428 research outputs found

    Groundwater trends in the agricultural area of Western Australia

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    In 1994 it was estimated that salinity affected more than 1.8 million ha of agricultural land in Western Australia (Ferdowsian et al. 1996). This area was predicted to expand to over three million ha by about 2020 and, if nothing is done to stem the expansion, to eventually affect some six million ha, or 30% of the agricultural land in the state. Damaging levels of salt accumulation in the root zone of both native and introduced plants can generally only occur when the groundwater levels are relatively cl te the variability of responses. Several depict episodic recharge (recharge as a result of either large storm events or a very wet year) and clearly show the need for long term monitoring of groundwater levels

    Water movement through soil

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    Even a good quality stock water moving to the surface can cause a salinity problem in only a few years

    Hillside seepages

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    \u27Hillside seepage\u27 is a local, descriptive term applied to almost any wet patch occurring out of the valley bottom. Depending on their surface appearances, \u27hillside seepages\u27 are described as \u27springs\u27, \u27soaks\u27, \u27wet patches\u27, or seeps. Whatever they are called, seeps can cause problems. The land in the seep is wet, unworkable and non-productive. If the seep is saline and the water flows downhill, further land is lost from production, bared and subject to erosion. Even small seeps, while not affecting much land, break up a paddock and complicate the working pattern for tillage and harvest

    On the soft X-ray spectrum of cooling flows

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    Strong evidence for cooling flows has been found in low resolution X-ray imaging and spectra of many clusters of galaxies. However high resolution X-ray spectra of several clusters from the Reflection Grating Spectrometer (RGS) on XMM-Newton now show a soft X-ray spectrum inconsistent with a simple cooling flow. The main problem is a lack of the emission lines expected from gas cooling below 1--2 keV. Lines from gas at about 2--3 keV are observed, even in a high temperature cluster such as A 1835, indicating that gas is cooling down to about 2--3 keV, but is not found at lower temperatures. Here we discuss several solutions to the problem; heating, mixing, differential absorption and inhomogeneous metallicity. Continuous or sporadic heating creates further problems, including the targetting of the heat at the cooler gas and also the high total energy required. So far there is no clear observational evidence for widespread heating, or shocks, in cluster cores, except in radio lobes which occupy only part of the volume. The implied ages of cooling flows are short, at about 1 Gyr. Mixing. or absorption, of the cooling gas are other possibilities. Alternatively, if the metals in the intracluster medium are not uniformly spread but are clumped, then little line emission is expected from the gas cooling below 1 keV. The low metallicity part cools without line emission whereas the strengths of the soft X-ray lines from the metal-rich gas depend on the mass fraction of that gas and not on the abundance, since soft X-ray line emission dominates the cooling function below 2 keV.Comment: 5 pages, with 2 figures, submitted to MNRA

    Saltland Drainage : case studies

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    Over the past five years farmers have become increasingly interested in the use of drainage to overcome saltland problems. Experimental work by the Department of Agriculture on sub-surface drainage includes tube drainage and drainage by pumping. The Department is also monitoring the performance of open drains installed by farmers. Major sites are at Esperance, Dalwallinu, Namban and Watheroo. Some of these projects have been reported in an earlier issue of the Journal of Agriculture. In this article P. R. George, Research Officer and R. A. Nulsen, Principal Research Officer with the Salinity and Hydrology Research Branch, discuss recent results from tube drainage experiments at Esperance, Dalwallinu and Namban and pumped drainage trials at Dalwallinu and Frankland

    Climatic change in Western Australia

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    The greenhouse effect is now an established scientific fact. Evidence published in the US and Australia in 1987 leaves little room for doubt. Carbon dioxide sent into the air whenever fossil fuels are burnt traps reflected heat from the Earth\u27s surface - just as a greenhouse traps heat on a summer\u27s day. The uncertainties currently present in any prediction of future regional climate are very large. This paper presents a synopsis of current literature related to the future climate of Western Australia.https://researchlibrary.agric.wa.gov.au/books/1009/thumbnail.jp

    Clay cover for roaded catchments

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    RECENT dry years have stimulated interest in improved catchments for farm dams. Although roaded catchments have been installed on many farm dams in Western Australia, most of them fall short of their potential for increasing run-off
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