Mediterranean) there are strong seasonal patterns of rainfall- time of year determines the precipitation input within the drainage basin

▪ Variability - sudden or long term changes to the climate can happen, which would affect precipitation levels and so the drainage basin as a whole.

→ Secular Variability – long term (for example as a result of climate change trends)

→ Periodic Variability – annual, seasonal or monthly context

→ Stochastic Variability – random factors like localisation of thunderstorm

▪ Latitude - In most cases, the higher the latitude from the Equator, the colder the climate, and so snowfall occurs more often than rainfall.

Interception

the direct intervention of plants’ leaves in changing the direction or temporarily stopping precipitation as it falls to the surface. Any moisture retained by the surface of the leaf (interception store) is generally greatest at the start of storms. A plant’s interception capacity varies depending on the type of vegetation.

Infiltration

The movement of water from the surface into the soil. The infiltration capacity is the maximum rate at which water can be absorbed by the soil, and can be affected by:

▪ Soil Composition – Sandy soils have higher infiltration rates compared to clay.

▪ Previous precipitation - The saturation of soils will reduce infiltration rates, hence surface runoff increases after long, intense periods of rainfall.

▪ Type and amount of vegetation - dense root growth can inhibit the infiltration of water, and interception of plants’ leaves will delay infiltration

▪ Compaction of soils will reduce the infiltration rate.

▪ Relief of land – sloped land will encourage more runoff, therefore less infiltration as a direct result.

Surface Runoff

Water flows overland, rather than permeating deeper levels of the ground. Overland flow occurs faster where the gradient of land is greater. Surface runoff is the primary transfer of water to river channels, influencing discharge

Throughflow

Water moves through the soil and into streams or rivers. Speed of flow is dependent on the type of soil .

Clay soils with a high field capacity and smaller pore spaces have a slower flow rate . Sandy soils drain quickly because they have a lower field capacity, larger pore spaces and natural channels from animals such as worms.

Percolation

Water moves from the ground or soil into porous rock or rock fractures. The percolation rate is dependent on the fractures that may be present in the rock and the permeability of the rock

Groundwater Flow

- The gradual transfer of water through porous rock, under the influence of gravity. Water can sometimes become trapped within these deeper layers of bedrock, creating aquifers and long-term water stores for the drainage basin

Evaporation

This is the direct loss of water moisture from the surface of a body of water, the soil and interception storage (on top of leaves) to the atmosphere. Evaporation rates increase when the weather is warmer, windier and dryer. Alternative factors also influence evaporation rates:

● Volume and surface area of the water body - the larger the surface area (more spread out), the faster the rate of evaporation.

● Vegetation cover or built environment surrounding the water - anything that reduces direct sunlight to the water body will reduce evaporation.

● The colour of the surface beneath the water - black tarmac will absorb heat faster than white snow, and so evaporation will occur faster on the tarmac.

Transpiration

This is a biological process where water is lost to the atmosphere through the pores of plants (stomata). Transpiration rates are affected by seasonality, the type of vegetation, moisture content of the air and the time of day.

Stores in a drainage basin (5)

1)Soil Water - Water stored in the soil which is utilised by plants

2)Groundwater - Water that is stored in the pore spaces of rock

3)River Channel - Water that is stored in a river

4)Interception - Water intercepted by plants on their branches and leaves before reaching the ground

5)Short-term Surface Storage - Water stored in puddles, ponds, lakes etc

Location and use of the water table

The water table is the upper level of the ground at which the pore spaces and fractures become saturated. It is used by researchers to assess drought conditions, health of wetland systems, success of forest restoration programmes

Physical factors influencing the drainage basin (5)

• Climate – influences amount of rainfall and vegetation growth.

• Soil Composition – influences rate of infiltration and throughflow.

• Geology – affects percolation and groundwater flow

• Relief – steeper gradients of land will encourage faster rates of surface runoff

• Vegetation – affects interception, overland flow

Human factors influencing the drainage basin (5)

➢ Deforestation – Less vegetation means less interception, less infiltration, more overland flow leading to more flooding.

➢ Afforestation – More vegetation means interception, less overland flow, more evapotranspiration

➢ Dam construction – Dams reduce downstream river flow and discharge, increase surface stores so more evaporation

➢ Irrigation – Drop in water tables due to high water usage. Example: Aral Sea in Kazakhstan shrank in 1960s due to farmers using the water to grow cotton

➢ Urbanisation – Impermeable surfaces reduce infiltration, increase surface runoff, river discharge increase.

River Regimes

A regime is the annual variation in discharge of a river at a particular location. Most of this river flow isn’t from immediate precipitation, but is supplied from groundwater between periods of rain, which slowly feeds water into the river system.

There can be seasonal variations in the regime - glacial meltwater, snowmelt or monsoons can cause sudden fluctuations in river input.

Storm hydrographs

Storm hydrographs represent variation in discharge within a short period of time . Before a storm begins, the main supply of water to the river is through groundwater or base flow. However, as a storm develops, infiltration and surface runoff will increase which causes greater throughflow.

Management of drainage basins: reducing runoff (loss of water)

▪ Create permeable pavements (gaps within paving blocks) to increase infiltration and reduce surface runoff .

▪ Rainwater Harvesting – collecting rainwater to use as domestic greywater

▪ Creating wetlands (areas with marsh and wetland vegetation) that will act as natural sponges and increase temporary water storage.

deficits in the hydrological cycle

An imbalance in inputs and outputs of water can have serious implications for the hydrological cycle. A deficit (more commonly known as a drought) refers to when input is less than output. This deficit can be caused by natural and/or human factors.

El Nino Southern Oscillation

El Nino is the change in water body patterns within the Southern hemisphere, leading to unusual weather conditions.

Normally cool water is found along the Peruvian Coast and warm waters are found around Australia. - EN causes this to switch and usually occurs every 3 to 7 years, generally lasting for 18 months.

Bringing Drought to Australia and flooding to South America (Peru)

Wetlands

Wetlands act as temporary water stores within the hydrological cycle, help reduce river flooding after storms.

Chemically, wetlands act like giant water filters by trapping and recycling nutrients and pollutants, which helps to maintain water quality of the river.

Wetlands have very high biological productivity and support a very diverse food web, providing nursery areas for fish and refuge for migrating birds. All these functions contribute towards their natural importance as well as a value for human society (for example, providing fish for food or a clean water supply).

Impact of meteorological droughts on wetlands

reduced interception (less rain)= vegetation to wilt and die, impacts soil nutrients.

Physical causes of desertification

Reduced Precipitation - vegetation dies= the protective layer it provided for the soil will also be removed. soil will be exposed to wind and rain, accelerating rate of soil erosion, worsening soil conditions. positive feedback= desertification

▪ Global Warming - increased rate of evaporation . more moisture has evaporated= less water available for convectional rainfall= plant growth will be stunted and vegetation dies

Human causes of desertification

Population growth= demand for food, water and other resources also increases.

• agricultural methods change to supply the demand.(cattle farming is becoming intensified resulting =forest being cut down to provide enough land for grazing) etc.

Areas vulnerable to surplus in the hydrological system

▪ Low-lying land, the base of a river valley and estuaries - River flooding can occur along with groundwater flooding as the ground become saturated, therefore any surface close to the water table is vulnerable to flooding.

▪ Urbanised, built environments – Impermeable surfaces increase surface runoff, reducing lag time and so increasing the risk of flash flooding.

Mitigating flood risk (methods)

(3)

▪ Afforestation of upland areas - increasing vegetation cover will reduce rapid surface runoff

▪ Restricting construction on floodplains

▪ Establishing temporary extra flood plains, in the event of extreme weather - some UK councils have designated football pitches or parks next to the river, to channel some of the storm discharge and reduce the flood risk for towns living close to the flood banks.

Impacts of Climate Change on the Hydrological Cycle

▪ If land and sea surface temperatures continue to rise,= more frequent el nino events

▪ Increasing average global temperatures would increase rates of evaporation,=potential droughts and increasing water scarcity.

etc.

Unequal water distribution

• Important stats

66% of the world’s population live in areas which only have access to 25% of the world’s annual rainfall.

2 billion people don’t have access to safe drinking water.

Only about 3% of the Earth’s water is potable

Why has water demand risen ?

● Population growth - generally more people = more water needed.

● Growing middle class population as countries develop and industrialise, increasing domestic demand.

Why can water supply not meet demand ?

● Aquifers and deep-water wells are being dug, especially for water-intensive agriculture =Water tables (groundwater storage) are dropping as a result.

● Water is being extracted at a faster rate than the soil is able to recharge.

Factors affecting the localisation of water availability (3)

- Precipitation: mid-latitude areas generally receive the most rainfall

- Topography : areas with high relief = more precipitation and surface runoff is greater

- Geology:permeable rocks can be infiltrated, and water can be easily stored underground.

Ways in which humans are reducing the freshwater supply (2)

1)pollution:Industrial activity (especially in developing countries with slack environmental laws) and population pressure = reduced access to clean freshwater.

2)Saltwater encroachment due to over extraction and rising sea levels (Climate Change) is reducing freshwater stores.

— Bangladesh case study

£ consequence of water insecurity

the price of clean water has increased in certain regions, and may increase globally in the future.

The Water Poverty Index (WPI)

The WPI is an index used to measure localised water stress, for the use of national governments to improve provisions. Based on 5 categories.

(1) Water resources – the availability and quality of water

(2) Access to water – the distance from safe water for drinking, cooking, cleaning and industries

(3) Handling capacity – management, infrastructure and income

(4)Use of water – for domestic, agricultural and industrial purposes

(5) Environmental indicators – ability to sustain nature and ecosystems

Key players involved in water management (3)

UN – UNECE (UN Economic Commission for Europe Water Convention) aims to protect and ensure the quality and sustainable use of transboundary water resources.

EU – Water Framework Directive agreed in Berlin 2000 – Targets to restore river, lakes, canals, coastal waters to suitable condition.

National Governments – e.g. the UK’s environment agency which checks compliance with EU frameworks.

CASE STUDY 1: COLORADO RIVER

(Background and agreements that have been made)

BACKGROUND:

• Drains 7% of the USA, drainage basin the size of France.

• supplies 8 states with water, irrigates 1.4 million hectares of farmland & supplies drinking water to 50 million people.

What agreements have been made?

• 2007: instead of sharing Colorado’s water, the 7 US States divide up the shortages. The amount of water available determines supplies to each state= California reduced the amount it extracts by 20%

CASE STUDY 1: COLORADO RIVER PT 2

ATTITUDES AND ACTIONS TOWARDS WATER SUPPLY:

Water is seen as an entitlement in the USA( high living standards). Increasing water restriction= conflict between water providers and users. Following actions and policies are now being considered/ adopted:

• Domestic conservation (30% of water could be saved repairing leaks/metering supplies, planting drought-tolerant plants in gardens, and using smart irrigation systems)

• Re-using waste water from sewage treatment for landscape irrigation & industry, or to recharge aquifers .

• Concrete storm-drains could save water and redirect it into urban parks for irrigation.

• Farms use 80% of California’s water. Reducing irrigation by 10% would double the amount of water available for urban areas.

Desalination

(removal of excess salt and minerals from sea water)

As water costs and demand increases, desalination has become a key future water strategy.

CASE STUDY 2: DESALINATION IN ISRAEL

Israel has built one of the world’s largest desalination plants (using reverse osmosis to treat 624,000m3 of sea water a day).

• The Sorek desalination Plant (TelAviv) covers 10 hectares with investment expected to be $400 million.

  - providing 10% for drinking water and 20% for domestic use.

Desalination sustainability

NOT SUSTAINABLE;

• Energy to produce the water is high (2kwh energy to produce 1m3 of freshwater).

• Minerals in water are chemically different to that of normal freshwater (potential future environmental detriment).

IS SUSTAINABLE:

• Increased water in water stressed areas.

• Suitable for drinking= sanitation in poorer areas (helping people escape poverty).

CASE STUDY 3: ISRAEL MANAGING SUPPLIES SUSTAINABLY

• Due to their climate, natural geography and politics , Israel has been forced to manage their limited water supply effectively.

• They recycle sewage for agriculture (65% of crops are produced in this way), they change the price of water to the ‘real price’ to reflect supply (inc. environmental damage). A national water carrier has been developed to transfer water from the sea of Galilee (North) to the populated center and dry South.

  • new supplies:

    • Importing 50 million tonnes of water per year from Turkey (Manavgat project, agreed in 2004) and piping seawater from the Red Sea & Mediterranean to new inland desalination plants.

CASE STUDY 4: restoring aquifers in Saudi Arabia

1980s- Saudi Arabia pioneered use of circular irrigation systems to grow enough wheat to feed itself and its neighbours, using water from its own aquifers= water levels in its aquifers fell sharply.

Now- government exports of grain and wheat have been abandoned to reduce demands upon aquifers supplying irrigation water.

CASE STUDY 5: Holistic management in Singapore

• Small country - its 5.4 million people are urban. Malaysia (neighbour) traditionally supplied 80% of its water, by 2010 this volume had halved.

• Per Capita water consumption fell (165 litres per day in 2000 to 150 in 2015) through metering water supply and educating the public.

• Leakages have been cut to 5%( UK= 20%).

• Water prices are scaled up if water usage goes above a certain level.

• Subsidies enforced to protect poorest citizens from expensive water.

• The whole of Singapore is a water harvesting catchment. Diversified supplies, including local catchment water, recycled water and desalinated water.

CASE STUDY 6: THREE GORGES DAM, CHINA

The three gorges dam is located on the Yangtze River in China and is the world’s largest dam.

PROS:

-(economic)Safe trade route (increased trade)- water made less shallow. FDI: Building and tech associated with the dam.

-(social)Increased amount of water available for crop irrigation. Hydroelectric power created, reducing cost for local homes.

-(Environmental)Clean, renewable power, reduced reliance on coal.

CONS:

-(economic)$22.5 billion to build + maintenance. Loss of agricultural land=less crop export.

-(social)100,000 hectares of farmland flooded to create reservoirs, 1.4 million people displaced and relocated. Increased saturation of river =landslides (homes destroyed).

-(environmental)Flooded land= vegetation is degraded by bacteria. These respire anaerobically=methane and CO2 produced.

CASE STUDY 7:China South-North water transfer

$62 billion scheme (launched 2002). The scheme moves water along 3 distinctive routes

• one of the largest water transfer projects in the world, expecting to be completed by 2050. The aim is to divert 45 billion m3 of water a year from the water surplus basins in the South and East to the North where there is frequent deficit (places such as Bejing).The project is expensive and involves resettlement.

• Key player: Government sponsored ‘South to North’ Water transfer project company, which works with each provinces’ water company.

CASE STUDY 8: Conflict over water resources

Turkey, Syria and Iraq

A situation with serious international implications is the demand for the waters of the Euphrates by Turkey, Syria and Iraq.

The Euphrates = primary water source for millions of people who depend on it for power generation and irrigation in an extremely arid climate. Conflict over water in this area is decades old. It has intensified in recent years as a result of a massive Turkish dam building programme known as the Greater Anatolia Project (GAP), designed to provide a supply of water and power adequate to fuel the development needs of Turkey’s population, which is growing at 1.6% annually.

It provides Turkey with a generating capacity of 7500 MW of electricity as well as improving incomes in Anatolia (least developed part of Turkey)

GAP consequences

GAP=40% reduction of the Euphrates’ flow into Syria +80% reduction of flow into Iraq. This will reduce the electrical output of Syria’s Tabqa Dam by up to 12% & Iraq could lose irrigation water. The levels of salinity will increase, as well as the amounts of agricultural and industrial pollution, in the remaining water.

Syria and Iraq have already threatened war over their access to the Euphrates. As the populations of these nations grow, the competition for fresh water could endanger stability in the region.