40 "The Effect of Mountain River Reservoirs on the Environment Caused by Global Climate Change"

Tuesday, 26 June 2018
New Mexico/Santa Fe Room/Portal (La Fonda on the Plaza)
Giorgi Metreveli, Tbilisi State University of Ivane Javakhishvili, Tbilisi, Georgia; and L. Matchavariani V

Global climate change continues to affect all areas of our planet. In the near future (2050-2070), the air temperature of the Black Sea region will rise by 1.0-1.2 Celsius and the annual precipitation will increase by 10-15%. Subsequently, the glaciers will recede, causing a sharp rise in river deposits of sediment and erosive materials. This will also influence existing trajectories of moisture and seasonal distribution of atmospheric precipitation. The Black Sea’s level will rise by 0.10-0.12 meters. Due to these developments, population migration will increase, as well as demand for water and hydroelectric power.

To adapt to these changes, one effective solution would be to construct river reservoirs and manage water volume volatility with the cascades. This method will also help to use accumulated river sediment in different and complex ways. Under these circumstances it will become necessary to expand reservoir chains and anticipate their individual and cumulative impact on the environment.

Needless to say that the reservoirs themselves alter surrounding areas by causing:

  1. Change in climate
  2. Accumulation of river deposits
  3. Deprivation of beach-building materials on seashores
  4. Increased probability of flooding in the adjoining settlements
  5. Activation of groundwater, which induces landslides, slope failure and other mass wasting processes.

Here is how that happens:

  1. Climate change – the actual water temperate and condensation cool down and humidify surrounding lands.
  2. River deposits – change reservoir volume and create silting prism.
  3. Seashores – the dam stops natural river deposits flow.
  4. Flood risk – is due to rising silting prism.
  5. Landslides and slope failures – is caused by hydrostatic pressure and artificial quakes.

In addition to these changes, the reservoir’s volume constantly shrinks due to accumulated river drifts and modified shores. This is an irreversible process; however, it can decelerate by as much as 30-50%. For that, we need to construct reservoirs and tributaries with drift catchment pits and small dams. During flood season, these construction will restrict 70-80% of large deposits. When the season ends, we will have to empty out these constructions from the drifts and sediments using special conveyors and transport them to their end users: construction sites or beach developers.

In the last phase of their existence, the reservoirs will be transformed into accumulative terraces. At that stage, the terrace’s length (L) will be greater than the length of the reservoir (I). On the surface of the terrace, the river will create "Equilibrium Bed." After its formation, accumulation of deposits in fore bay will stop, because at that time the deposits had completely transported to after bay.

When making decision about constructing new reservoirs and calculating their anticipated exploitation timelines we need take into consideration both the individual and cumulative effects of probable outcome and the result it will have on the region. In order to do that, we suggest using methods developed by different scientists: Shazi-Pavlovsky, Erie, G. Shamov, A. Avakian, L. Gvelesiani and others. In addition, we need to use natural experiments and field observations. This will enable us to develop methods with the following criteria:

  1. Algorithms and mathematical formulas to calculate the reservoir’s silting prism and equilibrium bed
  2. Prediction of the expected total effect of individual and cumulative effects of the reservoir and its impact on the environment.

*Edited by Anna Metreveli

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