International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XXXIX-B8, 2012 
XXII ISPRS Congress, 25 August — 01 September 2012, Melbourne, Australia 
      
Using MODIS Normalized Difference Vegetation Index to monitor seasonal and inter-annual 
dynamics of wetland vegetation in the Great Artesian Basin: a baseline for assessment of 
future changes in a unique ecosystem 
Caroline Petus', Megan Lewis and Davina White 
School of Earth and Environmental Sciences, The University of Adelaide, Adelaide 5005, Australia - 
caroline.petus( gmail.com, (megan.lewis, davina.white)(gadelaide.edu.au 
KEY WORDS: Environment, Vegetation, Mapping, Monitoring, Analysis, Satellite, Change 
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. 
1. INTRODUCTION 
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 
la). 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). The GAB springs are of great national and 
international importance for their ecological, scientific and 
economic values, and are culturally significant to indigenous 
Australians. In the recent decade, the sustainability of these 
groundwater-dependent ecosystems has become uncertain and 
numerous cases of spring extinction have been observed. In the 
near future, demands for this precious groundwater resource 
are likely to be considerable, particularly from proposed 
mining and petroleum activities, (Fensham et al., 2010; Mudd, 
1998). It is thus particularly 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. 
Direct measurements of spring flow are notoriously difficult and 
expensive if precise estimates are required (Niejalke and Lamb, 
2001). Relationships have been established between the wetland 
area associated with individual springs and their discharge (L.s’ 
), providing a potential means of monitoring groundwater flow 
using measurements of vegetated wetland area (Fatchen, 2001; 
Fatchen and Fatchen, 1993; White and Lewis, 2011; Williams 
and Holmes, 1978). Previous studies using this relationship to 
monitor Great Artesian Basin springs have used sporadic aerial 
  
* Corresponding author 
photography or high resolution satellite images calibrated to 
Normalized Difference Vegetation Index (NDVI) (Niejalke and 
Lamb, 2001, White and Lewis, 2011). These intermittent high 
resolution studies have only given "snapshots" of vegetated 
wetland area dynamics at selected springs in the DSC. They 
need to be placed within a longer and more regular context to 
better assess changes in response to aquifer draw-downs (White 
and Lewis, 2011). 
Since the launch of the MODIS satellite in 1998, medium 
resolution (250-m) MODIS NDVI time-series data have been 
applied successfully to quantify vegetation activity and to 
monitor vegetation dynamics (e.g. Jacquin et al., 2010; Jónsson 
et al., 2010) at high temporal frequency (16 days composites). 
In this study, 8 to 10 years of MODIS NDVI images were used 
to monitor and quantify vegetation activity and dynamics of the 
Dalhousie Spring Complex wetlands located on the southwest 
margin of the Great Artesian Basin (Figure la and b). DSC is 
the most important spring complex in the GAB and discharges 
90% of total spring flow in South Australia through 148 
separate spring vents (Gotch, 2010). Recent field work (March 
2009) increased knowledge about wetland vegetation associated 
with active Dalhousie springs (White and Lewis, 2010a, b). The 
dominant vegetation comprises reeds and sedges or tall reeds 
dominated by Phragmites australis (Common Reed) and open- 
forest, woodland and open woodland dominated by Melaleuca 
glomerata (White Tea-tree) trees 10-12 m tall. Ephemeral 
vegetation in spring tails mainly comprises mixed sedgelands 
including Cyperus spp. and Juncus sp.