Transcript ENVIRONMENTAL FLOWS

WATER QUALITY IN THE
EFA PROCESS
Jay O’Keeffe,
UNESCO-IHE Institute for Water
Education
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WATER QUALITY
• Efficient functioning of river ecosystems
requires provision of suitable hydrological
regime and water of suitable quality
• 2 aspects of water quality:
– How will modified flow regimes affect water
quality? (Incorporate in env. flow recommendations)
– What have human activities in the catchment done to
modify the present water quality from natural
conditions? (Rehabilitation measures at source)
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WATER QUALITY IN THE BBM
METHODOLOGY
• Key questions:
– Impact of flow on water quality
– Impact of water quality on riverine biota
• Difficulties in assessment of water quality
aspects in BBM
– Sporadic data availability
– Water quality models often not available
– Biota response affected by a range of synergistic and
antagonistic effects, rate of concentration change
and acclimation
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Water quality variables
• Required:
– Physical and chemical water quality conditions
– How these conditions change seasonally / yearly
– Similar data in non-impacted state
• System variables: pH, Temp, O2
• Non-toxic constituents: EC/TDS, TSS, cations (NA, K,
Ca, Mg) and anions (SO4, Si, alkalinity)
• Nutrients: total P, total N, NO3, NH4, NH3, NO2, TOC
• Toxic constituents: metals, pesticides, other
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PROTOCOL FOR INCORPORATING
WATER QUALITY IN EFA
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Preparation for the workshop
Identify broad climatic region and ecoregion
Take note of geomorphological reaches
Identify significant hydrological features
Delineate reaches / segments with expected
similar water quality
• Establish reference / natural conditions
– System variables, nutrients, toxic chemicals
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PROTOCOL FOR INCORPORATING
WATER QUALITY IN EFA (cont.)
• Preparation for the workshop (cont.)
• Determine present water quality status
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Use water chemistry data
Identify likely threats (sources of contaminants)
List potential point sources of contamination
Identify major land use areas
• Assess the data (completeness of data)
• Prepare the report
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PROTOCOL FOR INCORPORATING
WATER QUALITY IN EFA (cont.)
• Roles and responsibilities (at workshop):
• In absence of water quality modeling, make
predictions with regard to effect of flow changes
on water quality
– Based on examination of cross-sections and
hydraulic characteristics
• Advise on flows that should maintain required
EMC
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MINIMUM DATA SET
• Seasonal (three-monthly) water chemistry and
biomonitoring data over complete annual cycle
• If data not exist:
– Make extrapolation from adjacent and comparable
river reach, or
– Derive data from reference site
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CONCLUSIONS
• For aquatic ecosystems to function adequately,
not only appropriate flows of water, but also of
suitable quality are required
• Assessment of water quality requirements for
riverine ecosystems entails considerable degree
of subjectivity
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