HYDROLOGY AND ECOLOGY

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

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)

StressStress  % 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

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)

Application of objectives to define ecological category B

Thukela IFR4 Based on dry season flows BB/C

Ecological Reserve procedures PHABSIM DRIFT Database DRIFT Flow Stressor Response Classification and objectives Reference conditions Present Ecological State Ecological Importance and Sensitivity