Conceptual Model Case Study Series About this case study: Aquatic connectivity: This case study was created by the Department of Environment and Resource Macintyre River Management (DERM) Aquatic Ecosystem Health The function of the vertical slot fishway can be Macintyre anabranches Science Integration and compromised if water levels are kept high. Capacity Building Team The Macintyre River from Goondiwindi downstream to as part of the Queensland Boomi sits in a low relief area of complex geomorph- Flow regimes and connectivity Wetlands Program. The ology. The river system comprises a maze of anabranch* Anabranch ecology varies, depending on connection to study is written for wetland channels receiving varied flows depending on their the main channel. In high flow, anabranches connect with managers. Its purpose is connection to the main river channel. Flows at various and function in a similar way to the main channel; when to synthesise and present levels and times are important to inundate the many disconnected they are more like off-stream wetlands. As information about aspects of wetland connectivity. channels and drive the region’s ecosystem dynamics. wetting regimes vary across different anabranches, so does Hydrological, biotic and categorisation in the Queensland wetland mapping— The Integrated Quantity– Anabranches are a significant component of the lower ecological connectivity are Quality Model (IQQM), Macintyre River. In the 150-km river reach between as riverine, palustrine or lacustrine—depending on discussed, as well as how developed by the Goondiwindi and Boomi, there are 69 anabranch channels geomorphology and water regime. Palustrine and these types of connectivity Department of Land and with a total length of 236 km. Anabranch channel length lacustrine anabranches are classed as semi-arid tree influence each other and Water Conservation (DLWC swamps and floodplain lakes respectively. how they change over time. 1996), was used as the varies from 0.32 km to 113 km, most being shorter than 1 source of the flow data for km. The largest anabranches in the area are Whalan and Conceptual diagrams on the following pages demonstrate the analysis of connectivity Callandoon creeks and the Boomi River (see page 4). how different flow regimes influence connectivity at in this wetland guide. The the local scale across a generalised river–anabranch– IQQM model simulates flows There are also many modified and man-made wetlands floodplain landscape. Flow regimes are general under natural conditions throughout the reach. Alterations to flow are common and under conditions which in the area. Weirs and other structures regulate flows descriptions of water discharge levels that result in assume human water use (i.e. for irrigation and some anabranch wetlands have been different levels of connection. The diagrams include an water resource allocation) dammed to provide on-farm storage. indication of the expected duration for each flow regime. is at a maximum. The term Generic floodplain landscape ‘developed condition’ is Boomi and Goondiwindi town weirs are located at each used through this guide to end of the Macintyre River reach discussed in this case refer to the condition under study. Silver perch and Murray cod have been recorded Late maximum human use. A flow ral con Regime nectiv crossing the fishway at the Goondiwindi Weir but the Off-stream wetland ity regime analysis was based duration Floodplain c effectiveness of the fishway for other species is unknown. Vertical on the modelled IQQM flow o n Anabranch channel n data. The analysis was used Boggabilla Weir, 8 km upstream of Goondiwindi, is a e c t i Off-stream v to discuss the impacts of significant barrier to fish passage. Although this weir is i t wetland y changes in water resource outside the case study reach it is likely to affect the reach. Main channel Floodplain allocations on a range of It is an undershot weir, a type shown to cause fish larvae connectivity processes. death. ty Groundwater aquifer vi cti * An anabranch is a stream branching off a river and rejoining it further ne on downstream. l c Woody debris na di itu ng Lo Lateral connectivity No connection Regime duration Moderate duration ity v ti c e n n n co tion o y al c i t n i t i e v d n c i No flow o u t t n e i c g o N e n n c n o n L o n o Vertical Though periods of no flow are normal for the Queensland Murray–Darling Basin and plants o N c and animals are generally adapted to cope with it, extended dry periods can stress the c system. Dry periods can be advantageous to ‘reset’ the system and kill off pest fish. Water in disconnected pools tends to be turbid and its quality decreases with time as part of the Lateral connectivity natural process of drying. If these periods are protracted, biota in these water bodies might Low connection suffer and aquatic species can be lost completely until subsequent recolonisation occurs if Regime connected to other populations. Furthermore, ecosystem processes (e.g. decomposition) duration slow down in the absence of water. Nutrients accumulate after they are deposited from High the riparian zone and other terrestrial sources (e.g. leaf litter and woody debris) into duration y it iv the stream bed, off-stream wetlands and onto floodplains. There may be some vertical ect n n o c connectivity between groundwater and surface water; however, this will depend on local l y a t n i i d geomorphology and the state of the groundwater. v i u t it w c g e n o o n L L n o Vertical c connection Moderate connection Low flow Compared with no flow, low flow benefits fish populations by helping maintain water Lateral connectivity quality. Low flows link in-stream habitats, sustain longitudinal connectivity for movement Low connection of biota, raise water levels increasing available habitat and refresh in-channel pools improving water quality. Connection to groundwater can occur in either direction, Regime duration depending on the local geomorphology. In some cases the low flows of surface water may be provided entirely by the groundwater (this is known as baseflow) or low flow may seep Low into the earth and recharge the groundwater. Groundwater recharge during low flow is duration likely to be limited because hydraulic pressure from the stream will be low. ity n iv o ct ti n c nne o y o ne i t c i t l n v c a o i t w in c e c o d e e Flow pulse n tu L n i at n g r n n o Vertical o o L c Short flow pulses cause rapid changes to physicochemical aspects of water quality. c Mode These may be used as biological triggers, e.g. flow pulses bring food sources into an area, followed by low flows to maintain water quality. Pulses can briefly connect anabranches and off-stream wetlands, depending on the size of the flow pulse and the local topography, resulting in improved water quality and therefore improved health of aquatic habitats. Nutrients accumulated in the channels of anabranches can mobilise as a result of these pulses and sediments can be flushed out, resulting in reduced turbidity. 2 Regime Moderate duration duration y i t v ti e c tn e r ao Verticaln i n e t o d c c o e n M n o c M L o a de te ra l ra c o te n n c e c o t n iv Regime n i e ty duration c High duration t ion y it v ti c n e h io Verticaln t High flow n ig o c c He n High flows inundate or mobilise organic material n o c accumulating in dry stream beds, increase turbidity in channels by increasing sediment transport and allow fish to migrate. High flows provide connectivity to additional L a habitat and will result in connection to anabranches F te u ra l ll c Longitudinal connectivity and secondary channels (depending on flow level o c n o n e and channel shape). High flows can benefit fauna by nnec c Full connectio t n iv i inundating benches (flat areas of sediment deposited t ty ion Regime in stream channels above the bed but below the banks) Moderateduration duration providing more habitat. During summer, this is especially y it v e important for breeding. Higher water levels increase t i t n c a o e r ti water flow vertically into the groundwater. The increased n e Verticaln c o de c o n hydraulic pressure in the groundwater aquifer can result n M o c in lateral movement of water to off-stream wetlands and anabranches through subsurface flows, depending on local geomorphology. Legend Overbank flow Longitudinal connectivity Overbank flows inundate the floodplain and refresh Vegetation L a Full connection L te water supplies in off-stream wetlands, improving water ra o l w c o Woody co n quality. Floodplains can be accessed by biota; organisms n e debris c n t and seeds can move into off-stream wetlands, and n iv e i Small fish c ty t nutrients accumulated in the floodplain can shift into the (e.g. gudgeon) io n channel ecosystem. Vertical water movement into the groundwater is at its greatest rate. Predator fish (e.g. yellowbelly) Receding flow As flow drops back, off-stream wetlands retain water Terrestrial fauna and can become hot spots for biological processes (e.g. decomposition, habitat for fish populations).