Water Resources Management with a Focus on Agriculture, Water Footprint

Question 1

What is the use of freshwater?

Answer 1

• For almost all human activities freshwater is needed: recreational use, industrial use, power use, home use, agricultural use
• Only about 0,01% of global water resources is directly accessible freshwater!
  > Only a certain amount of water is available for all these uses at any one time
  > Agriculture uses 70% of global freshwater use, mostly for irrigation
• Freshwater resources distribution is characterised by:
  > Strong regional differences
  > Annual and seasonal variation
  Freshwater scarcity differs between
  regions.

Question 2

What is the use of water in agriculture?

Answer 2

• Agriculture: 70% of global water use, mostly for irrigation
• Crop water use is consumptive; but water losses by lack of efficiency are not necessarily lost (recharge, downstream use)

Question 3

Explain the globalisation of agricultural water use.

Answer 3

PRODUCTION of water-intensive goods

TRADE Local water consumption and pollution related to export

CONSUMPTION of water-intensive goods

Water saving, but also water dependency related to export

Question 4

How is water footprint of crop, animal and agricultural product calculated?

Answer 4

• Crops: crop water use per crop yield (m3/ton) (opposite of crop productivity)
  a. Calculate reference crop evapotranspiration, ET0
  b. Calculate crop evapotranspiration ETc = ETo * Kc
  (temp coefficient)
  c. Calculate crop water requirement = ETc over growing
  period (m3/ha)
• Animal: sum of water for feed, drinking and servicing
• Agricultural product: distribute water footprint of the
  base product over its derived products

Question 5

What is water footprint of crops?

Answer 5

• Water footprint = crop water use/ crop yield
• How much = volume of freshwater used to produce product summed over the production chain
• When and where water was used
• Types of water use:
  > Green: vol of rainwater evaporated
  > Blue: vol of freshwater (surface + GW) evaporated
  > Grey: vol of freshwater required to dilute polluted
  water to acceptable quality

Question 6

Which factors affect the water footprint of crops?

Answer 6

• Evapotranspiration depends on weather variables, temperature
• Type of crop - some crops require more water than others e.g. in Colorado River alfalfa uses 35% of total crop water use
• Water quality - if water contains ions/nutrients and is used for irrigation, salt accumulation can become a problem