Irrigation and Agriculture

ARAL SEA FACTFILE

map of Aral Sea

Where is Aral Sea?

map of Aral Sea

Aral sea is situated in the far western Asia, to the east of the Caspian sea, the Aral Sea is located in the countries of Turkmenistan and Uzbekistan with two main rivers running into it; Syr Darya and Amu Daraya.

Causes of Shrinking

Aral sea used to be the fourth largest lake in the world and produced thousand tons of fish for the local economy annually. However,since the 60s the Aral Sea has been shrinking.

WHY is it shrinking ?

In 1920s, the former Soviet Union turned the lands of Urbekistan into cotton plantation and ordered the construction of irrigation canals to provide water for the crops in the middle of the plateau region. These irrigation canals moved water from Rivers Syr Darya and Amu Darya, which were the rivers that runs freshwater into Aral Sea.

Until 1960s, everything was pretty stable, however, in the 60s the Soviet Union decided to expand the canal system and drain more water from the river which lead to a destruction of the Aral Sea.

Aral Sea timeline

THE DESTRUCTION OF ARAL SEA 

In the 1960s, Aral Sea started to shrink rapidly.

By 1987, the single sea dried up and was dry enough to create a northern and southern lake. In 2002, the southern lake shrunk and dried up to become an eastern and western lake. In 2014, the eastern lake completely evaporated and disappeared.

Environmental consequences/impacts

• dust storms
• salt blown
• cancer/respiratory problems
• no fishing commercial industry gone economy devastated
• water high salt content
• salt changes the colour of the lake —> microclimate change

Impacts on water levels

Due to the drop in water level of approximately 23 meters which caused the rate of water loss from the Aral sea to be explained by a positive feedback between the rate of evaporation and sea surface temperature. The dessication of the Aral Sea was also caused by the sharp increase of salinity in sea water. As a result due to the loss of water, the inflow of salts to the sea exceeded the salt discharge causing the level of salinity to increase. As the groundwater was close to the surface maybe evaporated, leaving behind more soluble salts.

Furthermore, there was also a change in Sea Surface temperature. Since the volume of the sea is declining, the largely reduced the heat capacity and therefore warming up and cooling off faster than usual causing the Aral Sea is starting exhibit a monsoon climate.

Impacts on Desertification and Dust storms

The drying off of the Aral Sea resulted in two different kinds of desertification; the newly dried sea bed and the artificial water logging of irrigated lands. Desertification was one of the main impact, including the decline of groundwater level .The decline in the groundwater level in the Amudarya and Syrdarya deltas caused and increase in salt content in the area. Therefore, vegetation in the region died and was reduced by at least 40% which leads to intensified winds as well as causing an increase of dust storms and salt storms in the area.

The pressure from the water surface reduced the strength of the northerly and north-easterly winds, the retreating of the sea meant that the protective action from the winds was significantly reduced causing it to leave behind large amount of salt as well as increasing groundwater evaporation which increased the amount of salt from the exposed seabed.Eventually, the wind picks up the salt and dust , creating huge dust storms.

Impacts on salinisation

One of the most negative impacts of the dessication of Aral sea is the increase of salinisation of soil. This was caused due to the decline in groundwater level causing the salt to accumulate in the subsoils in which leading to an increase in salt deposition in the soil. Salinization of soils accerlerated the desertification process due to the sharp decline in ground water level as well as the drying up of subsoils. As a result, leading to soil erosion and degradation which was one of the results of extensive fertiliser use. 

Impacts of climate change

Due to the evaporation of water, leaving behind huge amount of salt changing the surface colour of the lake in which affecting the surface reflectivity of the sun’s incoming solar radiation. ( Albedo effect) As the earth’s albedo is a powerful drive of climate therefore if the albedo or reflectively increases, more incoming sunlight is reflected back into space. It has a cooling effect on global temperature. Consequently this means that a drop in albedo warms the planet leading to a microclimate.

Impact of humans

With the increase of dust and salt storms, there was an increase of illnesses in children that are mainly related to respiratory system difficulties.

Irrigation

Irrigation: artificially watering the land with water taken from reservoirs,rivers,lakes or from the underground

Different types of irrigation are as follows:

1)  Terrace irrigation

Image showing terrace irrigation

–  Usually used in steep slope by cutting steps into the land, water is retained and also allowed to effectively drain down slopes.

2) Drip Irrigation

– Drip irrigation helps the system to save water by applying only where and when it needed, with less runoff and less evaporation from leaves and soil, however, it is very expensive to set up.

3) Ditch irrigation

ditch irrigation

– this is conducted by creating small parallel channels along the field length in the direction of predominant slope.

4) Sprinkler Irrigation

sprinkler irrigation

• central pivot system

Impacts of irrigation

Little moisture for evapotransporation to occur

Increased moisture levels and vegetation caused an increased in evaporation and precipitation

Cause a raise in the water table

Pakistan floods

example: Pakistan

During the 1992, there was a raise in the water table of 6 m in Pakistan due to its monsoon climate including salinisation. This was cause by the extensive irrigation.

salinisation in Pakistan

The impacts of irrigation in Pakistan 

– In hot areas, there will be high evaporation rate which means that water will evaporate leaving behind salty deposits in the soil and reduces yields.

• Irrigation also causes changes to the natural water balance of irrigated land
• Large quantities of water in irrigation areas are not consumed by plants and must go somewhere, therefore surplus water may caused water erosion to occur. Since there are no drains in most of the LEDCs, no excess water can be taken away.
• In irrigation projects it is impossible to achieve 00% irrigation efficiency where all the irrigation water used by plants
• The maximum attainable irrigation efficiency is about 70%. This means that minimum 30% of the irrigation water is not evaporated and must go somewhere.
• Most of the water lost this ways is stored underground which can change the original hydrology of local aquifers considerably
• Many acquifers cannot absorb and transport these quantities of water and, the water rises leading to water logging in which causes salinisation.
• Water logging was also on of the causes behind the rise in the level of the water table. Often not all the irrigated water is used , a lot is left to runoff and a lot is not infiltrated at a fast rate leading to water logging which leads to salinisation. Over the years, about 40 percent of the irrigated cropping land in Pakistan, which produces around 90 percent of the total agricultural output of the country has come under water logging, This causes the land non-cultivable and poses a serious threat to the agriculture sector and to the country, as agriculture is the bloodline of Pakistan’s economy.   
• Since many fertiliser are used on the crops to increase yield, water will flush them into the sea causes eutrophication

Agriculture

agriculture : Agriculture is the artificial cultivation (growing or rearing) of plants or animals

Arable agriculture

Agriculture that grows crops is known as arable agriculture, whereas, agriculture that involves rearing animals is known as pastoral.

Pastoral agriculture

Growing demands for Agricultural products

• The world’s population is growing. The current population is about 7 billion, but it is expected to peak at nearer to 9 billion.
• Because fossil fuels are finite, alternative forms of energy are being looked at. One form of renewable energy being used are biofuels. Biofuels are made out of biological matter and therefore are increasing the demand for agricultural products.
• Economic development. As more of the world’s population is removed from poverty, their calorific intake increases. This increase in food consumption, is increasing the demand for agricultural products.
• Pastoral farming. As the world population increase, the demand for meat also increases. Most farm animals are omnivores or herbivores so need agricultural products like corn to eat.

Decreasing supply of agricultural products or land

• Urbanisation: As the world develops, urbanisation increases tends to happen increasing the size of urban areas. As urban areas grow they eat into greenfield sites in rural areas, reducing the amount of agricultural land.
• Land degradation and desertification:Land that is overcultivated or overgrazed can become degraded (less fertile). AS farmers try to react to demand by growing more intensively, more land is being degraded. In extreme circumstances, the land may turn to desert (desertification).
• Rising sea levels. Some of the earth’s most fertile agricultural areas are floodplains and deltas. As world sea levels (eustatic changes) increase much of this fertile land is lost.
• Conversion to biofuels: Although not strictly reducing the amount of agricultural products (biofuels are agricultural products), this does decrease the supply of agricultural products available for human consumption. Biofuels are often favoured by farmers, because they demand a higher price.
• Hazards: Natural hazards like tropical storms, volcanoes and tsunamis can reduce the amount of agricultural land available for cultivation.
• Disease: There is an increasing amount of intensive monoculture (growing of one crop) taking place. Monoculture always runs the risk of been impacted by the outbreak of diseases or pests that attack the particular crop e.g. wheat leaf rust fungus.

Increasing agricultural land

Land reclamation : with land on the earth running out, more land is being reclaimed. This can be done by reclaiming land through drainage (above) or infilling coastal areas. Although this increases the amount of available land, the land can have a high water table with a high salt content. However, it does mean coastal reclaimed land can be used for urban growth, leaving more greenfield sites for agricultural production.

Irrigation:  By irrigation areas of land, areas that were previously too arid to support agriculture can be used for agricultural production e.g. a long the banks of the River Nile in Egypt.

Drainage : Areas of wetlands can be drained, or that they can be used to grow agricultural products. The East of England used to be largely covered in fens. The fens have now been drained and it is England’s most productive agricultural area.

drainage

Deforestation: By removing trees, this can increase the amount of agricultural land. However, areas that have been deforested tend to degrade very quickly. By removing trees you are removing the grounds source of humus and reducing its stability (tree root network). With the trees removed the ground becomes very vulnerable to wind and water erosion.

deforestation

Fertilisers: Land that lacks nutrients can be brought into production by increasing the fertility of soil. This can be done by adding nutrients to the soil. It might also be possible to use previously unsuitable farm land by growing GM crops.

Terracing: Terracing tends to happen on volcanic mountains, because the soil is so fertile. Terracing is simply cutting multiple layers into the mountainside to create small areas of agricultural land.

Clearing of lands

1. Forest – changing the local hydrology, both surface and ground water will cause an increase in flooding
2. Soil erosion through wind and water, reducing and altering the biodiversity
3. Draining wetlands, destroys habitats and reduces water supply
4. Farming can also lead to runoff and leaching of nutrients into rivers, streams and underground water

clearing of lands

The biggest pollutants are : nitrogen , phosphate, animal waste

• With various chemicals typically enter water ways through infiltration or runoff.
• Fertiliser can be eaten by animals containing nitrogen. Nitrogen is present in urine runoff or infiltrate/leached , entering streams rivers and lakes causing eutrophication.

eutrophication

• This can cause aquatic weed growth and pollute water ways.