Stable isotopes composition of river water across peninsular Spain

Stable isotopes composition of river water across peninsular Spain

Stable isotopes composition of river
water across peninsular Spain
1Rut
Sánchez-Moral, 2María Fe Díaz-Teijeiro, 1Silvino Castaño, 2Javier Rodríguez-Arévalo
Geological Survey of Spain (IGME). [email protected]
Centro de Estudios y Experimentación de Obras Públicas (CEDEX)
INTRODUCTION: The Spanish network for stable isotopes in rivers (REVIR) consists of 80 sampling stations distributed along the major River Basin Districts in
peninsular Spain, shown in the map over a digital elevation model (DEM), where quarterly (seasonally) water samples are taken for δ18O and δ2H analysis. REVIR
makes use of the Radiological Environmental Monitoring Network managed by the Nuclear Safety Council and the Ministry of Agriculture, Food and Environment,
that operates since the late 1970s. After two consecutive water years (2008-09 to 2009-2010), 579 stable isotope analyses have been produced by the REVIR.
RESULTS & DISCUSSION: A preliminary study of the data in the δ18O-δ2H space reveals the different isotopic signature and hydrological behaviour of the river
basins caused mostly by their different geographic and climatic conditions. The isotopic values of the closest REVIP stations (Spanish network for isotopes in
precipitation) are also shown for comparison:
1) The effect of evaporation is noticeable with decreasing latitude. Isotope values for surface waters lie along evaporation lines with slopes between 4.9 and 5.7 in
southernmost watersheds. This is also the case for the longest rivers more regulated by dams (Duero, Tajo, Guadiana and Guadalquivir) in which residence time in
a semiarid climate has been artificially increased;
2) More negative values for δ18O and δ2H are found in the watersheds that include the higher mountain ranges, and are influenced by seasonal processes of snow
accumulation and melting, such as the Ebro basin, which drains the Southern Pyrenees;
3) Noticeably, watersheds from the “Norte River Basin Districts”, clearly dominated by the input of Atlantic Ocean and the Bay of Biscay rainfall, show the higher
values of the deuterium excess, 13.6‰. These values have been previously reported in Spain and other European countries for precipitation typical of a
Mediterranean Sea origin. Alternative hypotheses for the origin of the vapour causing precipitation in this area are under study, including the North Atlantic Ocean
or the local Bay of Biscay where the relative humidity over the ocean may be lower;
4) The spatial distribution of sampling stations, which belong to a previous network not designed for this purpose, may impose a bias in these preliminary
observations that will be analysed in depth in further studies.
Cuencas Internas de Cataluña River Basin District
Norte River Basin District
0
C.I.C RBD
REVIP Gerona
LMWL (Spain)
Lineal (C.I.C RBD)
0
Norte RBD
REVIP La Coruña
REVIP Santander
LMWL (Spain)
Lineal (Norte RBD)
-10
-10
-20
-20
δ2H (‰)
-30
δ2H (‰)
-30
-40
-40
-50
-50
Bay of Biscay
δ2H = 7.33δ18O + 9.00
r² = 0.92
δ2H= 7.54δ18O + 6.91
r² = 0.93
-60
-60
-70
FRANCE
-70
-80
-12
-11
-10
-9
-8
-7
-9
-8
-7
-6
-5
-4
-3
-2
-1
0
δ18O (‰)
-4
-3
-2
-1
0
Duero River Basin District
0
Duero RBD
REVIP León
REVIP Valladolid
LMWL (Spain)
Lineal (Duero RBD)
-10
-20
-30
-40
-50
-60
δ2H
=
4.95δ18O
- 15.34
r² = 0.85
-70
-80
-12
-11
-10
-9
-8
-7
-6
-5
-4
-3
-2
-1
Ebro River Basin District
0
Ebro RBD
REVIP Tortosa
REVIP Zaragoza
LMWL (Spain)
Lineal (Ebro RBD)
-10
-20
-30
δ2H (‰)
-10
PORTUGAL
-11
ATLANTIC OCEAN
-12
δ2H (‰)
-5
δ18O (‰)
-80
-40
-50
-60
δ2H = 6.93δ18O + 1.25
r² = 0.96
-70
-80
-12
0
-11
-10
-9
-8
-7
δ18O (‰)
-6
-5
-4
-3
-2
-1
0
1
2
δ18O (‰)
Júcar River Basin District
Tajo River Basin District
0
0
Júcar RBD
REVIP Valencia
LMWL (Spain)
Lineal (Júcar RBD)
Tajo RBD
REVIP Madrid
-10
-10
REVIP Cáceres
-20
-20
δ2H (‰)
-30
δ2H (‰)
-6
-40
-30
-40
-50
-50
δ2H = 5.68δ18O - 9.6
r² = 0.91
-60
δ2H= 5.85δ18O - 8.15
r² = 0.94
-60
-70
-70
-80
-12
-80
-12
-11
-10
-9
-8
-7
-6
δ18O
-5
-4
-3
-2
-1
-11
-10
-9
-8
0
-6
-5
-4
-3
-2
-1
0
-3
-2
-1
0
δ18O (‰)
Guadalquivir River Basin District
(‰)
-7
0
Guadalquivir RBD
REVIP Morón
LMWL (Spain)
Lineal (Guadalquivir RBD)
-10
Guadiana River Basin District
Segura River Basin District
0
Guadiana RBD
0
-20
Segura RBD
REVIP Ciudad Real
-10
LMWL (Spain)
-10
δ2H (‰)
-20
δ2H = 5.74δ18O - 6.378
r² = 0.98
-20
-40
-30
-30
δ2H = 5.13 δ18O - 10.13
r² = 0.96
-40
δ2H (‰)
δ2H (‰)
REVIP Murcia
-30
Lineal (Guadiana RBD)
-50
-60
-50
-50
-60
-70
-70
-60
-80
-70
-12
-11
-10
-9
-8
-7
-6
-5
δ18O (‰)
-80
-12
-11
-10
-9
-8
-7
-6
δ18O (‰)
-5
-4
-3
-2
-1
0
1
2
-40
-4
-3
-2
-1
0
1
δ2H = 5.00δ18O - 13.57
r² = 0.94
2
-80
-12
-11
-10
-9
-8
-7
-6
-5
-4
δ18O (‰)
CONCLUSIONS: The spatial variability of the stable isotopic composition surface waters in Spain has been characterised by the information supplied by REVIR.
This information provides a reference for: 1) the study of the processes modifying the isotope signals observed in river waters from the isotope input of
precipitation (i.e. evaporation, interaction with ground water,…); 2) the calibration of the models to simulate the spatial distribution of isotopes in precipitation;
3) the study of the evolution of these isotope signals in relation with changes in climate factors; 4) the study of the effect of evaporation from surface water bodies
(lakes and dams) in water resources. It will also facilitate the application of the European Union Water Framework Directive in a context of climate change by
providing a better knowledge of the origin and evolution of surface waters through the study of their characteristic isotope signature.
Acknowledgments : This work has been performed under the Project CGL2009-12977 of the Spanish R&D Programme 2008-2011 and the Collaborative Agreement for the Joint Laboratory IGME-CEDEX.