IWRA Executive Office

abstract 179

Enhanced risk management strategies for mitigating future droughts in Central Asia

Author(s): Oliver Olsson, Malika Ikramova, Matthias Obermann, Melanie Bauer, Jochen Froebrich
Malika Ikramova: Central Asian Scientific Research Institute of Irrigation (SANIIRI), Complex regulation of river flow department Karasu – 4, 11/41, 700187 Tashkent, Uzbekistan Oliver Olsson, Matthias Obermann, Melanie Bauer, Jochen Froebrich: Divis

Keyword(s): reservoir, storage capacity losses, water scarcity, hydrological risk assessment, Amu Darya

Article:

Poster:

Session: Poster session 4

AbstractIntroduction
Glacial and snowmelt is essential for the well being of all Central Asian

states and provides over 90 % of their water requirements. Climate change is causing rapid recession of the glaciers,

which helps to meet in short-term the states ambitious water requirements, but in the long term decreased runoff and

increased evapotranspiration from higher temperatures will result. Additionally, climate change has an effect on the

frequency and intensity of extreme droughts, with the consequence of increased exceptional water deficits as

occurred for the lower Amu Darya River during 2000-2002.

The development of effective risk-management

strategies for securing future water supply under varying conditions of water shortage in semi-arid and arid river

basins needs (i) to revise the existing storage capacities, (ii) to improve the forecasting methods, (iii) to associate

possible water saving mechanisms and improved crop growth patterns at the downstream areas, and (iv) to adapt

the dam operation at upstream and downstream regions accordingly. Therefore, a risk assessment is substantial to

investigate the changing conditions and the interaction of processes within the run-off generation upstream, reservoir

storage capacity losses and increased water consumption downstream.

Objective
The focus of the study lies

on the assessment of ongoing reservoir storage capacity losses and its effect on the compensation of water deficit

volumes during exceptional drought events, in order to provide critical values for an enhanced drought

management.
The objective is to analyse current capacity losses and the impact of past reservoir operation

strategies on the sedimentation processes, to characterise the risk of future reduction in the reservoir storage

capacity. The obtained results will be used for the estimation of adapted reservoir operation strategies related to a

combined sediment and drought management.

Methods
The study uses actual reservoir bathymetric data

for its comparison with the design capacities, to assess the current storage capacity losses. Furthermore, the three-

dimensional water quality model mohid will be used to analyse the effect of past and current reservoir operation on

the inside sedimentation processes. The mohid model will use the outcomes of the characterisation of sedimentation

processes to analyse sediment management options. The applicability of enhanced strategies, addressing sediment

management as well water availability under water deficit conditions, will be assessed by water balance criteria.

Results
Results are presented for the in-stream Channel Reservoir, which is the largest of four reservoirs of

the Tuyamuyun Hydro Complex (7.8 km³) and is located at the lower Amu Darya River, at the border of

Turkmenistan and Uzbekistan.
The results for investigating the risk of storage capacity losses and therefore the

opportunity to compensate water deficits by drought events indicate an increased risk of failure for the THC storage

volume. The obtained risk assessment has been used for enhanced reservoir operation schemes, including the

estimation of effective and applicable options (e. g. flushing or sluicing), and combining improved sediment

management to shorten future capacity losses with adapted drought management plans.

Conclusion

The

study has emphasized that a more precise understanding of reservoir sedimentation processes and resulting storage

capacity losses provides necessary background information for assessing management options during drought events

and the impact of climate change on water availability during the next 50 years.

Events

The congress

Programme

Practical Infos

Enhanced risk management strategies for mitigating future droughts in Central Asia