Unit 1 Mini Case Studies Flashcards
im never learning this
Five largest drainage basins
Amazon
Congo
Nile
Mississippi
Rio de la plata
How much of the Earth’s surface is made up of endorheic drainage basins
18% much of which is in central Asia (Caspian and Aral sea)
Name 3 famous aquifers
Great artesian basin
Edwards aquifer
Floridian aquifer
Example of an arcuate delta
Nile river
Example of a cuspate delta
Ebro delta
Example of a birds foot delta
Mississippi delta
UK isostatic rebound
Sea levels in the West of England reduced by up to 120 meters during the last ice age. This will have significantly changed to base level or rivers in this region
Colorado precipitation
According to Colorado’s National Centre for Atmospheric Research, there are over 150 weather modification programmes in 37 countries
Cloud seeding examples
Cloud seeding is inconclusive. In Australia, it has increased precipitation by 10-30% short term
China has invested in 40000 field operatives
Lake Nasser
Lake Nasser loses up to 1/3 of its water per year due to evaporation
UK water abstraction example
In the UK, the Environmental Agency is responsible for assessing the impact of activities with their Catchment Abstraction Management Strategy for a sustainable approach to water usage. Water abstraction laws in the UK are based on weather and climatic predictions and trends
Ica Valley irrigation example
The Ica Valley (desert area in Andes) is one of the driest places on Earth. The asparagus beds developed in the last decade require constant irrigation so the local water table has plummeted since 2002 when extraction overtook replenishment. 2 wells serving 18,500 people in the valley have dried up. Traditional small-medium scale farms have had water supplies severely diminished
Groundwater withdrawal on the Peruvian Coast
The rate of extraction for large commercial agriculture purposes is rapidly exceeding that of domestic and industrial use. Many locals are suffering from a lack of accessible water in neighbouring aquifers as large farms redirect the flow to ready their produce for export and profit. Agriculture consumes 50% of all water withdrawn. Little is left for small subsistence farming
Nevada mining example
In Nevada, the driest desert in the US, the Humboldt River is being drained to benefit gold mining along the Carlin Trend. Mines in the NE of the Nevada desert pumped out more than 580 billion gallons of water between 1986 and 2001
The Aral sea facts
4th largest lake in the world spanning 68000km^2
Shrinking since waters were first redirected by soviet irrigation in 1960
Catchment zone 500km away
Frequency and intensity of rainfall declined in last 30 years
Catchment was built from 1954-1960
5% of nearby reservoirs and over 50 lakes have dried up
In 2005, the world bank and Kazakhstan government built a 13km dam fro $85m
By 2008 it returned to 1960 levels
In 2005, the north Aral was subject to a $250m project to rejuvenate
UK flood warning
Over 50% of properties on floodplains in the UK get less than 6 hours notice of a flood
The three gorges dam
Length of 2335m
Height of 185m
Combined generator capacity of 22.5 million KWh
Annual energy output of over 100 billion KWh
Planning in 1955, building started in 1970, completed in 2008
Flood control capacity of 22.15 billion cubic meters
17 year build time
Cost $20 billion USD
Displaced over 1.2 million people
Cloud seeding in Idaho
Since 2017, a team from the NCAAR has been collecting and analysing data from the SNOWIE experiment. Many local farmers rely on melting snow from the mountains for irrigation. As demand for water rises, pressure is put on existing stores but by increasing winter snow, the balance for towns like Boise could stabilise
Natural flood management in the UK
In 2016, 500000 pound tree-planting projects helped Yorkshire towns miss winter floods. The ‘Slowing the Flow’ scheme saw 40000 trees planed, reduced peak river flow by 20% after 50mm of rain in 36 hours. Slow the flow included:
-construct soil embankments
-plant trees
-restore dams
-restore wetlands
It aims to increase interception and infiltration
Urbanisation in Texas
In the last 50 years, Houston’s population has doubled to 2.3 million. They have lost 10000ha of wetland and built 7000 homes on floodplains. Hurricane Harvey in 2017 gave many areas over 400mm of precipitation. Without the wetland, there was substantial flooding. Abstraction from the 3 main aquifers below the city has led to 10-25mm of subsidence per year
Deforestation in Sierra Leone
In August 2017, after an intense rain season, people were missing or dead when there was a mudslide in Babadorie River Valley and existing flooding in front of it. Freetown is particularly vulnerable to flooding and mudslides. As the capital has grown, the city has crept onto surrounding hills. The Central Highlands have been deforested.
Afforestation in Ireland
From just 1% forest cover in 1990 to 11% cover now while continuing to rise to its target 19%. The Sitka tree is planted which is a large, evergreen, coniferous tree but it has a damaging effect on local ecology. These trees have stiff, sharp, acidic needles. It only has a shallow root system. Can lead to increasing overland and river floods
Grand Ethiopian Renaissance Dam
Construction began in April 2011 and the reservoir was filled until 2020. The hydroelectricity will feed into the national grid and could export to Sudan. Increased evaporation rates and a rise in the surrounding water table. Concerns by Sudan and Egypt about local ecology but it will reduce flooding and prevent silt downstream however it could increase riverbank erosion
Ogallala aquifer in the USA
Covers 450000 kilometres squared underlying 8 states. Provides about 30% of the groundwater for irrigation in the US. Since the 1950’s water level have dropped by up to 150 feet in places. Low precipitation and high evaporation causes relatively slow recharge. It it was fully depleted it would take 6000 years to replenish
Kissimmee river restoration location
165 kilometres and once meandered though central Florida. Its floodplain is up to 5 km wide and was inundated by heavy seasonal rains
Why did the Kissimmee River get restored?
Between 1962 and 1971 engineering deepened, straightened and widened the river transforming it into a 90 km, 10m deep drainage canal. It was channelised to provide an outlet canal for draining floodwater from the upper lakes basin and to provide flood protection for adjacent land
Impacts of the Kissimmee river restoration
Loss of 2000-14000 hectares of wetland
90% reduction in wading bird and waterfowl usage
Continuing long-term decline in game fish populations
How was the Kissimmee river restored?
Concerns about the sustainability of ecosystems led to a state and federally supported restoration study. The result was a huge restoration project. It restored over 100 kilometres squared of river and floodplain wetlands. It was started in 1999 and completed in 2015. It benefits 320 fish and wildlife species including the endangered bald eagle, wood stark and snail kite. It has created over 11000 hectares of wetlands. Seasonal rains now inundate the floodplain in restored areas. Restoration required dechannelisation. This entailed backfilling about half of the flood-control channels and establishing the flow of water through the natural river channel. In residential areas, flood-control channels will remain
Costs of the Kissimmee river restoration
Estimated to cost over 400 million dollars of which 20 million was initial channelisation being shared by the state of Florida and the federal government
Benefits of the Kissimmee river restoration
Higher water levels should support and natural river ecosystem again
Re-establishment of floodplain wetlands and nutrient filtration is expected to result in decreased nutrient loads to Lake Okeechobee
Populations of avian species like wading birds and waterfowls have returned to the restored areas and numbers have more then tripled in some cases
Dissolved oxygen levels have doubled which are critical for the survival of aquatic species
Potential revenue from recreation and ecotourism could enhance local and regional economies
