Abstract
Abstract. The Great Artesian Basin mound springs (Australia) are unique wetland ecosystems of great significance. However, these unique ecosystems are endangered by anthropogenic water extraction. Relationships have been established between the vegetated wetland area and the discharge associated with individual springs, providing a potential means of monitoring groundwater flow using measurements of wetland area. Previous studies using this relationship to monitor Great Artesian Basin springs have used aerial photography or high resolution satellite images, giving sporadic temporal information. These "snapshot " studies need to be placed within a longer and more regular context to better assess changes in response to aquifer draw-downs. In this study, the potential of medium resolution MODIS Normalized Difference Vegetation Index data for studying the long-term and high frequency temporal dynamics of wetland vegetation at the Dalhousie Spring Complex of the GAB is tested. Photosynthetic activity within Dalhousie wetlands could be differentiated from surrounding land responses. The study showed good correlation between wetland vegetated area and groundwater flow, but also the important influence of natural species phenologies, rainfall, and human activity on the observed seasonal and inter-annual vegetation dynamic. Declining trends in the extent of wetland areas were observed over the 2000– 2009 period followed by a return of wetland vegetation since 2010. This study underlined the need to continue long-term medium resolution satellite studies of the Great Artesian Basin as these data provide a good understanding of variability within the wetlands, give temporal context for less frequent studies and a strong baseline for assessment of future changes.
Highlights
The Great Artesian Basin (GAB) of Australia is one of the largest groundwater resources in the world (Ponder, 2002), underlying about one fifth of the Australian continent (Figure 1a)
The aim of this study was to test the potential of MODIS Normalized Difference Vegetation Index (NDVI) data as long-term tracer of wetland vegetation in the DSC
In terms of NDVI values, the wetland vegetation are characterized by P90 values systematically equal or greater than 0.2, with maximal NDVI values registered for the Phragmites australis sites (Figure 2)
Summary
The Great Artesian Basin (GAB) of Australia is one of the largest groundwater resources in the world (Ponder, 2002), underlying about one fifth of the Australian continent (Figure 1a). Groundwater from the GAB supports a series of mound spring which contain a number of rare and relic endemic flora and fauna (Fensham and Fairfax 2003; Gotch et al, 2008; Ponder, 2002). Demands for this precious groundwater resource are likely to be considerable, from proposed mining and petroleum activities, (Fensham et al, 2010; Mudd, 1998). It is important to develop reliable methods for monitoring the long term artesian flow to inform management of the GAB and better protect this sensitive environment and its ecosystems
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