Malta and Water: Irrigating a Semi-Arid Landscape.
On the evening of 22nd June the FAA organized a talk entitled ‘Malta and Water: Irrigating a Semi-Arid Landscape’ given by Dr. Keith Buhagiar at the Catholic Institute, Floriana. Dr. Keith Buhagiar is a visiting lecturer in Palaeochristian, Byzantine and Medieval archaeology with the Department of Classics and Archaeology at the University of Malta. He specialises in rural landscape development, related water management systems, archaeohydrology as well as Maltese and Sicilian medieval and Early Modern cave-settlements and rock-excavated oratories. The talk related to water management and the relationship between water and the landscape covering the period Early Medieval (900 A.D.) through to Late Medieval (1530 A.D. the time of the arrival of the Knights) periods and up to 1900 A.D. The lecture was followed by a visit the following day to the Valletta underground cisterns beneath the Archbishop’s Palace.
Dr. Buhagiar stated that water is a vital resource for Malta, which is classed as a semi-arid climate (~560 mm/year rainfall). Last year, rainfall was of around 370 mm and if less than 250 mm/year, then crops will fail. Water shortage from 900-1900 A.D. was always a problem for Malta, as the local population grew from 10,000 to 20,000 persons. Vertical shaft wells, the source of fresh quality water, discovered from Maltese pre-history were drilled to intercept water, which was collected throughout the year in cisterns (tanks, reservoirs excavated in rock). If there was no rainfall, water in cisterns would dry up or would stagnate due to bacteriological contamination. For centuries the perched aquifer galleries and cisterns provided a perennial water supply sufficient to allow crop cultivation during the arid summer months and for farmers tilling their arable land.
The first organised settlements in Malta were established from about A.D. 1000 onwards and many appear to have developed in the vicinity of water sources. On the Geological map of Malta, the northwest of the island had the best hydrological exposed Upper Coralline Limestone deposits which had faulting and pumping stations and its perched aquifers were underlain by the impermeable Blue Clay. The central, east, and southeast had hydrological potential in the Globigerina Limestone where rainwater seeped down and lay above saline water at mean sea level. Due to present day over-extraction which exceeds the recharge rate of the mean-sea-level aquifer, this aquiferous body is becoming contaminated with saline water from beneath. However, within the Globigerina Limestone, there are also localised impermeable marly/clayey deposits which can support an aquifer. In each case, the water is extracted from boreholes by pumping stations. The west of the island had less hydrological potential. Examples of Lower Globigerina Limestone aquifers are found at Ghajn Dwieli, Paola and in Sliema near the Union Club, both underlain by impermeable marly deposits. Other similar localized aquifers are found in Middle Globigerina Limestone in Birkirkara, and at Tas-Silġ, where a well is now dried up and sonar scans of the surrounding area show underground galleries.
Dr. Buhagiar then displayed a map of Malta showing Raћal-type settlements concentrated around localized water deposits in the centre and southern part of the Maltese island in Lower and Middle Globigerina Limestone between 1419 and 1530 A.D. Localised aquifers, underlain by deposits of impermeable marls, are found at Has-Safi, Hal-Kirkop, Qrendi, Mqabba, and Hal-Millieri. A map dated 1551 indicates a spring at Marsa and a large subterranean water storage reservoir in Valletta. Marked on another plan of Late Medieval Malta are ‘fiefs’ for agricultural crop use and much larger estates called ‘giardini’, where citrus trees, olive trees, cotton, vineyards exist on green landscapes below the perched aquifers. These are all shown located in west and northwest Malta, irrigated by water supplied from several perched aquifer galleries cut into the brittle Mtarfa Member of the Upper Coralline Limestone.
Dr. Buhagiar talked about other perched aquifers in the Upper Coralline Limestone at Wied ir-Rum, Wied Hazrun, Wied Mtaћleb, Simblija, and Mellieћa which are very fertile districts known for the quality of their cultivated crops. He also mentioned the spatial distribution of springs in the Pwales and Mellieћa areas and the 120 metres long water gallery starting at St. Paul’s Church in Rabat leading to the Ghariexem fountain. Dr. Buhagiar described the latter subterranean water gallery having several access shafts, characteristic of ‘qanat’ technology, which was introduced in Malta during the Islamic and post-Muslim periods between the eleventh and the fourteenth centuries A.D. In Mdina there are three probable ‘qanat’ system water galleries with fronting reservoir. Dr. Buhagiar ended his fascinating and informative talk by mentioning that various Medieval water galleries were connected to the Wignacourt aqueduct system in the 17th century.