water resources

Water Resources

Lecture 8

Integrated Catchment Management

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.

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

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.

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.

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.

CONTINUUM

• The catchment forms a continuum of environmental process which operate together to form a functional unit

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

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)

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

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.

Phenomena within a catchment that can degrade the water

resource• Urbanisation• Industrialisation• Alien invasion• Afforestation• Agriculture• Unsustainable rangeland farmingAnd many more

The urban environment

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

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.

Alien plant invasion

Percentage Alien Plant Cover

From Versveld et al, 1998

Density Distribution – alien invasives

From Versveld et al, 1998

Water Use: % MAR

From Versveld et al, 1998

From Versveld et al, 1998

Photo: Rowntree 2000

Photo: Rowntree 2000

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