Добірка наукової літератури з теми "Salts in Victoria Goulburn Region"

The introduction of watertable control by groundwater pumping on a salt-affected dairy farm in the Goulburn Valley resulted in large increases in butter fat production. Since intensive pumping started, in 1981, watertable levels showed an overall downward trend but were still subject to major fluctuations caused by irrigation and rainfall. During this period butterfat production increased from about 300 to 390 kg/ha (of productive land) and yearly pasture production rose from about 560 to 650 t/ha DM. These productivity increases are attributed to both a reduction in average soil salinity in the top 60 cm of the profile from 2400 to 1200 mg total dissolved salts per kg dry soil and an increase in irrigation water use from less than 10 M litre/ha before to nearly 12 M litre/ha after pumping started.

The Shepparton Irrigation Region Land and Water Salinity Management Plan promotes groundwater pumping and re-use for irrigation where groundwater quality and availability allow dilution with channel water (‘conjunctive water use’) to levels that produce minimal production losses from annual and perennial pastures used widely for dairying. In addition, municipal and industrial waste waters are used on a smaller scale for irrigating pastures (and crops). An upper level of irrigation water salinity (expressed as an electrical conductivity of 0.8 dS/m) is currently recommended in the plan. This recommendation is based on empirical data from experiments on unstocked, perennial pasture collected over 2 decades on red-brown earths in the region. While the strategy has, so far, achieved acceptable control of soil salinity levels, while generally maintaining pasture yields, a concern that ‘conjunctive water use’ may not be sustainable in the long term arises from the sodicity of the groundwater and waste waters. The continual addition of sodium to clay soils, initially low in both sodium and electrolytes (upper 0.5 m depth), risks the soils becoming sodified, with attendant soil physical problems should salts be leached to below threshold electrolyte concentrations, as in winter for example. We show that clay soils supporting pastures in the Shepparton Irrigation Region sodify with time under ‘conjunctive water use’. We review evidence for adverse effects of such sodification on soil physical properties affecting plant productivity and hydrologic processes important in the long-term sustainability of the strategy. On-farm management implications of the strategy are discussed and important issues for research are identified.

Polar subglacial hydrologic systems have garnered much interest since the recognition of Lake Vostok in 1996. In Antarctica, these environments are hydrologically diverse, including isolated lakes of different sizes, river–lake flow-through systems, “swamps” and groundwater (Siegert 2016). The refreezing of subglacial meltwater is also an important process beneath a large portion of the East Antarctic Ice Sheet (Bell et al. 2011). As subglacial water refreezes it exsolves salts, potentially leaving behind saline and hypersaline brines. Brines thought to derive from this cryoconcentration process have been observed in the northern polar permafrost regions and in the McMurdo Dry Valleys (MDVs) region of Antarctica. Additionally, sediments in the Victoria Land Basin have diagenetic signatures produced by brine movement dating from 3–11 m.y.a, suggesting hypersaline brines have existed in the McMurdo region since at least this time (Staudigel et al. 2018).

In response to a local survey that revealed that many farmers in the Goulburn Valley region of Victoria did not adhere to recommendations for safely applying saline irrigation water to perennial pasture, an experiment was conducted at Tatura. Six irrigation water quality treatments, which differed in the timing of the application of saline water, were applied to perennial pasture plots over 4 irrigation seasons. Measurements made included soil EC1:5, soil SAR1:5, soil ESP, pasture dry matter production and composition, dry matter digestibility, tissue ion concentrations and mineral ash content. After 4 seasons, in which the winter rainfall for each season was significantly lower than the long-term average, soil sodicity and salinity levels appeared to reach steady values. Plots irrigated with non-saline water (0.1 dS/m, treatment 1) performed the best in terms of lower soil salinity and sodicity levels and higher dry matter production and pasture quality levels. However, for most of these measurements and for most seasons, there were no significant differences between the control plots and those irrigated with water at 1.2 dS/m (treatment 2). Soil EC1:5 and SAR1:5 levels were highest, and dry matter production and dry matter digestibility levels the lowest (particularly for the clover component), in plots irrigated with water at 2.4 dS/m throughout the season (treatment 6). There were no significant differences in soil characteristics or biomass production between the remaining 3 treatments (treatments 3, 4 and 5) or between treatment 2. These treatments had the same amount of salt applied throughout the season but differed in the pattern of salt application — whether it occurred at the beginning or end of the season, or was alternated with fresh water throughout the season. This study confirmed that in the long term, there is a reduction in the yield of perennial pastures when saline irrigation water at levels greater than 0.8–1.2 dS/m is used on the red-brown earths of the Shepparton Irrigation Region. However, the soil and pasture were more sensitive to the total amount of salt applied rather than to the pattern of salt application throughout the season. It was concluded that farmers should monitor the salinity levels of their irrigation water to avoid a build up of Na+ and Cl– in the soil profile and consequent long-term reductions in herbage production and quality.

Seabee Hook is a low lying gravel spit adjacent to Cape Hallett, northern Victoria Land, in the Ross Sea region of Antarctica and hosts an Adélie penguin (Pygoscelis adeliae) rookery. Dipwells were inserted to monitor changes in depth to, and volume of, groundwater and tracer tests were conducted to estimate aquifer hydraulic conductivity and groundwater velocity. During summer (November–February), meltwater forms a shallow, unconfined, aquifer perched on impermeable ice cemented soil. Groundwater extent and volume depends on the amount of snowfall as meltwater is primarily sourced from melting snow drifts. Groundwater velocity through the permeable gravel and sand was up to 7.8 m day−1, and hydraulic conductivities of 4.7 × 10−4 m s−1 to 3.7 × 10−5 m s−1 were measured. The presence of the penguin rookery, and the proximity of the sea, affects groundwater chemistry with elevated concentrations of salts (1205 mg L−1 sodium, 332 mg L−1 potassium) and nutrients (193 mg L−1 nitrate, 833 mg L−1 ammonia, 10 mg L−1 total phosphorus) compared with groundwater sourced away from the rookery, and with other terrestrial waters in Antarctica.

This paper illustrates the hydrological limitations and underlying assumptions of 4 catchment modelling approaches representing different generic classes of predictive models. These models are commonly used to estimate the impacts of land use and management change on stream flow and salinity regimes within a target region. Three approaches are based on a simple conceptual framework that assumes a single layer groundwater aquifer and requires minimal information and calibration (Zhang-BC2C, CAT1D-BC2C and LUCICAT), whereas the fourth approach (CAT3D) adopts a fully distributed highly parameterised catchment model capable of simulating complex multi-layered groundwater aquifer systems. All models were applied to the Gardiner subcatchment within the Goulburn–Broken region of Victoria, identified as a National Action Plan for Salinity priority subcatchment. Current condition simulation results were compared with observed stream flow and groundwater hydrograph data. Results show that the simple frameworks predicted whole-of-catchment mean annual salt and water yield with minimum parameterisation. The fully distributed framework produced similar catchment-scale responses to the simple approaches, but required more intensive input data and solution times. However, the fully distributed framework provides finer temporal and spatial scale information within the catchment. The more detailed models (such as CAT3D) also have the predictive capacity to assess the within-catchment dynamics at a range of scales and account for landscape position and complex surface/groundwater interactions. This paper concludes that the simple frameworks are useful for judging the whole-of-catchment impacts of broad-scale land use change on catchment water yields and salinity and therefore provide valuable tools for community engagement. However, the within-catchment dynamics are not well represented and particular care must be taken when applying such models in those catchments where the interaction between groundwater and surface features result in saturated areas that are disconnected from streams. Adoption of a distributed groundwater modelling environment similar to that of CAT3D provides higher spatial resolution relative to the lumped broad scale groundwater glow system (GFS) based parameterisation adopted by the BC2C rapid assessment approaches. The developers of the BC2C model acknowledge that such models are currently limited to upland local and intermediate groundwater flow systems. Given that the majority of land salinisation is located in regions dominated by intermediate and regional groundwater systems, this tool is not well suited to adequately model regional processes. In contrast, the CAT3D distributed groundwater models are likely to be applicable across a range of scales and provide the capacity to assess the trade offs between salinity recharge and discharge intervention strategies. We conclude that more complex models (e.g. CAT3D) are needed to identify at the land management scale (paddock/farm) cost effective land use and land management changes within the catchment to improve catchment health.