The Aral Sea is situated in Central Asia, between the Southern part of Kazakhstan and Northern Uzbekistan. Up until the third quarter of the 20th century it was the world?s fourth largest saline lake, and contained 10grams of salt per liter. The two rivers that feed it are the Amu Darya and Syr Darya rivers, respectively reaching the Sea through the South and the North. The Soviet government decided in the 1960s to divert those rivers so that they could irrigate the desert region surrounding the Sea in order to favor agriculture rather than supply the Aral Sea basin. The reason why we decided to explore the implications up to today of this human alteration of the environment is precisely that certain characteristics of the region, from its geography to its population growth, account for dramatic consequences since the canals have been dug. Those consequences range from unexpected climate feedbacks to public health issues, affecting the lives of millions of people in and out of the region.
By establishing a program to promote agriculture and especially that of cotton, Soviet government led by Khrouchtchev in the 1950s deliberately deprived the Aral Sea of its two main sources of water income, which almost immediately led to less water arriving to the sea. Not only was all this water being diverted into canals at the expense of the Aral Sea supply, but the majority of it was being soaked up by the desert and blatantly wasted (between 25% and 75% of it, depending on the time period). The water level in the Aral Sea started drastically decreasing from the 1960s onward. In normal conditions, the Aral Sea gets approximately one fifth of its water supply through rainfall, while the rest is delivered to it by the Amu Darya and Syr Darya rivers. Evaporation causes the water level to decrease by the same amount that flows into the Sea, making it sustainable as long as inflow is equal to evaporation on average. Therefore the diversion of rivers is at the origin of the imbalance that caused the sea to slowly desiccate over the last 4 decades.
Level of salinity rose from approximately 10g/l to often more than 100g/l in the remaining Southern Aral. Salinity of the rivers varies with place and time, as well as through the seasons. When going through the desert, rivers often collect some salt compounds residues in the ground that result in higher salinity, but may well be lowered again after going through irrigated lands. Dams also affect salinity, notably by reducing its variability with the seasons. Smaller lakes within the Aral Sea that have stopped being fed by river flows tend to have higher salinity due to evaporation, causing some or all fishes that either survived or had been reintroduced in the 1990s to die. Even re-watering those lakes does not compensate for the increased salinity over the years. In 1998, water level was down by 20m, with a total volume of 210km3 compared to 1,060km3 in 1960.
Most of the changes in climate and landscape in the Aral Sea basin that we are about to explore are at the least indirect products of Human induced changes. While we must remember at all times that society is responsible for the crisis that has unfolded in and around the Aral, the point we want to make is that most of the actual changes that have afflicted the Sea since the 1960s are the result of our environments reaction to the stresses society has imposed on it. Thus, the difficulty lies as much in understanding the way climate and other natural systems function as in being capable of weighing the potential consequences of our actions before we undertake them. Risk assessment combined with scientific understanding should undercut our actions more efficiently; adding an ethical dimension to the equation remains more than welcome in addition to those more accessible and quantifiable factors, but is too fragile to be the centerpiece on which our decisions rely before we commit to large scale actions which can often, as we are about to see, engender even larger responses from our environment.
Aral Sea is located in the Central Asian Republics of Uzbekistan and Kazakhstan, with the southern section located in the Autonomous Republic of Karapakalstan. Aral Sea is a large inland sea that has no outlets. The Sea is connected to two rivers that supply the sea with water. These two rivers consist of water that is from glaciers. One river is called Amu Darya and the other Syr Darya. Amu Darya is 2,580 km long and flows northwest from the sources in the snow-capped Pamirs. The waters from this river are used for irrigation in Turkmenistan and Uzbekistan. Syr Darya is 2,220 km long and it is also used extensively for irrigation.
It is formed in the Fergana Valley by the confluence of the Naryn and Kara Darya rivers. When combining the two rivers we see that it is quite large with a combined annual flow of 111 cubic km, this is higher than the river Nile which is only 90 cubic km. The fresh water from these two rivers held the Aral’s water and salt levels in perfect balance. Even though much of the water in the river is lost to evaporation, transpiration and seepage as the river flow across the desert. There is still enough water in the river to maintain the Aral Sea normal surface area. But more recently due to human intervention not enough water is entering the sea.
This is because locals tried using the rivers as an economy advantage and started many irrigation schemes to produce cotton. But this lead to the shrinking of the Aral Sea and it was shrinking so fast nothing could be done to prevent it. So in this case study I will be looking at how the whole surrounding was affected by the Shrinking of Aral Sea. The Biophysical Environment “The area around Aral sea consists of dry, flat plain with few rivers. Aral Sea is situated in the middle of the Asian land. So the area around it experience hot, dry climates which have the land similar to that of a desert or steppe grassland.
The Average annual precipitation rarely exceeds 150mm per year. The range between the minimum and maximum temperature is a huge difference. The maximum temperature is 47 degree centigrade in the summer and in the winter it falls to -20 degrees centigrade. The air around the Aral sea is very dry. In the summer the humidity by day is less than 25% and my midday it can fall below 10%. In winter the humidity averages to 40 to 65% during the day. It is has also been noticed that many parts of Kazakhstan and Uzbekistan experiences hot, dry winds called the sukhoveya, these winds can cause severe damage to crops.
The soil around this region is quite sandy this means that they do not retain the moisture that falls on them. And because of the winds it picks up the salt from the area where the sea has retreated backwards and blows them over the soil. When salt settles on the top of the soil it does not allow water to seep through the soil and water evaporates from the surface of the soil. Therefore the plants then die out. As they’re not getting enough water. This destroys the present crops and also in the near future the land will be suitable to grow crops.
This process of the wind blowing salt over the land is called salt deflation. edited from the book Planet Geography by Stephen Codrington Change in Climate Conditions & the impact to the surroundings During the last five to ten years the drying of the Aral Sea, has bought many changes in the climate conditions. Before the drying of the Aral Sea it was a regulator mitigating cold winds from Siberia and reducing the summer heat. But as of now the climate has change this is because evaporation has decreased due to low volume of water in the rivers and in Aral sea. Thus the climate change has led to a dryer and shorter summer in the region, and longer and colder winters.
The vegetative season has reduced to 170 days. This result in the pasture productivity has decreased by half, and meadow vegetation has decreased by 10 times. The Air temperature during winter has fallen, and summer temperature has increase by 2 to 3 degree centigrade. There has also been frequent occurrence of long dust storms and ground winds. Strong winds blowing the area now, there most intensive on the western coast, with around 50 days of storms per year. The maximum wind velocity reaches around 20- 25 m/s. And now by looking at this we can see that in these climate conditions agriculture without irrigation is not possible.
But in this dry climate people started making cotton through irrigation instead of food. So even when the people knew that due to irrigation the Aral Sea is shrinking they cannot stop the scheme as there using this to grow cottons. So if they do stop they will lose their jobs and money. So this led to an increase in irrigated land in Uzbekistan. Below is a diagram that shows the change in climatic conditions. And we can clearly see the difference from the two. The above one is from before the drying of the Aral Sea and the second one is after the drying of the Aral Sea.