Capturing early First Wannon flows of 2023! Right time and right place for a water nerd

If you are a regular reader of our newsletter, you’ll know we have been investigating the Wannon River system for a few years now, which begins in the Grampians National Park and influences several important wetlands, such as Walker Swamp and Brady Swamp. You can read our article comparing last year’s wet spring to longer-term data here. Lachie was on site recently and managed to capture on video the moment when the first flows of the season came down the dry bed of one of the upper Wannon River’s headwater streams. What good timing! Check out the video below.

On the back of an out-of-the-box flow season, the Upper Wannon is now flowing below Lynchs Crossing. This particular location is a point of interest to us in terms of flows because it is a place where the Wannon River begins to leave the Grampians before distributing out onto the Brady Swamp floodplain. After flows cease, and particularly after lower flow seasons, it takes quite a bit of water to fill up the floodplain and river sections which run between Jimmys Creek and Lynchs Crossing (see below for geographical context). We’re used to seeing the flows make this point by June or July so it seems early. But we do know that historically it ran much earlier and the system is still wet from last year, so it’s not really that surprising!

Beyond seeing the flows at Lynchs Crossing, we ventured further up the watercourse, seeing most of the other tributaries carrying water. The only exception being the First Wannon Creek, at the top of the system. This boulder strewn creek is quite steep and runs directly off the Major Mitchell Plateau. It’s not a waterway which I have seen running very often but I was surprised that it was bone dry. This is one of the headwater streams which is intercepted and diverted to fill Lake Bellfield but, given the diversions don’t start until June, diversion wasn’t the reason why it hadn’t started flowing yet.

Curiosity meant a short detour so we headed up to the diversion point for a closer look. When we got there I could hear water running and firstly thought that the water must be running under ground. I found a pool and as I sat there and watched I noticed the water was rising. As chance would have it, we had turned up at the very moment flows were making there way down. It’s not the first time I’ve been there to meet the first flows. Back in 2014 we dropped into Brady Swamp just at the Wannon had started to flow in. Beyond being a unique encounter, it is also highly informative. Mount William received almost 80 mm of rain over the 7th and 8th of April. We were there on the 12th so that means, despite it being a steep and relatively short catchment, it still took several days for flows make the 4 km journey from their origin on the Major Mitchell plateau to where we were, at the First Wannon diversion. The video below gives you a sense of how this journey unfolds, noting that it is sped up in the later parts of the video.

Lachlan Farrington