open file - Viru Peipsi

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Introduction Global climate change due to the increase of greenhouse gas concentration in the atmosphere is a powerful factor expressing the anthropogenic stress on natural environment. The highest warming is expected to take place in high latitudes. Water resources are very sensitive to climate change and studies on this topic have been carried out for many regions in Europe. Possible climate warming can cause significant changes in hydrological regime and water resources, including the rivers runoff. Understanding the sensitivity of water resources is the first and one of most important steps in the climate change impact assessment. Impact research needs to address these problems include development of 1) a more physically based understanding of hydrological processes and their interactions, 2) hydrological parameter measurement and estimation techniques for application over a range of spatial and temporal scales, and 3) modular modelling tools to provide a framework to facilitate water management research (Leavesley, 1994). Water balance model WatBal An assessment of climate change impacts on water resources is a complex process. Different macro-scale and landscape-scale hydrologic models are used for this purpose. These models usually require detailed climatic and other input data on the site or area of interest. Examples of these models include also hydrological catchment models, by which can be simulate changes in local hydrologic regime of rivers under climate change scenarios. Hydrological models provide a framework in which to conceptualize and investigate the relationships between climate and water resources. Results of this study could also be necessary information in general water resources planning; however they are seldom used for it at present. Possible climate warming can cause significant changes in hydrological regime and water resources. The key problem is, how will change precipitation amounts and snow cover regime. Rivers runoff, groundwater level and recharge, land drainage and water resources management directly depend upon them. To investigate the influence of climate change on river runoff, the point model WatBal (Yates, 1994) was applied. This model, realised as a MS Excel macro, is considered to be a suitable tool for assessments of climate change impact on river runoff (Yates, Strzepek, 1994). It was validated for Estonia and used within the implementation of climate change impact research programmes (Järvet et al, 2000). General calibration and validation of the WatBal model for Estonian conditions was made. Different decades within the baseline period (1961–1990) were used for calibration and validation of the model.
Climate change scenarios used in modelling of river runoff MAGICC model and SCENGEN program were applied for climate change scenario generation in this study. Three alternative greenhouse gas emission scenarios developed by IPCC (IS92a, IS92c, IS92e) are combined with results of two general circulation model (GCM) experiences (HadCM2, ECHAM3TR). As a result, six climate change scenarios up to the year 2100 are prepared for modelling climate change impact on river runoff. The following abbreviations are used: HAD - HadCM2 model, HAM - ECHAM3TR model, MID - IPCC medium emission scenario (IS92a), MIN - IPCC minimum emission scenario (IS92c), MAX - IPCC maximum emission scenario (IS92e). GCM results are available for 5x5 degree cells. Therefore, the territory of Estonia is covered by two cells. The border between West and East Estonia is, in this case, 25°E. The studied watersheds, presented in Table 1, are located in eastern sector. In general, results of the both GCMs are quite similar. They project higher increase of air temperature during the winter half-year (October–March) and lower increase in the period April–September. Although, the German model (ECHAM3TR) developed by Max Planck Institute for Meteorology in Hamburg expects higher warming than the British (Hadley Centre) one – HadCM2. The increase of air temperature in East Estonia should be higher than in West Estonia, especially in winter. Modelling results Using the WatBal model, changes in river runoff in case of the six climate scenarios were calculated for all 14 studied river basins. The modelled changes in annual mean runoff in different basins and scenarios range from +5% (River Kunda) to +72% (Emajõgi River in station Tartu). Changes in annual runoff are presented in Table2. The HadCM2 model shows less increase of runoff while the ECHAM3TR model indicates more increase. The emission scenarios have rather linear differences. The lowest increase in river runoff is projected by the HADMIN scenario, the highest one – by HAMMAX. The highest increase in annual runoff is calculated for Emajõgi River (catchment area 7840 km 2 ), and also for small river basin Kääpa in not far from Lake <strong>Peipsi</strong>. In general, an increase of annual runoff by 20–30 per cent (HADMID) or by 40–50 per cent (HAMMID) are modelled for the year 2100. These changes can be consider as significant.
Page 1: LIFE-Environment project “Viru-Pe
Page 5 and 6: mm/day 1.60 1.40 1.20 1.00 0.80 0.6
Page 7 and 8: Tagajõgi- 0.69 0.74 0.71 0.74 Tudu
Page 9: will start not in June but in May.

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