5.5: Irrigation Methods

Question 1

Largest human use of freshwater

Answer 1

Irrigation (70%)

Question 2

Types of Irrigation

Answer 2

Furrow, flood, drip, spray

Question 3

Definition, efficiency, pros and cons

Furrow Irrigation

Answer 3

• Trench is dug along crops and filled with water
• It’s 66% efficient meaning 33% is lost to evaporation and runoff
• It’s easy and inexpensive, high sediment water can be used and it allows for some precision
• It is not efficient on sandy soil, it can cause soil erosion

Question 4

Flood irrigation

Answer 4

• Water is diverted from surface water or pumped from groundwater and used to flood fields
• It is 80% efficient
• It’s easy and inexpensive, there’s no mechanization required
• This method is not for all plant types and runs the risk of waterlogging and salinization

Question 5

Drip Irrigation

Answer 5

• Holes in a hose or pipe allow water to sloly drip out
• 95% efficient
• Avoids waterlogging, reduces nutrient leaching, and it conserves water
• Most costly, hose/pipe clogs easily, requires mechanization

Question 6

Spray Irrigation

Answer 6

• Ground and surface water is pumped through spray nozzles
• It’s more efficient than flood and furrow irrigation with <25% lost
• It allows for precise application, you can add supplements and nutrients to the water and you can program it to go off at certain times
• More expensive, more mechanization, nozzles can clog

Question 7

What is waterlogging?

Answer 7

When too much water is left to sit in soil leaving the plant roots unable to get the oxygen they need for cellular respiration leading to the roots dying followed by the plants dying

Question 8

How can you fix waterlogging?

Answer 8

• Left the field dry out
• Add more sand to the soil
• Soil aeration
• Drip Irrigation

Question 9

What is salinization

Answer 9

• When ground and freshwater evaporates, the salt contained is left behind in the soil and overtime becomes toxic to the plants and inhibits their growth

Question 10

How to fix salinization?

Answer 10

Flush with water, drip irrigation, switch to freshwater, soil aeration

Question 11

Global Human water use?

Answer 11

• Industrial: power plants, metal manufacturing
• Municipal: toilet, shower, drinking water
• Ag: irrigation and water for livestock

Question 12

Groundwater

Answer 12

Water stored in the pore space of permeable rock and sediment layers

Question 13

Aquifers

Answer 13

Useable groundwater deposits. They can be unconfined and recharge quickly or confined and recharge slower by long-term deposits

Question 14

Saltwater intrusion

Answer 14

Excess pumping near coast lowers water table pressure allowing saltwater to seep into groundwater

Question 15

Cone of depression

Answer 15

When water table is lowered by excessive pumping, depleting water and drying nearby wells