Topic 12: Water Quality

Question 1

Most prevalent water-quality problem

Answer 1

Eutrophication (due to phosphorus and nitrogen)

Question 2

Most serious water-quality problem globally

Answer 2

> 80% of sewage in developing countries is discharged untreated into water bodies

Question 3

Economic analysis (economic perspective: private)

Answer 3

Costs of preventing salinity by perennial vegetation outweigh the avoided costs of salinity

Question 4

Economic analysis (economic perspective: public)

Answer 4

Some impacts are off-farm (external costs)

Water, infrastructure, environment

Including external benefits raises the marginal benefit curve

Difference made to optimal level of abatement depends on magnitudes of external benefits and private costs

If external benefits internalised -> optimal abatement +ve but low

Question 5

Typical time lags for water quality projects

Answer 5

Project implementation: 3-10 years

Behaviour change: 5-20 years

Physical change: 1-100+ years

Biological change: 5-50 years

Delay in onset: 0-50 years

Question 6

Delay in onset- salinity

Answer 6

Impacts only occur after groundwater has risen sufficiently

Can take decades

If project fully implemented today, doesnt prevent any damage for 40+ years

Question 7

Physical change

Answer 7

If project implemented today, takes decades for benefits to emerge