M. Kalinin

(Belarus)

The Republic of Belarus has a large number of aquatic ecosystems including rivers (around 21 000), lakes (11 000), water storage reservoirs (153) and ponds (1 500). 125 hydrological stations operate on rivers and canals, and another 14 stations are installed on lakes and water storage reservoirs in the frames of the national monitoring programme.
21 small hydroelectric power plants (HEPP) with a total installed capacity of about 10 MW operate in Belarus. At the same time the hydro potential is used by 3 % only.
Impact of Hydraulic Reclamation on River Hydrological Regime, groundwater levels and climate. Up to date, nearly 1 million 400 thousand hectares have been reclaimed in the south of the country which is called Belarusian Polessye.
Water resources are highly vulnerable to the climate change. Therefore to develop adaptation measures under changing climate, a unified information exchange system is needed to assess the water regime of both – the whole region and specific states. Climate Impact on River Ecosystems. Asynchrony in variation of the major runoff types is characteristic for the large Belarusian rivers.
At present the new Guidance on water and climate adaptation was finished under the UNECE Convention on the Protection and Use of Transboundary Watercourses and International Lakes and its Protocol on Water and Health for possible adoption by the Meetings of the Parties to both instruments in 2009/2010. On of the main objectives is desing of the climate change in the transboundary river basins. There are 6 of them in Belarus. National experience in solving issues related to the above problem is considered in the current paper.
To design a future climate in Belarus two approaches are used: computer estimates and analog data. The analog data have been obtained by two techniques – geographical analog and time analog. The European part of Russia, on the one hand, and Poland, on the other hand, were taken as geographical analogs for Belarus to analyze internal differences in warming scenarios, the Baltic Region was taken as an analog for northern part of Belarus, and the Ukrainian Polessie – for southern.
To assess the possible change in Belarusian water, two methods have been used: statistical and water-balance.

On the basis of the existing assessments of possible climate change, the initial archive of meteorological variables for projected watersheds was transformed using the following scenarios:

Scenario 1 – average annual air temperature increases by 2 C compared to the current level with the unchanged precipitation;
Scenario 2 – reduction in annual precipitation by 10 % with unchanged air temperature;
Scenario 3 – annual precipitation reduces by 10 %, while average annual air temperature rises by 2 С;
Scenario 4 – Peat formation (through drainage) and percentage of forest (through felling) in the watershed area is reduced and the river network density (building irrigation and drainage canals) and percentage of tilled area (intensive cultivation of new agricultural land) is increased by 5, 10, 20 and 30 % of the current ones, with unchanged climate conditions. 
The change in water resources caused by warming is expressed in relative values - in percent against the current level.
On the basis of calculations using the above regression, the following conclusions have been made: 5 % precipitation reduction may lead to the reduction in the average discharge by 4.5-8 % in hydrological year, while 10 % precipitation reduction may lead to the runoff reduction by 7-16 %. Increasing air temperature with unchanged precipitation slightly reduces the runoff (3 %). Increase in temperature by 2 °C and reduction in precipitation by 10 % leads to the reduction in the river runoff by 13-14 %.
4 scenarios allow making an integrated assessment of the river runoff transformation in terms of climate conditions (scenarios 1, 2, 3) and anthropogenic impact on river watersheds (scenario 4).
On the basis of calculations, the following conclusions have been made:

First scenario: the river runoff would reduce by 10% on the average and total evaporation may increase up to 4.7 %.
The data analysis provides a clear view regarding the reduction in the river runoff with increasing temperature related to the increased total evaporation especially in summer months. Asynchrony of the variation in annual river runoff and total evaporation may be also stated; for example, in April, when the runoff reduces by 9.2 % on the average, evaporation increases by 8.3 % that may be explained by a spring flood peak (intensive snow melting) and increase in air humidity.

Second scenario: the river runoff may reduce by 24.5% and the total evaporation would reduce by 5.4 %. The maximum runoff reduction would be observed in July (29.7 %) and minimum in April (23.8 %), total evaporation in July (7.0 %) and in April (4.2 %). It has to be stated that the river runoff and total evaporation reduce synchronously. Precipitation reduces – lower supply of moisture leads to lower evaporation.

Third scenario: the runoff may reduce by 29.3 % on the average, the total evaporation would increase in April by 6.2 % and reduce in July by 5.1 %, with an average reduction being 0.7 %. The river runoff appeared to be very sensitive to a simultaneous precipitation reduction and air temperature rise. Runoff values may reduce significantly for summer months that may be explained by low discharges during the summer runoff.

Fourth scenario, the degree of peat formation and percentage of forestry area in the watershed decrease, while the river drainage density and percentage of tilled area increase by 5, 10, 20 and 30 %, the river runoff would change.

The runoff reduction in April-July may gradually reverse to increase in August-October. It may be stated that a simultaneous effect of such factors as bog drainage, deforestation, new reclamation systems and increasing percentage of arable land would lead to reduced river runoff during the spring flood and increase in the fall months. Although the influence of these anthropogenic impacts on the river runoff is ambiguous, the component-wise influence of each factor on the river runoff may be investigated and quantitative variation in average monthly discharges of the Belarusian Polessie rivers may be designed. The tendency in increase in average values of the river runoff in relation to the degree of the anthropogenic impact is observed, but it would require significant investments in building new reclamation systems which is unreal due to the current economic situation and the river runoff in the near future would not be much affected.
Therefore, the third scenario (runoff reduction reaches 45.2 %) is the most unfavorable forecast of the anthropogenic variation of the Belarusian Polessie rivers’ runoff out of the first 3. Superimposition of 10 % anthropogenic impact on the river watershed (from 4th scenario) on the 3rd scenario may lead to 50% reduction in the annual runoff.