In order to assess climate change impacts on river runoff patterns at the end of this century, the hydrological model METQ2007BDOPT was applied to 8 river basins and sub-basins in Latvia, which is a part of the southeast Baltic Sea basin. The climate data we used originate from the PRUDENCE project and were prepared in a separate study. Changes in hydro-climate were analysed using one control run ) and 2 IPCC scenario runs (A2 and B2; 2071-2100). For the A2 scenario, both annual and seasonal analysis predicted the major significant changes in most cases. For both scenarios, an increase of the mean annual climate data (air temperature, precipitation and evapotranspiration) is forecast, whereas the mean annual river runoff is predicted to decrease. The seasonal runoff pattern is expected to change towards significantly higher runoff during winter, following a decrease in spring and autumn. Maximum river discharge will occur in winter instead of spring. No considerable change in streamflow is predicted for summer. Future climate will change, leading to modifications in the river runoff regime and the shape of the hydrograph, which will be similar to that of the present Western European rivers, i.e. 2 principal periods instead of 4: one with high flow, mostly falling in the cold period of the year; and one with low flow, mostly in the warm period.

In this study a conceptual rainfall-runoff METQ model-the latest version METQ2007B-DOPT-was applied to simulate the daily runoff and water level of the Lake Burtnieks watershed from 1990 to 1999. The model structure and parameters were basically the same as in the METQ98, with some additional improvements and semi-automatical calibration performance. Model calibration was done for four rivers and one lake gauging station. The results of calibration showed a good correlation between the measured and simulated daily discharges. The Nash-Sutcliffe efficiency R 2 varied from 0.90 to 0.58 and correlation coefficient r from 0.95 to 0.83. The highest values of R 2 = 0.90 and r = 0.95 were obtained for the River Salaca and the lowest R 2 = 0.53 and r = 0.83 for Lake Burtnieks. We observed some relationships between the model parameter values and physiographic characteristic of the sub-catchments.

Changes of total annual runoff distribution, high and low discharges in Latvian rivers The paper examines climate change impacts on the hydrological regime of nineteen different river basins in Latvia. Hydrological data series for the period of 1951-2006 were analysed for river basins of four hydrological districts: Western, Central, Northern and Eastern. Climate change has influenced the temporal and spatial distribution of total annual river runoff and high and low flows in Latvia at the turn of century. The results confirm the hypothesis that the main tendency in the run-off change is a decrease in spring floods and increase in winter. Generally, statistically insignificant long-term trends were observed for summer and autumn.

The growing urbanization level significantly impacts the hydrological regime of streams and rivers. Land use is changed and natural areas are transformed to living areas or industrial parks. The conceptual hydrological model METQ is developed by the Latvia University of Agriculture to calculate total runoff for different purposes. However, it was developed for rural areas and is missing the urban hydrological response unit. The aim of this research is to calibrate and verify the urban hydrological response unit parameters of the conceptual hydrological model METQ. In Latvia, there is no hydrometric station with urban catchment area and in Europe there was not possibility to get enough long runoff and meteorological data set. Free access runoff and meteorological data from the United States Geological Surveywere used in this research. The calibration was made using MonteCarlo simulations. To evaluate the calibration results Nash-Sutcliffe efficiency index (NSE), determination coefficient R 2 , percent bias (PBIAS), ratios the root mean square error to the standard deviation of measured data (RSR) in addition to the graphical method were used. The calibration and validation results of the urban hydrological response unit parameters were satisfactory and achieved the recommended limits NSE > 0.5; R2 > 0.75; RSR < 0.70 and PBIAS +/-25 % for all six catchments. There is variation of the parameter values between catchments, which is related with the urbanization level and hydrogeological conditions of the catchment. This paper gives recommendations for hydrological response unit parameter application for the conceptual hydrological model METQUL2012.

The urbanised areas have a significant impact on hydrological processes of the catchment. The average annual urbanisation temp in EU is 0.6%. The existing version of conceptual hydrological model METQ is developed for natural hydrological response units such as forests, swamps and agricultural land. The growing urbanisation level force to add to the model urban hydrological response unit. This study aims to analyse local parameter sensitivity of urban hydrological response unit of conceptual hydrological model METQ. The local sensitivity was made using Monte-Carlo simulations. To evaluate local sensitivity Nash-Sutcliffe efficiency index (NSE), determination coefficient R2, percent bias (PBIAS), ratios the root mean square error to the standard deviation of measured data (RSR) in addition to the graphical method were used. The results show seven parameters to be calibrated the other 16 parameters have to stay as constant values for urban hydrological response unit.