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

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Thanks for your attention!