HYDROLOGY AND ECOLOGY. HYDROLOGY WATER QUALITY HYDRAULICS GEOMORPHOLOGY ECOLOGY SOCIO/ECONOMICS RESEARCHTEACHINGPOLICYCONSULTANCY VERTICAL INTEGRATION.

HYDROLOGY AND ECOLOGY

HYDROLOGY

WATER QUALITY

HYDRAULICS

GEOMORPHOLOGY

ECOLOGY

SOCIO/ECONOMICS

RESEARCH TEACHING POLICYCONSULTANCY

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HORIZONTAL INTEGRATION

CATCHMENT PROCESSES: rainfall, evaporation, runoff infiltration, erosion Hydrology production, decomposition etc. Water quality Geomorphology Hydraulics Instream habitats Instream biota

The process used for assessing the water quantity aspects of the ecological Reserve for rivers

Relating Biota to Hydrology

THE FLOW STRESSOR RESPONSE METHOD

A Generic Stress Index

• An index of 0 to 10 where 0 indicates no stress, and 10 the highest level of stress

• Stressors: Flow-related hydraulics and habitat• Biological responses: Reduced abundance (1 to 3),

increasing risk to critical life stages (4 to 6), and disappearance of populations (7 to 10)

• Flow-related hydraulics: Velocity, depth and wetted perimeter

• Habitat: Quantity and quality (the diversity and connectivity of habitat types)

Stress

% Duration

Natural (A)

Inc. Flow (C)

Decreased Flow (C)

Assessing increased and decreased stress

The process for applying the FS/R method

• Select a site, survey and model hydraulic characteristics

• Specialists apply the stress index to the site, in relation to selected species/groups, to develop stress curves

• The hydrologist converts the resulting critical stress curve to stress time series for flow scenarios

• Analyse the stress profile of each scenario in terms of the magnitude, frequency and duration of different stresses

• Assess the severity of each stress profile in relation to the natural stress profile

AN EXAMPLE OF A SITE SPECIFIC STRESS INDEX FOR INVERTEBRATES

Flowrate

(m33/s)

Stress Response

4 0 Average velocities > 0.6 m/s, and average depth > 0.4m provides abundant fastdeep and fast shallow habitat for rheophilic species (such as simuliids andhydropsydhids.

3.8 1 Average velocity 0.61 m/s, average depth still > 0.4m. Abundance of criticalhabitats is slightly reduced, but all species are still abundant.

0.3 3 Average velocity 0.2 m/s (therefore maximum velocity approximately 0.4 to 0.5m/s). Average depth 0.17m, maximum 0.4m. Still some critical habitat, butrheophilic species abundance much reduced.

0.13 5 Average velocity 0.12 m/s (therefore maximum velocity 0.2 to 0.3 m/s). Averagedepth 0.14m, maximum 0.34m. Wetted perimeter 9m - marginal vegetationhabitats only just in the water. Rheophilic species confined to very small areas,egg and early larval stage probably non-viable.

0.03 7 Average velocity 0.05 m/s (maximum approximately 0.1 m/s). Average depth0.12m, maximum depth 0.28m. Wetted perimeter 6.4m, no longer in marginalhabitats. Loss of all critical flowing habitat, only remnant areas for short-termsurvival of hardy rheophilic species.

0.01 8 Average velocity 0.01 m/s, only slow trickles and standing water habitats remain.All rheophilic species will disappear if this flow condition persists.

0 9 Standing water only

Note: Stresses of 2, 4 and 6 have not been specifically motivated, and are simply extrapolations of theadjacent stress motivations.

0.001

0.01

0.1

1

10

100

0 2 4 6 8 10 S tress

Barbus Cpre Inv Rip Veg Total

B lyde R iver

Black = Natural, Red = Recommended, Blue = Present day

Blyde River spell analysis (Stress = 1.5)White = natural, Red = recommended, Blue = Present day

EXAMPLE OBJECTIVES(e.g. to maintain Category B)

• Maintain perennial flow • Summer flows > winter flows• Av. velocity > 0.1 m/s at all times for target fish (stress never > 6)• Sufficient depth (30 cm) to allow target fish to feed and breed 85%

of time in summer (stress < 1 for 42.5% of time)• Av. velocity > 0.3 m/sec for 80% of time, to ensure Trichoptera

habitat (stress < 3 for 80% of time)• Wetted perimeter in reeds for 60% of summer to provide marginal

habitats (stress < 0.8 for 30% of time)

10

8

6

4

2

0

Stress

% Time Exceeded

0 10 20 30 40 50 60 70 80 90 100

Inverts:Stress <380% time

Fish:Stress <1

42.5 % time Riparian veg:Stress <0.830% time

Fish:Stress never >6

Application of objectives to define ecological category B

10

8

6

4

2

0

Stress

% Time Exceeded

0 10 20 30 40 50 60 70 80 90 100

B

Inverts:Stress <380% time

Fish:Stress <1

42.5 % time Riparian veg:Stress <0.830% time

Fish:Stress never >6

Application of objectives to define ecological category B

10

8

6

4

2

0

Stress

% Time Exceeded

0 10 20 30 40 50 60 70 80 90 100

D

CB

Inverts:Stress <380% time

Fish:Stress <1

42.5 % time Riparian veg:Stress <0.830% time

Fish:Stress never >6

Application of objectives to define ecological category B

Thukela IFR4 Based on dry season flows  

B B/C

Ecological Reserve procedures

PHABSIM

DRIFTDatabase

DRIFT

Flow StressorResponse

Classification and objectives

Referenceconditions

PresentEcological

State

EcologicalImportance

andSensitivity