5.5

• Furrow irrigation: trench dug along crops and filled with water

  • easy & inexpensive; water seeps into soil slowly
  • 66% efficient, 33% lost to runoff and evaporation
• Flood irrigation: flooding the entire field

  • easy, but disruptive to crops
  • can waterlog the soil and drown plants
  • 80% efficient, 20% to runoff/evaporation
• Spray irrigation:

  • ground water or surface water pumped into spray nozzles
  • more efficient than flood or furrow
  • more expensive, requires energy for pumps and sprinklers
• Drip irrigation: holes in hose allow water to slowly drip out

  • most efficient but also more expensive
  • over 95% irrigation
  • avoids waterlogging & conserves waters
• Water logging: overwatering can saturate the soil, filling all soil pores with water

  • depletes oxygen
  • can stunt growth

  Solution: drip irrigation or soil aeration
• Soil salinization: process of salt buildup in in soil

  • caused by excessive groundwater use
  • dehydrates soil

  Solution: drip irrigation, soil aeration, flushing with fresh water, switch to freshwater source
• Human water use:

  • Industrial: power plants, metal/plastic manufacturing
  • Municipal: household uses
  • Agriculture: water for livestock, irrigation water
• Groundwater: water stored in pore space of permeable rock and sediment layers
• Aquifers: usable groundwater deposits for humans

  • replenished by groundwater recharge (rain water percolation)
  • unconfined aquifers recharge quickly
  • confined aquifers are longer-term water deposits the recharge more slowly
• Depletion of aquifers:

  • Cone of depression: forms when water table is lowered by excessive pumping, depleting water and drying nearby wells
  • Saltwater intrusion: excessive pumping near coast lowers water table pressure, allowing saltwater to to seep into groundwater