
Lower Punrak Drain 2
Basin : Murray River
Catchment : Murray - Serpentine rivers
The condition of the Lower Punrak Drain 2 site (site code: MR64PUNR2, site reference: 6140264) was assessed between 23 and 24 November 2022. Results are compared to a previous assessment in 2017.
Healthy Rivers assessments are conducted using standard methods from the South West Index of River Condition (SWIRC), which incorporates field and desktop data from the site and from the broader catchment. Field data collected include the following indicators, assessed over about a 100 m length of stream:
- Aquatic biota: fish and crayfish community information (abundance of native and exotic species across size classes, general reproductive and physical condition)
- Water quality: dissolved oxygen, temperature, specific conductivity, and pH (logged in situ over 24 hours) as well as laboratory samples for colour, alkalinity, turbidity and nutrients
- Aquatic habitat: e.g. water depth, substrate type, presence of woody debris and detritus, type and cover of macrophytes and draping vegetation
- Physical form: channel morphology, bank slope and shape, bioconnectivity (barriers to migration of aquatic species), erosion and sedimentation
- Fringing zone: width and length of vegetation cover within the river corridor and lands immediately adjacent, structural intactness of riparian and streamside vegetation
- Hydrology: measures of flow (velocity) at representative locations (compared against data from stream gauging stations within the system)
- Local land use: descriptions of local land use types and activities (compared against land use mapping information for the catchment)
The MR64PUNR2 site is about 350 m upstream of a site assessed in November 2017 (MR64PUNR1). The site was moved because of issues with site access.
Other departmental data: The Lower Punrak Drain 2 site is about 4.5 km downstream of the Department of Water and Environmental Regulation’s (the department) flow gauging station known as Yangedi Swamp (site reference: 614094), which has been in operation since 1995.
Search the site code or site reference in the department’s Water Information Reporting (WIR) system to find data for this site and nearby sampling points (flows, surface water quality, groundwater monitoring, the department's meteorological data). See also the Bureau of Meteorology website for additional meteorological data for the area.
Condition summary
The image below indicates the conditions at the Lower Punrak Drain 2 site in November 2022. November is within the Noongar season of Kambarang (second spring), which is traditionally seen as a transformational time of year with many plants flowering. The season is marked by longer periods of dry weather and rising temperatures. Further images are provided in the gallery at the bottom of the page to show general site conditions.
A summary of site condition over the latest monitoring period is provided in the sections below. For other site data, please contact the department’s River Science team (please reference the site code and sampling dates).
River setting
The Lower Punrak Drain 2 site is on Punrak Drain, a tributary of the Serpentine River on the southern Swan Coastal Plain, about 50 km south of Perth.
Punrak Drain is mostly a deeply incised drainage channel, which incorporates Karnet Brook and Dirk Brook to the east, before becoming modified to drain the low-lying lands to support agriculture in the region below. In the last 500 m, before discharging to Lake Amarillo, the drain becomes more natural in its course but still flows within artificially engineered levees to promote drainage and reduce the risk of flooding.
The assessment site is within a low-gradient section of the Lower Punrak Drain at the transition between grazing land and remnant vegetation surrounding Lake Amarillo. The image below shows the assessment site in the foreground and Lake Amarillo in the background (left).
The site is a connected channel habitat, typical of modified, open drain-like waterways. Water depth was varied, largely because of variation in areas of sediment (sand) deposition. Average water width and depth at the time of sampling was 6 m and 0.5–0.99 m respectively. Channel depth (to the top of the banks) was 1.5–2 m and the bankfull extent of the floodway (between the engineered levees) was about 20 m wide. The banks were steep to vertical and convex in shape, and the channel was U-shaped throughout the site.
Aquatic habitat
The site was connected channel habitat during the November 2023 assessment, with no pools, riffles or runs as might be expected in a more natural river reach.
Aquatic habitat was suboptimal, having been impacted by historical training and de-snagging activities and clearing of vegetation through the catchment. Substrate diversity was predominantly sand and clay, typical of drains. There was a minor amount of silt deposition through the site that generated a moderate plume when disturbed. Woody debris of 2–3 size categories was observed in moderate abundance, both reduced from what would be expected naturally. Woody debris was also unevenly distributed through the site, being more abundant in the downstream section of the site where there was more overhanging tree canopy. Biological substrate cover, consisting of leaves, detritus and algae, was also unevenly distributed, covering up to two-thirds of the site substrate in a moderate density.
In-stream vegetation was sparse and covered about 2 per cent of the site, evenly split between inundated rushes on the banks and some emergent Potamogeton crispus (curly-leafed pond weed). Overhanging banks occurred along less than half the site, and roots draped in the water were present over about 10 percent of the total bank length, both providing additional habitat. Vegetation draped in the water provided habitat along almost the entire bank length in the site, which included exotic grass, rushes and sedges.
Stream shading varied, with more extensive cover through the downstream section where mature Eucalyptus rudis (flooded gum) stood closer to the banks. Further upstream the larger trees were present but set further back from the banks.
Flow & connectivity
At the time of sampling the site was flowing uniformly with little variation, typical of drains. Flow was slow (about 0.1 m/s) and the site was connected in terms of fish passage. At the department’s Yangedi Swamp gauging station, 4.5 km upstream, the daily discharge over the assessment period was about 5.5 ML.
A known barrier to fish passage exists about 1 km upstream at the Gull Road crossing, where the drain flows through three culverts. The Gull Road crossing is 5 m wide, and at the time of sampling the culverts were 50 cm above the water level in the drain.
Vegetation
The riparian zone (containing species adapted to living at the interface between aquatic and terrestrial environments) was typical of remnant vegetation with a largely intact tree layer, a reduced shrub layer, and a ground cover layer that was largely exotic species – including grass, Watsonia spp. (bugle lilies), arum lilies and dock. Because of the low-lying landform and proximity to Lake Amarillo, the riparian zone was extensive with Melaleuca spp. (paperbarks) observed 50–100 m from the banks.
The image above illustrates the dominance of weeds in the understory with dense stands of Watsonia and grass lining the banks and draped into the water. In the background, paperbarks and flooded gum can be seen, and some of the aerial images show the extent of the riparian vegetation from either bank.
Water quality
Below is a graph of the water quality recorded during the 24-hour assessment.
Water quality over the 24 hours was suboptimal for some parameters.
Water temperature exceeded the 25°C threshold1 for 19 per cent of the 24-hour deployment. The diurnal range in water temperature was also suboptimal at 5.61°C, which is above the desired maximum range of 4°C. Sampling took place in November (early part of the hot/dry season). It is reasonable to assume stress from higher water temperatures would increase through summer, though deeper areas were identified within the site which would be expected to provide refuge areas for aquatic biota from water temperature extremes. Note: the water quality logger was 15 cm from the surface, whereas maximum depth through the site was about 1.5 m. Lake Amarillo further downstream may also provide deeper refuge habitat for aquatic species.
Dissolved oxygen was optimal during the assessment period, remaining above the 4 mg/L minimum threshold.2 However, conditions would be expected to worsen over summer months. A relatively high diurnal range in dissolved oxygen was recorded (5.35 mg/L) which suggests some biological influences (i.e. algal photosynthesis and respiration). It is reasonable to assume that conditions will worsen through the later dry season with greater algal activity (greater dissolved oxygen demand) because of higher temperatures. Refuge from suboptimal diurnal fluxes in dissolved oxygen would exist in deeper and more shaded parts of the site downstream, as well as further downstream towards the old MR64PUNR1 site, which had some deep sections (>2 m).
Specific conductivity (which can be used as an indicator of salinity) was classed as fresh for the 24-hour assessment period. Turbidity levels were moderate (8.8 nephelometric turbidity units [NTU]), and pH (mean value of 6.71) was optimal, based on expectations of natural ranges for freshwater rivers of south-west Western Australia.
Nutrient concentrations were varied; total nitrogen was low (0.69 mg/L) but total phosphorus was high (0.099 mg/L). Elevated phosphorus is likely related to nutrient run-off from agricultural land use in the catchment. With heavily cleared streamside riparian vegetation in much of the catchment, there is limited capacity to buffer this run-off and any excess nutrients largely run straight into the waterways. This is consistent with the suspected algal activity that is probably driving the suboptimal diurnal flux in dissolved oxygen conditions.
Footnote:
1 An upper limit for temperature is nominally set at 25°C based on the range recorded in sites where south-west native fish species are typically found to occur (Beatty et al. 2013).
2 A lower limit of 4 mg/L is taken from the SWIRC where it is used as a guideline limit for condition scoring. This level aligns with Beatty et al. (2013) where south-west native fish species were shown to typically reside in sites with levels above 4 mg/L.
Species found in subcatchment
Native Species
- Blue-spot gobyPseudogobius olorum
- Carter's freshwater musselWestralunio carteri
- GilgieCherax quinquecarinatus
- NightfishBostockia porosa
- South-west glass shrimpPalaemon australis
- South-western snake-necked turtleChelodina oblonga
- Western hardyheadLeptatherina wallacei
- Western minnowGalaxias occidentalis
- Western pygmy perchNannoperca vittata
Species found at the site
Fish and crayfish
The species recorded at the Lower Punrak Drain 2 site in 2022 are provided in Table 1 below. The table includes a list of all species previously reported in the subcatchment, which provides an indication of species that may occur at the assessment site. As differences in habitat within a subcatchment naturally influence species distributions, and variability in methods between sampling programs can affect the species caught, this list is only indicative.
Six species of fish and two species of crustaceans were recorded during the 2022 sampling. This included three native freshwater fish species (western minnow, western pygmy perch, and nightfish) two native freshwater crustaceans (gilgie and south-west glass shrimp) and two native estuarine-freshwater species (blue-spot goby and western hardyhead). The goby and hardyhead can complete life cycles in both freshwater and estuarine environments but are most common in the lower reaches of rivers where they can move into estuaries. This diversity of native species was similar to that recorded in 2017 at the MRPUNR1 site 350 m downstream. The 2022 assessment was the first time the western hardyhead have been recorded in this subcatchment. Encouragingly, juveniles were recorded for the western pygmy perch, nightfish, blue-spot goby and gilgie, indicating a habitat of sufficient quality to support the life history of these species.
One exotic species (eastern gambusia) was recorded, which was an improvement on observations at the MR64PUNR1 site in 2017 when two additional exotic species were recorded (goldfish and yabby).
Note: collection of fauna from inland aquatic ecosystems across Western Australia requires a licence from the Department of Primary Industries and Regional Development (DPIRD) and the Department of Biodiversity, Conservation and Attractions (DBCA). All species collected must be reported to these agencies as part of licence conditions.
Other aquatic fauna
Only freshwater fish and crayfish that typically inhabit river channels are targeted by the standard SWIRC sampling methods; however, other species are sometimes captured or observed. The following species were detected at the site:
- South-western snake-necked turtle (Chelodina oblonga)
- Carter’s freshwater mussel (Westralunio carteri) was observed during the 2022 and 2017 assessments. This mollusc is the sole endemic freshwater mussel species in Western Australia and is currently listed as vulnerable on the International Union for Conservation of Nature’s (IUCN) red list of threatened species (because of declining range, which is largely attributed to the effects of salinity).
For more information on these and other aquatic species, please see the River Science fauna page.
References & recommended reading
Explore other sites in the catchment
- Buchanans Drain
- Hotham River - Hotham River Nature Reserve
- Hotham River - Popanyinning
- Hotham River - Pumphreys Bridge
- Hotham River - Ranford Pool
- Lower Nambeelup Brook
- Lower Nambeelup Brook 2
- Lower Punrak Drain
- Murray River - Wyllie Farm Downstream
- Murray River - Wyllie Farm Upstream
- Murray River - Yunderup Road
- Murray-Marrinup Brook
- Serpentine River - Birriga Drain
- Serpentine River - Dog Hill
- Serpentine River - Downstream Peel Main Drain
- Serpentine River - Lowlands
- Serpentine River - Lowlands Road
- Serpentine River - Manning Road
- Serpentine River - Rapids Road
- Serpentine River - Ruperts
- Serpentine River - Summerfield Road
- Williams River - Boraning Reserve
- Williams River - Quindanning