Potable water for a city: a historic perspective from Bruges, Belgium
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Hydrogeology Journal (2014) 22: 1669–1680
DOI 10.1007/s10040-014-1154-9
Potable water for a city: a historic perspective from Bruges, Belgium
A. Vandenbohede & E. Vandevyvere
Abstract Contributing to the optimisation of drinking- ingenuity resulted in each city coming up with its own
water supplies is a key responsibility for professional and sometimes remarkable solutions. During the early
hydrogeologists. Thus, it is interesting to look back and put Middle Ages, the majority of Roman water-supply
current-day practices in the framework of historic evolution systems were gradually abandoned. Surface water (rivers,
and past achievements. The water supply of Bruges lakes, etc.), springs or large-diameter open wells tapping
(Belgium), with an innovative supply system already phreatic aquifers supplied water to communities
established by the end of the 13th century, forms an (Magnusson 2001). This remained essentially the same
interesting case study. The supply system consisted of an until the 19th century, although there was continued
underground network of pipes feeding public and private evolution in the methods of distribution and different
wells. A special construction, the Water House, was built to designs of pipes and conduits developed.
overcome a topographical height difference. Population Industrialisation and demographic growth influenced
growth and industrial expansion during the 19th century water supply at the end of the 19th century and marked the
increased the water demand and new solutions were start of evolution to the current-day systems. The connection
necessary. Tap water became available from 1925 onwards was made between hygienic living conditions, drinking-
and, as a stopgap measure to meet demand, deep ground- water quality, sanitation and health. The outbreak of
water was used. This invoked a lively debate among the city waterborne diseases and epidemics increased the interest in
council, scientists and entrepreneurs, whereby both water groundwater (e.g. de Vries 2013). Groundwater gained
quality and quantity were discussed. Although based on a steadily in importance for the water supply of cities, as
lack of modern understanding of the groundwater system, illustrated from studies of Prague and Brno in the Czech
some arguments, both pro or contra, look very familiar to Republic (Muzakir 2013), several German cities (Loehnert
current-day hydrogeologists. 2013), Moscow and other large Russian cities (Zaltsberg
2013), Great Britain (UK; Mather 2013) and Spain
Keywords History of hydrogeology . Water (Custodio 2013). In some cases, innovative systems were
supply . Belgium designed, for instance in Göteborg (Sweden) where the
quality of river water was improved by infiltrating it to the
groundwater before extraction with wells (Svensson 2013).
Introduction This report reviews the historic development of the
public water supply of Bruges, Belgium. This city is
The evolution of public water supply, from the first interesting as a case study because an innovative public
beginnings in the early Middle Ages (5th to 10th century) water supply was established at the end of the 13th
until the distribution of modern-day tap water, has century. Important changes were necessary at the end of
similarities in different European countries but the details the 19th century that led to the consideration of
differ for each city. Available natural resources, social and groundwater for the supply of potable water. The use of
political context, scientific thinking and technical groundwater evoked a lively discussion in the early 20th
century, in which both the quality and quantity were
considered.
Received: 26 October 2013 / Accepted: 28 May 2014
Published online: 25 June 2014
* Springer-Verlag Berlin Heidelberg 2014 Hydrogeology and hydrography
Bruges is situated at the boundary of two major
A. Vandenbohede ()) geographical units: a flat coastal plain towards the north
Geology and Soil Science,
Ghent University, Krijgslaan 281 (S8), 9000 Gent, Belgium and a sandy region towards the south (Fig. 1). The coastal
e-mail: avdenboh@yahoo.co.uk plain is the result of the geological evolution after the last
Tel.: 32-9-2644652 Ice Age and is influenced by recent human intervention
Fax: 32-9-2644653 (e.g. Baeteman 2008; Ervynck et al. 1999; Vandenbohede
E. Vandevyvere and Lebbe 2012). In the early Middle Ages it was a
Invalidenstraat 70, 8310 Sint-Kruis (Brugge), Belgium dynamic mud flat environment and became reclaimed
1670
Fig. 1 a Location of the study area in Belgium, and b topography and major geographical regions. In a the black dots are towns or cities.
The hatched area in b is the recharge area of the Ypresian aquifer, and Y1–Y5 refer to groundwater samples. m TAW is the Belgian datum
level, whereby 0 m TAW is 2.36 m below mean sea level
from about the 7th century AD. Most parts of the coastal consists of glauconitic clay of very low permeability. At
plain were turned into polder, an artificially drained land, Bruges, it reaches a maximum thickness of 10 m. The
which was completed in the 12th century AD. The sandy Ypresian aquifer consists of glauconitic fine sand. It has a
region is characterized by a more pronounced topography, thickness of 10 m in the south but increases towards the
determined by the underlying lithology, and was formed north of the city to 30 m. The underlying Ypresian
during the Pleistocene by fluvial and aeolian processes. aquitard consists of 100 m of clay and is considered an
Rivers originated on different plateaus and made their way impermeable base in most groundwater studies.
towards the coastal plain. One such river, which does not
exist in its medieval course anymore, was the River Reie.
It originated northeast of Torhout, found its way towards Medieval water supplies
the north, and connected with a major tidal gully at the
location of Bruges. Potable water
The geology consists of a Quaternary top layer and two Bruges originated at the boundary of the two geographical
aquifers subdivided by an aquitard (Fig. 2). The units (Hillewaert et al. 2011). Agriculture and hunting
Quaternary has a varying thickness between 5 and 20 m were possible in the sandy region and sheep could be kept
and consists of fluvial and aeolian, mainly sand, deposits. or salt could be harvested in the coastal plain. The higher
The upper aquifer, the Panesilian aquifer, is of Eocene age ground of the sandy region protected the settlement from
and consists of glauconitic fine sand that becomes clayey flooding and the Reie provided water from inland.
fine sand at its base. Thickness is variable, between 20 and Moreover, the Reie provided a connection with the sea
40 m. The Panesilian aquifer and the Quaternary layer through its transition into a tidal gully. In Roman times,
together form the phreatic aquifer. The Panesilian aquitard Bruges evolved to one of the larger settlements along the
Fig. 2 Hydrogeological north–south oriented cross-section through the centre of the city
Hydrogeology Journal (2014) 22: 1669–1680 DOI 10.1007/s10040-014-1154-9
1671
coastal plain and it became an established trade centre the conduit. A number of private connections were present
with a harbour in the second part of the 10th century. The besides the public fountains.
Reie was without doubt important for the water supply It is not known exactly when this system was built,
during this early development. Additionally, the phreatic since the fire of the belfry in 1280 destroyed the older
aquifer was exploited with large diameter wells sunk in city’s archive, but the oldest preserved municipal accounts
the Quaternary sediments, as is evidenced in archaeolog- clearly suggest the existence of three conduits already
ical sites. before 1280. The other three systems were built after the
Bruges experienced economic growth during the city moats were dug out (1297–1300), but were certainly
second half of the 12th and during the 13th century established between 1299 and 1331.
because of its connection to the sea. The city became one The original water source for the most important
of the most important trade centres in western Europe, and conduit was a lake about 800 m outside the city
the region, the County of Flanders, was one of the most (Vandevyvere 2012a). This Sint-Baafs Lake was fed by a
prosperous. This economic and political power developed brook with its source less than 10 km beyond in the higher
and enhanced the health and comfort of Bruges’ inhab- topography southwest of Bruges. City accounts of 1292/
itants. Presence of a public water supply was a clear 1294 mention Sint-Baafs Lake and imply it was already in
expression of this. Bruges had a relatively high population use for some time. The importance of the lake was clearly
at that time. The number of inhabitants in 1,338–1,340 is realized and the water quality and supply from the brook
estimated to be 33,000–45,000 (Prevenier 1975). Thus, was monitored. It is, for instance, known that the lake was
there was a demand for water of good quality, not only as cleaned in 1308 and that the brook was cleaned in 1318.
drinking water but also for different trades such as
breweries, soap-boilers, tanners and the all-important
textile industry. Bruges’ marvel
At the end of the 13th century, a well-developed Because water in the conduits must flow under gravity, the
system to supply potable water was established, which conduits had to be placed deeper with increasing distance
consisted of an underground system of lead conduits that from the inlet. A rough estimate shows that the depth had
supplied a network of open reservoirs, called fountains, to be between 5 and 6 m below surface for the major
from which water could be hauled (Boone 1958; conduit starting from the Sint-Baafs Lake because it had
Vandevyvere 1983). The conduits were made of connected to cross a topographical height. With the tools of the 13th
lead tubes. Six such conduits were present, starting at the century, this was all but impossible and an ingenious
border of the city (Fig. 3). The least important was only solution was applied. A noria, i.e. a lifting machine for
50–60 m long. The five others were much longer and water, was constructed to bring the water from the lake
formed a pattern to the inner city, each conduit providing a level (or later from the town’s moat level) into a higher
different part with water. Water was taken from a lake or reservoir which fed the conduit. Consequently, the conduit
the moat surrounding the city and water flowed by gravity could be placed less deep and could cross the topograph-
through the conduits. The fountains consisted of a ical height. The noria consisted of a vertical wheel (4.2 m
reservoir with an inlet and, in some cases, an outlet for diameter) which was slung with a chain of buckets. A
Fig. 3 The Medieval system of conduits (red lines) superposed on the 1562 city map of Marcus Gerards. This reconstruction is based on
the work of Boone (1958), Vandevyvere (1983) and a similar map preserved in the Biekorf Public Library of Bruges. Notice the compass
card which shows north towards the lower left corner. The outer city boundary was a dual-moat system
Hydrogeology Journal (2014) 22: 1669–1680 DOI 10.1007/s10040-014-1154-9
1672
horse mill provided the necessary power and a work Lake was no longer necessary and water for the Water
supervisor was appointed by the city council for its House came, from then on, from the moat.
working. Where the system was probably in open air Between 1758 and 1760, a new Water House was build
before 1398, it became covered afterwards in what using a water mill instead of the horse-mill. The energy to
became known as the Water House. Remnants still exist drive the water mill was provided by the (about) 1-m
today (Fig. 4). height difference between the city’s inner and outer moats.
The noria and the Water House were remarkable Another important change was that, from the 17th century
constructions in medieval Europe and were praised by onward, water was raised with hand pumps instead of by
many chroniclers. One of the reasons for this was that, buckets from the subsurface reservoirs fed by the
besides a prime utilitarian function, the Water House conduits.
developed also an entertainment function (Vandevyvere
2012b). The lead reservoir provided water and pressure
for the working of a fountain in the garden next to the
Water House. There was also a system of hidden pipes Renewed challenges in the 19th century
which could spray water for the delight, and sometimes to
the dismay, of visitors as is described by, for instance, Quality and quantity issues
Swiss doctor Felix Platter in 1599 (Bonneure 1984). The system of conduits was so well designed and
Interestingly, the Water House was open to visitors and technically sound that no major changes happened from
this made it a real attraction for Bruges. It is thus the Middle Ages to early modern times. However,
rightfully that the Water House is depicted as one of the problems with the water supply to the system emerged
seven marvels of Bruges by Pieter Claeissens on his during the mid-19th century. Population growth and
painting “Septem Admirationes Civitatis Brugensis”, expansion of industrial activities increased the water
dated between 1550 and 1560 (Fig. 4a). demands and resulted in water shortage during summer.
Therefore, it was decided in 1862 to block a part of the
inner moat to form a reservoir of surface water. This was a
very temporary measure as the key issue, delivery of
Conflicts and further developments water, was not tackled. There was also a qualitative issue
The turbulent 14th century had consequences for Bruges’ as degradation of water quality was recorded. During the
water supply. At some point the idea arose to dig a canal periods in which parts of the inner moat were dammed,
connecting the River Leie near Gent with Bruges. This the water mill could not be used to produce the necessary
would provide an extra source of water for the drinking- energy for the Water House, as too much water would
water supply of the city but also to flush (and prevent have been lost to drive the water mill. The water mill
silting up) the connection of Bruges with the sea through needed 80 L of water to get 1 L of water into the city and
the Swin estuary. This canal would have also provided that was considered a waste of resources during the latter
new opportunities for trade and this was realised by the part of the 19th century. Installation of a permanent steam
city of Gent. A military intervention in 1378 ended the machine was suggested but was met with resistance:
construction works. However, the capture area of the energy from water is free, while a steam machine forms an
already built section provided an extra source of water and important investment. Whereas the Water House and the
made it possible to deepen the moat (1382–1384) which system of conduits were innovative in the 13th century,
acted now as a valuable water reservoir. The Sint-Baafs the system became finally obsolete during the 19th
Fig. 4 a Detail of the painting “Septem Admirationes Civitatis Brugensis” by Pieter Claeissens (dated between 1550 and 1560) showing
the Water House, compared to b the current-day remnants. Notice the garden for entertainment in front of it
Hydrogeology Journal (2014) 22: 1669–1680 DOI 10.1007/s10040-014-1154-9
1673
century. Necessity to modernise water supply systems was 134 pumps present, only 21 delivered water that was
encountered all over Europe in the second part of the 19th considered suitable for human consumption.
century (e.g. Baret-Bourgoin 2005; de Moel et al. 2006; Degradation of water quality, the need for more water,
Hanni 1999; Howden and Mather 2013; Loehnert 1985; and the lack of a decision by the city council to address
Serneri 2007). these concerns resulted in exploitation of deep groundwa-
ter, initially an initiative of industrialists. The city council
undertook a first effort to exploit deep groundwater in
1870: a Norton tube well was constructed to a depth of
Alternatives about 11 m below surface (Panesilian aquifer). A 30 m
Different proposals were made to enhance the water
deep well was drilled in 1893, tapping the lower part of
supply of Bruges. Captain Verstraete suggested in 1875
the Panesilian aquifer. These first experiences were not
to use groundwater from a hilly area north of Torhout. He
positive and water from such wells was not known for its
was inspired by Brussels and Paris where groundwater
good quality. Deep drillings in neighbouring cities were
was extracted by means of galleries. Interestingly, this
also not encouraging. A 308 m deep well in Oostende and
proposal was rejected based on environmental issues. The
a 218 m deep well in Blankenberge resulted in brackish
area is located at the northern side of the Wijnendale
water. These wells exploited the Landenian aquifer below
plateau and is a seepage area of groundwater recharged on
the Ypresian aquitard, which contains brackish water
the plateau. It is thus a wet area containing marshlands
because of the mixing of old saltwater with younger
and the city council feared that the marshes would dry up
recharged freshwater, a fact that is nowadays well
by extracting groundwater. Without being aware of the
understood from the large-scale groundwater quality
general groundwater flow pattern, this is an early
patterns (Walraevens et al. 1989). In general, lack of
intuitional application of the fact that sustainability of an
hydrogeologic background resulted often in the failure of
extraction is measured against the impact of a decreased
boreholes (Mather 2013). Notwithstanding these initial
discharge of the groundwater system (Bredehoeft 2002).
restraints, deep groundwater wells were accepted by many
A second attempt to develop groundwater extraction in
as a temporary measure pending a decision about a more
this region was made by a firm based in Amsterdam. The
reliable water supply. However, the negative experiences
proposition was to extract water from the Ypresian aquifer
urged the city council not to promote deep wells as serious
but was never realised.
(temporary) sources of water, while, at the same time, the
Count Ficquelmont, on the other hand, was inspired by
number of wells for private and industrial use increased
the dune water supply of the Dutch cities Amsterdam and
(Fig. 5) and many (if not most) provided water of
Den Haag. Since 1853, freshwater was drained from the
acceptable or good quality. This won over the city council,
dunes by a channel and transported to Amsterdam by a
and a number of public wells in the Ypresian aquifer were
pipe. Ficquelmont suggested extracting groundwater for
drilled. Most of these Ypresian wells extracted water from
Bruges from the dune area between Heist and the Dutch-
the lower part of the aquifer. Additionally, national
Belgian border. However, his financial demands were
support was obtained to drill 23 Ypresian wells in 1907/
extensive and this plan was also abandoned.
1908.
Water supply to Brussels provided further inspiration.
The growing number of wells in the Ypresian aquifer
Brussels got its drinking water from the source area of the
led to, what would be currently called, overexploitation.
River Bocq, a tributary of the River Maas. It was
Pre-development levels are not known but can be
estimated that the area could provide much more water.
estimated at about 5–10 m below surface level from the
It was proposed in 1899 to set up a consortium to provide
scant early drilling data. Levels in the Ypresian aquifer
water to the cities of Oostende, Bruges, Gent, and Aalst
had dropped in 1913 to between 20 and 25 m below
with Bocq water. Discussions dragged on until 1908
surface level. Extraction limitations were therefore or-
before a final approval was given and the first tap water
dered. It was decreed that not more than 25 L per person
was realised in 1925. However, in the meantime, local
per day could be extracted from public wells, but this limit
groundwater was used as stopgap measure to meet the
could not be inspected and was never implemented.
increasing water demand.
Questioning groundwater
Groundwater as an alternative Use of groundwater seemed to be an effective temporary
measure. However, physician Merchie (1908) questioned
Groundwater use the availability of Ypresian water and argued that the
Besides the use of surface water through the conduit water was contaminated from a chemical and bacteriolog-
system, groundwater was exploited through wells sunk in ical viewpoint. Merchie estimated an extraction of about
the Quaternary sediments and Reie water was also used 500 m3/day, of which more than half was needed for
before the 19th century. However, water from the Reie and industrial purposes. He expected an increase with 325 m3/
from many shallow wells became unusable for human day (a ratio of 10 L/day per resident) to cover the water
consumption. Notifications about water quality were hung demand of the city but doubted this would work based on
on each pump just before the turn of the century: from the the necessary number of wells (a ratio of 3 m3/day per
Hydrogeology Journal (2014) 22: 1669–1680 DOI 10.1007/s10040-014-1154-9
1674
Fig. 5 Workman and the yard foreman pose next to a Ypresian well they had drilled. Of note is the bottle with a water sample which was
just taken for analysis. It illustrates the sampling methods in 1914
well). Merchie argued that the distances between wells scientific error”. They quoted a number of distinguished
would be too small, affecting each other negatively as he scholars from universities in Louvain, Berlin, Paris, and
referred to a similar situation in Paris; however, especially Bucharest to state that it is common knowledge that
the bacteriological quality of the Ypresian water was bacteria cannot survive in the subsoil at a depth larger than
alarming to him. He concluded that the water was of 8 m. This was also the opinion expressed by a Hungarian
mediocre quality based on the bacterial count. From a physician and recognized specialist on hygiene, von Fodor
chemical point of view, some wells were also considered (1893). The Nelis and Vanhove (1908) conclusion was
of inferior quality, which was mainly based on chloride that the contamination was due to the drilling fluid and of
concentrations which exceeded the limit of 100 mg/L. temporary nature.
Salts (NaCl) and ammonia were at that time considered as Nelis and Vanhove (1908) mentioned results for two
a sign of contamination with urine and bacteria. Merchie wells where no bacteria were encountered in the water,
attributed this contamination to a non-continuous nature of and eleven new samplings also with no bacteria counts.
the Panesilian aquitard or short-circuiting of the wells. In Moreover, samples above and below the Panesilian
both cases, Ypresian wells captured contamination present aquitard were analysed. For the chemical contamination,
in the phreatic aquifer. Another possibility he suggested, Nelis and Vanhove (1908) argued that chloride cannot be
was contamination by the fluid used for drilling the wells. used as a proxy for contamination. Contamination from
Merchie’s results were unexpected and were not well- urine or faeces would also mean an increase in nitroge-
received by the city council which had finally concluded nous species such as ammonia, nitrate or nitrite, of which
to promote Ypresian water as the stopgap measure before none were detected in the Ypresian wells. They constitut-
River Bocq tap water would be available. The council ed the presence of chloride simply from water-rock
discounted the conclusions with the argument that interactions. Finally, a number of analyses were done on
Merchie had studied recently drilled with contamination the demands of the Ministry who became suspicious of
due to drilling or originating from the sampling. A second awarding subsidy to unhealthy wells. Dineur, an Antwerp
study was published by Nelis, a physician in Bruges, and physician, confirmed the results of Nelis and Vanhove
Vanhove, a professor of mineralogy at Ghent University. (1908) with new samples. Putzeys (1908) added to the
The study was clearly influenced by the on-going political discussion with analyses from a Panesilian well just
discussion. The authors (Nelis and Vanhove 1908) argued outside Bruges. This well had good chemical and
that the Panesilian clay can be considered as a continuous bacteriological quality and delivered 400 m3/day.
layer, separating the Ypresian aquifer from the phreatic
aquifer. Geological arguments, based on drilling descrip-
tions, were therefore used but also basic hydrological Discussion
observations were described. They stated that a head
difference of about 6 m over the Panesilian aquitard Medieval water supply in perspective
pointed to its continuous nature. The occurrence of During the early Middle Ages, the majority of Roman
bacteria in the Ypresian aquifer was disposed of as “a water-supply systems gradually decayed and were
Hydrogeology Journal (2014) 22: 1669–1680 DOI 10.1007/s10040-014-1154-9
1675 abandoned. Most communities obtained water from rivers, used. Increase in population led, in the mid-13th century, shallow wells, and cisterns. The growth of cities increased to the construction of the first of what would become 12 the demand of potable water and opened the way for more conduits in London. Each conduit started near a spring complex water-supply systems. However, the ability to and brought water to cisterns in the city; also, water from construct and maintain an underground system for the the River Thames was still used. For housing located on distribution of potable water for a city should be the higher topography, water had to be carried uphill by considered as a remarkable accomplishment. professional water carriers. This changed in 1580 when Infrastructure similar to Bruges is known from two Dutchman Morice gained permission to build a water other cities in the County of Flanders (Boone 1958)— wheel and pumps to uplift Thames water to a conduit Damme and Ypres. Damme was founded at the end of the house from where it was further distributed. 12th century and became Bruges’ connection to the sea Consequently, for the time, the technically more through the Swin estuary. Because of its location in the complex solution as used in Bruges was not unique but polder, surface water and shallow groundwater were it was at least notable and stands out from contemporary saline. Therefore, permission was granted in 1269 to water-supply systems in Western Europe. The combina- extract surface water from a lake at Male, 4.2 km from tion of an underground system of conduits and a noria for Damme. A subsurface lead conduit was constructed to a large-scale public water supply was innovative during transport the water to Damme where it was further the late high Middle Ages. Maintaining the system from distributed via four underground reservoirs. Ypres needed the late 13th to the 19th century is also an a large amount of water for its textile industry, and river accomplishment. water did not supply the necessary amounts and the clay subsurface was not suitable for wells. Therefore, water from surrounding hills was collected in two lakes and Ypresian aquifer quantitative issues these lakes provided a constant water level in the moat. Merchie (1908) seriously questioned the ability of the From the moat, different conduits provided the city with Ypresian aquifer to sustain additional exploitation, where- water using a number of fountains. First notices of the city as Nelis and Vanhove (1908) argued otherwise. Evaluating lakes on documents appear in early 13th century. their arguments objectively is difficult, because historic The fact that three cities close to each other developed a extraction rates are not known. For private wells, similar system of conduits during the latter part of the 13th construction time is also unknown. However, an attempt century cannot be a coincidence; a transfer of knowledge is made to estimate early 20th century drawdowns from must have happened. Who conceived the idea and which city the scant data. put the system in operation first remains shrouded in the The Ypresian aquifer is considered a confined aquifer mists of time. Most other cities in Flanders had less technical with infinite extent and with all water released from solutions; shallow large-diameter wells tapping the phreatic storage so that the Theis solution (Theis 1935) can be aquifer provided the main source of water (Van applied. Drawdown as function of distance from each well Craenenbroeck 1991). Gent, which was with Bruges and is calculated and results are superposed to obtain the Ypres a trade and political center in Flanders, met its water drawdown in the aquifer. A mean aquifer thickness of needs from the River Schelde. In other cases, water from 15 m and a hydraulic conductivity of 1.5 m/day (Lebbe surrounding hills was captured and was brought to the city and Van Meir 2000) are used. The location of most wells through conduits. Examples are the 15th century systems at is known from maps and descriptions retained in the City Geraardsbergen and Brussels, and a similar 16th century Archives Bruges. Some extraction rates are known such as system at Oudenaarde (Boone 1958). from a yeast and spiritus plant which extracted 145 m3/ Outside the County of Flanders, Amsterdam (The day (Merchie 1908) and from the St Jans Hospital which Netherlands) and London (UK) are two interesting cases extracted 75 m3/day (Nelis and Vanhove 1908). Extraction for comparison. Around 1200, the first inhabitants of rates from public wells realistically range between 3 and Amsterdam depended on the River Amstel for drinking 15 m3/day (Merchie 1908; Nelis en Vanhove, 1908; water (de Moel et al. 2006) since groundwater was saline. reports from drillers retained in the City Archives Population growth caused pollution of the Amstel and a Bruges) and a mean value of 7.5 m3/day is used. The 1413 prohibition against casting dead animals, manure, discharge rate from private wells is difficult to estimate. A and other refuse in the river was hardly sufficient. In 1480, value of 15 m3/day is used which is a maximum value brewers in Amsterdam organised a supply of fresh water extractable with a hand pump (Nelis and Vanhove 1908). by ship from a 30-km distant lake which was an arduous The resulting drawdown pattern is concentric with the and costly task. Problems with water supply and the city enclosure (Fig. 6) because the wells are randomly quality of it remained throughout the 15th and early 16th distributed over the city. Maximum drawdown in early century, mainly because clean and disposed water where 1907 (before the planned 23 subsidized wells) is estimated not separated from each other. London, in the early 13th to be 12 m (Fig. 6a). This is after 5 years of operation of century, was a relatively small community. The River the wells. The increased drawdown in the northern part of Thames and a number of small rivers were the most the city is due to the extraction by the Yeast and Spiritus important source of water (Barton 1992). Farther away plant. Drawdowns have increased another 5 years later to from the river, shallow wells or water from springs were a maximum of 18 m, taking into account the 20 (of 23 Hydrogeology Journal (2014) 22: 1669–1680 DOI 10.1007/s10040-014-1154-9
1676
Fig. 6 Estimated groundwater level depth (m), illustrating drawdown, a just before bringing the 20 subsidized Ypresian wells into use in
early 1907, and b 5 years afterwards. Groundwater-level contours are superposed on the 1904–1907 city map made by the Public Work
Service
planned) new wells. This compares with the observation hydraulic conductivity of about 10−4 m/day (Lebbe and
that water levels had dropped to 20–25 m below surface Van Meir 2000). Connectivity between the Panesilian
level in 1913, considering a depth of 5–10 m below aquifer and the Ypresian aquifer, as was assumed by
surface for the pre-development situation. Merchie (1908), is therefore highly unlikely, except in the
Merchie (1908) and Nelis and Vanhove (1908) were in case of short-circuiting because of ill-constructed wells.
agreement that the water extraction from the Ypresian A number of groundwater analyses are available from the
aquifer was not sustainable. The argument of Merchie archives of Applied Geology and Hydrogeology (Ghent
(1908) was that an unrealistically high number of wells University) (1970s data) and from the monitoring network of
would be needed to meet the water demand, influencing the Flemish Environmental Agency (recent data; Table 1).
and diminishing each other’s discharge rate. He made a These Quaternary and Panesilian groundwater sampling
final statement which sounds familiar for current-day locations are all in the city center; sampling points for the
hydrogeologists but can be considered innovative for Ypresian groundwater data are located (Fig. 1b) in Bruges
early 20th century (Belgian) hydrogeological thinking. He (Y1), east of Bruges (Y2) and near the recharge area (Y3,
warned that water from such deep wells is a limited Y4, Y5). The classification of Stuyfzand (1989, 1993) is
resource and should not serve exclusively for the water used to subdivide the water samples into a number of water
supply of cities. Although he did not elaborate on this types. The determination of a water type implies the
statement, this translates to today’s basic principle that successive determination of a main type, type, subtype and
water resources should serve different purposes and that class of the water sample. For a detailed description of the
extractions should be sustainable on the long-term. classification, the reader is referred to the cited references.
The groundwater levels were also calculated with the The samples are plotted on a Piper plot (Fig. 7), which helps
preceding discussed method for the situation 25 years after to visualize evolutions in water quality.
the 20 subsidized Ypresian wells were brought into use, Quaternary samples are fresh, have a moderately high
which gives an estimated maximum drawdown of 22 m, to high alkalinity and are of the CaHCO3 or CaSO4
without taking into account the increase in population. A subtype. Groundwater is determined by carbonate mineral
50 % increase in water demand increases the maximum dissolution. Locally, SO42− can become important (e.g.
drawdown to 33 m, which comes close to the top of the sample Q2) because of contamination or oxidation of
Ypresian aquifer. It was thus indeed correct to state that organic matter or pyrite in the Quaternary deposits. A
the Ypresian aquifer was not capable of meeting the long- similar composition is found in the Panesilian aquifer
term water demand of the city (Merchie 1908; Nelis and since it forms the phreatic aquifer with the Quaternary
Vanhove 1908); however, it did serve its purpose as a sediments. By contrast, samples from the Ypresian aquifer
temporary measure before tap water became available. in Bruges (Y1) are brackish, have a high alkalinity and are
of NaHCO3 subtype. This composition is also distinct
from Ypresian water samples 5 km east of Bruges (Y2)
Ypresian aquifer qualitative issues and near the recharge area (Y3, Y4, Y5). These differ-
ences reflect the large-scale water quality evolution from
Current analyses and insights the end of Tertiary times.
Recent geological studies have shown that the Panesilian Marine conditions were prevailing before the last
aquitard is a continuous semi-pervious layer with a regression at the end of the Tertiary, and sediments,
Hydrogeology Journal (2014) 22: 1669–1680 DOI 10.1007/s10040-014-1154-91677
B4NaHCO3+
Table 1 Major ion chemistry of Quaternary (Q), Panesilian aquifer (P) and Ypresian aquifer (Y) groundwater samples. All concentrations are in mg/L, depth of sampling is indicated in m
f4CAHCO3+
F4CaHCO3+
F3CaHCO3+
F1CaHCO3+
g0NaHCO3+
g2CaHCO3+
including the Ypresian aquifer, contained saltwater. This
Water type
F3CaMix+
F3CaSO4+
F*CaSO4+
F0CaSO4+
saline water was then gradually displaced by fresh
recharge water. Mixing of water types, cation exchange
and calcite dissolution are the main factors determining
water quality patterns in the aquifer. Under natural
conditions, there was a groundwater flow from the
7.3
6.9
7.8
7.9
7.7
8.4
5.2
7.3
6.2
8.3
pH
7
recharge areas towards the northwest (i.e. towards the
North Sea). Because of the displacement of saline water
1406
1437
1268
1048
1557
TDS
670
259
271
359
301
382
with fresh recharge water, freshwater is found near the
recharge area (samples Y3, Y4, Y5). Carbonate mineral
dissolution results in a CaHCO3 or CaSO4 subtype.
17.713
NO3−
Because of the freshening, saltwater is pushed in the
0.02
0.66
0.66
1.18
1.36
1.7
upstream direction. When sediments in equilibrium with
–
–
–
–
saltwater are flushed by freshwater, CaHCO3, MgHCO3,
PO43−
NaHCO3 and NaCl subtypes are found in succession
1.068
0.785
0.631
0.19
0.32
1.62
0.88
downstream from the recharge area because of cation
–
–
–
–
exchange (Beekman and Appelo 1990; Valocchi et al.
1981; Walraevens et al. 2007). This evolution follows a
SO42−
249.7
100.5
324.6
63.5
51.5
64.4
10.6
530
190
170
characteristic path on a Piper plot (Fig. 7). CaHCO3 is
–
found in Y3, Y4 and Y5, close to the recharge area.
MgHCO3 is not found because of the sparse coverage of
HCO3−
683.24
595.4
475.8
463.6
524.6
50.05
observation wells but NaHCO3 is observed at the well in
79.3
18.7
33.6
323
6.7
Bruges. Y1 is characterized by very low Ca2+ and high
Na+ in comparison with Y3, Y4 and Y5, typical for the
22.8
NaHCO3 subtype. The sample to the east, Y2, is fresh, but
186
316
116
Cl−
48
44
95
42
18
49
60
has low Ca2+ and high Na+, which distinguishes it from
water close to the recharge area. The Y1 sample is more
4.757
NH4+
brackish because of its more western position, towards the
2.15
0.18
2.06
0.54
0.41
0.21
0.65
0.35
0.6
original saltwater. Both Y1 and Y2 plot on the freshening
–
line in the Piper plot.
0.031
0.052
0.175
0.211
Mn2+
0.43
0.04
0.57
0.6
–
–
–
Historical analyses in retrospect
0.095
0.185
0.035
0.325
0.145
Analyses of water from all Ypresian wells were
Fetot
0.12
0.66
3.67
2.62
0.11
19
performed in 1911, 1912, 1914, and 1942 and these
are retained in the City Archives Bruges. Some earlier
13.53
analyses for wells tapping the shallow aquifer are
31.6
2.16
2.55
14.9
12.9
3.2
4.7
3.5
K+
72
11
given by Cornet et al. (1876). Together with the results
of Merchie (1908), Nelis and Vanhove (1908), analyses
made right after the drilling of some wells, and the
46.83
13.82
23.04
43.9
18.8
35.6
Na+
145
467
182
current insights in aquifer evolution, these put the
98
26
1908 discussion about the quality of deep groundwater
in perspective.
24.61
48.84
20.18
28.58
27.84
Mg2+
4.58
Cl−, considered as a sign of contamination with urine
4.5
6.7
8.4
6.9
3
and bacteria, varies between 10 and 330 mg/L (Fig. 8).
These values range between Cl− observed near the
244.87
270.75
106.22
176.36
231.42
52.03
Ca2+
Ypresian aquifer recharge area (Y3, Y4, Y5) and Y1 in
3.9
55
42
51
6,
the modern samples. The wide range indicates the transi-
tionary position of Bruges between fresh CaHCO3 or
Sampling depth (m bsl)
CaSO4 water south of the city and saline water to the
below surface level (m bsl)
north-west. 70 % of the samples are to be considered
contaminated applying the limit of 100 mg/L Cl− used by
Merchie (1908). The current drinking water limit of
250 mg/L Cl− classifies all but a few samples as drinkable
water. Most samples have a total hardness less than
13.5
19.7
61.5
52.5
11.3
150 mg CaCO3/L which is classified as soft water (Fig. 8).
5.8
6.5
5.5
7.3
6
5
A limited number of samples classify as hard (250–420 mg
CaCO3/L) or very hard water (>420 mg CaCO3/L) and
Q1
Q2
Q3
Y1
Y2
Y3
Y4
Y5
P1
P2
P3
these are, with the exception of two samples, related to
Hydrogeology Journal (2014) 22: 1669–1680 DOI 10.1007/s10040-014-1154-91678 Fig. 7 Piper plot of the groundwater samples of Table 1 high Cl−. Nelis and Vanhove (1908) praised water from the phreatic aquifer. Well construction and quality in this aspect for industrial purposes. Low proximity to sources of faecal contamination are Ca 2+ , because of cation exchange, explains the identified by Wireman and Job (1998) as important favourable hardness values. By contrast, the few risk factors and Gellasch et al. (2013) point out the samples from the shallow aquifer show a wide range role of fractures. Although not conclusive by lack of of chloride concentrations ranging between 18 and more and reliable historic data, it could be concluded 500 mg/L. The large concentrations are considered due here that a number of wells were indeed contaminated to contamination. from a microbial point of view but that this was rather Poor bacteriological quality of the Ypresian wells as the exception than the rule. sampled by Merchie (1908) remains enigmatic, because all later analyses contradict his results. Contamination of (deep) production wells with microbial pathogens is Concluding remarks possible (Macler and Merkle 2000), especially consid- ering the less sophisticated well-construction methods Bruges provides an interesting case study on how and mixing with contaminated surface water or water water supply to a European city evolved historically. Fig. 8 Total hardness as a function of chloride for Ypresian wells and shallow groundwater during the late 19th to early 20th century Hydrogeology Journal (2014) 22: 1669–1680 DOI 10.1007/s10040-014-1154-9
1679
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