120
4.4 Response Curves and Development Space
King and Brown (2010) introduce the concept of development space in the context
of relatively natural river networks. Approaching the issue of sustainable development, which can be defined as development that meets the needs of the present
without compromising the ability of future generations to meet their own needs
(WCED 1987), King and Brown propose an integrated basin flow assessment procedure to identify the optimum trade-off between costs and benefits of developing
river resources through projects such as dams. The procedure involves evaluating
multiple potential scenarios for future resource development, ranging from no
development to complete development. The procedure also explicitly recognizes
spatial variations that can result in a mosaic of different levels of river development
and health, although the basin-wide effects of development in each portion of a river
network are considered.
In order to evaluate different scenarios, King and Brown (2010) use response
curves between physical drivers such as flow characteristics and response variables
such as habitat area, abundance of particular aquatic species, or water temperature
(Vanderpoorten and Durwael 1999) (Fig. 4.8). Response curves are quantitative
where appropriate data exist and conceptual in situations where data are not available. Response curves in King and Brown (2010) use ratings of change from 0 for
no change to 5 for severe change to describe predicted change in an ecosystem
indicator to flow development (King et al. 2003). Response curves for numerous
ecosystem characteristics are then combined into the decision support software
Downstream Response to Imposed Flow Transformation (DRIFT) to evaluate differing scenarios of development (Brown and Joubert 2003; King et al. 2003) and to
identify development space. Development space is the difference between current
conditions in a river network and the furthest level of water-resource development
found acceptable to stakeholders through consideration of the scenarios (King and
Brown 2010; Fig. 4.9). Individual stakeholders will differ in what they consider
acceptable development and consensus definitions of acceptable development will
differ between river drainage basins. Nevertheless, the process provides a systematic method for considering the cumulative effects of multiple development projects, rather than discovering after all the projects have been built that the cumulative
effects are unacceptable.
King et al. (2014) summarize an example of this type of analysis that was conducted for the Okavango River system in southern Africa. Using the information in
59 specialist reports on the 700,000 km
2
river basin, an environmental flows team
divided the basin into 12 homogeneous biophysical and social units, 8 of which
were identified as priorities for analysis because of proposed development. The
team then identified 70 biophysical and 9 socioeconomic indicators responsive to
flow changes and used 1100 response curves in DRIFT to analyze potential changes
in the drainage basin under four scenarios of present-day conditions and low,
medium, and high water-use development in future (King et al. 2014).
4 Toward Sustainable Rivers and Water Resources
4.4 Response Curves and Development Space
King and Brown (2010) introduce the concept of development space in the context
of relatively natural river networks. Approaching the issue of sustainable development, which can be defined as development that meets the needs of the present
without compromising the ability of future generations to meet their own needs
(WCED 1987), King and Brown propose an integrated basin flow assessment procedure to identify the optimum trade-off between costs and benefits of developing
river resources through projects such as dams. The procedure involves evaluating
multiple potential scenarios for future resource development, ranging from no
development to complete development. The procedure also explicitly recognizes
spatial variations that can result in a mosaic of different levels of river development
and health, although the basin-wide effects of development in each portion of a river
network are considered.
In order to evaluate different scenarios, King and Brown (2010) use response
curves between physical drivers such as flow characteristics and response variables
such as habitat area, abundance of particular aquatic species, or water temperature
(Vanderpoorten and Durwael 1999) (Fig. 4.8). Response curves are quantitative
where appropriate data exist and conceptual in situations where data are not available. Response curves in King and Brown (2010) use ratings of change from 0 for
no change to 5 for severe change to describe predicted change in an ecosystem
indicator to flow development (King et al. 2003). Response curves for numerous
ecosystem characteristics are then combined into the decision support software
Downstream Response to Imposed Flow Transformation (DRIFT) to evaluate differing scenarios of development (Brown and Joubert 2003; King et al. 2003) and to
identify development space. Development space is the difference between current
conditions in a river network and the furthest level of water-resource development
found acceptable to stakeholders through consideration of the scenarios (King and
Brown 2010; Fig. 4.9). Individual stakeholders will differ in what they consider
acceptable development and consensus definitions of acceptable development will
differ between river drainage basins. Nevertheless, the process provides a systematic method for considering the cumulative effects of multiple development projects, rather than discovering after all the projects have been built that the cumulative
effects are unacceptable.
King et al. (2014) summarize an example of this type of analysis that was conducted for the Okavango River system in southern Africa. Using the information in
59 specialist reports on the 700,000 km
2
river basin, an environmental flows team
divided the basin into 12 homogeneous biophysical and social units, 8 of which
were identified as priorities for analysis because of proposed development. The
team then identified 70 biophysical and 9 socioeconomic indicators responsive to
flow changes and used 1100 response curves in DRIFT to analyze potential changes
in the drainage basin under four scenarios of present-day conditions and low,
medium, and high water-use development in future (King et al. 2014).
4 Toward Sustainable Rivers and Water Resources