2017-09-13

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WATER SAVING CHALLENGE Field Study 2:

Ronan le Goaster at the main well (Forage 5”) on Houat

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WATER SAVING CHALLENGE Christian Pleijel

[email protected] Tel +358-457-342 88 25

FIELD STUDY: HOUAT

Content 1 Summary 2 2 Introduction 3 The assignment The client Study objects The three levels of an island Methodology 3 The water of the island 6 Location Geology Hydrology and climate Vegetation 4 The water of the islanders 9 Human pressure Virtual distance Water consumption 5 The water of the community 10 Governance Water procurement Wastewater Water quality Cost and taxes Future plans 6 Water saving 13 Benchmark #1 Benchmark #2 7 References 17

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1 Summary Houat is a 3 km2 island outside in . It has a resident population of 250 in- habitants but, given the large number of summer residents (3,000) and visitors 100,000), the human pressure on the islands' freshwater system (as well as energy distribution, sewage and waste recuperation and treatment, roads, ports, telephones, internet, trans- ports, postal services, healthcare and fire brigade) is equivalent to a population of 554 persons and the need for water is 22,5 million litres for 2015 and 23,3 millon litres for 2016, according to SAUR. Water procurement, distribution and management on Houat is organised in cooperation with the mainland municipalities in a joint company. Although being highly competent, it is not the company’s primary interest to save, but to sell water. The legal framework PLU puts restrictions on the citizens and the landowners, but not on water management. Resi- dents’ water consumption is half of the island’s total needs but when calculating the amounts needed from a consumer’s perspective, it does not meet the producer’s perspec- tive. The will, efforts and a mindset for saving water on Houat were mainly be found with the mayor of Houat, Mme Andrée Vielvoye, who pushes the issue in her private life as well as on the municipal level through Houat’s PLU (Plan Local d’Urbanisme), which stipulates that all new buildings are to be built with a rainwater reservoir, prohibits swimming pools and private drillings.

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2 Introduction 2.1 The assignment The Houat study is part of an assignment to search for, find, describe and share good ex- amples of water saving practices on eight European islands, islands who do not solve wa- ter scarcity just by bringing more water through pipelines, desalination plants and tank- ers, but are making efforts to save water. The project is looking for best practices within four areas of water saving actions: 1 Training: Information, good examples, schooling, campaigns, understanding that water has different qualities which can be used for different purposes. 2 Engineering: Technologies for reducing water consumption in households (water taps, showerheads, toilet sinks etc), for reducing leakages in mains and pipes, for more effi- cient desalination/reverse osmosis processes, treatment of wastewater etc. 3 Billing: Differentiated pricing of (municipal) water that lead to water saving. 4 Cutting: Switching off the (municipal) water: mostly for shorter periods of time. Obstacles to save water can be found in governance (water saving is not a political issue), regulations, cost, taxes and financial obstacles (the water company does not earn money by saving water), no ‘sense of urgency’, sustainability indicators are underdeveloped or inexistent, management (saving is not an objective), human behaviour, business threats (water saving might ruin the visitors’ experiences and damage the island’s brand), tech- nology and over-capacity (the island has a system which procures more water than the island needs, even in peaks). 2.2 The client The assignment has been given to the Royal Institute of Technology (KTH) in Stockholm by MEP Tonino Picula from Croatia, the Hellenic Small Islands Network, l'Association des îles du Ponant, the Irish Islands Federation/Comhdháil Oileáin na hÉireann and ESIN – the European Small Islands Federation.

2.3 Study objects Eight islands are included in the project: Tilos and Ithaca in Greece, Lastovo and Vis in Croatia, Sein and Houat in France, Inisheer and Cape Clear in Ireland.

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Figure 1. The eight islands in the study They have been chosen because (a) they all have a scarcity of freshwater, (b) they repre- sent different sizes, seas, hydrogeology, climate, size of population and remoteness, (c) they have what seems to be interesting solutions for saving water, and (d) they have been in previous contact with us which makes it easy to obtain true data within a limited time and budget. 2.4 The three levels of an island To understand the freshwater situation of an island, the whole island must be observed (not just the technologies). We describe three interlinked levels: a The water of the island This is the basic geophysical system level which encompasses the physical geographical conditions on the island no matter if people live there or not: geology, oceans, skies, hydrology, meteorology, flora and fauna – the physical landscape. b The water of the islanders At the next level, humans move in and make their human footprints: they build houses and villages, till the soil and water, eat, drink, walk, arrange their social life with chil- dren, schools, elderly care, health care and security – the cultural landscape. c The water of the community

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At the top level, the humans build a common infrastructure of roads, water, sewer, tel- ephone, broadband, fossil and renewable energy sources, ports and ships. Water is produced, distributed, managed, financed and administrated – the technical landscape. 2.5 Methodology Data about the islands has been collected through desktop research and field studies, dur- ing which we made make semi-structured interviews with politicians, technicians and citizens, investigated technical installations, took part of documents, plans, studies, maps and earlier research. This field study on Houat was undertaken by Christian Pleijel and Maxime Bredin on 20th and 21st of april, 2017, under supervision of professor Anders Nordström from the Univer- sity of Stockholm and professor Louis Brigand from the University of Brest (Maxime Bre- din is one of professor Brigand's students). We are most thankful to the mayor of Houat Mme le Maire Andrée Vielvoye and water consultant Ronan Le Goaster from Eau du Mor- bihan for their time and efforts to answer all our questions and guiding us around the is- land.

Figure 2. Ronan Le Goaster, Maxime Bredin. Andrée Vielvoye et Christian Pleijel

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3 The water of the island

Figure 3. Houat

3.1 Location Houat (Enez Houad in Breton) is a French island in the Atlantic Ocean, off the south coast of Brittany in the department of . It is located, along with two other major is- lands, in the entrance to the Baie de . The surface of Houat is 2,9 km2. The island is 5 km long and 1.5 km at the widest. It is mostly granite cliffs except for a long beach lined with dunes on the eastern coast.

Figure 4: Hoat on a sea chart

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Figure 6: Geology of Houat, from…

3.2 Geology

Houat is a massive of gneiss and granite in slight slope. There are sand dunes in the north- east and the south east, the rest of the coast is steep from 14 to 29 meters, cut by ravines with sandy beaches. Inside the islands, the terrain is mostly flat between 25 and 28 me- ters.

3.3 Hydrology and climate West coast climate with relatively large annual precipitation. The three summer months have little rainfall which makes the island a nice holiday island. The average rainfall for the years 1993-2002 on Houat is 910 mm per year and the total of water falling on the island 750,000 m3 per year 1. The variations in rainfall are big, see the table below. Groundwater recharge is about 480 mm in most parts of the island (ref 4). The same reference indicates that the runoff is about 220 mm and the groundwater for- mation is only 260 mm. The thin soil cover on a large part of the island's surface, as well as the bedrock's thin cracks, hamper infiltration in the bedrock. Groundwater can be the source of the island's total water use. Caution to drill for deep wells should be observed to prevent saltwater penetration in the wells. The bedrock has varying size and amounts of cracks, which gives a wide variety of possibilities for outlets across the island.

1 Étude hydrogéologique Houat 2004, page 21

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Table 1: Rainfall on Houat 1993-2002, source Météo France sur la station de l’île d’Houat

3.4 Vegetation The top of the island plateau was practiced until the 1960s; today, pastures have given way to brushwood (gorse, ferns, brambles).

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4 The water of the islanders For a general introduction to the island, its culture, history and society, see http://www.mairiedehouat.fr, http://www.ina.fr/video/CAF93010642/l-ile-de-houat- video.html and http://www.iles-du-ponant.com/visitons-nos-iles/ile-de-houat. 4.1 Human pressure Houat has 242 all-year inhabitants (2013). In summer (about 10 weeks), the population rises to 1.360. Day visitors are around 500 in July and August, and 250 in June and Sep- tember. The human pressure on the islands' freshwater assets, energy distribution, sewage and waste recuperation and treatment, telephones, transports, postal services, healthcare and fire brigade can be calculated as follows:

Residents (365 days) 242 88,330 man-days Summer residents (90 days) 600 54,000 man-days Visitors (1 day x 120) 500 60,000 man-days Sum of man-days 202,330 man-days Table 2: Human pressure on Houat The human pressure on the island is 202,330 man-days. If divided by 365 days, it is the equivalent to a resident population of 554 inhabitants (the official population figure based on census is, as mentioned, 242). The human pressure is very uneven, peaking in summer when water is scarce. A hot day in July, almost 1,000 visitors, plus 600 summer residents, plus 242 all-year residents can be on the island = 1,842 p/2,9 km2 = 635 p/km2. See also https://abpo.revues.org/112.

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Figure 7: land use on Houat, source: the Mayor’s office 4.2 Water consumption CONSUMER PERSPECTIVE In Europe, the average daily water consump- tion rate per capita varies between 40 and 150 liters per day. In France, it is 90 liters/person and day2, whereof 6 liters for food and drink- ing, 36 liters for bath and shower, 15 liters for dishes, 9 liters for washing, 6 liters for other purposes and 18 liters for flushing the toilet. The darker the colour of the water in the dia- gram, the less purified does it need to be. Data from the municipality says a resident household on Houat uses in average 70 m3 per year. To this must be added the use of rainwater for example in the gardens.

2 http://ec.europa.eu/eurostat/statistics- ex- plained/index.php/File:Total_freshwater_abstraction_by_public_water_supply,_2013_(m³_per_inhabitant)_YB16.p ng

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Most houses have rain- water collection but at least half of them seem to be not in use, the pipes have been detached from the water tanks and are leading rainwater out in the streets. It may be that summer residents no more care/are able to to man- age their rainwater sys- tems, while all-year resi- dents still do. Based on earlier studies of small island water consumption3, we can assume resident is- landers use 75% of the national average, summer residents 100% of the national average, and day tourists 20 litres/day. Calculated this way, the total need for the island of Houat is 13,238 m3:

Residents (365 days) 88,330 man-days 5,962 m3 Summer residents (90 days) 54,180 man-days 4,876 m3 Visitors (1 day x 120) 120,000 man-days 2,400 m3 Total water consumption/year 13,238 m3 Table 3: Total freshwater need on Houat, consumer’s perspective Of these 13,328 m3, less than 1 million litres is for drinking, over 5 million litres for show- ers and 2,5 million litres is flushed in the toilets. PRODUCER PERSPECTIVE From the producer’s (Eau de Morbihan) perspective, the consumption has increased. The average per day in the 1990’s was 55,1 m3/d in June, 127,6 m3/d in July, and 116,8 m3/d in August, with a maximum consumption of 152 m3/d. In 2003, the consumption in winter was estimated to 45 m3/d, in summer 160m3/d, with peaks at 270 m3/d. Today, according to the municipality, a resident household on Houat uses in average 70 m3/per year and the total water need for municipal water on Houat is 35,600 m3/year4, more than double the consumption as calculated from the consumer’s perspective above. Divided by total man-days (202,330), the water consumption per individual would be 176 l/day, which seems a bit high.

3 Pleijel: VA Kosteröarna (2017) 4 Étude hydrogéologique Houat 2004, page 21

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5 The water of the community 5.1 Governance The island, with its neighbouring islets, forms the commune of Houat in the Finistère de- partment of Brittany in north-western France. Houat is member of association “Les îles du Ponant” and it is since 2014 part of Quiberon Terre Atlantique local. Mrs Andrée Vielvoye is the current mayor. Water supply, treatment and storage is managed by the public drinking water service company Eau de Morbihan Syndicat (http://www.eaudumorbihan.fr), SAUR (a French Urban and Rural Development Society created in 1933, specialized in the production and distribution of drinking water and wastewater treatment). Distribution is managed by Auray Quiberon Terre Atlantic community of communes.

Figure 9. Morbihan, administrative organisation 5.2 Water procurement system Running municipal water was installed on Houat on the 1970s, using rainwater and a well using a spring close to the Treac’h Salus beach. These were supported by a reversed osmo- sis desalination plant with a capacity of 50 m3/d, providing 20 percent of the needs of the island, being estimated at 100-120 m3/d. In the 1980s, a search was undertaken for addi- tional water sources. Four drills were made to 50 meters deep. Three of these were put to work, the fourth one had too salty water. In 1990, a new 100 m deep drill was made next to the stadium (F5).

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Drillings There is one well on Houat (P4) and there is a tiny brook in the middle of the island. There are five drillings (“forages” in French) on the island, 40-100 meters deep (F1, F2, F4, F5 and F7), see the map below. No Name Year F1 Forage du Nord 1986 F2 Forage de Salus 1986 F4 Forage des Bâches 1986 F5 Forage du Stade 1992 F7 2012 P4 Puits de Salus 1975 Table 4: the drillings and the well

Figure 10: the location of the drillings and the well

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Figure 11. The water on Houat

Figure 12. Driling F2 Figure 13. Drilling F4 Figure 14. F5 and Ronan le Goaster To protect the ground water from the salt water intrusion, an hydraulic modeling has been made, function of the four seasons and the rainfall. The conclusions of this study have shown that the flow of each drill must absolutely be controlled and adapted to avoid the intrusion of salt water in the ground fresh water. Indeed, the salty bevel phenomenon is irreversible. The exploitation of each drill is resumed below:

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No Name Winter May-June, Oct-Nov Summer F1 Forage du Nord 0,8 m3/h 0,35 m3/h 0,25 m3/h F2 Forage de Salus 1 m3/h 0,2 m3/h 0 m3/h Puits de Salus F4 Forage des Bâches 1 m3/h 0,35 m3/h 0,25 m3/h F5 Forage du Stade 4 m3/h 2 m3/h 2 m3/h F7 1 m3/h 1 m3/h 0,55 m3/h Sum 156 m3/h 78 m3/h 61 m3/h Rainwater collection The municipality does not collect rainwater, but the islanders do individually, and store it in underground tanks. If rainwater collection equipment is maintained in order it might be used as a reserve for temporary disruption of the municipal water distribution.

Figure 15. The 2,600 m3 raw water reservoir Reservoirs The water from the drillings is pumped to a raw water reservoir holding 2,600 m3 of wa- ter, processed through a filter system and then stored in 4 reservoirs of 2,500 m3 each each close to the raw water reservoir. On the day of our visit, the amount of pretreated water was 9,000 m3 (full capacity 10,000 m3). Two water tower of 200 m3 each, located above the castle ruins, are storing the potable water before distribution. Distribution The water is distributed through a pipe network (details). All households are covered by the network. Estimated distributions losses?

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5.3 Wastewater How is wastewater managed? Treated wastewater reuse? Costs?

5.4 Quality and shortage aspects

Every Tuesday, a water report is set up including water level (in the drills and in the res- ervoirs) and quality (especially chloride to measure salt water intrusion). The degree of nitrate is (very) low, there is a slight concentration of manganese and iron and organic matter, locally, of chloride. The seasonal variations are low.5

5.5 Costs and taxes The water price on Houat is 2,0€ per m3. Is there any estimation about water supply/distribution cost? Do water payments cover the water cost? Are there any subsidies from the central/regional government?

Figure 16. The PLU

5.6 Future plans Houat is currently developing its Local Urban Plan – Plan Local d’Urbanisme (PLU), http://www.mairiedehouat.fr/upload/document/arrete-plu-53.pdf. A major challenge is the price of land which is very high on Houat (prices are now at 400€/m2, the price of a private road is estimated at 160 €/m2). The municipality would like to increase the water capacity from drills by 8 to 13 m3/d in high season.6

5 Étude hydrogéologique Houat (2004), page 12

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6 Water saving 6.1 Benchmark #1 The Mayor of Houat is well aware of the water situation of the island and its assets: “l’eau douce est un trésor” (“freshwater is a treasure”). She is herself an excellent example of water saving: she has a dual water system, being connected both to the municipal water distribution net, and having a WISY rain water collector system reservoir with a 5 m3 wa- ter tank buried in her garden. She uses the rainwater to flush the toilets and to water in the garden.

Figure 17. What is seen in the garden The system Monitor 6.2 Benchmark #2 Water issues are clearly and fairly controlled through Houat’s PLU (Plan Local d’Urbanisme), which stipulates that all new buildings are to be built with a rainwater res- ervoir, prohibits swimming pools and private drillings.

Figure 18. Madame le Maire

6 Étude hydrogéologique Houat (2004), page 24

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7 References Association les Îles du Ponant: Profil Énergie et Gaz à effet de serre (2014) Brigand, Louis: Les îles du Ponant : Histoires et géographie des îles et des îlots de la Man- che et de l'Atlantique (2002) Chiron, Thomas: Quel risque de pénurie d’eau sur les îles du Ponant? (2007) Conseil Général du Morbihan: Étude hydrogéologique et modélisation des eaux souterrai- nes de l’île d’HOUATPrésentation (2004) Conseil Général du Morbihan: Etude hydrogeologique et modelisation de l’île d’Houat (2004) Eurostat: http://ec.europa.eu/eurostat/statistics-explained/index.php/File: To- tal_freshwater_abstraction_by_public_water_supply,_2013_(m³_per_inhabitant)_YB16.png Le Courrier 29/9/2106 http://www.lecourrier-leprogres.fr/2016/10/03/l-eau-enjeu- majeur-pour-les-iles/ Nordström, Anders: Dricksvatten för en hållbar framtid (2005) Spilanis et al, the ESPON 2013 Programme The Development of the Islands – European Islands and Cohesion Policy (EUROISLANDS) Targeted Analysis (2013) Pleijel: How to Read an Island (2015) Pleijel: VA Kosteröarna (2017) http://www.stromstad.se/byggaboochmiljo/vattenochavlopp/vakosteroarna.4.fc6ae6c15 3c5fdf8ad127e2.html http://www.ina.fr/video/CAF93010642/l-ile-de-houat-video.html

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