Impacts of irrigation (Essay Sample)

Describe irrigation impacts on water resources
Irrigation is the supply of water to agricultural areas that have no sufficient water for crop planting. This can be done in various ways depending on the source of water through a system of tubes, pumps and sprays. The source of water can either be natural or alternative. The natural sources are the rainfall and surface water like that from lakes and rivers. According to Crase & Dollery (2006), alternative water sources are the reuse of municipal wastewater and drainage water. In either way, the water must be used sustainable way. Alternative water sources however have adverse effects on public health and environment. There are several types of irrigation depending on how the water is going to be spread through out the field. They include surface and sprinkler irrigation among others.
Irrigation degrades land in which it is applies in several ways; salinization, alkalization, water logging and soil acidification. Water logging is the effect irrigation has on water resources in this impact. Water logging usually results from the over use or poor management of irrigation water. Worldwide 10% of irrigated land has been water logged reducing productivity by 20%. In most areas this problem is normally compounded by salinization. This is a process that has affected the world especially semi-arid areas that are poorly drained. It occurs when water evaporates from the soil leaving behind the salt concentration from the rain water and irrigation that has passed over land and other materials. Though usually in low concentration, after evaporation the concentration rises (Gondim et al 2012).
Ground water increase and salinity
It has been found that when water for irrigation goes down to the soil level, the water table water level rises. When this phenomenon occurs the dissolved salts within the soil structures are brought to the surface. Too much salt on the surface where the crops; rice, grapes and cotton are grown especially in Australia causes salinity. No crop can grow with too much salt. As a result there is crop failure. This is a direct consequence of increased level of ground water.
Ground water depletion
There is competition for the water source to be used in irrigation. Surface water sources are the main sources of water for irrigation in Australia. They include; the Murray-Darling system in eastern Australia and the Ord River in the Kimberley region of Western Australia. Queensland hosts another significant river and dam system for irrigation on the Burdekin River. This is in the south-west of Western Australia as well as the MacAlister district of Victoria. Water is used only in the dry seasons and for double cropping in the Queensland region (Brown 2012).
Only 6% of Australia’s rainfall; is received in the Murray-Darling basin making the area to have a concentration of 70% of all irrigation activities carried out in that area. This therefore means that the region provides 40% of the nation’s food as 42% of the nation’s farms are found in the same region. Most surface water sources are overwhelmed as they are also used to generate electricity among other uses. This makes ground water the other alternative as a source of water for irrigation. This therefore means that a lot of water will be generated from the ground water sources depleting them in the end (Pfeiffer & Cynthia Lin 2012).
The ground water that Australia depends on majorly is found in the Great Artesian Basin. This region has natural springs as a result and man made bores that help provide for both livestock and crops in the north-eastern region of Australia. Another problem that faces ground water due to irrigation is intrusion of sea water into; the coastal aquifers and rivers. This is as a result of lateral and upward movement of coastal water giving rise to saline water on crop level. This will significantly affect crop production. Examples are found in the Jordan River basin. Sea water intrusion in rivers occurs when with continued use of use of river water for irrigation purposes, fresh water reaching the sea is reduced. Sea or ocean tides therefore rise and gets into the river upstream such that those using fresh water have a mixture of water depleting its quality (Forkuor, Pavelic, Asare, Obuobie 2013.).
Detail why it is important to study these processes and previously researches in Australia;
Water logging
This is one of the global phenomenon most ignored irrigation problem affecting over 22million hectares of land. This is just 10% of land in the world put under irrigation. It is caused by the excessive irrigation of a poorly drained land. The irrigation water can not be therefore absorbed deeply. This effect can also result from the occurrence of a clay layer below the water table such that any excess water does not go through but remains and thus rises to the ground. It is usually detected late because the tests for such a process are usually expensive for most of the farmers (Stevens, Harvey & Johns 1999).
Water logging is important to understand for farmers who practice irrigation because as we have mentioned they detect it when it’s already done and can therefore do nothing to reverse the damage. According to Bowonder et al (1987) the effects of water logging are that the roots are suffocated. This occurs when the air spaces on the root zone of plants are filled with water thereby denying the root the required amounts of oxygen for growth. This is not the only problem they create, they also result in salinization. When water rises as we had mentioned in the question above, they bring with them dissolved salts such that when evaporation takes place the salt remains behind. This is bad for crop growth as the salt is too much for further growth therefore the plants die early (Wu-qun, Ren, Yilei & Yaqing 2009).
There are three available solutions for such eventualities which a farmer can adopt to avoid and prevent further water logging to recur. They can improve the efficiency of the water irrigation system. This means that the soils should be well drained and the land is not excessively irrigated. Another solution is planting appropriate crops; these are crops that do not require so much water for growth and can consequently grow in arid and semi-arid areas without much water. The third and equally important solution is the cost of water. As it is water is not worth its true value. Its cost should be increased for purposes of conserving it unlike in some countries like where policies encourage wastage of water (Bowonder, Ramana & Rajagopal 1986).
Ground water depletion
This is water that feeds the surface water sources like lakes and rivers as well as water that is found in the aquifers. In southern Australia ground water is the most consumed water providing 65% of horticulture, viticulture and also drinking water to the population both in the rural and general southern Australia. Beer production is also another use ground water finds application in Australia (Stevens, Harvey & Johns 1999).
The main cause of ground water depletion is the overexploitation of this ground water. People’s ignorance also plays a major role in this case. There are therefore several reasons for people to understand the whole mechanism and inter relationship that make up ground water. Ground water finds most use in areas where the precipitation is quite low over the years. It also finds most use in areas where surface water is limited and inaccessible. In the Murray Darling basin, depletion of the ground water has been mostly affected by the competing interests of the states that have boundaries within the basin.
Excessive pumping of ground water leads to the following compounding the negative impact of depletion:
drying up of wells
reduction of water in streams and lakes
deterioration of water quality
increased pumping costs
land subsidence (Hren & Feltz 1998)
Drying up of wells
In this scenario it is usually the water table that declines. With the over pumping of water to the surface through the wells, the water might go further down below the normal water level. When this happens there will be no water in wells and the owner will be forced to either to dig the well deeper or dig another well (Stevens, Sweeney, Meissner, Frahn & Davies 1999).
Lakes and streams water reduction
No many people understand that surface water originate there water from ground water seepage. Most of the world surface water depends of ground water for their waters. All these depends on the climatic and geological conditions the area is in. over pumping of ground water can have two effects; faster rate of loss of water to the ground water aquifer from the surface water feature or slow the rate at which the aquifer feeds the lake or stream (Xianjun, Zhanyi, Jayawardane, Blackwell & Biswas 2003)..
Poor water quality
There usually exists a stable balance between the saline and fresh water in the ground. In fact there is more saline water than fresh water according to Gleick (1996). Over exploitation of ground water will therefore destabilize this balance especially in situations where there is sea water intrusion as has been described in the 1st question.
More pump costs
When the water table’s level decreases, it will require more energy to lift or pump the water to the surface. If it is a new well digging deeper and lifting the water is even more expensive. This makes ground water depletion an expensive affair to those who need water especially for drinking. It also increases the cost of water.
Subsidence of land
The main reason for this is the lack of proper supporting structure. With the removal of ground and human activities removing sub surface water, the soil collapses, compacts and the land above it drops thus the subsidence (Stevens, Pech & Grigson 2008)....