open file - Viru Peipsi

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.