A fresh start for floodplain vegetation

Posted on September 22, 2010


The health of native vegetation on the floodplains ofAustralia’sMurray River  is under severe threat, mainly due to soil salinisation.  This can be linked to river regulation activities since the 1920s, which have reduced the frequency of floods and raised the saline water table.  Prolonged drought has compounded these problems.  Starting in 2005, the Bookpurnong Experiment, located near Loxton inSouth Australia, examined how degraded floodplain vegetation responds to various water management measures.  In part, this involved drilling a network of wells to intercept saline groundwater before it discharged to the river and the floodplain.  In addition, a groundwater bore was constructed to induce river water to move through the bank and create a freshwater lens above the salty water table.  As a result of this bore, the water table at experimental plots was reduced by up to 88 cm and the zone of fresh groundwater increased from about 40m to beyond 150m from the river.  At the same time, the visual health (canopy cover) of live trees in the area improved and black box trees showed increases in leaf water potential (i.e., reduced stress).  The results show that groundwater freshening can help restore damaged riparian communities.  However, because of the high costs of implementation over large floodplain areas, applications of this strategy will probably be limited mainly to ecologically significant sites.

References:

Doody, T.M., Holland, K.L., Benyon, R.G. & Jolly, I.D.  2009.  Effect of groundwater freshening on riparian vegetation water balance  Hydrological Processes 23, 3485–3499.

Holland,K.L., Charles, A.H., Jolly, I.D., Overton, I.C., Gehrig, S., & Simmons, C.T.  2009.  Effectiveness of artificial watering of a semi-arid saline wetland for managing riparian vegetation health.   Hydrological Processes 23, 3474–3484.

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