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Home , Baltrum, Borkum, East Frisian Islands, Langeoog, Mellum, Memmert

Impact of tourism on groundwater extraction on the island of ,

Georg Houben Federal Institute for Geosciences and Natural Resources(BGR), Hannover, Germany [email protected] Water supply on the East Example Langeog

Baltic Sea The are a chain of barrier islands in The island of Langeoog has three freshwater lenses. North Sea N Niedersachsen PL the area of the North Sea. Extensive inter- NL Hannover l a n d s The separation was caused by storm flood inundations n I s s i a F r i t tidal separate them from the coast. a s Langeoog in historical times, especially during the 17th century. D CZ E F

0 200km a CH n S e d d e Rainwater infiltrating into the dunes forms freshwater len- W a

Jade ses in dynamic equilibrium with surrounding saline wa- SW NE W W E Norden Wilhelmshaven ter. Water supply on most islands depends on these len- Kaap dunes Heerenhus dunes Melkhörn dunes Eastern dunes (m) [Water work West] [Water work East] Kleine (m) Leybucht 20 Große Schlopp Schlopp Meierei 20 ses. Randzelgat sea level sea level

Aurich -30 -30 Jadebusen fresh water water well 0 12.5 25 km 0 1km saline water

Groundwater extraction [m³/a] Cross-section of the freshwater lenses of Langeoog Borkum 800,000 (modified after Streif 1990). Juist 300,000 Water supply solely depends on groundwater pumped Cross-section of the East Frisian coast (modified after Streif 1990) Norderney 940,000 from the western freshwater lens. To prevent upconing Langeoog 334,000 of underlying saline water, extraction is distributed over The economic base of the islands is tourism. The high Spiekeroog 140,000 seasonality of this business and the elevated water de- 20 shallow wells (10 to 18 m depth) which pump intermittently at low rates of around 10 m³/h. mand of tourists stress the limited water resources. Cli- The islands Baltrum and Wangerooge are mate change might exacerbate this situation. supplied from the mainland via pipeline

Water demand Historical development Seasonal variations Consumption steadily rose until the 1980s, parallel to Water demand varies strongly according to sea- (1) = X-mas/New Year (4) = Ascencion (2) = Carnival (5) = Pentecost increasing tourism. With the implementation of water- sons, vacation periods, public holidays and indivi- 1000 (3) = Easter (6) = Unification Day (4) saving household appliances in the 1990s, consumption dual weekends. The lowest water demand on Spiekeroog (7) = Autumn break 800 Q = 150,618 m³/a (5) significantly decreased. Langeoog during the off-season of 2011 was 238 tot (3)(?) (6) m³/d while the maximum during the Easter holidays 600 500 3 3000 (7) (1) groundwater consumption (1) (2) 2800 reached 1,894 m³/d, a factor of eight between maxi- 400 (?) 450 groundwater extraction (?) overnight stays 2600 mum and minimum! 400 2400 200 350 2200 At 125 liter per day and person, the 2,000 perma- 2000 0 300 nent residents consume about 92,000 m³/a. 1800 2000 (3) 250 1600 Subtracting this from 2011´s consumption, the re- Langeoog (4)(5) 2 1400 1600 200 maining 242,000 m³/a, equivalent to about 72 % of Qtot= 333,808 m³/a 1200 (6) 150 all extraction, must be attributed to tourism. 1200 (7) 1 1000 (1) (1) 1 = post-war refugees 100 800 2 = water work East activated Groundwater extraction [m³/d] 800 3 = water work West shut down 600

50 overnight stays per year [x 1000] groundwater volume [m³/a x 1000] 400 400 0 200 1940 1950 1960 1970 1980 1990 2000 2010 Groundwater extraction on the islands of Spiekeroog and Langeoog 0 The 2011 extraction of 334,000 m³/a is about a quarter in the year 2011 showing strong seasonal demand variation. Peaks are even more pronounced on the smaller island of Spiekeroog. less than the peak extraction of 452,000 m³/a recorded 01.01.201101.02.201101.03.201101.04.201101.05.201101.06.201101.07.201101.08.201101.09.201101.10.201101.11.201101.12.201101.01.2012 After data by OOWV. 1983, although the number of overnight stays has remained more or less stable at least since 1990! TourismClimate change Conclusions

Langeoog 2011: 25 air temperature 25 u Water supply on East Frisian Islands mainly de- moving average (48 months) (a) 2,000 permanent residents moving average (96 months) pends on freshwater lenses 20 20 (b) 150 seasonal workers u Tourisms accounts for more than 70% of all water (c) 1,540,000 overnight stays 15 15 consumption (d) 124,000 day visitors 10 10 u Strong demand variations over the course of the

220 1700 year due to tourist seasons 5 5 200 guests overnight stays 1600 u Water consumption has decreased due to imple- 180 0 0 160 1500 mentation of water saving installations although 140 1400 -5 -5 number of overnight stays has become constant 120 Average monthly air temperature [°C] 1,000 guests per year u 100 1300 Tendency towards more frequent but shorter vaca- 15 -10 -10

1,000 overnight stays per year tions might increase demand again (more frequent 14 13 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010 washing and cleaning) 12 11 Air temperature records from the island of Norderney u Future effects of climate change (rising temperatu- 10 per guest 9 indicate an increase of the average annual res in summer) might be a game-changer. 8 7 temperature of about 2.0° C over the last 115 years. average overnight stays 1990 1995 2000 2005 2010 Especially summers in the last 20 years have become

Guest numbers rise but the number of overnight stays re- warmer and cold winters have become less frequent. The results presented on this poster were elaborated in the framework of the BGR project FLIN mains constant = shorter vacations Will this cause an increase in water demand? (Freshwater Lens Investigations) References: = more frequent cleaning of rooms and washing of to- Streif, H. 1990. Das ostfriesische Küstengebiet: Nordsee, Inseln, Watten und Marschen. Sammlung wels and linen geologischer Führer 57, 376 p., Berlin. Acknowledgement: We thank the Oldenburgisch-Ostfriesischer Wasservernband (OOWV) for data on water consumption