Hydro-technologies in the Minoan Era

The basic characteristics of the Minoans were briefly described by Evans (1921–35) as: ‘The colorful frescoes in Minoan palaces reflect a life full of creativity, good taste and coexistence in harmony with the natural environment.’ Also, recently Hirschfeld (2013) reported that: ‘This culture [Minoan] is an amazing paradox: A great power without military aristocracy, a palace was a royal residence, where neither glorified the King, a religion without greatness and that women were equal to men.’

In the list of wars worldwide before ca. 1000 bc (including those related to conflicts over water resources), and especially during the Bronze Age (ca. 3200–1100 bc), one can observe that most occurred in the eastern Mediterranean region, where the Minoans dominated (http://en.wikipedia.org/wiki/List_of_wars_before_1000). For example, in the Early Minoan period Libyans and Egyptians fought against the Levante and others, in the Middle Minoan period Sumerians fought against Babylonian cities, Babylonians against Elamites, Sumerians and Assyrians, and Hittites against Babylonians and Hurrians, and finally during the Late Minoan period, Egyptians fought against Libyans, Persians and Phoenicians. However, it is remarkable that in none of these wars and/or hostilities did the Minoans have any direct or indirect military engagement. Not only that, but the Minoans, known as naval, were always playing a conciliatory role between the warring parties (Angelakis 2015a). Thus, the Minoan Era was named by Evans (1921–35) as Pax minoica or Minoan peace, a period in which cities did not have walls.

The control of water resources in ancient Greece was affected by its geophysical characteristics and climate (Koutsoyiannis & Patrikiou 2013). Earlier civilizations bloomed in large river valleys, which had water in abundance (Mesopotamia near the Tigris and Euphrates, Egypt near the Nile, and India near the Indus). However, the island of Crete does not have large rivers, and it is divided by mountains into small plains; it is in these plains where the major part of land cultivation takes place. Historically, Minoans preferred to settle and grow in these plains with dry microclimates, which led to the development of urban centers, mainly palaces and villas (Angelakis et al. 2014). The locations of nearly all major cities of Cretan civilizations, for millennia, are in areas with low precipitation (<500 mm), which seems to be a paradox (Markonis et al. 2016). Whilst there are only small rivers and lakes in Crete, the Minoan palace and other urban areas were established apart from them. This could suggest that the Minoans preferred to install their palaces, towns and other urban areas in places with hot and dry climatic conditions for hygienic reasons and for protection from diseases and natural hazards (such as floods and droughts) (Koutsoyiannis et al. 2008).

Finally, an interesting feature of Minoan culture was the remarkable architectural and hydraulic adequacy of infrastructures for the management of water resources, such as water supply, fountains, dams, aqueducts, the sewerage and drainage systems, baths and toilets, and irrigation and drainage of agricultural land (Angelakis & Spyridakis 1996a, 2013; Koutsoyiannis & Angelakis 2003). Thus, the remarkable progress in the Minoan Era, especially during the Neopalatial period (ca. 1700–1450 bc) when Minoan technology peaked, appears to be linked inextricably with peaceful coexistence with the natural environment and neighboring cultures as well as with the highly hygienic standards and comfort of living (Angelakis 2015a). To achieve these, the Minoans developed the appropriate hydrological and hydraulic technologies and water, wastewater, and stormwater management infrastructures.

The scope of this paper is to present the main achievements in hydrological and hydraulic works in Crete, Hellas, in prehistoric times. Emphasis is given to the great achievements by Minoan civilization (ca. 3200–1100 bc) and the importance of this not only to following civilizations but even to the present times. Water resources management and use in Crete and examples of hydro-technologies in Minoan Crete follow.

Crete has a strategic location, positioned between Asia, Africa and Europe and forming a natural and vital bridge between the three continents. This unique geographical position has determined its historical course throughout both ancient and modern times. The total population of Crete is 623,065 inhabitants or 5.8% of the total population of the country. In addition, more than 5 mil. tourists/yr have visited the island in recent years. In 2011, more than 73% of the total population was living in urban areas (i.e. the five major cities located on the north coastal area of the island. Of this, 225,000 or 36.11% of Crete's permanent population is living in three coterminous municipalities (Iraklion, Gazi, and Chersonissos) located in an area of 809.4 km² (or 9.7% of the total area of Crete) in the north central regions (Hellenic Statistical Authority 2011).

In present days, the climate in Crete is primarily temperate. The western and northern parts of the island are generally more humid than the eastern and southern, and the two parts are separated by a central mountainous region, where snowfall is common in the winter. The three main mountains (White, Ida, and Dikti) play an important role in the rainfall and runoff regimes of the island. In the lowlands the winters are milder, while during the summer the temperature averages at 30°C, with maxima reaching 40°C. The average and maximum temperatures are higher throughout the year on the south coast of Crete, a region where climate, vegetation and landscape resemble more Mediterranean Africa (Angelakis 2016a).

Today, the atmospheric precipitation in Crete shows intense spatial and temporal variation. Generally the precipitation decreases from west to east and from north to south, and also it increases with altitude. In particular, the average precipitation of 927 mm/yr ranges from 440 mm/yr on the plain of Ierapetra in southeastern Crete to 2,000 mm/yr in the Askifou highlands in western Crete (Angelakis 2016a). Potential evapotranspiration (ET), as estimated using the Penman–Monteith method, a system which provides the most accurate estimates, varies from 1,240 mm/yr to 1,570 mm/yr. The mean annual actual ET has been estimated to represent 75% to 85% of the mean annual precipitation in low elevation areas (less than 300 m absl) whilst it drops to 50% to 70% in high elevation areas (Decentralized Region of Crete 2015).

The island of Crete has been characterized by a significant increase in urban and touristic activities, especially in the past 20 years. As a result, the majority of the population is concentrated in the coastal areas. In many cases the infrastructures required to support this type of economic development are inadequate (Angelakis 2016a). However, agricultural water demand continues to be the major water consumer on the island, accounting for over 86% of the total use as based on both surface and underground water resources. Although underground water resources are estimated to be sufficient to satisfy all water needs, the lack of proper management and infrastructures has led to serious problems, particularly during dry periods when water demand is high (Angelakis 2016a).

Water consumption and use in Crete is less than 7% and 18% of the annual precipitation and total water potential, respectively (Table 1). However, in many cases there is a severe water imbalance due to the temporal and regional distribution of precipitation. This worsens during the summer months when water demand rises due to the needs of agriculture and tourism. Furthermore, a high percentage of the annual precipitation occurs in the mountainous areas of western Crete and transport of water to the rest of the island suffers from technical, social, and economic limitations. An alternative, integrated water resources management plan is needed by which non-conventional sources (e.g. rainwater harvesting, treated wastewater, desalinated water, brackish water) should be considered (Angelakis 2016a).

The available water resources and water uses for Crete are shown in Table 1 (Hellenic Central Water Agency 2008, 2013). The real water use in 2010 was 421 Mm³/yr, and the total water potential 2,941 Mm³/yr, resulting in a consumption index of 14.31%. Note that the desirable water demand in 2010 was 515 Mm³/yr (Decentralized Region of Crete 2015). Thus, water resources are more than adequate to meet the current and future needs of the islands several times over by reconsidering the management plan, which should include traditional practices (e.g. rainwater harvesting and water recycling and reuse).

In the Minoan palaces, towns, and villages water supply was differentiated according to the local conditions. Thus, the water supply at the Minos palace in Knossos was originally dependent mainly on the Mavrokolybos spring and later on the Karidaki and Fundana springs. In Zakros palace, it was entirely dependent on groundwater. On the other hand, in Phaistos palace the water supply system was dependent directly on surface runoff, where rainfall water was collected in special cisterns from the roofs and yards of urban areas.

Another characteristic tykti fountain was found in the southwest corner of the room of the palace of Zakros (Figure 4(b)). An opening leads into a small chamber where the water is collected and lifted under the floor at the base of a square underground fountain (Angelakis 2015b). Its dimensions are 3 × 4 m and it is dated to the Late Minoan period (ca. 1500 bc).

In addition to the cisterns used for water supply, lustral basins were sacred spaces necessary in Minoan settlements for cleansing, something similar to Christian cleansing places (Figure 5(b)). This type of ‘cistern’ was necessary in all Minoan settlements because Minoan religion required believers to always wash themselves before the religious ceremonies (Platon 1990). Also the facilities at the Caravanserai located opposite the main entrance of the palace of Knossos are characteristic. There was always water available from the aqueduct of Knossos for washing the visitors. It was the so-called sacred fountain (Pendlebury 1965).

As mentioned before, in the Minoan Era the water supply conditions of palaces and other residential areas were differentiated not only according to time periods, but were also dependent on the hydrological conditions of each region (Koutsoyiannis & Angelakis 2003; Koutsoyiannis et al. 2008; De Feo et al. 2011). In places in southeastern Crete with limited surface water available underground, such as in the Minoan village of Agios Ioannis and the town of Palaikastro, digging and use of groundwater practices were implemented (Figure 7). The depth of Minoan wells was less than 20 m, usually 12 m, and their diameter less than 5 m, usually 1.5 m (Mays et al. 2007; Floods 2012). The practice used to lift the water was remarkable. Yannopoulos et al. (2015) reported that there is evidence that the Minoans were using the device known as the shadoof (in Greek κηλώνειον ή γεράνι). More on groundwater utilization in Minoan Era is given in Angelakis & Voudouris (2014) and Angelakis et al. (2016).

Similar hydraulic structures are found on the island of Pseira (Mochlos), located in the gulf of Mirabello in northeastern Crete (Betancourt 2012). The Minoans, in order to ensure water for irrigation of agricultural crops and livestock on the island, built two water management systems: (a) small dams to intercept runoff waters in the seasonal streams and (b) a larger dam for storing water (Tsatsanifos 2015). The dams were made of stones and clay mortar (Figure 8(b) and 8(c)). The first had a length of 15.5 m, height 3.6 m, thickness 2.5–2.8 m, and a capacity of 500–600 m³ (Betancourt 2012). They were constructed in the Neopalatial period (ca. 1700–1450 bc). The upper part of the main dam was built in the Byzantine period (ca. 6th–8th century ad).

One of the salient characteristics of Minoan civilization was the architecture and operation of the hydraulic drainage and sewerage systems in palaces and other settlements (De Feo et al. 2014). Of the total infrastructure of the Minoan palace at Knossos nothing was more remarkable than the complex but very functional sewers and drains, passing through the municipal facilities of the palace and its neighboring districts. Evans (1921–35) and MacDonald & Driessen (1988) described these hydraulic structures and proposed their original form, with particular reference to their architecture and performance. This plan provides the visitor with a basic orientation of the site and helps for a full understanding of the whole network. The total length of the sewerage and drainage system, including the central and secondary conduits beneath the domestic quarter, exceeds 150 m (Angelakis et al. 2005).

The most advanced ancient Minoan drainage system seems to be that in the villa of Hagia Triada (Figure 10(b)). This system was admired by several visitors, including the Italian writer Mosso (1907), who visited the area in the early 20th century. During heavy rain, he noticed that the pipes functioned perfectly and he recorded the incident saying: ‘I doubt if there is another case of a stormwater drainage system that works 4000 years after its construction.’ Also, the American Gray (1940), said: ‘you can enable us to doubt whether the modern sewerage and drainage systems will operate at even a thousand years’. Therefore, the Minoan plumbers planned and constructed projects that functioned for centuries, unlike today, when if a project operates well for 40–50 years it is considered satisfactory (Koutsoyiannis et al. 2008).

In Minoan palaces, drainage in the baths was not necessary, but useful. Evans (1921–35) recognized the existence of three such baths in Knossos palace.

Toilets, similar to those of Knossos, were found in Phaistos, in Malia, and in other settlements (Graham 1987). A house in the area of the palace of Malia (Figure 11(b)) has a toilet seat in almost perfect condition, built of solid stone, as in the palace of Knossos. This stone seat had dimensions of 68.60–45.70 cm width and 35–38 cm height (Graham 1987). It was built opposite an exterior wall, through which passes a spacious drain. It is evident that its use was for seating and not for support, more like the Egyptian toilets than those of ‘Turkish type’ (Antoniou & Angelakis 2015), found in the palace of Mari on the Euphrates. A similar toilet was discovered on the west side of the so-called Department of the Queen in Phaistos palace, connected with a small drain, part of which still survives, and another in house C, in Tylissos.

A room of interest was identified by Evans (1921–35) as a toilet with a wooden seat. As with today's toilets, it had a flushing/washing system. The flushing and outflow tube from the outer entrance crossed along the toilet, passing under the seat and ended at the outside sewer (Castleden 1993). In the palace of Minos and probably in other Minoan settlements, sewers and toilets more likely were cleaned thoroughly for some days of the year, with rainwater that was collected in tanks.

In Minoan Crete agricultural development was necessary to support the population explosion. At that time population growth, combined with economic, technological and cultural development, contributed to increasing agricultural productivity (Koutsoyiannis & Angelakis 2003). In the Neopalatial period (ca. 1700–1450 bc), the practice of irrigation was very important. Thus, irrigation and drainage of agricultural lands seem to have developed at that time.

The outputs of sewer systems in palaces and towns, like Knossos, Phaistos and Malia seem to be similar. Wastewater and rainwater were discharged in existing rivers (streams or creeks) or in the sea, as in Knossos and Zakros palaces, respectively. In the palace of Phaistos, raw collection facilities instead diverted the sewage and stormwater to the farmland. Similarly, in the villa of Hagia Triada sewage and rainwater were collected in a typical rectangular storage cistern (dimensions 1.6 × 2.0 × 6.0 m³) from where it was possibly used for washing or other household uses or irrigation. Such collection techniques have been found in other towns and palaces of Minoan Crete (Angelakis & Spyridakis 1996b). Crete and especially the eastern regions are under low water availability and several periods of the Minoan Era seemed to be characterized by severe water shortages (Markonis et al. 2016). Accordingly, the reuse of water was a necessary practice. Thus, it appears that bath water could be reused for irrigation of gardens and farmlands (Antoniou & Angelakis 2015). Also Tzanakakis et al. (2014) propose that Minoans should be considered as pioneers in the recycling and reuse of water.

Another indication of such water use is the underground cistern, with a diameter of 7 m, which was discovered in the central part along the so-called royal apartments of the palace of Zakros (Figure 13(b)). The room is called Tank Room (Platon 1974). For the use of this pool several theories and opinions have been reported, such as use for swimming, as an aquarium, and for religious ceremonies (Alexiou 1964). Today, it is believed that this pool had multiple uses, including recreational (Angelakis & Spyridakis 2010).

It should be noticed that Minoans lived in harmony with nature and their environment; others that did not, failed. ‘The multicolored wall-paintings in Minoan Palaces depict a life full of creativity, good taste and in complete harmony with the natural environment’ (Evans 1921–35). Local water supply sources were first used by the ancient Cretans of the Minoan Era. When these were exhausted, local and temporary transfers were instituted and the necessary hydraulic structures built such as water cisterns (Angelakis 2016a).

Archaeological and other evidence suggests that mainly during the Middle Minoan period a cultural explosion, unprecedented in the history of ancient civilizations, occurred in Crete. This is demonstrated by the advanced techniques applied to water, wastewater, and stormwater management. These techniques include various disciplines of water resources, water networks, especially those in urban areas, recovery and use of surface resources, construction of baths and other sanitary and purification structures, drainage and disposal of wastewater and rainwater systems, rehabilitation projects and farmland irrigation and drainage and finally water use for recreation (Angelakis 2015a).

One of the most prominent features of the Minoan civilization was the hydraulic architecture, the construction and operation of water supply systems and those for collection and disposal of waste and rain waters in the palaces and towns. In most Minoan palaces and towns nothing was more remarkable than the complex and highly functional water supply, drainage and sewerage systems. Moreover, the use of wastewater for irrigation of agricultural lands is also indicated. The design philosophy of Minoan hydro-technologies has to be further considered in light of its success. Thus, the development of effective water supply management projects in short–water areas should also include historical knowledge. This rich inheritance of Minoan hydraulic works should not be restricted only to its cultural value, but also, and more importantly, be viewed as an example for sustainable water hydro-technologies (Markonis et al. 2016).

From these and other reports on technologies related to water resources and wastewater in the Minoan Era, we can conclude the following:

• (a)

  The Minoans lived in harmony with the environment.

• (b)

  No fundamental differences are noticed in the design and construction of water projects since then. The main differences concern the scale, and the available equipment.

• (c)

  In many cases, these constructions operated efficiently for millennia.

• (d)

  There was integrated management of water resources, with provision for matching demand and supply and possible future increased needs.

• (e)

  Looking back to the long past of human habitation on the island, one can clearly outline some principles on which past water hydro-technologies were based; notably they are the very same that are used in many applications of the present.

Research priorities based on past hydro-technologies that have the potential to advance the sustainable management of water resources should be identified. To put in perspective the ancient water management principles and practices discussed in this paper, it is important to investigate Minoan hydro-technologies in terms of the following:

• (a)

  Evolution. An important question to be considered is whether all Minoan technologies were entirely developed by the Minoans or whether some of them existed during Neolithic times. The same holds for the technologies later on used in Archaic and Classical Greece. We cannot be sure whether or not the Minoans' knowledge of water resources survived after the collapse of Minoan civilization about 1100 bc (Angelakis et al. 2013).

• (b)

  Technological advances. To some extent, the differences between Minoan and modern hydro-technologies are mostly found in the apparatus and the scale of applications with practically no differences in the fundamental principles used. For example, flushing toilets equipped with seats resembling present-day toilets and drained by sewers existed from Minoan times.

• (c)

  Design and construction principles. Naturally, it is difficult to estimate the design and construction principles of Minoan ‘engineers’ but it is notable that several ancient works have operated for very long periods, some until recent times. For example, waste- and stormwater drainage systems functioned for millennia. On the other hand, engineers in our times typically design constructions to function for about 40 to 50 years, as dictated by economic considerations. Thus, the sustainability and durability of Minoan water technologies should be further studied.

• (d)

  Today's applicability. Minoan hydro-technologies could be updated by considering today's apparatus and knowledge and looking for possible applicability particularly in regions under water shortage.

(a) Part of this work was presented at the 4th IWA International Symposium on Water and Wastewater Technologies in Ancient Civilizations, September 17–19, 2016, in Coimbra, Portugal, http://www.wwac2016.com/.

(b) The contribution of Dr Emman. Dialynas, DIALYNAS, sa, Environmental Technology, Headquarters: Troulos Kallitheas, Industrial Area, P.O. Box 4, Alikarnasos, 71601 Iraklion, Greece, for the preparation of Figure 1 is highly appreciated.