Search

The préalpine Rietholzbach research catchment provides long-term continuous hydroclimatological measurements in northeastern Switzerland, including lysimeter évapotranspiration measurements since 1976, and soil moisture measurements since 1994. We analyze here the monthly data record over 32 years (1976-2007), with a focus on the extreme 2003 European drought. In particular, we assess whether the well-established hypothesis that the 2003 event was due to spring precipitation deficits is valid at the site. The Rietholzbach measurements are found to be internally consistent and representative for a larger region in Switzerland. Despite the scale discrepancy (3.14 m2 versus 3.31 km2), the lysimeter seepage and catchment-wide streamflow show similar monthly dynamics. High correlations are further found with other streamflow measurements within the Thur river basin (1750 km ) and--for interannual anomalies--also in most of northern Switzerland. Analyses for 2003 confirm the occurrence of extreme heat and drought conditions at Rietholzbach. However, unlike findings from regional-scale modeling studies, they reveal a late onset of the soil moisture deficit (from June onward), despite large precipitation deficits from mid-February to mid-April. These early spring deficits were mostly compensated for by decreased runoff during this period and excess precipitation in the preceding weeks to months (including in the 2002 fall). Our results show that évapotranspiration excess in June 2003 was the main driver initiating the 2003 summer drought conditions in Rietholzbach, contributing 60% of the June 2003 water storage deficit. Finally, long-lasting drought effects on the lysimeter water storage due to rewetting inhibition were recorded until spring 2004. [ABSTRACT FROM AUTHOR]

Focuses on mountainous catchments where the quality of runoff modelling depends strongly on the assessment of the spatial differences in the generation of the various runoff components and of the flow paths as coupled with the amount and intensity of precipitation and/or the snow melting. View that these catchments are suitable for the intercomparison of different kinds of hydrological models: Catchment models applied on the pre-alpine Rietholzbach research catchment within the period 1981?98, and on the high-alpine Dischmabach catchment within the period 1981?96 for the simulation of hydrological processes and of the runoff hydrographs; Discussion of the simulation results and the differences resulting from the application of the two models; Comparison of results from the two models including observed catchment discharges, with measurements of evapotranspiration, soil moisture, outflow of a lysimeter, and of groundwater levels in three access tubes; Model intercomparison indicating that the two approaches performed with similar statistical efficiency over a period longer than 15 years. What analysis of the simulated runoff components indicates.

Abstract: The revised empirical model for in- and outflow calculation of Upper Lake Constance has provided satisfying results supported by measured values. The given model was implemented to simulate total water inputs of the lake during the period from 1941 to 2000 with emphasis on the flood conditions of 1999. Analysis of annual water input development reveals a tendency toward slight increases until the 1960s. Thereafter, a reduction in inputs can be noted. This trend probably continues to hold true to present. Weather conditions of given individual years have caused distinct fluctuations to the water budget. Unusual meteorological conditions led to extreme flooding in early May of 1999. Daily water inputs of up to 200 mio m3 generated the highest water levels ever observed for this time of the year. Continual extraordinarily high water inputs occurring from February until July and then again from September until the end of 1999 resulted in the second largest annual total water input recorded since 1941. [Copyright &y& Elsevier]