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River runoff modelling for ungauged basins in Estonia

Congress: 2008
Author(s):
AbstractMultiple forces of change such as climatic variability, economic activities and national policies result in extensive alterations in land cover and use, which in turn have impact on the hydrological system. Estonia is situated in North-East Europe, on the east coast of the Baltic Sea and occupies an area of 45,215 km2. Climatically it belongs to the mixed-forest subregion of the Atlantic continental region of temperature zone. Despite being a small area, the local climate conditions have a significant spatial variability. In Estonia, precipitation exceeds evaporation; therefore drainage of arable land is carried out in the majority of lowland territories. Thus, approximately 70% of the total agricultural land area has artificial drainage systems. The area with drainage systems grew rapidly during the period 1960-1980. After 1990 the construction of new drainage systems stopped. Moreover, the reduction of more than 40% of the hydrological and meteorological monitoring stations during the last decade has created problems for the reliable determination of river runoff in Estonia. This has caused difficulties in the assessment of river runoff and has reduced the effectiveness of water resource management. The objective of this study is to simulate the river runoff for ungauged catchments and attempt to assess the sensitivity of water resources on land use changes, as well as climatic variability in Estonia, through the hydrological modelling. The reduced type (semi- distributed) model has been used for this study. This type of model is important for river planning preparation, water management systems, in planning flood mitigation and prevention systems. Additionally, the model can be linked to the water-quality model and applied for environmental assessment. The major issue in application of this model may be estimate the effects of climate change on the extreme (flooding/low flow) conditions of rivers and, future, regional economic impacts of climate change. The data inputted into the model is meteorological, hydrological and land- use related. In this study, the model was applied to the runoff simulation of 30 catchments for the period 1990-2000. A water balance is computed daily for each catchment. Future regionalisation of the calibrated parameters allows getting the actual spatial variability of hydrological regime over all Estonia.
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