STUDY AREA

2.1 Geographical location

Stable isotopes of water were sampled at two sites located in the southwest of the Iberian Peninsula, in the Region of Andalusia (Fig. 1). Site 1 is in Seville city on the roof of the North Tower at Plaza de España and an altitude of about 31 m.a.s.l. Site 2 is located in a coastal dune of the Doñana National Park at the province of Huelva, at the Atlantic coast (rural area with an altitude of 38 m.a.s.l. (Fig.1).
[Insert Figure 1]

2.2 Climate

The climate at the Doñana National Park is sub-humid Mediterranean, which is affected by the Atlantic influence, dry summers and humid winters (CUSTODIO; GIMENA; MANZANO; MONTES et al. , 2009). In Doñana, the rainfall, which occurs mainly between October and March, has an annual average between 500 and 600 mm with a great interannual rainfall amount variability, between 250 and 1100 mm in extremely dry or wet years, respectively. The average annual air temperature is about 18 °C in the center of the National Park and there are around 3,000 hours of sunshine per year (MANZANO; CUSTODIO; MEDIAVILLA; MONTES, 2005). Within our sampling period the highest recorded temperature was 43°C on 05/09/2016 and the lowest was 0 °C on 03/02/2018. Relative humidity measured on site between 2000 and 2020 shows a mean value of 70% with 60% and 81% in the first and third quartile respectively.
Seville city has a Mediterranean climate, featuring very hot, dry summers and mild winters with moderate rainfall. The annual average temperature is 25.4°C during the day and 13°C at night (with an annual average of 19.2°C). Precipitation varies from 500 to 600 mm per year, with frequent torrential rain. December is the wettest month, with an average rainfall of nearly 100 mm. On average there are 50.5 days of rain (KOTTEK; GRIESER; BECK; RUDOLF et al. , 2006). Relative humidity measured at the nearby La Rinconada station between 2000 and 2021 shows a mean value of 66% with 53% and 78% in the first and third quartile, respectively.
Both sites are of the Csa climate type according to the Köppen classification.