Chowilla icon site - floodplain vegetation monitoring 2017 interim report.
Abstract
The aim of this study was to monitor and assess vegetation condition at the Chowilla Icon Site against the objectives and the associated TLM site specific ecological targets. A network of vegetation survey sites was established in areas of herbland and grassland in 2006. These sites were surveyed to provide baseline data in 2006, and have been re-surveyed on an annual basis to monitor medium-term vegetation changes and assess the aforementioned site specific ecological objectives. Between 2013 and 2017, an additional 58 sites in temporary wetlands that were part of a previous intervention monitoring program were added to the network to gain a better understanding of floodplain and temporary wetland condition at Chowilla. Throughout this monitoring program (2006-2017), variable hydrology in the MDB and site specific management interventions within Chowilla, have resulted in spatio-temporally variable patterns of inundation. When monitoring sites were established in 2006 the MDB was in extended drought and overbank flows had not inundated large areas of floodplain since 1996. In spring 2006 and spring 2009, site-scale environmental watering (pumping) occurred at discrete wetlands (i.e., Coppermine Complex and Gum Flat). An extensive and prolonged overbank flow, and subsequent floodplain inundation, occurred from spring 2010 to autumn 2011 and another shorter but higher overbank flood occurred in spring 2016. Several in-channel flow pulses were also experienced from 2011 to 2016. The Chowilla Environmental Regulator was operated for the first time in spring 2014, raising water levels 2.75 m above normal pool height in lower Chowilla Creek with levels held at the peak for two weeks in October 2014, inundating 2142 ha of floodplain and temporary wetlands. The regulator was operated for a second time in spring 2015, raising water levels 1.5 m above normal pool level and inundating 535 ha of riparian areas and some temporary wetlands. In winter-spring 2016 the regulator was operated for a third time raising water levels 3.4 m above pool level resulting in 7653 ha of floodplain and temporary wetlands being inundated at the peak in late September 2016. The 12th annual floodplain vegetation condition monitoring survey was undertaken in February 2017. A total of 58 species, from 25 families (predominantly from the Chenopodiaceae and Asteraceae) were recorded from the floodplain sites (established in 2006). With the inclusion of the temporary wetland sites surveyed in 2017, species richness increased to 67 species from 26 families (also predominantly from the Chenopodiaceae and Asteraceae).