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A multidecadal analysis of groundwater level and streamflow decline in Southern Forest catchments, Western Australia
No full textPrevious analysis of hydrological data in the eucalypt dominated forests of Western Australia’s Darling Ranges show that reduced winter rainfall over the last 50 years has lowered groundwater levels and diminished streamflow by up to 70%. Consequently, climate-independent reverse osmosis seawater desalination and groundwater resources now supply Perth and nearby regional areas, as runoff from forested catchments is no longer sufficient or reliable. In the high rainfall (~1200 mm/yr) mixed forest areas dominated by Eucalyptus diversicolor (karri) and Eucalyptus marginata (jarrah) 200 km to the south of Perth (the ‘Southern Forest’), similar analysis of climate impacts on watertables has not been conducted. In this paper we collate over 48 years of groundwater data (1975/76–2024) along with climate and streamflow records to understand changes in the Southern Forest catchments. We assemble data from eleven research catchments that were intensively studied from 1975/1976 until mid-1990s, then abandoned. Some of these small watersheds were logged (1976–78 or 1982–83) and others left as unlogged controls. Both were monitored to study impacts on streamflow and water quality. We returned to these catchments after two decades of lapsed monitoring, comprising a period of reduced rainfall and forest regrowth, to determine how watertables contained in the deeply weathered regolith had responded. Analysis of climate data indicates that, like the Darling Ranges, annual rainfall reduced during the latter part of the 20th century. There have also been changes to seasonal rainfall and temperature patterns. Relative responses vary depending on location. Results from over 48 years of groundwater monitoring, comparing levels taken at the end of each dry season, show watertables in the deeply weathered regolith have fallen on average by 5.1 to 6.7 m ( \u3c 0.16 m/yr) beneath the stream zone and hillslopes in the paired and comparison catchments. In all cases, watertables are now \u3e 5 m below the stream zone (range: 5 to 13 m bgl), indicating little or no connection. Average falls were greater in the intermediate and higher rainfall catchments (paired catchments – 6.3 m (treated), 5.9 m (control); comparison catchments, 8.9 m (treated), 4.6 m (control)), with maximum falls of 10-12 m in some individual bores. In the low rainfall Yerraminnup catchments, falls were less (~2 m), however most bores are now dry. The timing and magnitude of reductions in watertables was variable between catchments, but in all cases had accelerated since 2000 and especially after 2010, when the driest years in the region were recorded. Reduced watertables at the end of the dry season equate to losses of 42% of the saturated zone storage under the stream zone and up to 64% storage under hillslopes. If rates of fall are sustained into the future, extensive areas of saturated regolith under hillslopes and stream zones would be depleted. Regionally, reduced rainfall and watertable decline has contributed to a 66% reduction in streamflow of the Donnelly River since monitoring commenced in 1952. From 2000, the Donnelly River has become intermittent, with dry periods in summer regularly exceeding 100 days. Ecologically important forests and riverine systems may become vulnerable to receded streamflow if these trends remain. In dry years, seasonal flows are dominated by water generated from upland cleared catchments, with first and last flows resulting from overflowing farm dams. CSIRO modelling, that accounts for the effects of non-stationarity, and uses current Global Climate Models, indicates a potential for additional reductions of streamflow of 32–45% by 2059, if forecasts of reduced rainfall remain classified as ‘almost certain’. This paper presents several metrics to help explain recent drying recorded in the Southern Forest. It suggests some drivers that explain the change in streamflow regime and outlines actions to improve data available to inform future decision making
West Coast Demersal Scalefish Resource recovery support package: 2024-25 report
No full textThe West Coast Demersal Scalefish Resource (WCDSR) includes over 100 species in inshore (20–250 m deep) and offshore ( \u3e 250 m) demersal habitats of the West Coast Bioregion. These species are caught by charter, commercial and recreational fishers. The WCDSR is in recovery and managed under a 20-year recovery plan (2010–2030). DPIRD tracks recovery progress through scientific stock assessments of indicator species (snapper, WA dhufish, and baldchin groper) every 3 years. The 2021 WCDSR stock assessment showed limited recovery and additional management action was required. In December 2022, the Minister for Fisheries announced commercial and recreational (including charter) sector management packages and a $10 million package to support recovery
Insights into spinifex (Triodia species) pastures and their management
No full textInterviews about various aspects of spinifex pastures were conducted with 21 pastoralists, five Traditional Owners, and seven rangeland scientists from the Pilbara, Kimberley, and central Australia regions. Interviews sought to provide insights into spinifex pastures and covered topics such as plant identification, burning, grazing systems, tree/grass balance and Indigenous uses of spinifex and burning practices; knowledge gaps were also identified.
The interviews made it clear that fire plays a significant role in spinifex pastures and is frequently used to enhance grazing productivity by removing old or moribund spinifex and allowing palatable new growth to replace it. Additionally, fire is used as a tool for wildfire mitigation by creating different-aged fire scars and subsequent variations in fuel levels across the landscape. The amount of non-spinifex material in the diet of grazing animals was also commonly discussed where, after rain, cattle primarily grazed on a non-spinifex diet by selecting the soft fresh growth of annual and perennial grasses and forbs where available.
At the conclusion of each interview, interviewees were asked what additional information they would like regarding spinifex pastures and their management. The most common request was for accurate identification of spinifex species. Interviewees also wanted more information on the nutritional value of spinifex seed heads and leaves; specifically, how nutrient content and digestibility change throughout the year and between fire intervals. Additionally, they expressed interest in comprehensive information on various aspects of spinifex biology, including growth habits, reproduction, response to fire, and the formation of spinifex rings
Fisheries Science Update - Western Australian Shark Resource: 2024 stock assessment outcomes
No full textThe Western Australian (WA) shark resource includes more than 100 species of sharks and rays.
Key shark species are sustainably harvested in two commercial shark fisheries that provide fresh, local, affordable seafood to the WA community.
The WA shark resource has been in recovery since the 1990s–2000s when stocks were found to be at risk.
The Department of Primary Industries and Regional Development (DPIRD) tracks stock status by undertaking periodic weight of evidence stock assessments of indicator species.
Gummy, whiskery, dusky whaler, and sandbar sharks, are the indicator species for the WA shark resource, and make up ~80% of the total shark catch.
This latest assessment provides an update on the recovery of indicator species and for the first time, assesses more than 100 shark species in WA.
The 2024 stock assessment shows that management arrangements have successfully recovered stocks of gummy, whiskery, and sandbar sharks to sustainable levels, whilst dusky whaler sharks are still recovering.
Most non-indicator species are also classed as sustainable stocks.
The current management arrangements within the shark resource, are expected to maintain the sustainability risk of indicator species at acceptable levels.
The next assessment of the WA shark resource is scheduled for 2029
An economic analysis of cell-fencing in semi-arid rangelands
No full textIn Australia, livestock predation by dingoes (Canis familiaris) has contributed to what some livestock producers consider a dire situation for rangeland pastoralism, driving demand for cooperative regional-scale exclusion (‘cell’) fencing (i.e. pest-proof fences that encompass one or more individual properties) and landscape-scale predator control. The present case study predicted the effect of four cell-fences in the state of Western Australia (WA) on the gross margin of sheep (for meat or meat and wool) and cattle pastoral enterprises. We modelled the potential effects of the following four key variables: (1) four levels of commodity prices, (2) five levels of livestock weaning rate (based on livestock records collected 1985–1995; weaning rate is defined as number of lambs or calves that are born and survive to weaning, expressed as percentage of total mated females), (3) three predicted levels of time required to remove dingoes from within the fenced area, and (4) five levels of macropod (mainly kangaroo) response as competitive grazers, with a total of 3600 scenarios representing all combinations of these factors. Each scenario was assessed for profitability (i.e. net present value (NPV) over 25 years) and benefit of fencing (i.e. NPV compared with an unfenced enterprise of the same livestock type, region, and commodity prices). Finally, the benefit–cost ratio (BCR) of investment in cell fencing was calculated for each fenced scenario. The majority (67%) of scenarios representing continuation of current management (i.e. no cell fencing) returned a negative NPV (i.e. livestock enterprises were projected to make a loss). However, only 37.4% of cell-fenced scenarios returned a positive NPV, meaning that even with a cell-fence and successful removal of dingoes, the enterprise was still unlikely to be profitable. Only 43.4% of cell-fenced scenarios returned a BCR of cell fencing greater than one. Weaning rate following dingo removal was the most important factor determining return on investment for cell-fencing. Survival and reproduction of small livestock, particularly wool sheep, benefit most from cell-fencing, whereas cell-fencing and dingo removal did not result in greater profits for cattle enterprises. Running sheep for wool and meat within cell fencing coupled with removal of dingoes would maximise the likelihood of achieving a positive return on investment in cell fencing (although the enterprise may remain unprofitable overall); otherwise, unfenced enterprises affected by dingoes should run cattle as this will be more profitable
Fluke egg sedimentation test procedure
No full textThe department’s approved procedure for detecting trematode eggs and the Eimeria leuckarti sedimentation method (FEST) on faecal samples
Seasonal variability in the South West Land Division: what’s in store for 2025?
No full textClimate trends in the South West Land Division (SWLD): Analysis of three time periods, 1950–1974, 1975–1999 and 2000–2024, reveals declining April–October rainfall, stable November–March rainfall, an increase in days exceeding 32°C between August–November, and a stable number of nights below 2°C during August–October. Performance of probabilistic rainfall outlooks: Evaluation of three-month probabilistic rainfall outlooks over 60 months (12 months × 5 years) indicates multi-model consensus occurred 48 times. Of the 48 times, the outlooks were correct 48% of the time and incorrect 13% of the time. 2025 seasonal outlook: Current projections for the 2025 season suggest neutral El Niño Southern Oscillation (ENSO) conditions in the Pacific Ocean and a neutral Indian Ocean Dipole (IOD). Most models indicate above median rainfall for February to April, accompanied by above normal maximum and minimum temperatures for the SWLD
Fisheries Research Report No. 345: Metropolitan monitoring program 2024
No full textOngoing monitoring of recreational fisheries in the Metropolitan zone is essential to ensure the sustainable use of fisheries resources. Surveys of shore- and boat-based recreational fishers within the Metropolitan zone of the West Coast bioregion provide information on human dimensions and catch-per-fisher as well as mean length and weight of key recreationally caught species. For shore-based fishers, estimates of fishing effort, catch and harvest are also presented for key nearshore species. Information in this report is used to support ongoing assessments for key nearshore species and inform the development and evaluation of harvest strategies and other management actions, such as for Australian Herring and Southern Garfish.
A roving creel survey was used to collect data from shore-based fishers between Ocean Reef and Point Peron (30% of coastline within the Metropolitan Zone) from February to June 2024. Estimates of fishing effort and catch therefore align with the spatio-temporal sampling frame of this survey. An access point (boat ramp) survey was used to collect data from boat-based fishers at key boat ramps between Two Rocks and Mandurah from January to July 2024. These data are considered to be representative of the entire Metropolitan zone
Training sensor-agnostic deep learning models for remote sensing: Achieving state-of-the-art cloud and cloud shadow identification with OmniCloudMask
No full textDeep learning models are widely used to extract features and insights from remotely sensed imagery. However, these models typically perform optimally when applied to the same sensor, resolution and imagery processing level as used during their training, and are rarely used or evaluated on out-of-domain data. This limitation results in duplication of efforts in collecting similar training datasets from different satellites to train sensor-specific models. Here, we introduce a range of techniques to train deep learning models that generalise across various sensors, resolutions, and processing levels. We applied this approach to train OmniCloudMask (OCM), a sensor-agnostic deep learning model that segments clouds and cloud shadow. OCM demonstrates robust state-of-the-art performance across various satellite platforms when classifying clear, cloud, and shadow classes, with balanced overall accuracy values across: Landsat (91.5 % clear, 91.5 % cloud, and 75.2 % shadow); Sentinel-2 (92.2 % clear, 91.2 % cloud, and 80.5 % shadow); and PlanetScope (96.9 % clear, 98.8 % cloud, and 97.4 % shadow). OCM achieves this accuracy while only being trained on a single Sentinel-2 dataset, employing spectral normalisation and mixed resolution training to address the spectral and spatial differences between satellite platforms. This approach allows the model to effectively handle imagery from different sensors within the 10 m to 50 m resolution range, as well as higher resolution imagery that has been resampled to 10 m. The OCM library is available as an open source Python package on PyPI
Challenges in modelling the impact of frost and heat stress on the yield of cool-season annual grain crops
No full textFrost and heat events at critical growth stages could cause large yield losses. These temperature extremes are increasing in frequency and intensity due to climate change in many parts of the broadacre cropping regions globally, presenting challenges to food production. For cool-season grain-growing regions, where summers are already too hot, heat and frost risks can limit adaptation options. Capturing these stresses in crop models accurately is increasingly important for evaluating the timing, severity, and yield consequences of extreme events. However, most existing process-based models were not designed to simulate short-duration temperature extremes, limiting their ability to assess climate risk and inform adaptation to frost and heat. Yield responses to heat and frost are associated with pollen sterility, grain abortion, accelerated senescence, and grain filling. Six challenges limit current modelling approaches: (1) inadequate spatial and temporal resolution of extreme events, (2) threshold-based and non-linear crop responses, (3) interactions between phenology and management, (4) cumulative and interacting stress effects across development stages, (5) limited representation of genotype-specific sensitivities, and (6) reliance on daily temperature data. Addressing these challenges requires improved use of sub-daily climate data, incorporation of physiological damage mechanisms, and enhanced crop- and genotype-specific parameterisation. These developments are critical for improving crop yield predictions under extreme temperatures in the context of climate change