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Reconstruction and homogenization of some water temperature series in the Ebro River basin
Jordi Prats (jordi.prats-rodriguez@upc.edu), Rafael Val,Marina Arbat-Bofill, Josep Dolz
Why water temperature?
An increase in water temperature can affect river biota in different ways:
● Species distribution: local extinctions, colonization by exogenous species...
● Life cycles: acceleration of life cycles, change in the number of life cycles per year...
● Metabolism: more intense metabolism, shorter life expectancy...
● Behaviour: more aggressive behaviour in some species of fish...
The study
Objectives:– To obtain long term annual water temperature
series at different points of the Ebro basin
– To analyse the river water temperature trends
Study cases– Case I: Ebro at Escatrón, (Sástago); 1949 – 2000
→ Prats et al. (2007)
– Case II: Ebro at Mequinenza, Cinca at Fraga; 1980 – 2010.
Case I: data usedOrigin of the data Period Type of
measurementEstimator of mean annual temperature
Thermal power plant of Escatrón (Arrúe & Alberto, 1986)
1949-1977 Daily Max & Min
Annual average of (Max+Min)/2
Thermal power plant of Escatrón
1996-2000 Daily temp. at 9 a.m.
Average
Confederación Hidrográfica del Ebro (Sástago)
1975-2003 Monthly (variable hour, variable day of month)
Average
Val (2003) 1998-1999 Continuous(10 min)
Average
Case I: bias analysis
Analysis of bias for each type of estimator of annual water temperature through a resampling method:
– Av. of max/min → no bias
– Daily, 9h → -0.3 ºC
– Monthly → bias depending on average hour of measurement
Case I: water temperature trend
0.05 ºC/yr (1955 - 2000)
Case II: data usedOrigin of the data Period Type of
measurementEstimator of mean annual temperature
Confederación Hidrográfica del Ebro (Mequinenza, Fraga)
1980-2010 Monthly (variable hour, variable day of month)
Average
Val (2003) (Mequinenza, Fraga)
1998-1999 Continuous(10 min)
Average
Case II: bias correction
Correction in function of the day of the month and hour of measurement
Case II: water temperature trends
● Bias correction can make a difference● In 1981 – 1995 water temperature at Fraga was measured around 10 – 11 a.m. → bias of -0.8 ºC
● In 1996 – 2010 water temperature at Fraga was measured between noon and 3 p.m. → bias of 0.1 ºC
Temperature trends in world rivers
River (country)
Period Trend (ºC/yr)
Loire (France) 1881 - 2003 0.0008
Danube (Austria)
1901 - 2000 0.0014-0.0017
Danube (Croatia)
1948 - 2005 0.0-0.06
Danube (Austria)
1951 - 2003 0.001
Loire (France) 1976 - 2003 0.06-0.07
Saône (France)
1977 - 2002 0.02-0.07
Rhône (France)
1979 - 1999 0.05
Ebro (Spain) 1954 - 2000 0.05
Ebro (Spain) 1980 - 2010 0.06
Cinca (Spain) 1980 - 2010 0.04
Possible causes:– Climate change
– Thermal discharges
– Reduction in discharge
Sou
rce:
mod
ified
fro
m W
WF
(20
09)
Thanks for your attention!
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