California - Example of major water extraction

• California - Main Sources of Water:

  • The majority of California’s water supply comes from surface water.
  • 30% from groundwater aquifers.
  • Very small portion from desalinated sea water.
  • Six main, local, state and federal funded water systems manage and redistribute water from 10 drainage basins across California.
• California - Why does Water Stress occur:

  • The population growth has caused a spatial imbalance with 3/4 of water demand coming from hugely populated areas such as Sacramento in the south, whilst 75% of the precipitation is falling in the north. 
  • The increasing demand of water is currently exceeding the natural supply.
  • Groundwater demand rises to 60% in drought years, which puts huge stress on unsustainable where recharge sine 1999 has not kept pace with extraction.
• California - Climate links to water sources:

  • Mediterranean climate - seasonal winter and spring rainfall occurs due to the passage of depressions across the state.
  • This is sufficient to generate river systems that can flow throughout the year unless sustained droughts occur.
  • Snow melt = high surface flow, maintains river levels.
  • Climate change - more frequent and extensive droughts = reduced precipitation = need for higher levels of irrigation.
  • Reduced snowfall will cause rivers to drop and aquifers to not be replenished.
• California - Geology links to water sources:

  • Permeable rocks between the Sierra Nevada and the coast allow water to percolate into artesian reservoirs, which provides a source of water in dry summers.
  • Some areas are geologically unstable, so there is a risk of earthquakes and as such are not suitable for dams.
• California - Drainage links to water sources:

  • The Sierra Nevada mountain range to the east promotes relief rainfall, which drains west towards the Pacific Ocean giving ten major drainage basins supplying surface water.
• California - How is water supply being increased:

  • Catchment abstraction management strategy
  • Diversion
  • Storage
  • Water Transfers
  • Desalination
• California - Consumption management:

  • To prevent a full water crisis, water companies and governments are having to introduce new measures to conserve water:
  • Swapping grass for drought-tolerant plants reduces the demand for water during the long dry summer months.
  • Hosepipe bans and offering incentives to install water-efficient appliances, the rain garden initiative has helped reduce domestic water consumption by 12%.
• California - Impacts of consumption management on human welfare:

  • All California’s residents have seen their water bills rise significantly in part to fund new infrastructure to keep the water flowing. 
  • For those with lower incomes, water can account for more tha 10% of household income.
  • Prices of water have risen ten times.
  • Due to competition from cheaper food sources from China, farmers say they’re selling their crops at a loss.
• California - Water management:

  • Water management strategies are largely effective.
  • In wealthier areas, residents will still use large quantities of water in search of their 'perfect lawn' and do not follow advise of local organisations and governments.
  • Water supplies do not seem to be increasing.
  • Precipitation levels are not high enough and groundwater aquifers are not recharging as a direct result of this.
• California - Conflicts:

  • California shares the Colorado River with six other states and Mexico and the river is heavily regulated through compacts, federal laws, court decisions and international treaties.
  • As water availability decreases, tensions over water allocations increase and the need to renegotiate agreements to reflect the current state of the water can lead to conflicts.
  • There is often a direct conflict between environmental conservation efforts and economic interest, particularly in agricultural and development sectors.
• California - Environmental Impacts of the Water Supply:

  • Over-abstraction has led to the depletion of aquifers, water supply and land subsidence.
  • Diversion of water from rivers and streams reduces the natural flow required for aquatic ecosystems, leading to declining fish populations and reduced biodiversity.
  • Southern California especially, heavily relies on water transported from the Colorado River and Northern California, which experiences much higher levels of rainfall.
  • Makes them vulnerable to water shortages.
• California & The Oroville Dam - Location:

  • Lake Oroville lies east of the city of Oroville.
  • 112km north of Sacramento, California.
  • Built on the Feather River - a tributary of the Sacramento River.
• California & The Oroville Dam - Size:

  • It is the second-largest reservoir in the state.
  • 210m deep.
  • Can store 4.3 billion cubic metres of water.
  • 230m high.
• California & The Oroville Dam - Overview:

  • Built by the California Department of Water Resources and is one of the key features of the California State Water Project.
  • Built to provide water for arid Southern California.
  • Provides a major supply of water for irrigation in the San Joaquin Valley and municipal and industrial water supplies to coastal Southern California.
  • Prevented large amounts flood damage to the area.
• California & The Oroville Dam - Environmental Impacts (People):

  • Tens of thousands of people have had to leave their homes and set up elsewhere, and
  • Many people have not been given adequate compensation for their losses, and some were not given new places to live.
  • Existing communities are broken up and moved to different areas.
  • People who made their living from farming the land or fishing from the river, suffered when they were relocated, as they were not given new land to work on and were too far to fish.
  • They required new skills to get other jobs, for which training was not always provided.
• California & The Oroville Dam - Environmental Impacts (Plants & Animals):

  • Upstream of the dam, the river is flooded and becomes a reservoir.
  • The nature of the river flow downstream is changed.
  • The dam can hold back sediment that normally finds its way downstream.
  • A dam across a river can form a barrier to fish that migrate.
• California & The Oroville Dam - Environmental Impacts (Sedimentation):

  • When a river enters a reservoir, the speed of the flowing water slows down and sediment can be deposited on the reservoir bed.
  • The sediment in the reservoir can build up, and reduce the space available for storing water.
  • Too much sediment means the natural balance of the river downstream can be changed.
  • Farming land can be deprived of silt and its nutrients, which are important for fertilising the soil, which are normally deposited during floods.
• California & The Oroville Dam - Environmental Impacts (Water Quality):

  • River water contains dissolved oxygen, which is needed to maintain aquatic animal and plant life and to prevent some types of chemical reactions that form unwanted pollution in the water.
  • Organic material in the water can use up oxygen as it decomposes.
  • Pesticides from farmland and toxic materials from industrial land can pollute the water, as well as, streams and rivers flowing into the reservoir may be carrying pollutants.
• California & The Oroville Dam - Environmental Impacts (Historical Sites):

  • Many of the world’s archaeological sites and historial buildings and monuments can be found in areas close to river valleys, which can be of greate value to the local inhabitants. This may be lost in the event of the creation of a reservoir.