Aral Sea Project I reaching completion
Images of fishing boats stranded on the desertified, salt-encrusted bed of what was formerly the Aral Sea, the world's fourth largest inland lake, caused widespread shock when they came to public attention in 1997. Michael Haigh, divisional director in Mott MacDonald's Water and Environmental Management division, reports exclusively for World Water on the first phase of the Aral Sea Basin Project, which is designed to secure the existence of the North Aral Sea, sustain and increase agriculture and fishing, and improve human health.
The project stretches from the 5 billion m3 Chardara Reservoir in the south-west of Kazakhstan, close to the border with Uzbekistan, along 1000km of the Syr Darya River flowing in a north-westerly direction to the Aral Sea.
The project's overall objectives were to:
- Sustain and increase agriculture, including livestock and fish production, in the Syr Darya basin.
- Secure the existence of the NAS and improve the ecological/environmental conditions in the delta and around NAS, leading to improved human and animal health and biodiversity.
- Stabilisation of the level of the NAS
- A halt to the drying out of lakes and wetlands in the river delta
- A fall in the salinity level in the NAS
- Re-establishment of a sustainable fishery in the NAS with an increase in the yields of freshwater fish
- Measured mprovements in the quality of air, water, biodiversity and the health of people living in Kazalinsk/Aralsk
- Improvements to crop production on land irrigated by the Syr Darya River.
The Syr Darya project includes three main components:
1. Rehabilitation of the NAS
Construction of a dike across the Berg strait, a deep channel connecting NAS and LAS. The dike will be include a spillway for regular use. These measures are designed to stabilise the level of the NAS and allow for flushing to maintain an acceptable salinity level and pass flows during periods of high inflow.
2. Improving hydraulic control
The rehabilitation and construction of structures, which will contribute to regulation and improvement of water management, and controlling allocations to various water users, including an increased inflow for the NAS. Works under this component include:
- Reconstruction of Aklak weir to regain control of water levels in the delta region
- Reconstruction of two major water control structures at Aitek and Karaozek
- Repairs to two other major water control structures at Kazalinsk and Kzylorda barrage
- Rehabilitation and construction of low flood protection bunds along the river
- Rehabilitation and improvements to the outlets from Chardara Reservoir, which are currently limited to 40% opening owing to vibration problems, hence increasing the discharge from the reservoir into the Syr Darya River in Kazakhstan.
In addition to the works to the outlets from the dam, other significant repair works were required and in this phase of the project, priority works will be dealt with. In particular it was found that the hydraulic fill silty sand dam had been piping through a fractured joint in an irrigation draw-off culvert when sinkholes were observed in the crest of the dam.
To date, over 300m3 of grout has been pumped into cavities below the culvert. Repairs are also required to the dam's drainage system, upstream concrete facing and hydro-mechanical equipment and rehabilitation and improvements need to be made to the dam's instrumentation.
Other elements of the project include: Aquatic Resources Restoration and Fisheries Development, Monitoring and Evaluation and Project Management and Institutional Development.
Full project implementation is anticipated to take five years from July 2001 to 2007. The Committee of Water Resources of the Ministry of Agriculture has overall responsibility for project implementation.
This phase of the Syrdarya Control and Northern Aral Sea project comprised the implementation of around 12 separate construction contracts, which is now largely completed with the exception of the rehabilitation of the Chardara Dam which is on-going.
The Aral Sea Basin: a brief history
Ever since the nineteenth century, there has been an interest in increasing cotton production in the Aral Sea Basin, a region well suited for the crop. Cotton production, irrigated by the basin's two great rivers, increased steadily from the 1870s until the 1960s, when a vast new irrigation expansion drew off so much water that the Aral Sea began to dry up.
In 1990 the Aral Sea split into a small North Aral Sea (NAS) and a Large Southern Aral Sea (LAS) as the waters receded. Derelict freighters and fishing boats in a vast salt landscape, which used to be the bed of the Aral Sea, drew the world's attention to the environmental crisis the Aral Sea has been facing.
People living in the delta and lower river stretches suffered from increasing health problems, as the final stretches of the river carried less and less freshwater and correspondingly higher concentrations of pollutants and salt. Fish died as the water became more saline, and so the commercial fishing industry failed.
Agriculture in the deltas failed as well, owing to the shortage of clean water. As the lakes and wetlands of the deltas desiccated, habitats of birds and mammals vanished.
Whilst the Aral Sea and environs were being degraded through human interference in the river system, resulting in less water reaching the Aral Sea, water was also being wasted. Not all the water reaching Kazakhstan could be passed down the Syr Darya River, as it was being increasingly diverted into desert depressions when there was insufficient storage and flow capacity in the system.
Between 1993 and 2002 an average of 2.8 billion m3 per year was going into the Arnasai Depression via a 2100m3/s spillway from Chardara Reservoir. It was not possible to pass all the available water to the Aral because of the storage available in Chardara Reservoir when the water reaches Kazakhstan and the capacity of the river between Chardara and the Aral Sea.
Means were sought to mitigate the crisis of the Aral Sea through improved water management. It was noted that water shortages were exacerbated by failures of water control structures in the Syr Darya river basin.
As the sea level dropped, the river level fell too, exposing the foundations of river control infrastructure to erosion. Delta lakes were soon elevated above the level of the rivers and sea, which were no longer fed by the rivers. The lakes evaporated or drained away, refilled only when the river flooded its banks.
Much of the major hydraulic infrastructure in the Syr Darya basin was developed in the 1960s and 1970s. Owing to severe downstream erosion, caused by the lowering of the Aral Sea, the first structure at the mouth of the river, namely Aklak weir, became non-functional. Left unchecked, riverbed erosion would have moved upstream and in time most of the hydraulic and transport infrastructure would have been undermined.
The carrying capacity of the Syr Darya was also limited owing to the inadequacy of the hydraulic infrastructure and because the embankments along many stretches of the river provided insufficient protection against flooding to the towns and villages that had encroached onto the rivers flood plains. During the post-Soviet period, maintenance of water control infrastructure fell short of what was required and this exacerbated the situation by reducing the capacity of the Syr Darya further.
An additional challenge was posed by the conflict between the management of resources to maximise hydropower whilst still satisfying the irrigated agriculture demands. Chardara was not being drawn down sufficiently prior to the main winter inflow periods when water was being released from the upstream reservoirs.
As a result, storage was not always available for periods when the inflow exceeded the capacity of the downstream Syr Darya River and therefore water had to be diverted into the Arnasai Depression. The rehabilitation of major hydraulic infrastructure thus became a major priority.
The government of Kazakhstan and the other riparian states have worked together and with the World Bank for several years to develop a sound strategy to improve water management and rehabilitate the NAS. This project is one part of that strategy.
Contact: Mott MacDonald
Tel: +44 1223 463500