Institute of Hydrometeorology

Enguri River Basin

North Liadeshti

Let us consider the retreat of the North Liadesh glacier of the Enguri basin using the SRS. Let us compare the resulting contour with the glacier contour shown on the topographic map. We found that the area of the North Liadesh glaciers according to the TDS is 3.4 km², while the catalogue gives the same value, which indicates that there is an inaccuracy in the catalogue. Correction with the topographic map determined that its area was 4.3 km².

A detailed analysis of the retreat of the North Liadesh glacier showed that the glacier retreat is described by a parabolic curve:

Y = 0.1321 x²+7.148 x-12

North Liadesti Glacier: a − Schematic representation of retreat, shown against the background of a September 29, 2020 image from the SPOT 6 satellite; b − Retreat graph

Kvishi

The Kvishi Glacier is the next large glacier in the Enguri Glacial Basin, from west to east, which needs to be studied. Similarly, as in the previous cases, let us consider its retreat and obtain that the glacier retreat is described by a parabolic curve:

Y = 0.5138x²+3.2826x

Kvishi Glacier: a − Schematic image of glacier retreat; b − Retreat graph

Adishi

The Adishi Glacier, located near the Mestia meteorological station (1,500 m a.s.l.), exhibits a clear response to regional temperature increases. Mean summer temperatures (T_mean) increased by 0.6 °C between 1987–2001 and 2001–2016.

These data support the conclusion that Adishi Glacier retreat as other glaciers is closely linked to regional climate warming.

Average air temperature data according to Mestia weather station

Similarly, as in the previous cases, let us consider the retreat of the Adishi glacier. It is accepted that the retreat of a glacier is described by the following parabolic curve:

Y = 0.3173x²-0.3186x – 10.556

The length of the Adishi Glacier according to 2022 data is 6821 m. According to satellite data, the retreat of the Adishi Glacier from 1977 to 2022 was 601 m. The sum of these two numbers, 7422, should equal the trend equation, and then the resulting quadratic equation should be solved

0.3173x² - 0.3186x - 10.556=7422
that is
0,3173x² – 0.3186x = 7432.6

The positive solution of this equation is approximately 154. This result means that if the current trend of retreat continues, the Adishi Glacier will probably melt completely in 154 years, or in 2131 (the starting point is 1977).

Also, according to ground-based data from field observations, the retreat of the Adishi Glacier from 1985 to 2022 was 614 m. The sum of these two numbers, 7435, should equal the trend equation, and then the resulting quadratic equation should be solved:

0.3712x² - 2.2985x + 3.4954 = 7435
that is
0.3712x² - 2.2985x = 7431.5

The positive solution to this equation is approximately 145. This result means that if the current trend of retreat continues, the Adishi Glacier is expected to melt completely in 145 years, or in 2130 (the starting point is 1985).

The figure shows a schematic image of the retreat of the Adishi Glacier on the background of the Landsat 8 OLI TIRS satellite image of August 25, 2022. The location of the glacier in different years is shown with different colored contours. The white dashed line crossing the contours allows you to calculate the length of the glacier's retreat. From September 13, 1977 to August 25, 2022, this indicator was approximately 601 m.

A comparison of the analytical forms of the SRS and field data shows that the ground-based data of the SRS and field observations of the Adishi Glacier are in good agreement with each other.

Adishi Glacier: a − Schematic image of retreat against the background of the Landsat 8 OLI TIRS sensor image of August 25, 2022. Green pins show the results obtained based on field expeditions; b − Graphs comparing the ground data of the SRS and field observations

Shkhara

To determine the contours of the retreat of the Shkhara glacier, data from various Landsat satellite sensors were used for the time points indicated on the drawing.

The picture shows a schematic image of the retreat of the Shkhara glacier against the background of the Landsat 9 OLI TIRS sensor image of September 18, 2022. Additionally, on the same image the locations of glacier determined based on GBO with green pins are shown.

Using the SRS data, the location of glaciers at different points in time has been determined, which are shown by contours of different colors on the schematic image of retreat. The contours have been drawn using manual digitization. The numerical value of glacier Shkhara retreat is calculated by means of the white dashed line crossing the contours. Based on these values retreat graph is created and corresponding trend is shown. As indicated in the drawing, the initial state of the Shkhara Glacier corresponds to 1986.

The conducted analysis showed that the nonlinear retreat of the Shkhara Glacier is described with high accuracy by a second-order polynomial, which in this case is a parabola. The Shkhara Glacier retreat graph constructed based on the field expedition data used for the quality assessment and control of the results is also described with high accuracy by a parabolic curve. As can be seen from graphs comparing the ground data of the SRS and field observations, the ground-based data of the Shkhara Glacier SRS and field observations are in good agreement with each other.

Shkhara Glacier: a − Schematic image of retreat against the background of the Landsat 9 OLI TIRS sensor image of September 18, 2022. Green pins show the results obtained based on field expeditions; b − Graphs comparing the ground data of the SRS and field observations.

The retreat of the Shkhara glacier based on SRS is given by the equation:

Y = 0.1868x² + 4.0426x – 5.4252

Using GBO the corresponding equation is:

Y = 0.13x² + 5.0426x - 5.4252

The comparison of these equations and consequently of the obtained analytical equations shows that they are in good agreement with each other, which confirms the relevance of using GBO for QA/QC of the results.