5.5 - Irrigation

Question 1

4 Types of Irrigation

Answer 1

Furrow Irrigation
- Trench dug along crops & filled with water
- Easy & inexpensive; water seeps into soil slowly
- ~66% efficient, 33% lost to runoff & evap.

Drip Irrigation
- Most efficient, but also most costly
- Over 95% efficient
- Holes in hose allow water to slowly drip out
- Avoids waterlogging & conserves waters

Flood Irrigation
- Flood entire field; easier but more disruptive to plants
- Can waterlog the soil & drown plants
- 80% efficient - 20% runoff/evap.

Spray Irrigation
- Ground or surface water pumped into spray nozzles
- More efficient (less water loss) than flood or furrow
- More expensive (requires energy for pumps & movement of sprinklers

Question 2

Waterlogging

Answer 2

• Overwatering can saturate the soil, filling all soil pore space with water
• Doesn’t allow air into pores, so roots can’t take in O2 they need
• Can stunt growth or kill crops

Solution
- drip irrigation, or soil aeration - poking holes or cores in soil to allow air in & water to drain through soil

Question 3

Soil Salinzation

Answer 3

• Salinization is the process of salt building up in a soil over time
• Groundwater used for irrigation naturally has small amounts of salt
  - Water evaporates, and salt is left behind in soil. Over time, it can reach toxic levels, dehydrating plant roots & preventing growth

Solution - drip irrigation, soil aeration, flushing with fresh water, switch to freshwater source

Question 4

Global Human Water Use

Answer 4

Industrial - power plants, metal/plastic manufacturing
Municipal - households (toilet, shower, drinking water)
Agriculture - water for livestock, irrigation water for crops

Question 5

Aquifers and Groundwater

Answer 5

• Groundwater - H2O stored in pore space of permeable rock & sediment layers
• Aquifers - useable groundwater deposits for humans
• Replenished by groundwater recharge (rain water percolating down through soil into aquifer)
• Unconfined aquifers recharge quickly
• Confined aquifers recharge are longer-term water deposits that recharge more slowly

Question 6

Depletion of Aquifers

Answer 6

• Saltwater Intrusion - excessive pumping near coast lowers water table pressure, allowing saltwater to seep into groundwater
• Cone of Depression - forms when water table is lowered by excessive pumping, depleting water & drying nearby wells