Lecture 3

• Groundwater: water beneath Earth's surface

  • stored in acquifers: geological formations that contain pore spaces in soil and fractures in bedrock - only accessible by drilling/pumping from a well
• Freshwater: Surface water

  • snow and land ice e.g. glaciers, ice sheets, ice caps
  • lakes, ponds, wetlands, rivers, streams
• Freshwater: renewable resource that is replenished by the hydrological cycle
• Watershed/Catchment/Basin: a land area that channels rainfall and snowmelt to creeks, streams and rivers, and eventually to outflow points such as reservoirs, bays and the ocean
• Metro Vancouver Water supply: surface water from 3 watersheds; Capilano, Seymour and Coquitlam
• Importance of winter snowpack:

  • storage of water
  • helps in the prediction of trends in water supply
  • water used for drinking, lowers risk of forest fires at higher elevations
• Why is there a planetary boundary for freshwater:

  • water is being used at a faster pace than it is being replenished
  • natural fluctuations also exist
• Global Freshwater Movements:

  • droughts
  • increased rainfall
  • melting of ice caps into the ocean
  • water from acquifers used for irrigation of crops
  • evaporation
• Blue water: freshwater available for human use (rivers, lakes, reservoirs and renewable groundwater stores)
• Green water: freshwater available for ecological functions (includes terrestrial precipitation, evaporation and soil moisture)
• Green water relationships - Slide 28 diagram
• Root-zone soil moisture: water that is available to plants - usually upper 200cm of soil
• Impact of human activities on root zone soil moisture:

  Directly: - agricultural intensification

  - agricultural expansion

  - urbanisation

  Indirectly: - precipitation and evaporations changes caused by anthropogenic climate change, land system change and water use
• Why is root-zone soil moisture important?

  • transpiration - plants take up that water to release it
  • biomass production - plant growth
  • soil moisture drought - lack of adequate water for plant uptake
• Tipping point: Amplifying Feedback Cycle

  Tree loss - less evaporation - decreased rainfall - longer dry season - less humidity - more fires - Tree loss