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Structural Adaptations
                              (Canada in a Changing Climate)

In contemplating structural adaptations, one should consider whether the system will be capable of dealing with the projected hydrological changes, as well as the economic, social and ecological costs of the adaptation.

Physical infrastructure, such as dams, weirs and drainage canals, has traditionally served as one of the most important adaptations for water management in Canada. There are conflicting opinions, however, on the potential of building new structures for climate change adaptation.  Given the substantive environmental, economic and social costs associated with these structures, many experts advocate avoiding or postponing the
construction of large-scale infrastructure until there is greater certainty regarding the magnitude of expected hydrological changes. On the other side of the coin is the fact that water infrastructure improves the flexibility of management operations, and increases a system’s capacity to buffer the effects of hydrological variability. In the Peace River, for example, stream regulation will allow operators to potentially offset the effects of climate
change on freeze-up dates by reducing winter releases. Similarly, communities in the southern Prairies can use small-scale water infrastructure to increase water storage through snow management, and reduce regional vulnerability to drought.
Most existing water management plans, as well as water-supply and -drainage systems, are based upon historic climatic and hydrological records, and assume that the future will resemble the past.  Although these systems should be sufficient to handle most changes in mean conditions associated with climate change over the next couple of decades,
management problems are likely to arise if there is an increase in climate variability and the occurrence of extreme events. Case studies in Ontario indicate that increases in the intensity of precipitation events have the potential to increase future drainage infrastructure costs and decrease the level of service provided by existing systems (Box 4).

                                            BOX 4:  How vulnerable is our infrastructure?
Since the majority of urban water drainage systems are designed based upon historical climate records, a change in precipitation patterns may cause these systems to fail.  More intense precipitation events are expected to decrease the level of service that existing drains, sewers and culverts provide, and increase future drainage infrastructure costs.  While making the necessary changes (e.g., increasing pipe sizes) would be expensive, the overall costs are expected to be lower than the losses that would result from not adapting.  For example, insufficient pipe sizes would lead to an increase in sewer backups, basement flooding and associated health problems. 
Several studies suggest that the design of water management systems should focus on thresholds, such as the point at which the storage capacity of a reservoir is exceeded, rather than mean conditions. Thresholds can induce nonlinear and therefore less predictable responses to climatic change, which would significantly stress the adaptive capacity of water resource systems.
In many cases, modification of existing infrastructure operations, rather than the introduction of new structures, will be an effective adaptation option.  For example, models indicate that the Grand River basin will be able to adapt to all but the most severe climate change scenarios through modifications in operating procedures and increases in reservoir capacity.  A drainage infrastructure study of North Vancouver suggests that the system can be adapted to more intense rainfall events by gradually upgrading key sections of pipe during routine, scheduled infrastructure maintenance. Adaptations such as these can be incorporated into long-term water management planning.
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