California

• California = western state of U.S.A and faces severe droughts = depleted snowpacks, rivers and lakes hence increase in groundwater use to makeup for shortfall
• Stanford Uni: nearly 60% state's water need met by groundwater (increase of 40% when rainfall was normal)
• Climate: mostly dry for almost 1/2 the year - relies on rain and snow in winter months to carry it through the year
• Precipitation:

  • 200-500 mm annual precipitation hence it is arid
  • Rainfall only 10% what it should be
  • 65% rainfall lost through evaporation/transpiration
  • 13% flows out to sea
  • 22% for human use
  • 50% falls between November and March so there are seasonal shortages
  • 4 years below average rainfall
• Mountain ranges:

  • Run on coast hence stop moist air reaching inland. Prevailing wind from Pacific Ocean forced up by mountains so cools and condenses causing relief rainfall (snowfall at high altitudes)
  • South and far East of California e.g Death Valley and Mojave dessert receive < 100 mm of rain caused by rainfall shadow effect due to coastal ranges and Sierra Nevada mountains
• Weather systems:

  • La Nina events bring drought to South East
  • Recently: extended droughts = ground water and surface storage decrease
• Population:

  • Growth: 2 mn [1900] to 37.7 mn [2007]
  • Spatial imbalance: 3/4 of water demand from hugely populated areas e.g Sacramento in South California but 75% of rainfall falls in North California
  • Increasing demand exceeds supply. San Luis Reservoir in July 2007 decrease to 20.8% of its capacity and decrease 62 m from normal level. Supplies water to South California central valley and Silicon Valley
• Political impacts:

  • Increased tensions between different water users e.g farmers vs. urban residents vs. Native Americans
  • Challenged existing water policies and institutions
• Environmental impacts:

  • Raised awareness and urgency of addressing climate change
  • Wetlands drained so natural habitats altered and fish stocks depleted in order to secure water supplies
  • Polluted water supplies., overabstraction of groundwater and increasing salinity can cause hypoxia
  • Bay Delta Region and Salton Sea = environmental disasters e.g huge Colorado river reduced to a trickle entering Gulf of California
  • Fires - vegetation becomes very dry and intense hear e.g lightning can set it alight easily
• Social Impacts:

  • Increase in vector-borne disease e.g West Nile Virus
  • Arid = dusty = increase in respiratory disease
  • Lack of food due to insufficient water
  • Loss of jobs in agriculture (direct and indirect) = increase unemployment
• Economic Impacts:

  • Less income as less food ( less spending )
  • Less exports
  • 2021 drought: cost agriculture sector $1.1 bn
  • Compared to 2019, statewide crops ( irrigated ) dropped by 563,000 acres [2021]
• Wetlands drained
• System of dams and aquaducts are used to supply 60% of water to southern California
• $92 mn distributed to California communities in 26 different countries for drought-related projects
• Groundwater recharge, stormwater capture and reservoir storage to reduce impact of droughts ( management strategy )
• Gavin Newsom (governor) signed package of climate action bills which included $5.2 bn for drought response and long-term water resilience
• Californians allowed to and encouraged to voluntarily reduce water use by 15%
• Fund solutions for disadvantaged communities who lack access to safe drinking water
• Increasing frequency of water use reporting
• Outlined by Gavin Newsom in 'California's water supply strategy adapting to a hotter, drier future' : investing in new sources of water supply, modernizing management of water through new technology and accelerating projects
• Convened Interagency Taskforce (Management)

  • Many agencies to prepare for drought. Helps state quickly protect communities, economic activity and natural environment.

  Includes the following departments:

  • California Department of food and agriculture
  • California Environmental Protection Agency
  • Governor's office of Emergency Services
  • California Health and Human Services Agency
  • Governor's office of Planning and Research
  • Governor's office of Business and Economic Development
• Mountain Ranges = Origins of Existing Supply

  • Increase surface run off as gradient is greater
  • Impermeable surface (baked hard in hot sun)
  • River system hence has an increased amount of water during seasons when there is high precipitation
• Aquifers = Origins of Existing Supply

  • Surface run off infiltrates through hard impermeable surfaces and percolates through groundwater supply
  • Nearly 1/3 of water comes from aquifers
• Melting snow = Origins of Existing Supply

  • Most river systems fed from snowmelt from Sierra Nevada Mountains
  • Sacramento River flows southward meeting the north flowing San Joaquin River at San Francisco Bay
  • Huge volumes of water that these two rivers produce feeds the agriculture and urban population (note that this can have reduced flow)