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Riparian forest and woodlands of the lower River Murray floodplain are exhibiting deteriorating health as a result of anthropogenic alterations to flow regimes and south-eastern Australia’s long-term ‘Millennium Drought’ from 1997 to 2009. Extensive flooding in 2010/2011 brought the drought to an end, providing an opportunity to monitor ecological floodplain recovery. The relationship between flooding and lateral recharge and condition of the dominant riparian tree species, Eucalyptus camaldulensis, was determined between 2007 and 2011 using the Landsat (LTM5) Normalised Difference Vegetation Index (NDVI). Linking the river hydrograph with the River Murray Floodplain Inundation Model (RiM-FIM) allowed exploration of the relationship between inundation duration and E. camaldulensis water requirements. Results indicate lateral bank recharge is an important mechanism in the maintenance of vegetation condition along the River Murray channel. Higher in-channel irrigation water delivery during summer months was identified as critical to survival of trees adjacent to the channel during the drought. The research suggests that weir pool manipulation to create in-channel flood pulses will aid E. camaldulensis maintenance. Furthermore, release of environmental flows once every 3 to 5 years to create bank-full flow or preferably overbank flows, will increase hydrological connectivity between river banks, wetlands and riparian zones, providing positive ecological benefits to E. camaldulensis and other floodplain and aquatic ecological assets.

The sources of groundwater and the patterns in groundwater dissolved N and DOC concentration in the floodplain of a subtropical stream (Wollombi Brook, New South Wales) were studied over a 2-year period using three piezometer transects. While the stream was generally a discharge area for regional groundwater, this source represented only a small contribution to either the water or N budget of the alluvial aquifer. Groundwater-surface water interactions appeared mostly driven by cycles of bank recharge and discharge between the stream and the alluvial aquifer. DON and NH 4 + were the principal forms of dissolved N in groundwater, consistent with the primarily suboxic to anoxic conditions in the alluvial aquifer. A plume of groundwater NO 3 À was found at one transect where oxic conditions persisted within the riparian zone. The origin of the NO 3 À plume was hypothesized to be soil NO 3 À from the riparian zone flushed to the water table during recharge events. When present, NO 3 À did not reach surface water because conditions in the alluvial aquifer in the vicinity of the stream were always reduced. The concentration of groundwater DOC was variable across the floodplain and may be related to the extent of the vegetation cover. Overall, transformation and recycling of N during lateral exchange processes, as opposed to discharge of new N inputs from regional groundwater, appears to primarily control N cycling during groundwater-surface water interactions in this subtropical floodplain.

No abstract

In nonmarket valuation, practitioners must choose a format for the valuation questions. A common approach in discrete choice experiments is the 'pick-one' format, often with two alternative policy proposals and a status quo from which the respondent selects. Other proposed formats, include best-worst elicitation, where respondents are asked to indicate their most and least favoured alternative from a set. Although best-worst formats can offer efficiency in data collection, they can also lead to responses that are difficult to reconcile with neoclassical welfare estimation. The current article explores methodological issues surrounding the use of pick-one versus best-worst data for nonmarket valuation, focusing on framing and status quo effects that may occur within three-alternative discrete choice experiments. We illustrate these issues using a case study of surplus groundwater use from Western Australian mining. Results identify concerns that may render best-worst data unsuitable for welfare estimation, including a prevalence of serial choices in which the status quo is universally chosen as the worst alternative, rendering part of the choice process deterministic. Asymmetry of preferences and serial choices can be obscured when models are estimated using 'naively' pooled best-worst data. Results suggest that caution is warranted when using best-worst data for valuation, even when pooled results appear satisfactory.