At the southeast part of the valley of Choiromandres extends a rocky ravine with a steep east-to-west gradient. In winter, rainwater flows down from the mountainous terrain extending on the east, causing soil erosion. In cases of severe storms, rainwater forms a torrent into the ravine, which then enters the lower part of the valley.
In the 2nd millennium BC it was attempted to regulate the flow of the torrent by means of a system of dams and barriers, aimed at protecting arable land from the onrush of rainwater, while improving the productivity of the soil by using the water to moisten its surface.
In the Old Palace period (1900 – 1700 BC), two walls were erected in the streambed at the upper end of the ravine (altitude: ca 120 meters above sea level), in an early attempt to keep the rushing water in check, as well as to support the surface soil and prevent its erosion. The walls survive to a height of only 0.70 meter, since they were used as a source of building material during the construction of a larger wall, a dam, that succeeded them.
This wall is stoutly built in megalithic masonry. It has a length of 27 meters, while its height currently reaches 3.10 meters. It was erected during the New Palace period (1750 – 1430 BC). The wall is traversing the streambed, bridging the gap between the protruding rocks that form the sides of the ravine. The position of the wall and its particularly strong construction imply that is was a dam, aiming to retain the swift flowing water. The wall is substantially thicker at its base, to ensure the necessary stability. To the east a channel is formed on the surface of the rock, which may have served as a funnel for diverting excess rainwater. The dam must have been built during the dry summer months, when the ravine was dry. The upper part of the wall was reconstructed during the late Classical or Hellenistic period.
To the east of the dam a catchment area is formed. The rainwater rushing down the steep ground would be retained by the dam. Excess water would be channeled into the ravine through the aforementioned funnel.
Inside the ravine, short walls were built between protrusions of the bedrock. They were set up parallel or perpendicular to the streambed, so as to channel the rainwater and slow down its flow. These walls aimed at protecting the structures lying at the mouth of the ravine and in the lower parts of the valley from the onrush of the rainwater. It is possible that at periods of mild flow, small-scale manufacturing units exploited the water that collected in the small hollows of the bedrock, which were defined by the aforementioned walls. Movement within the ravine was facilitated by means of ramps and carved or built steps, which extend along its southern side.
At the lower end of the ravine extended a megalithic enclosure. Being over 540 meters long and 1.20 meters wide, this wall marks out an area of about 35,000 m². The wall crosses the bed of the ravine at an altitude of ca 110 meters above sea level. This part of the wall, which is particularly stoutly built, formed the lowest boundary of the entire water retention system, providing the second line of defense against the swift flowing torrent. It served as a check dam, temporarily trapping the rainwater that had initially slowed down at the upper dam and further decelerated in its downward course within the ravine thanks to the barriers built therein.
Two megalithic retaining walls that converged to –and possibly joined – the check dam complemented the system of dams and barriers. The water that was temporarily retained by the lower dam was diffused to the agricultural terraces retained by the two walls, providing moisture to their soil and increasing their productive potential. Surplus water would seep through the aforementioned walls towards the stepped terraces that are lying lower down at the southeast part of the valley. These terraces are also retained by strong elongated walls. They were set on a slant to the contour lines, so as to improve moisture diffusion within the soil they retained or, possibly, for the irrigation of their surface through dug-out channels. This mechanism ensured the best possible exploitation of rainwater, maintaining the soil sufficiently moist for a prolonged period of the agricultural year.
The Minoan dams and land reclamation structures were again in use for a short period during the late Classical or Hellenistic period, as indicated by a carefully constructed rectangular building erected adjacently to the dam at the upper end of the ravine. The building was probably built in the course of the 4th century BC.
Τhe water management system at Choiromandres may be regarded as an example of a public work of the Aegean Bronze Age. So far, it is one of the few excavated examples of Minoan hydraulic and land reclamation structures. Advanced land reclamation techniques are mostly documented in the Mycenaean world. The case of Choiromandres could offer insight to other archaeological sites in Crete, contributing to a better understanding of the Bronze Age practices related to the management of the water resources.