fereed paper
RESTORATION PLAN FOR A WETLAND AFFECTED BY SALINE GROUNDWATER S Jewell, J Muller, A Telfer, M Thompson Abstract
box) and Eucalyptus camaldulensis (red gum), rhe spread of mistletoe in trees, and an increase in abundance of salr-toleranr species such as A triplex rhagodioides (salrbush) and Halosarcia pergranulata (samph ire).
Austraha
River regul ation is rhe primary cause SO<th Austnlla of soil salinisation and subsequent wetland degradation in the MurrayDarli ng Basin. A Ramsar Wetland experiencing these problems is Paringa Island Wetland, located two kilometres upstream of Lock 5 near Renmark in Sou th Australia. A network of 11 groundwater mo ni toring wells was installed and a monitoring program initiated as pare of chis study. The groundwater salinity levels in the so uthern island were fo und to exceed seawater. Vegetation su rveying has shown that this has resulted in dieback of black box and pro liferation of sa lr-rolerant species. Preliminary modelling and Figure 1. Location of Paringa Island Wetland. ionic co mposition resting indicated salt in the wetland was primarily Pari nga, approximately rwo kilometres from regional sources, concentrated by upstream of Lock 5, as shown in Figure I. evaporation of shallow groundwater. It is a 57-hecrare sire, pare of a Ramsar Results suggest char sale accumulation could Wetland extend ing alo ng the River Murray be remedi aced by lowering of the River floodplain from Renmark to che Victorian weir-pool level for several months at a rime and New South Wales borders. on a regular basis or im plemen ting continuous groundwater pumping as pare of There has been a significant decline in rhe a future salt interception scheme. In health of the wetland vegetation over the conjunction with chis, regular flood ing lase 20 to 30 years. This has been evident in overtopping che permanent creek banks the dieback of Eucalyptus largiflorens (black char connect rhe central lagoon to rhe river would promote red gum growth NEW SOUTH and flush accum ulated sale from WALD affected areas.
This paper secs out background research and current approaches co solving rhe problem of decli ning health in the Murray-Da rling Basin. le then discusses rhe field invesrigarions cond ucted at Paringa Isla nd Wetland, leading to a proposal of remediation options for rhe wetland.
Background to Problems and Solutions Salinity in the Murray-Darling Basin T he River Murray is rhe only natural drain for groundwater and rhe associated salt loads for the entire Murray Darling Basin. The Murray Darling Basin is a naturally saline environment, with regional gro undwater salinities ranging from l 4,000 to over 35,000 mg.L- 1 (Doble, 2004). Figure 2 shows che direction of regional groundwater flow, indicating groundwater discharge in the Paringa region.
Introduction The aim of rhis research project was to gain an understanding of che existi ng problems in Paringa Island Wetland and co develop possible remediation options co assist in developing a restoration plan. This wetland is experiencing degradation resulting from salinisacion, and is located on the Murray River near
River regulation is believed to be rhe primary cause of rhe salini ty observed in Paringa Island Wetland. Weirs and irrigation works on the flood plain and adjacent areas impede flow down che river to che ocea n, and are now causing che groundwater table to rise Qolly et al., I 996) . Salt pans are fo rmed when saline groundwater rises close co rhe surface. Changes in the flow regime have caused half of rhe wetlands along rhe river to disappear, and many ochers have suffered significant degradation of riparian vegetation (Blanch, 2004).
VICTORIA
Thi s p aper won the 2006 AWA National Undergraduate Water Prize. It has si nee been peer-reviewed and slightly amended.
Figure 2. Regional groundwater flow (after Evans et al. , 1990).
Trying to protect a Ramsar wetland.
Journal of the Australian Water Association
Water
NOVEMBER 2007 69