Civil Engineering Reference
In-Depth Information
agreements, threatened and endangered species protection, and habitat and
ecological function preservation policies and laws. In the above Victorian
example, these broader benefits are implicitly recognised through the
'environmental value' criteria. While it is important these are not overlooked,
this needs to be moderated by cost and availability of data, and whether
certain features can provide a proxy for others. For example, while aquatic
biodiversity is not explicitly stated in the above list, naturalness and water
quality provide a proxy indication.
Sometimes what is important is defined by government policy. For
example, the 'Water Framework' Directive (WFD) of the European Union
aims to achieve 'good ecological status' (i.e. the protection and enhancement
of health and biodiversity of the aquatic ecosystem) in most European rivers,
lakes and wetlands by 2015 (European Commission, 2000), and nations
commit to maintain wetlands they list under the Ramsar Convention.
Assessing water regime requirements and risks
Assessment of the water regime requirements (flows, water levels, etc.) for
maintaining these identified ecosystem assets and functions is critical to
inform the water resource planning process. For ecosystems that are in poor
condition or in a state of decline, an understanding of cause and effect, often
complex, can lead to identification of what it would require for recovery or to
stem the decline. For ecosystems in good condition it should lead to under-
standing what is required to maintain that condition. This can be combined
with information on the likely range of water regime characteristics that are
projected to indicate where there is or could be a shortfall, and consequently
a risk to these assets and functions.
For rivers, these water regime requirements in rivers have commonly been
called 'environmental flows' where:
Environmental flows describe the quantity, timing and quality of water
flows required to sustain fresh water and estuarine ecosystems and the
human livelihoods and well-being that depend upon these ecosystems
(Brisbane Declaration 2007).
There is now wide recognition that environmental flows are more than
just minimum flows, but are rather a dynamic, variable water regime that
preserves important aspects of the natural flow regime, including such things
as high flow events and seasonal variability (Arthington
et al
.2010). As we are
discussing both rivers and groundwater, we use the more generic term 'water
regime' to cover the temporally and spatially varying flow regime for rivers
and the water level/pressure and flow regime for groundwater.
Estimating the water regime needed to maintain a water ecosystem in a
desired condition is a scientific assessment that draws on the best available
knowledge of causal links between different aspects of the regime and the
