Risk Management/Agricultural Water Pollution Management

Surface runoff: The hydrological dilemma edit

Surface runoff increases disproportionally to rainfall.

Artificial surface waters edit


  • artificial
  • drainage channels
  • channelized
  • cleared

Differences to natural surface waters:

  • lower plant density
  • higher flow velocity / lower retention time
  • higher flood potential (in downstream regions)
  • reduced self purification

Surface waters do not fulfil their full range of ecosystem services to humans and society!

Constructed Wetland (CW) edit

Characteristics edit

  • artificial wetland containing vegetation
  • created for treating anthropogenic
    • discharge (municipal or industrial wastewater)
    • storm-water runoff (urban or agriculture)
  • decrease of flow velocity / longer residence time
  • higher sedimentation rate
  • higher metabolisation rates: photodegradation and microbial processes
  • integration of nutrients in biomass
  • adsorption of chemicals to organic surfaces (e.g., plants or sediment)

Important factors edit

  • size
  • flow length
  • hydraulic loading rate
  • hydraulic retention time

Retention edit

The retention of a chemical or suspended solids can be calculated:





Study: a real constructed wetland edit

Study Concept edit

  • Application of Azinphos-methyl (AZP) to orchards
  • Measurement of AZP at inlet and outlet before and after application events
  • Calculation of AZP retention

Results edit

  • 90% AZP retention in the CW
  • Sorption of AZP to aquatic macrophytes
  • Retention of > 90% of measured insecticide substances observed
  • Sorption of AZP to aquatic macrophytes

Conclusion edit

Constructed wetlands are a good option for agricultural water management

  • A case study showed that pesticide retentions ≥ 90% are possible within a CW
  • Mortality of aquatic invertebrates was 90% lower at concentrations measured at the CW outlet compared to concentrations measured at the inlet
  • Plants play an important role in the retention of pesticides as shown in a meta analysis of literature data