TY - JOUR

T1 - Trends in beobachteten abflusszeitreihen in Niedersachsen

AU - Fangmann, Anne

AU - Belli, Aslan

AU - Haberlandt, Uwe

PY - 2013/10

Y1 - 2013/10

N2 - Observations of low-flow, medium-flow, and high-flow situations in rivers in the German Federal State of Lower Saxony were analyzed for trends. Two periods were selected, namely the years from 1951 to 2005 with sufficiently long records of mean daily flows from 34 gauging stations and from 1966 to 2005 with data from 110 gauges. Of these time series indices were derived that characterize both the extremes and the mean values of the flows within one year or one season and were subjected to trend analyses. Beyond the river-discharge data, temperature and precipitation indices were tested for trends in order to identify possible causal relations. Here the time frame chosen for the analysis was from 1951 to 2005, with data from 18 temperature stations and 263 precipitation stations. The largest, often significant changes were observed in summer, when all indices suggest reductions in floodflows, mean flows, and low flows. This applies especially to the eastern part of Lower Saxony. Striking was the large number of breakpoints detected in the summer flows in 1988, indicating a trend reversal after 1988. In spring and in autumn, a differentiation between an increase in the north-west and a decrease in the south-east was observed within the low-flow series. In winter, merely some upward trends in the floodflow indices proved to be field significant. Generally, the trends in river discharges are consistent with those in temperature and precipitation. In the mean temperature, consistently significant strong-positive trends were detected, while the analysis of the precipitation indices revealed increases in winter and decreases in summer.

AB - Observations of low-flow, medium-flow, and high-flow situations in rivers in the German Federal State of Lower Saxony were analyzed for trends. Two periods were selected, namely the years from 1951 to 2005 with sufficiently long records of mean daily flows from 34 gauging stations and from 1966 to 2005 with data from 110 gauges. Of these time series indices were derived that characterize both the extremes and the mean values of the flows within one year or one season and were subjected to trend analyses. Beyond the river-discharge data, temperature and precipitation indices were tested for trends in order to identify possible causal relations. Here the time frame chosen for the analysis was from 1951 to 2005, with data from 18 temperature stations and 263 precipitation stations. The largest, often significant changes were observed in summer, when all indices suggest reductions in floodflows, mean flows, and low flows. This applies especially to the eastern part of Lower Saxony. Striking was the large number of breakpoints detected in the summer flows in 1988, indicating a trend reversal after 1988. In spring and in autumn, a differentiation between an increase in the north-west and a decrease in the south-east was observed within the low-flow series. In winter, merely some upward trends in the floodflow indices proved to be field significant. Generally, the trends in river discharges are consistent with those in temperature and precipitation. In the mean temperature, consistently significant strong-positive trends were detected, while the analysis of the precipitation indices revealed increases in winter and decreases in summer.

KW - Flood flow

KW - Low flow

KW - Lower Saxony

KW - Streamflow

KW - Trend analysis

UR - http://www.scopus.com/inward/record.url?scp=84894132006&partnerID=8YFLogxK

U2 - 10.5675/HyWa-2013,5-1

DO - 10.5675/HyWa-2013,5-1

M3 - Artikel

AN - SCOPUS:84894132006

VL - 57

SP - 196

EP - 205

JO - Hydrologie und Wasserbewirtschaftung

JF - Hydrologie und Wasserbewirtschaftung

SN - 1439-1783

IS - 5

ER -