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 farming And 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
