Advanced water management and pioneer hydraulic technology in Minoan Crete (Bronze Age)

This post is a summary of information on water management and hydraulic technology in Minoan Crete, Greece, during the Bronze Age.

“Minoan technological developments in water management principles and practices are not as well known as other achievements of the Minoan civilization.

Archaeological and other forms of evidence indicate that, in the Bronze Age of Crete, advanced water management and sanitary techniques were practiced in several settlements.

The advanced water distribution systems in various Minoan palaces and settlements are remarkable, because there is evidence that several water techniques were unknown before the Minoan era. These techniques include the construction and use of water supply systems, such as aqueducts, cisterns, wells, collection and distribution facilities, and fountains. The hydraulic and architectural function of the water supply systems in palaces and cities are regarded as one of the salient characteristics of the Minoan civilization. These systems were so advanced that they can be compared with the modern systems, which were established only in the second half of the 19th century in European and American cities (Angelakis et al., 2010).

It should be noted that hydraulic technologies in ancient Greece are not limited to urban water systems. The progress in urban water supply was even more noteworthy, as witnessed by several aqueducts, cisterns, wells, and other water facilities discovered, including the famous Minoan aqueducts of Knossos and Tylissos, the cisterns of Zakros, Archanes, Myrtos-Pyrgos and Tylissos, the wells of Paleokastro, Zakros, and Itanos (e.g., Koutsoyiannis et al., 2008).

The Minoan and Mycenaean settlements (in Crete and the Peloponnesus, respectively) developed and applied various technologies for collecting, transporting and using water from rainfall, surface and ground resources (Angelakis et al., 2010; Koutsoyiannis et al., 2008). A great variety of remarkable developments have been marked in several stages of the Minoan civilization, a civilization that flourished during the Bronze Age in Crete. These included various scientific fields of water resources such as wells and ground-water hydrology, aqueducts, cisterns, water distribution and domestic water supply, construction and use of fountains, and even recreational uses of water.

In ancient Crete, the technology of transporting water with aqueducts was very well developed, due to the mountainous terrain (Mays, 2007; Mays et al, 2007).

Minoan aqueducts are of two types: (a) the open/ natural gravity flow system and (b) the closed/ pressured pipe system (Angelakis et al., 2010).

Closed/ pressured pipe system. The advanced urban water distribution system of the closed type in the Minoan palaces and settlements is very interesting. The evidence for it in Minoan Crete comes from the use of terracotta pipes, found at the palace of Knossos and Tylissos, along with several others, albeit in bad condition, at the palace of Phaistos and at Palaikastro, Gournia, Lykastos and Zakro (House B). Among them the best patterns are those of the palace at Knossos, belonging to the earliest middle period and at Tylissos, assigned to the earliest late period although an earlier date has also been proposed for it (Angelakis et al., 2005).”

[Photo: Minoan water transfer projects: The proposed course (A’- B) of the aqueduct at Knossos with higher spring elevation (Angelakis et al., 2007) (justify) and water supply pipes (terracotta pipe sections): cross section and dimensions (upper) and today view (down) (Koutsoyiannis et al., 2008) (right)]

(Source:  “The Evolution of Water Supply Technologies in Ancient Crete, Greece“, by E. G. Dialynas and Α. Ν. Angelakis)

“It is evident that during the Bronze Age extensive systems and elaborate structures for water supply and sewerage systems, irrigation, and navigation were planned, designed and built to supply the growing population with water for the cities and villages, commerce, and for the irrigated agriculture. Thus, it not by chance that the main technical and hydraulic operations of capture, conveyance, raising and measurement have been practiced in varying forms since ca. 3,500 B.C.. In the Minoan Crete various fundamental technologies such as aqueducts, wells, cisterns, and closed water distribution systems for water supply to the “palaces”, cities and villages were very well developed, as did techniques relevant to the recreational use of water.

In most of Minoan settlements the potable water was dependent on surface springs, rivers, wells and cisterns. The normal reasons an aqueduct was build was to supply the baths (Hodge, 2002). The achievements of this period in dealing with the hygienic and the functional requirements, toilets and baths, and wastewater and urban drainage systems of “palaces” and cities, are supporting this statement (Angelakis et al., 2005). However, the water was also used for other purposes, ranging from gardens irrigation to aquatic shows and decorative fountains. A possible second reason for Minoans to build an aqueduct was the civic pride. It seems likely that these technologies had been transferred to continental Greece and then to other European countries by the Minyans, another prehistoric civilization, by ca. 1900-1600 B.C., and had since created the so-called Mycenaean civilization. (Angelakis and Spyridakis, 1996a).

In ancient Crete the technology of transporting water to “palaces”, cities and villages by aqueducts was very well developed due to the mountainous terrain as early as at the Early Minoan era. Water was transported through the aqueducts by closed or opened pipes (teracotta) and/or opened or covered channels of various dimensions and sections. The main of these aqueducts are in Gournia, Karfi, Knossos (Mavrokolympos), Malia, Mochlos, Minoa, and Tylissos.

Minoan hydraulic engineers apparently were concerned with the solution of some water en-gineering problems and were able to provide cities and “palaces” with complete water supply systems. On the basis of their accomplishments it can be assumed that they were, in a sense, aware of the basic hydrostatic law, known today as the principle of communicating vessels. It is manifested in the water supply of the Knossos «palace» through pipes and conduits fed by springs; this is supported by the discovery of the Minoan conduit heading towards the Knossos «palace» from Mavrokolybos which suggests a descending and subsequently ascending channel (Evans, 1921-1935; Hutchinson, 1950).

Present knowledge of how Minoan cities were supplied with potable water is mainly acquired from the «palace» of Knossos. The «palace», which was surrounded by a town (with 80,000 inhabitants), lies on the gently sloping banks of the Kairatos river, close to its confluence with a small brook (Viollet, 2003). Evidences for advanced hydraulic structures are apparent in many areas of the “palaces”. However, the sources of water and the methods used for supplying the «palace» are only partially understood. Several wells have been discovered in the «palace» area itself, and a single well slightly to the northwest of the Little «palace». The latter, restored to its original depth of about 12.5 m and 1.0 m diameter, continues to furnish an excellent supply of potable water (Evans, 1921-1935).

The Knossos «palace», however, did not solely depend on the water of the wells. There are indications that the water supply system of the «palace» of Minos at Knossos, was initially dependent on the spring water of Mavrokolybos and later on the Funtana and the Mt. Juctas (Karidaki and Paradisi) springs. The water from the spring of Mavrokolybos was transported to the Knossos «palace» through pipes and conduits.

Water supply in the «palace» was provided through a network of terracotta piping located beneath the «palace» floors. The pipes were constructed in sections of about 60 to 75 cm each. These pipes with their expertly shaped, tightly interlocked sections date from the earliest days of the building and are quite up to modern standards. They imply a practical knowledge of the hydraulic principle that water seeks its own level. The sections of the clay pipes resemble those used in Greece in classical times, though Evans considered the Minoan to have been designed more efficiently; each section was rather strongly tapped toward one end with the objective of increasing the rate of water flow, thus helping to flush any sediment through the pipe (Buffet and Evrard, 1950).

[Photo: Parts of the Tylissos aqueduct: (left) central conduit located at the entrance of the three villas and before the little cistern and (right) secondary conduit, small lithic cistern used for the removal of suspended solids of water before its storage into the main] cistern.

The aqueduct of Tylissos was also developed in the Minoan period. The remnants suggest that part of the aqueduct was constructed from closed pipes and part of it was as curved channel. A stone made tank was used for pretreatment of water, mainly for the removal of sediments and/or suspended solids and the main cistern of cylindrical-shaped was used for the storage of water.

The Minoan aqueduct of Malia was probably using the water of a spring located west of the hilly area of Profitis Elias ‘Holly Hillock’. Water was supplied to the «palace» by closed pipes (terracotta pipes) or opened channels.

The advanced water distribution systems in various Minoan “palaces” and settlements is remarkable, because no aqueducts are known before the Minoan era, whilst strong evidence suggests that this technology was developed by Minoans. Thereafter, aqueducts were used by the Mycenaens in continental Greece. In the Minoan «palace» of Knossos terracotta pipes for water distribution have been identified, suggesting that some aqueduct systems should exist. Similar terracotta pipes were found in some other Minoan settlements such as Tilissos, Gournia, and Vathypetro, as well as in Malia.

The achievements of Minoans in dealing with the aqueducts and functional requirements of water distribution systems can only be compared to modern urban water systems, re-established in Europe and North America from the second half of the 19th century A.D. (Koutsoyiannis et al., 2006) until present day. Thus, with a few exceptions, the basis for present day progress in water transfer is clearly not a recent development, but an extension and refinement of the past.”

(Source: “Minoan Aqueducts: A Pioneering Technology“, by A.N. Angelakis, Y.M. Savvakis, and G. Charalampakis)

“It is impressive that Minoan hydraulic systems on the island of Crete were already advanced at the beginning of the Palatial period. Their hydraulic works display a remarkable sophistication of knowledge, empirical but wise-ly applied.

The water management systems of Minoan Crete include cisterns, wells, spring chambers, water basins, aqueducts, dams and drainage systems (Houseman 2013, 49) and possibly aqueducts on water bridge and ground-water replenishment pits.

Knossos has been settled in Neolithic times, probably 7000 years BC at a cen-tral location on the island of Crete (figure 1, top). The palace at Knossos has been built on a Neolithic settlement on a hill at an elevation of about 90 m, west of the Kairatos River, at a safe distance from the intruders from the sea.

As early as 1901, Evans (1901, 81) underlined that in the whole structure of the Palace, nothing is more remarkable than the elaborate drainage system that runs throughout the “Domestic Quarter” and adjoining halls.

After thirty years of excavations and important discoveries, Evans (1930, 252-255) was still impressed by the hydraulic achievements of the Minoans, in regard with the elaborate drainage system of the Palace, the connected sanitary arrangements and the water supply by means of scientifically shaped sections of terra cotta water pipes. The impact of admiration of Evans for the hydraulic and sanitation utilities of the Minoans is reflected in an article of the Canadian Medical Association, according to which: “More than two thousand years before Caesar‘s legions crossed over to Britain, and when our forebears were living in huts made of wattles and mud, there was a civilization in the island of Crete with houses that were fully equipped with toilets and baths, with tiled drains emptying into deep, well made, underground sewers – all built in a manner that was never again equaled until the Nineteenth Century” (Corrigan 1932, 77).

The primary objective of the drainage system was the management of rain-water with stone shafts descending from the upper stories of the five-storied Palace down below the floor to a well-built stone network of “plastered” conduits with flat covering slabs. Throughout the greater part of the network the drain conduits, one meter in height and half that width, were originally coated with cement (Evans 1901, 81).

A plan of the entire drainage system was illustrated by MacDonald and Dries-sen (1988, 235) along with stone-by-stone detailed plans and description. The total length of the drainage system exceeds one hundred and fifty me-tres. Remains of the hydraulic cement which once lined the entire system are sometimes visible. It appears that once the hydraulic cement lining of the drain had begun to disintegrate, water began to erode the dressed surfaces of ashlar blocks.

Aside from the drainage network, the system of water conveyance by means of terra cotta pipes is among the earliest hydraulic elements of the Palace. The advanced design of Minoan stone conduits and pressure pipelines was early appreciated by Evans. These Minoan pipes with their collars and stop-ridges are considered of admirable construction. Evans diagnosed what re-cent studies confirmed (Tseropoulos et al. 2013, 2057), that the tapering form of each section gave the water a “shooting motion” well adapted to pre-vent the accumulation of sediment. Some of them are comparatively near the surface and others run over three metres deep, beneath the foundations of the South Porch, and show an upward slope of 1 in 18.90 metres.

[Photo: Minoan pressure pipes (A), pressure pipe from the fountain at the Prop-ylon of the Vouleuterion, at the Athenian Agora (B) and Roman pipes from Cor-inth (C). Please note the different scales. Compilation and drawing by the Ar-chitect G. Michail]

Two types of terra cotta water pipes were found in the Palace, both of them with slightly tapering outline, those with plain outer surface and those pro-vided with two loops on each side. The loops would enable adjacent pipe sections to be corded together (Evans 1935, 147).

Similar terra cotta sections of water pipes were also found at a Minoan sta-tion at Sylamos, near large blocks from buildings (Evans 1928, 66). Tapering terra cotta pipelines were also in use at Tylissos, Phaistos, Gournia, Palaikastro and Zakro and all of them are considered as Minoan (Shaw 1973, 198-201; 2004, 143).

Despite the emphasis in the literature on the shape of the Minoan pipes from a hydraulic point of view, the most important achievement, I believe, was the knowledgeable experience of the principle of hydrostatic equilibrium in closed circuit, which took too long to be reapplied in siphons.

After all, the critical factor for the above mentioned effect of “water shooting motion” is not the external shape of the pipes but the internal geometry, in particular the diameter reduction at intervals, which can occur also in cylin-drical pipes.

Water jet: Evans considered that “perhaps the most illuminating record of the modern level attained by the Minoans at this epoch in their hydrostatic arrangements is to be seen in the actual representation of a jet d’ eau, brought to light in the House of the Frescoes” (Evans 1930, 253)

[Photo: Fountain (jet d’ eau) from painted stucco panel, House of the Frescos]

The Viaduct: Another important work of possible hydraulic application is the Minoan viaduct carrying the Minoan road from the south to a bridge over the Vlychia torrent. The viaduct consists of piers the upper parts of which were bridged over by means of corbelled arches to support the roadway (Ev-ans 1928, 96).

Spring chambers: The description of Evans of the “Mavrospelio or Black Cave with its artificial spring chamber and inner reservoir, as a Minoan Peirene” (Evans 1930, 274) indicates underground excavation for improved water capturing.”

(Source: “Minoan hydraulic tradition and technology transfer to Thebes and Corinth in Greece with emphasis on underground waterworks”, by Eustathios D. Chiotis)

“Over the past century archaeological excavations have brought to light impressive water engineering technology dating from the Minoan era on the island of Crete (Angelakis and Spyridakis, 1996; Webster and Hughes, 2010; Angelakis and Spyridakis, 2010; Koutsoyiannis et al., 2008; Antoniou and Angelakis, 2011, and others). From the early Minoan period (ca. 3200-2300 BC) issues related to water supply were considered of great importance and developed accordingly. Archaeological and other evidence indicate that during the Bronze Age advanced water management and sanitary techniques were
practiced. Several types of stone and terracotta conduits and pipes were used to transfer
water, and drain stormwater and wastewater. These types of conduits are summarized
below.

Stone conduits: In Crete due to dry summers rainfall harvesting was necessary and was accomplished from both roofs of the buildings and larger court areas. Hydraulic structures associated with the rainfall collection were found in Knossos, Phaistos, Tylissos, Aghia Triadha, Chamaizi, Myrtos Pyrgos and Zakros. These include stone-made conduits with branches that were used to supply collected water to cisterns. The Knossos palace provides a typical example (Photo below).

Also, alongside a stairway in Knossos is a small stepped channel consisting of a series of parabolic-shaped step chutes that was used to convey rainwater from terraces down to a sedimentation basin (Photo below).

In Tylissos houses, similar stone conduits were used to convey water from a stone made sedimentation tank to the main storage cistern (Photo below).

The same components of rainfall harvesting system, e.g. cistern, channel and sedimentation tank, also existed in other settlements (Angelakis and Spyridakis, 1996; Gorokhovich et al., 2011). Furthermore, in several palaces parts of the sewer systems were made of stone conduits.

Terracota conduits with open-shaped cross sections: While conduits of large cross section were stone made, those with smaller cross section were made from terracotta in the form of U-shaped tiles. Such terracotta conduits were discovered as parts of sewer networks at the Knossos and Phaistos palaces and other Minoan settlements (Photos below; see also Angelakis and Spyridakis, 1996; Angelakis and Koutsoyiannis, 2003; Antoniou and Angelakis, 2011).

Terracotta pipes: The most interesting Minoan conduits were the pipes made of terracotta. As shown in the Photos below, two types of such pipes were found, the prismatic and the truncated conic ones. The former, found in Myrtos – Pyrgos and used to supply the nearby cistern system with stormwater collected from the rooftops and open courtyards (Cadogan, 1978), probably operated under free-surface (open channel) conditions. Rectangular openings and covers of same material were used to interconnect of consecutive segments. These pipes were used for water supply and could operate at full-flow condition, perhaps under low pressure. Neither type of terracotta conduits is known to be used before by other Bronze Age civilizations or subsequent civilizations in the Mediterranean region.

The hypothesis that these pipes may have been used in low pressure conditions is supported by other archaeological findings indicating that pressurized flow was known. Specifically, a fresco found in the Knossos palace (Fahlbusch, 2008; Koutsoyiannis et al., 2008), depicts a jet d’eau (fountain) which would not be possible without pressurized flow.

Conical pipes are entirely unique to Minoan Crete, which have been used predominantly in the context of water supply. There is some reason to expect that the Minoans had a good reason to support their conical geometry. Based on Minoan water engineering skill as demonstrated in other infrastructure (e.g. drainage and sewage), it seems reasonable to expect that the Minoans were very deliberate in their choice of pipe design. The quality of pipe manufacture, featuring tightly fitting joints and cement-seals, also suggests that the pipe design was selected with care.”

(Source: “On the Geometry of the Minoan Water Conduits“, by An. Angelakis, D. Koutsoyiannis and P. Papanicolaou)

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