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Model of Toktogul Water Reservoir


Study of Formation Factors and Estimation of the Nizhny-Naryn HEPP Cascade Effect on the Quality of the Naryn River Catchments Using Isotopic Methods

Tech Area / Field

  • ENV-WPC/Water Pollution and Control/Environment
  • OBS-NAT/Natural Resources and Earth Sciences/Other Basic Sciences

8 Project completed

Registration date

Completion date

Senior Project Manager
Rudneva V Ya

Leading Institute
Institute of Water Problem & Hydropower Engineering, Kyrgyzstan, Bishkek

Supporting institutes

  • VNIIEF, Russia, N. Novgorod reg., Sarov


  • Pirkanmaa Regional Environment Centre, Finland, Tampere\nUniversità di Roma "La Sapienza", Italy, Rome\nInternational Bureau for Environmental Studies, Belgium, Brussels

Project summary

The Project Objective is to ascertain, for the first time, the character and the degree of the effect of water storage duration and regime in the CIS largest Toktogul Water Reservoir on its isotope composition, to develop a Continuously Functioning Model (CFM) of the Reservoir riparian territory.

This will provide decision-making authorities, scientific organizations and production companies of the Kyrghyz Republic with additional input information when working out clauses on interstate apportioning of water.

The cascade of water reservoirs of the Naryn River comprises the Toktogul, Kurpsay, Tushkumyr, Shamyldysay, Uchkurgan Water Reservoirs, and now being built the Kambarata-1 and the Kambarata-2 Reservoirs. The Toktogul Water Reservoir, when completely filled, stores 19.3 km3 of water; recharging seasonal and perennial water catchments from the Naryn River, the Reservoir causes river water metamorphism, however, this contribution of the Reservoir has not yet been studied much (Mamatkanov et al., 1996).

Not infrequently utterly complete consumption of the Naryn water (as a part of the Syr-Darya River) for irrigation in Kyrgyizia, Uzbekistan, Tadjikistan and Kazakhstan leads to interstate conflicts in Central Asia on the point of apportioning of water. In view of the fact that now in this circumstances not only the amount, but also the mineral composition of water is considered, the estimation of the role of the major Central Asia water reservoir, as is the Toktogul, is becoming an acute scientific and application problem.

At a part of the considered region since 2004 the ISTC Project KR-1103 Mathematical Model of the Syr-Darya River has been realized with participation of Institute of Physics, Academy of Sciences of the Kyrghyz Republic, as the leading institution. The now proposed Project has a ring of it with regard to investigation of some parameters of surface water of the region. However, the main task of the proposed Project is investigation of surface and ground water interconnection and interaction in the riparian territory of the Toktogul Water Reservoir and the effect of such interaction on the parameters of the water storages important for practical water consumption.

Water recharge in the Toktogul Reservoir with the annual oscillation amplitude several tens of meters must result in three processes specified below:

  1. Effective water mixing in the Reservoir bowl, causing chemical and isotope composition averaging in the water provided by different sources feeding the Reservoir;
  2. Water chemical and isotope composition evolution, conditioned by water, in particular, oxidation of reduced chemical forms, and shift of water isotope composition due to surface vaporization;
  3. Recurrent variations of ground water motion directions and, hence of the chemical and isotope composition in the riparian territory, caused by seasonal variations of Reservoir water level.

Thus, the key issues of Reservoir water-material balance modeling are correlated solutions of the following problems:
  1. Detachment of flowing and stagnant water zones, as well as estimation of mean time of fed water stay in the Reservoir;
  2. Quantification of conservativeness of each isotope tracer – isotope composition of water (hydrogen δ2Н and oxygen δ18О), uranium (234U/238U) and tritium fraction (3Н);
  3. Estimation of variation amplitude for these tracers in groundwater serving as the additional buffer water reservoir, where the formation of basic uranium and tritium isotopic systems features takes place;
  4. Estimation of possibility of subaqual groundwater discharge into the Reservoir bowl, since such act would significantly change the in-depth isotope distribution as compared to the riparian discharge of groundwater.

To solve the enumerated problems and, in particular, to study the surface and ground water interaction, besides isotope tracers (uranium, tritium and deuterium) the following aspects should be studied:
  • Radon distribution in cross-sections of the Water Reservoir and in groundwater to allow estimation of short-term Reservoir water balance variations;
  • Helium fields in cross-sections of the Water Reservoir and groundwater to allow estimation of the depth of wind-induced turbulence and long-term constituents of water balance;
  • Microelement composition of surface and ground water;
  • Temperature fields of surface and ground water in the Reservoir bowl;
  • General physical and chemical water characteristics – pH, Eh, mineralization.

To carry out sampling for radon and helium presence, field instrumentation will be used, allowing on-site express-detection of these components. To study the 234U/238U isotope ratio, utilization of an off-the-shelf alpha-spectrometer is supposed with preliminary uranium concentration on a carbon base.

To study the microelement composition utilization rather an inexpensive and accurate ICP MS method is proposed, which allows detection of several dozens of elements at one measurement and requires rather small-volume water samples.

Temperature measurements, determination of physical and chemical water properties and of mineralization degree will be conducted using off-the-shelf instrumentation.

Measurements and sampling will be conducted twice per year at the highest and the lowest Reservoir water levels. When the Toktogul Water Reservoir is used for irrigation its highest water level is in April, the lowest one is in September; when the Reservoir is used for energy production the maximum water level is in October, the lowest one is in April. At present the hydroscheme operation regimes should be determined by Central-Asia interstate agreements, but, since the near-term operation regime has not been agreed upon, our field research should continue for not less than two years to get, using CFM, as precise picture of the long-term effect of the Reservoir unstable operation regime as possible.

Apart from the Reservoir itself, groundwater will also be sampled from springs and wells, as well as the rivers flowing into the Reservoir, and precipitations.

Development of the Toktogul Reservoir riparian territory CFM will be carried out basing on the software complex NIMFA, developed in the Russian Federal Nuclear Center (FSUE RFNC-VNIIEF) with participation of the experts of S.-Petersburg Institute of Geoecology, RAS (S-Pb. IG RAS) and Chebotarev Science and Research Institute for Mathematics and Mechanics (NII MM), Kazan State University.

The software complex NIMFA is destined for simulation of a wide range of underground hydrodynamics processes; it has been tested and is widely used for CFM development for groundwater basins, hydraulic constructions and industrial objects. In particular, in the frames of the successfully completed ISTC Project #1565 the Satis River CFM has been developed (FSUE RFNC-VNIIEF territory, Sarov, Nizhny Novgorod Region, Russia).

On the side of the Leading Institution specialists of Institute of Water Problems and Hydropower, National Academy of Sciences of the Kyrghyz Republic (IWP and HP, NAS KR) will participate in the Project, who are very experienced in the research of water resource formation and dynamics in the conditions of highlands, as well as in application of isotope research methods, participating in several international and ISTC-funded projects. The creative collaboration of the leading institute with weapon scientists of the Russian Federal Nuclear Center and experts of the S.-Petersburg Institute of Geoecology, RAS, is a unique allegation of theoretical achievements, experience, novel techniques and high abilities in the field of numerical simulation.

Using isotope methods to study natural water of Toktogul Reservoir system will enable identification of the water balance structure, building CFM of the Reservoir riparian territory, pioneering determination of the character and the degree of water storage duration and regime effect on its isotope composition, providing decision-making authorities, scientific organizations and production companies of, primarily, the Kyrghyz Republic with additional input information when working out clauses on interstate apportioning of water.

Completion of this Project will enable not only solving the enumerated problems, but will also form the basis of the CFM development for the other cascade water reservoirs and, in the future, for monitoring of the whole catchments basin of the major Kyrgyzstan river.


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