Analysis Of Groundwater And Environmental Issues

Essay add: 22-10-2015, 20:34   /   Views: 133

Water as we all know, is one of the most important substances or natural occurring molecule that ever existed in our life. Indeed water is needed in almost every process, involving biotic or abiotic matter. There are many sources where water can be obtained, including from the lake, rivers and even the sea. Generally it's divided into two categories, surface water for example: river, sea and lake; or water below surface which is the main source I am writing about in this essay, the groundwater.

The three major points that will be discussed about in this essay, firstly how reliant is Western Australia on groundwater and how sustainable is the resource. Secondly, the major environmental issues associated with the use of groundwater from the Gnangara Mound which is located at the north of Perth. The third and last will be the discussion on the potential of treated wastewater to be used to recharge the aquifer.What exactly is groundwater? Groundwater is the water source obtained underneath the surface of land, an underground water source. Groundwater can be extracted through a water well from the aquifer which is located underground.

According to Pigram (2006), surficial aquifers occur in unconsolidated materials such as alluvium, colluviums and sands, as well as in calcrete and other carbonate deposits. The aquifers are highly productive and contribute about 60 per cent of total groundwater abstraction in Australia which is a very dominant water source. It is the major water sources of water for irrigation, industry and urban water supplies.

Groundwater, in one or more of the three broad aquifer types described, occurs in most parts of Australia. Groundwater is generally good in terms of its water quality. The quality is expressed either in terms of the total solids present in the water or its electrical conductivity.After a good introduction of groundwater, we move on to its sustainability factors and benefits, in order to find out why groundwater is the most dominant choice of water source in Western Australia. The sustainability principles of groundwater are basically divided into three major parts, environmental, socio-economic and strategic. Let's first take a look at the sustainability principle of which is environmental-related, it is somehow proven and believed that the usage of groundwater brings benefits biodiversity and ecological integrity which result in a net increase in ecological function or biological diversity in the region.

The extraction of groundwater is generally environmental friendly and safe which does not harm the threatened fauna and rare flora, as well as the groundwater dependent ecosystems. Not to mention that it the energy efficiency favours the usage of groundwater which operates at a level which is best practice in Australia, reasonable energy input and high availability in Western Australia.In the aspect of Socio Economic, usage of groundwater supports long-term economic health by assisting current and future economic growth, economic efficiency, economic diversity and business development. The reason behind that is due to the high availability and long lasting source of groundwater in Western Australia which only cost a reasonable affordable amount to sustain and extract. This leads to stable, efficient and quality public water supply for existing and future generations, which provides drinking water source protection.

This sufficient amount of water supply from groundwater source is then able to sustain the regional need for private water supplies will not be affected, which includes social, recreational and projected future development needs. Due to the sufficiency of water for regional development, there'll be no interruption disturbance of water supply insufficiency for the community, Western Australia community's well being and heritage are then maintained or even improved in terms of lifestyle, amenity and recreational use and access. There'll also be direct and indirect job generation.

Without doubt, it enhanced that sense of place, favours indigenous communities and assist development footprint.Finally the sustainability principle and factors of groundwater as water source which strategic-wise and beneficial. Groundwater source is strategic-wise to face the climate change issue right now in Western Australia, due to the low rainfall period and possible future climate changes, there'll be a major lack of surface water source as water level at rivers and lakes decrease or dry up. If that happens, ground water is the only water source that's able to facilitate the implementation of relevant government policies in a local regional due to equitable access to water to carry out government plans and enhance regional development.

Of course, by having a stable lasting sufficient source of underground water in Western Australia helps in terms of International and national competitiveness of water users by decreasing the cost of water by facilitating the competitiveness of local and regional industries in the national and international context. In other words, there is no need to spend extra money importing water from other regions, areas or even country which will cost a huge amount of money. Lastly it helps enhancing knowledge of resource to enable optimal use of the resource by self-suppliers which means independency as well as capability can be achieved.Now, it is clear to us about the origins of groundwater and it's sustainability as well as benefit in Western Australia, hence it's time to move on to the environmental issues associated with the use of groundwater, specifically the groundwater from Gnangara Mound which is located at the north of Perth, Western Australia.

As we know environmental issues do occur, it can be human cause or a natural phenomenon, but before moving into that, here's an introduction and facts about Gnangara Mound. Gnagara Mound's groundwater resources are considered as the most valuable and largest source of affordable good quality fresh water in the Perth, Western Australia. The area covered is approximately 2200 square kilometres and it is bounded to the south by Swan River and Gingin Brook to the north and extends inland to the Darling Fault.

The Gnangara Mound supplies approximately 70 per cent of the requirements of water for the greater Perth metropolitan area and supports a horticultural industry, as well as providing water to the Goldfields Agricultural Supply Scheme, towns in regional areas and Kalgoorlie-Boulder. However it is under stress from the current economic boom, rapid industrial and population growth and climate change.As we know from the previous paragraph, there are environmental issues associated with the use of groundwater from the Gnangara Mound. Initially the low rainfall due to climate change didn't cause a huge impact towards the use of Gnangara Mound groundwater.

However a major issue occurred when the combination of the low rainfall environmental issue with the excess 300 GL/year groundwater withdrawal and the drop by up to 5m of the water table in sandy unconfined aquifer as a result of reduction in recharge by pine plantations at its covered area and also about 500GL decline in aquifer storage over the last 20years.Another major environmental issue associated with the use of groundwater at the Gnangara Mound is the acidification of groundwater. The soil and shallow groundwater on the Gnangara Mound, Western Australia, is acidifying partially as a result of acid deposition from air pollution onto the soil. In the upper part of the saturated zone which is also the area of high drawdown revealed a reduced pH between 3.8 and 5 at 8 of 16 sites sampled. Depth profiles show a sharp acidification front, with a higher pH of 6 below the interface.

As a consequence, aluminium and trace elements (As, Cd, Pb, Cu, Zn and Ni) were released at low pH values. In the zone which is acidified, the Al concentration reaches as much as 8 mg/L. The sources and controlling mechanisms behind the observed geochemistry are explored by reactive transport modelling incorporating ion exchange, surface complexation and Al-hydroxide equilibrium.

These simulations estimate that the progression of the acidification front has taken place over 100 years at an average rate of 5 cm/year. Al-hydroxide dissolution and ion exchange involving Al with adsorbed Ca and Mg attenuates the progression of the front. Low pH releases trace metals from surface complexation, which accumulate by re-adsorption at the front due to the buffering mechanisms at this interface. Acidification and trace metal accumulation potentially causes severe impacts in a number of groundwater-dependent wetlands on the Gnangara Mound. As a result, indication towards the aquifer sustainable yields assessment needs to be considered under low rainfall in the aspect of geochemical interactions between groundwater, soils, aquifer sediments and vegetation, instead of just based on water-balance changes and aquifer hydraulics.As there is extraction, recharging will definitely be essential.

The recharging aquifer with water usually occurs naturally however due to the increase of underground water extraction, the amount of extracted water might be more than the amount of water recharged in a same period of time. The process of recharging the aquifer artificially requires an input of water which is only water possible to be used is treated used water, also known as treated wastewater. The potential to use treated wastewater to recharge the aquifer is not impossible and has already been proven to work. However there are a few biological factors that could influence the recharge rates of aquifer artificially, firstly algal and to a lesser extent bacterial growth, as well as sedimentation of fine particulate matter both organic and inorganic, ultimately the interaction of algae, bacteria and sediments. According to Jackes (1980), any procedures aimed at optimizing recharge rates must aim to reduce or at least controlling these factors.

Hence, it is proposed that a sedimentation pond to be established for the purpose of reducing the load of suspended solids carried by the recharged water, and that a trench to be constructed that favours minimal algal growth in the absence of algicides. Such trench should be shallow and slope gently downwards away from intake pipe and be lined with a coarse non-homogenous substrate. Similar biological factors is expected be important in any recharge system in Australia only differences is that the algal composition, due to the changes in temperature and nutrient levels.The potential to use treated wastewater to recharge the aquifer is said to be high due to its benefits, wastewater is treated which then recycled by recharging the aquifer which provides Western Australia's most dominant high demand water source, the groundwater. As a real example, wastewater recharge projects have been proposed for Alice Springs.

This great consideration is currently being given to the Alice Springs proposal since Alice Springs currently has wastewater effluent disposal problems. The source of Alice Springs water supply is the Mereenie Sandstone aquifer which is pumped at a rate faster than its natural recharge. After a long retention period, the water would reach the aquifer which then supplies water for all domestic purposes and would be subjected to dilution before extraction.

The higher salinity of the secondary treated wastewater due to evaporation from treatment lagoons precludes any direct beneficial use without dilution, for example: irrigation. The present ponding system of treatment could be abandoned due to such use of primary treated wastewater.As a conclusion, Western Australia is very reliant on groundwater, up to approximately 60 per cent of water source and the groundwater resource in very sustainable. The major environmental issues associated with the use of the groundwater from Gnangara Mound located at the north of Perth are due to the low rainfall climate change and the increase in acidity of the groundwater especially at high saturated area.

Finally the potential to use treated wastewater to recharge the aquifer is high and beneficial towards the present and future of the sufficiency of quality groundwater resource.



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