Global Change: Facing Risks and Threats to Water Resources

Global change: Facing Risks and Threats to Water Resources (Proc. of the Sixth World FRIEND Conference, Fez, Morocco, October 2010). IAHS Publ. 340, 2010, 32-39.

Groundwater drought development in the Nitra River catchment
MIRIAM FENDEKOVA & MARIAN FENDEK

Department of Hydrogeology, Faculty of Natural Sciences, Comenius University, Pavilon G, Mlynska dolina,
842 15 Bratislava, Slovakia

[e-mail]
Abstract Temporal and spatial changes in groundwater runoff were studied in the Nitra River catchment (central Slovakia). Data from five discharge gauging stations and five groundwater observation wells were used to assess drought propagation through the catchment hydrological cycle. Groundwater drought was expressed through changes in baseflow values and groundwater heads and compared with the streamflow drought occurrence. It was confirmed that the streamflow drought has higher occurrence frequency and shorter duration in comparison with the baseflow drought. In both cases, the drought develops mostly in summer months, and lasts until the end of autumn – up to the winter months (S/A, S/W type). The multiyear droughts were detected among the baseflow drought periods. The baseflow drought is delayed after the streamflow drought. The groundwater head drought develops with even longer delay after the streamflow and baseflow drought and develops mostly in the autumn months lasting until the late winter, in some cases until the next spring (A/W, A/Sp type). No spatial pattern was distinguished when studying the groundwater drought occurrence in the Nitra River basin.

Key words groundwater drought; groundwater head; baseflow separation; local minimum method;
temporal and spatial development; Nitra River basin, Slovakia

Global change: Facing Risks and Threats to Water Resources (Proc. of the Sixth World FRIEND Conference, Fez, Morocco, October 2010). IAHS Publ. 340, 2010, 40-46.

Influence of ice regime on hydroecological safety under climate change: case study in the north of the European part of Russia
NATALIA FROLOVA & NIKOLAY ALEKSEEVSKIY

Department of Hydrology, Lomonosov Moscow State University, 119899, Leninskiye Gory, Moscow, Russia

[e-mail]
Abstract Various features of the river ice regime in the north of the European part of Russia are of critical importance for hydroecological safety. Spatial and temporal variability of these characteristics was analysed using the most up-to-date hydrometeorological data from 146 gauging stations in the study region. Trends of ice regime changes during recent decades were identified and interpreted in the context of the changing climate. It was found that under low flow conditions, autumn ice and slashed ice drifts became longer, ice jams more frequent, and freeze-up periods shorter. More frequent thawing spells resulted in decreasing ice thickness and snow storage in river basins. Winter break-ups were accompanied by ice jams and floods. High water levels during further freezing-up, as well as large amounts of slashed ice in river channels increased the risk of catastrophic ice jams.

Key words hydroecological safety, ice regime; climate change

Global change: Facing Risks and Threats to Water Resources (Proc. of the Sixth World FRIEND Conference, Fez, Morocco, October 2010). IAHS Publ. 340, 2010, 47-53.

Projected changes in seasonal precipitation extremes in the Czech Republic
MARTIN HANEL^1,2, ADAM VIZINA^1,2 & MAGDALENA MRKVIČKOVÁ¹

1 Department of Hydrology, TG Masaryk Water Research Institute, pri, Podbabská 30, 160 00 Prague, Czech Republic

[e-mail]

2 Faculty of Environmental Sciences, Czech University of Life Sciences Prague, Kamýcká 129, 165 21 Prague,
Czech Republic
Abstract The paper describes results of an analysis of changes in seasonal precipitation extremes from a number of transient regional climate model simulations for the Czech Republic, which was conducted within the ENSEMBLES project funded by the EU. It is assumed that the precipitation extremes follow the generalized extreme value distribution (GEV) with time-varying parameters. The regional frequency analysis is employed to reduce the standard errors of the parameter estimates. The Czech Republic is subdivided into four homogeneous regions within which it is assumed that most uncertain parameters of the GEV model are constant. The uncertainty is assessed by bootstrap resampling. The projected increase in precipitation extremes is large for the majority of the RCM simulations and for all seasons. The uncertainty of the estimated changes is, however, considerable.

Key words seasonal precipitation extremes; non-stationary index flood model; Czech Republic

Global change: Facing Risks and Threats to Water Resources (Proc. of the Sixth World FRIEND Conference, Fez, Morocco, October 2010). IAHS Publ. 340, 2010, 54-60.

FRIEND’s contribution to the PUB Benchmark Assessment Report on low flow estimation
GREGOR LAAHA¹, Eric Sauquet², Hege Hisdal³, Charles N. Kroll⁴, Henny A. J. van Lanen⁵, Lena M. Tallaksen⁶ & Ross Woods⁷

1 Institute of Applied Statistics, University BOKU, Vienna, Austria

[e-mail]

2 Cemagref, Hydrology-Hydraulics Research Unit, Lyon, France

3 Norwegian Water Resources and Energy Directorate, Oslo, Norway

4 SUNY College of Environmental Science and Forestry, Syracuse, New York, USA

5 Wageningen University, Centre for Water and Climate, The Netherlands

6 Department of Geosciences, University of Oslo, Norway

7 National Institute for Water and Atmospheric Research, Christchurch, New Zealand
Abstract The prediction of runoff in ungauged basins (PUB) is one of the key challenges of water resources management. A Benchmark Assessment Report is currently being compiled, which summarises the state of hydrological predictions for ungauged basins with various runoff signatures. Members of the EURO-FRIEND Low Flow and Drought group contribute to one chapter on low flow estimation. In this paper, two major European benchmark studies from the PUB Benchmark Assessment Report on low flow regionalisation are presented. In each study several competing methods are compared by cross-validation to shed light on the performance of different methods for predicting low flows in ungauged basins. The chapter on low flows is an example of how UNESCO-FRIEND has stimulated international cooperation and has established links with a related international programme (i.e. IAHS-PUB) to help gain knowledge and exchange best practise.

Key words low flows; PUB benchmark report; prediction in ungauged basins; regionalisation;
statistical modelling; process-based modelling; case studies