water case studies

Drainage basin in the river Nile

• The Nile River flows through eleven countries (Burundi, DRCongo, Egypt, Ethiopia, Eritrea, Kenya, Rwanda, South Sudan,Sudan, Tanzania, and Uganda).

• The Nile basin comprises two broad sub-systems, these are the Eastern Nile sub-system and the Equatorial Nile sub-system.

• The Nile River is the longest river in the world at 6,695 km, flowing northward through the tropics and the highlands of eastern Africa and drains into the Mediterranean Sea.

• The basin covers about one-tenth of the area of the continent, drains a total land area of 3,176,541 km2.

Nile dam in Ethiopia conflicts

1929 - Nile Agreement between UK (Sudan) and Egypt. Most control to Egypt including to stop any river developments that threaten their supply.

• 1959 - the Nile Agreement was reviewed with no change: Egypt and Sudan given priority access to River Nile water

• Since then, growing Issues with upper basin countries [Ethiopia, Tanzania] who need to use water to feed growing nations.

• 1999- River Nile countries except Eritrea sign the Nile Basin Initiative to try to improve co-operation.

• A legal framework would be drawn up on fair use via the Cooperative Framework Agreement (CFA).

• By 2010 many had signed but Egypt raised strong opposition as the worried they would lose their share.

• In 2011 the Ethiopian Government began building a dam on the Blue Nile to help stimulate their economy.

• Egypt reacted angrily even threatening to bomb the dam if it impacted upon them as Egypt was concerned the reservoir behind the dam would cause higher evaporation rates and less flow of water into Egypt.

• They have since come to a partial agreement and this was formally signed (Egypt, Ethiopia and Sudan) in 2015.

• 2020, Ethiopia finished building the Grand Ethiopian Renaissance Dam for a

supply of hydroelectric power. The dam prevents drought and following

Explain contribution of human activity on risk of drought (Sahel)

One human active that increasies the risk of drought is farmin g. For example In the region of Sehal livestock numbers have increased by 40% in years preceding 1960s ( above the capacity of the fragile environment).

This means that more livestock will need to catered fr using more water supplies for their nutrients and machinery; more livestock also can lead to overgrazing of the land, which leaves the land infertile and dry. Therefore it becomes exposed to higher risks of desertification, if the expanses soil is eroded by wind a rain, which leads to less vegetation able to grow on the land, less vegetation also increases risk of drought due to less intercpetion and plant storage. Therefore human activity of farming will increase the risk of drought.

One human activity that increases the risk of drought is deforestation. For example, in the Amazon rainforest deforestation is occurring at the rate of 7,000km a year. This means that by removing trees the water cycle is interrupted on a regional scale. With fewer trees, there is less interception and thus a lower rate of evapotranspiration. This leads to less water condensing in the atmosphere, resulting in less cloud formation and decreased precipitation. Therefore, human activity of deforestation will increase the risk of drought.

Another human activity that increases risk of drought is population, population has increased rapidly in Sehal due to increased numbers of refugees from civil wars and droughts. The population is due to keep increasing in the mid century, estimated to double to 500 million people by 2050 because of high birth rates and low death rates. This means that a much higher demand for goods and services, like water, food and wood. An increased demand for wood because it is used for fuel, cooking, heating and products, this demand increases the rates of deforestation which can increase risk of drought. An increased demand for water can the water drainage beasin because urban areas in Sehal extract water formdround water stores, channel flow and lakes. Increased demand for food increases farming demands which increases soil erosion and desertification. Therefore human activity, increasing population will increase risk of droughts.

Facts about Sahel

• in Africa

• 30 degrees west prime Meridian and just over 60 genres east from the prime meridian

• Chad, Niger, Sudan, Eritrea, Mauritania, Mali, Senegal

• Lines of longitude between 20 degrees and 45 degrees

Why does Sahel experience droughts

Seasonally

• the Sahel region is on a transitional climate area ( in between 2 climate zones - tropical and arid) making the amount of rain that falls in the region varies from north to south ( 100mm on north and 800mm south) the majority of rain. (80%) falls in the Summer months

annually

• Rainfall varies annually especially in years with warmer sea surface temperature, there is a strong convection that causes a weakening of the west African causing non rainfall

Decadal

• From 1970 onwards rainflal is in defecity per year till 2010 shown by rainfall levels raining from 0 to -4

• Before 1970 most of the rainfall was in surplus so between 0 and 4

• Population is doubling every 20 - 20 years

• 1000 of bore holes have been drilled tapping into the deep aquifers, leading to over extraction of ground water

• 30 -40% decrease in rainflal each year

• Water table is dropping e.g lake chad 90% less of its 1960 size

• 1970 - 90s sahel saw a 30% drop in. Rainfall - leading to a famine that killed 100,000 people

• This was due to expansion of Hadley cell, increasing temps, c increasing evaporation from soils

• More recently the rains have returned n but were more violet - causing flash flooding - low infiltration rates

• Globally - increasing temp by 1 degree allows the atmosphere to hold 7% more moisture

Facts about boscastle

• north west coast of Cornwall

• Situated at the bottom of a series of steep sided, V-shaped valleys → faster rate of water flow

  The drainage basin was small and the ground beneath is impermeable rocks such as slate

Impacts And physical causes of boscastle flood

Eight hours of exceptionally heavy rain caused flash floods

Up to 75mm of rain fell in just two hours in the area, which is about the average rainfall for the entire month of August. 

Above average rainfall in the two weeks before the event meant the soil was already saturated → high surface runoff

A depression brought a thunderstorm on the 16th Of August

infrastructure: houses shops and pubs were flooded, 60 cars, walls and bridges were washed away. Trees were uprooted and swept into peoples' gardens. much soil erosion occured form river banks, which moved as suspension in the surface water flow, as a consequence the church was filled with six feet of mud and water 

human and environmental impacts 

environmental damage to local wildlife habitats, coastal pollution caused as debris and fuel from cars flowed out to sea. long-term disruption to the village, as a major rebuild project had to be carried out. long-term stress and anxiety to people traumatised by the incident.

Economical impacts: 

Loss of touring, which was a major income for the local area, damages to bussiness and farmland

Human causes which escalated the flood

Infrastructure has been constructed right up to the riverbanks leaving little room for the river to spread without causing damage

Low arch bridge

A temporary dam was created as debris became trapped under the bridge

The bridge gave way releasing an estimated 10 foot surge of water that rushed through the village

What is a river regime

It is the change in river discharge over a year

The Yukon - river regime

• during winter when much f the precipitation falls as snow the river is locked in the chryosphere (in Alaska)

• During winter discharge is 1500m3 per second

• Increasing in spring - to around 25,000 m3 per second as snow and ice begin to thaw

• This increases overland flwo and trough flow as soil begins to thaw

• So is dictated by seasonal climate change

The Indus River - in India and Pakistan regime

• Arson April glacial melt waters form the Himalayas

• Their ckbines with heavy monsoon rains which produce 70% of annual rainfall

• During winter moths rapidly returns to around 2000m3 Per second discharge

Amazon river regime

• very long lag time

• Amazon drainage basin in 2.9 million square miles

• Rainfall peaks during January and February

• Discharge peaks around June and July

• This is becasoem tributaries can be 3, 500 km long so the increased precipitaiton isn’t fed into the main channel for a few months

River Ock regime vs River Lambourne

• in the Uk

• Has a clay catchment mewing in its not very permeable - so high overland flow and high drainage density

• Lambourne has a chalky catchment - lists of infiltration and percolation (97% of the water reaches channel by ground water flow)

Storm hydrogen graphs - boscatle

• 2004

• 185 mm of rain fell in 5 hours

• Flashy graph

• Bottom of a steep sided valley

• Impermeable slate basin

• Multiples tributaries

• Lag time was less than 2 hours

• Peak discharge of 140m3 per second

Storm hydrograph London

• urbanisation - 40 - 50% of greater london is tarmac or concrete

• Where runs off in drains - direct route to Chanel which reduced lag times by 50% ( compares to 100 years ago)

• 5000 properties on flood plains - reducing stage capacity

River Eden Cumbria

• high ground in the Lake District which gets 2800mm rainfall a year But on very thin soils so rapid surface run off

• In 2015 the widens basment hist by storm Desmond

• Due to allow the rainfall over the purse of the year the drainage begins was already saturated so 0 infiltration capacity

• large drainage density - fed by 5 tributaries

• Other factors: increased deforestation and increased sheep farming leading to soil compaction

Drought - Australias big dry 1997 - 2009

• Australia hit by consecutive El Niño events and a positive Indian Ocean dipole causing high pressure water systems which inhibited rainfall adn 40 -60% reductions in rainfall fro 12 years

• Humans accelerated the over extraction (90%) of water form the Murray Darling basin, mostly fro irrigation

• 60% of Australias agricultural land was affected

• 2007 - 08 rice production reduced by 99%

• Social crisis - price of foood increased by 12%

Ethiopia dorught 2015

• rainfall dropped 50-75% below average

• Bcs the Kiremt rains - the main rainy season, responsible for 80% to 90% of Ethiopia’s total agricultural production stopped

• Leaving 10 million people in need of food assistance - famine extensive amounts of George aid

Fourth in Brazil

• Brazil sits on crystalline impermeable bedrock

• Means there no martial aquifers

• The area is relatively low lying, so decreased likely hood of a cyroshpere store

Aral Sea - drought

• In the 1960s the Soviet Union decided to divert main tributaries inot the Aral Sea to provide irrigation for fruit and cotton

• Input cut off so the sea began to evaporate

• By 2010 had lost 90% of its volume

• left per hind slaty layer contimainated wiht pedicels and herbicides whihc were the run off of agriculture

• Thriving fishing industry collapsed- 60,000 people lost their jobs

Environmental impacts of drought - Donana wetlands in Spain

• Donana wetlands in Spain

• One of Europes most important migratory stops from birds

• Expansion of Hadley cell is leading to lower levels of rainfalll in areas like Southern Spain

• Illegal abstraction - farmiers have dug throughsdna of illegal wells to water local strawberry crops

• Peatlands / wetlands become vulnerable to burning once there dry out - leading to a positive feedbakc system

Environmental impacts of dorught - amazon basin

• Severe droghts in 2005 and 2010 and the forest temporarily became a carbon source - could increase into the futre

• Forest die back because tree no longer has benighted water to phtotosntheses - dead plants released co2 storage back inot th atmosphere by decomposition

• Fear of reaching tipping point - if we lose 20. 25 % of the canopy the biological pump could collapse

• Would alter gloabl climate and water patterns as the forest would beocme a savanna

Floods - uk summer flood 2007

• Huge increase in overland flwo as the soil was satritrated and infiltration capacity is 0 due to a saturated basin

• In York 55,00 properties inundated and 13 peopl died

• My the water treatment works was a c trivial failure - leaving n 350,000 people without running water fro 17 days

• Significant nitrate run off form agricultural land - eutrophication

Pakistan 2022 - flood

• double threat due to climate change and monsoon rainfall

• Monsoon rains 7.8x the 30 year average

• And heat wave which hugely accelerated the himialeyn glacial melt water

• 17 death,

• 2 million acres of cropland destroyed

• 5000km of roads destroyed - economic totals damaged 30 billion

• Long term affects - extreme saltation intrusion to thousands of km of irrigation channels - increase food security

New Orleans 2005

• large volumes of rainflal form hurricane Katrina

• But main cause of flood due to the mismanagement of hard engineering strategies

• Levey system desinegd to protected the city was breached - this then reduced the degree to which water could return rapidly to teh river channel - keeping flood water in place

Durna 2023

• strucutural anginneirng fail

• Storm Daniel (hurricane)

• Tow of the aging dams collapsed sending a massive surge of a water inot teh town (30 million m3)

Impact of climate change on the water cycel - Tibet

• since the 1970s the temperature in the Himalayas have risen by very 1 degree creating 2000 glacial lakes

• Which are held back by unsustainable moraine dams - so lakes are starting to over flow

• In long term rivers such as indus and Ganges will see a permanent 30 - 40% reduction

California snow pack failure - case study

• si a the worlds 5th largest economy - the supply of water helped this

• Usually teh Sierra Nevada mountain store water as snow an release it very slowly over the year

• Climate change is turning sow inot rain so water runs off immediately overwhelming reservoirs and leave the state dry by July

Artic

• artic amplification

• Normally frozen water provides a white surface which increases the albedo affect - meaning solar radiant is reflected

• As the ice starts to thaw more dark surfaces so more absorption

• leading global implications

Water insecurity - water stress

• less than 1700m3 per person

Water scarcity

• when there’s less then 1000m3 per person

Physical scarcity - Saudi Arabia

• Surface water is 0

• So hugely expensive desalination plants

• But do ave an abundant fossil fuel supply so have the enegy to power these desalination plants

Econcomic scarcity - DRC

• Lies along 0 latitude whihc is along the inter tropical convergence zone

• So hihg levels of conventional rain fall and high water reserves but Less than 50% have access to clean water

• Because they lack money, government and pipes

Contamination of water in china

• 1/3 of all river water in china is considered unfit for human contact

• And 80% of shallow groundwater is contaminated by heavy metals and chemical run off sue to huge manufacturing industry

• E.g Huai river - disharge is so toxic its created cancer villages

Consequences of water insecurity - cost of water

• In denamer wat3er costs $9 per cubic meter becuase they use that revenue to put n annual investment into infrastructure and forces people to value every single drop

• USA - subsidise large volumes of water for certain sectors - the government provides approx $37 billion for agricultural sector

• In Cuba water is considered a right costing $0.004 per month but this means very title money into infrascure - 50% of water in Cuba pipes leaks out before it reaches a home

• Privatisation of water - Bolivia 1999 water wars, the private firm that owned the water increased prices by 35% overnight and so water for any costed 20% of their monthly income

• In Tanzania - 2003 - after the world bank invovlent