Download - Water Resources
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Water Resources
Lecture 8
Integrated Catchment Management
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Integrated Catchment Management
• Until now, water resources have been considered as separate components:– The river ecosystem (longitudinal)– Wetlands– Impoundments (reservoirs)
• ICM: A systems approach to water resources management.
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A Systems Approach:
• In the 1950s and 50 – environmental problems were managed reactively – focus on point sources. – Curing the symptom and not the cause
• Subsequent Approach: the environment is a complex system, or web of interactions. Each component can only be managed in the context of the whole system
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Integrated Environmental Management
• The management of the environmental system as a whole.
• Integrated:– Integrated Assessment– Integrated Management
• Integrated: – Considering the whole as greater than the sum
of the parts.
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The Catchment: a fundamental environmental system unit
• The hydrological system unit:– Wetlands, the river channel, groundwater, soil water, surface
runoff.• The geomorphic system unit (Chorley, 1969)
– Topographic, hydraulic processes. • Terrestrial ecological system unit (Montgomery et al
1995)• Land-use and community functioning (Grobicki 1999).All of the above interact within a river catchment to form
a unique, process oriented entity. A whole.
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Davis, 1899
• Although the river and hill-side waste sheet do not resemble each other at first site, they are only the extreme members of a continuous series, and when this generalisation is appreciated, one may fairly extend the “river” all over its basin and up to its very divides. Ordinarily treated, the river is like the veins of a leaf, broadly viewed, it is like the entire leaf.
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CONTINUUM
• The catchment forms a continuum of environmental process which operate together to form a functional unit
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Defining “Environment”
• ICM considers the environment in its broadest sense:– The biophysical environment– The social environment– The economic environment
• ICM operates on the principles of sustainable development
• Society and the environment form a highly interdependent cycle of interactions
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ICM: The Definition
• ICM represents a systems approach to the management of natural resources, in particular water resources within the catchment area of a single river system. ICM recognises the need to integrate all environmental, economic and social issues within a river basin into an overall management philosophy, process and plan. (DWA and WRC, 1996)
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Moral of the story:
• It is pointless trying to manage for a high quality water resource without at least taking into account all the system components that can directly or indirectly impact on the resource.
• Manage for the whole• Manage cooperatively between sectors • ICM as the starting point for a common vision,
and a common purpose
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Differentiate between
• Integrated Water Resources Management– Not confined to a catchment
• Integrated Catchment Management– The utilisation and protection of all water resources, as
an outcome of catchment management• Catchment Management
– The utilisation and protection of the water resource only.
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Phenomena within a catchment that can degrade the water
resource• Urbanisation• Industrialisation• Alien invasion• Afforestation• Agriculture• Unsustainable rangeland farmingAnd many more
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The urban environment
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Urbanisation
• Catchment Hardening – unnatural flow regimes: what effect does this have on
the river?• Canalisation
– Biologically sterile• Pollution:
– Non point source: roads, litter, air, poor sanitation– Point Source: Sewage outfalls, sewage effluent,
construction sites, industrial outflow, garbage dumps, informal settlements
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Urbanisation
• Informal Settlements• Planting of alien vegetation on river banks
– Desynchronising of organic inputs• Drainage and invasion of wetlands• Building on floodplains with resultant
problems (eg – Dykes/levees)• Abstraction of water from rivers or
groundwater for consumption.
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Alien plant invasion
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Percentage Alien Plant Cover
From Versveld et al, 1998
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Density Distribution – alien invasives
From Versveld et al, 1998
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Water Use: % MAR
From Versveld et al, 1998
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From Versveld et al, 1998
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Photo: Rowntree 2000
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Photo: Rowntree 2000
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Impacts of terrestrial alien invasives
• Reduced MAR• Reduced soil-moisture and water table• Reduced baseflow, but increased flooding• Reduced protection of topsoil and increased incision,
donga erosion and rill erosion. • Riparian invasion interrupts river flow, inducing
flooding.• Riparian invasion destabilises channel banks – unstable
channel processes.• Increased in-channel debris