2018 Drying of the Winton Wetlands

The drying we’re seeing at Winton Wetlands is part of a normal and regular process. With the dry weather over summer and autumn the site dried out this year. Drying drives very important ecological processes (such as nutrient transformation, trigging invertebrates to lay eggs and plants to germinate), so we welcome it. It also allows us to get on with some physical works that the big wet of two years ago has delayed!
When the reserves filled in 2016 (after being dry for two years), it took about 2 months for them to fill (July and August) to over 100 per cent as the wetlands then drained out for a couple of weeks and water slowly dropped over that summer and autumn. Unfortunately the winter rains last year only resulted in a small water rise and of course they have dried out now.

A more detailed explanation

The Winton Wetlands are an ephemeral wetland system. This means that there will be times when the wetlands dry out for example after periods of low rainfall.  experience both drying events, after periods of low rainfall, and filling events, from inflows following rain events in the catchment, and from local surface runoff.

Evaporation is happening all the time

At all times, the wetlands lose water through evaporation. Evaporation happens more quickly from November to March. During these hotter months the water level can drop rapidly. In drier periods it can completely dry out. The flooding-drying cycle is a natural and predictable event for all wetland systems.

Lake Mokoan aerial

Drying out can have benefits for the wetlands

Lance Lloyd, Restoration Scientist at Winton wetlands says:

“Drying is very important to the wetland ecosystem as it:

  • Triggers organisms to lay desiccation-resistant stages, eggs, or plants to set seeds in response to the lowering water levels;
  • stimulates edge and wetland plant colonisation; and
  • causes dried out sediments on exposed wetland beds to allow nutrients to be transformed and prepare the system for next refilling phase.”

A natural cycle of drying out and filling

The main, most visible body of water in the centre of the Reserve comprises the three largest wetlands in the complex – Sergeant’s, Winton and Green’s Swamps. These wetlands have historically dried every eight years, on average. At the moment Greens and Sergeants Swamps have already dried, as have the smaller wetlands. The large body of water in Winton Swamp is very shallow and is likely to dry completely in coming days or weeks.

A 10% drop in water level can span over two square kilometres of water surface. This means that drying out can seem to be a dramatic event affecting a large surface area, even though it is only a slight decrease in system volume.

Site improvement and ecological benefits

Jim Grant, CEO of the Winton Wetlands Committee of Management says “we work with these natural occurrences as opportunities to continue to develop the site across its many aspects and welcome the drying event as an effective control of exotic and potentially harmful fish such carp, which still occur in the system (although at lower levels than previously).” Firstly, he says “the low water levels assist water birds, such as pelicans, to feed upon the fish and secondly, the drying itself eliminates the harmful fish.” Restoration Scientist, Lace Lloyd said “Our recent fish survey indicated that Winton Swamp had fewer carp than usual but drying will eliminate this harmful species. Native fish have found refuge in our Mokoan Ponds along the old dam wall.”

Header photo by Liz Arcus


You might also like…

Lance presents some interesting information about carp in this video