IWRA World Water Congress 2008 Montpellier France
4. Development of Water Resources and Infrastructure
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
reservoir, storage capacity
losses, water scarcity, hydrological risk assessment, Amu Darya
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.
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
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.
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 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.
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.