Water conflicts Flashcards
Threats to California through precipitation
- Much of it is arid, with an annual rainfall of between 200-500mm
- 65% of the precipitation is lost through evaporation and transpiration while 13% flows out to sea leaving only 22% as runoff for human consumption
- 50% of California’s rain falls between November and March- leading to seasonal shortages
Threats to California through population
- California’s population has grown from only 2 million in 1900, to 10 million by 1950 and 37.7 million by 2007. It is likely to reach 45-50 million by 2025.
- There is also a spatial imbalance. Three quarters of the demand for water comes from the heavily populated areas. While 75% falls of north.
- The increasing demands for water exceeds California’s natural water supplies.
What have been the impacts on the natural environment after California’s 2000-2007 drought
- Wetlands have been drained, natural habitats altered, and fish stocks depleted, to secure water supplies.
- Additional problems are polluted waterways, the over-extraction of groundwater and increasing salinity.
- The Bay-Delta region and the Salton Sea have become environmental disaster zones, and the once mighty Colorado River has been reduced to little more than a trickle as it enters the Gulf of California.
What is the SWP
State water project
What is the CVP
Central Valley project
What do the SWP and CVP do
Provide water from the sacremento San Joaquin river delta for central and southern california
How much of southern californias water does the colorado river provide and how
60% and via a system of dams and aqueducts
How much more water does california take from the Colorado than it envisaged in 1963
20%
Where does surface runoff occur
Over impermeable, saturated or baked surfaces-eventually reaching river channels as streamflow
How does surface water become groundwater
Some surface water infliltrates through the surface layer and eventually percolates through the rocks to become groundwater
Where does California gain 1/3 of its fresh water from
Ground water surfaces known as aquifers
The Sacramento river and the San Joaquin river provide huge volumes of water for what?
Urban and agricultural use
What are most of the major rivers in california fed by
Snowmelt from the Sierra Nevada Mountains
What does the high pressure system cause for California
A high-pressure system over the pacific ocean blocks moist air currents from reaching southern california. Occasional shifts in the system allow storms and heavy rain to reach the area.
What does El nino cause for california
Brings above-average runoff and flooding to the south west, while la nina events bring drought
What in recent years have extended droughts meant
The groundwater and surface storage levels have decreased.
How much of the USA does the colorado river basin drain
7%
What does californias water mainly go to
The needs to its growing population-with its affluent, water-heavy lifestyle- also the needs of agriculture for irrigation
How much of colorados total flow does Mexico take
10%
How much of colorados total flow do states in the lower basin take
50%
How much more of the colarado’s water does california take now than its original 1963 allocation
20%
How much are native americans owed of the colarado
5% but could claim more as their reservations extend along the river and two of its tributaries
What did the colorado compact (1922) do
Divided the river into two basins-upper and lower
California has been given until 2016 to reduce the amount it extracts by
20%
What are some methods of saving water
- Domestic conservation: 30% savings by repairing leaks. 50% drought tolerant plants
- Groundwater plants: Saving storm water for release during dry periods
- Re-using waste water
- Saving storm water
- Reducing agricultural water usage: currently use 80% california’s clean water. 10% reduction would double amount available in urban areas
- Smart planning: Only new housing where enough supplies of water
What are the environmental issues surrounding the sacramento river delta
- Old poorly maintained, man-made levees and river banks alongside it have allowed salty water to submerge some of the islands and reduce water quality for all users and habitats.
- Several species of fish are on the endangered list-salmon migrant paths are blocked at Stockton on san joa river when fresh water O2 levels too low. SWP pumps also suck in a lot of fish so are turned off 3/4 times a year to allow stocks to recover.
- Chlorine is released into the waters from water treatment work and the build up of trihalomethanes as a result (which cause cancers), mean that safe water supplies cannot be guaranteed
What does CALFED aim to do
Aims to reduce conflicts by developing a sustainable, long-term solution to water management and environmental problems.
- levee restoration
- increased water storage
- improved water conveyance
- Maintained oxygen levels
What is the salton sea
An agricultural sump - it acts as a receiving basin for runoff from irrigated farmland. It formed when canal banks collapsed in 1905, allowing the colorado river to fill a natural hollow with water. Creating a large lake which became a wildlife refuge. Attracting lots of wildlife and over half million tourists/yr
What are the possible threats to the salton sea
- 75% of its inflow is from cotton, citrus and sugar beet farms in the Imperial and Coachella valleys - with a toxic mix of pesticides, fertilizes, defoliants and nutrients.
- High evaporation rates mean that the salt content here is 25% higher than in the pacific ocean.
- High salinity, algal blooms and eutrophication are thought to have caused the death of millions of birds and fish (7.5mil fish died in 1 day)
- The new river brings industrial pollutants and sewage to from mexicali in mexico
- The lands of the Cahuilla tribe are at risk from the de-oxygenated and poor quality water, also decreased fish stocks.
- Tourists have stopped visiting because of the high salt content, the stench of decay and perception that it is a toxic waste dump.
Issue of farmers efficiency and the salton sea
As farmers become water efficient there is less runoff into the salton sea, however, this means that the pesticides, fertiliser etc are more concentrated.
