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Piazza d'Oro - Normal watering and irrigation by capillarity

by Eugenia Salza Prina Ricotti

Water and irrigation.
Water both for the euripus and the irrigation was furnished by the Nympheum in the back of the pavilion and by the other fountains. It was collected in an underground canal and brought at the southern end of the euripus. Here it was divided in three parts. The first and central one fed the Euripus, the others two were divided and directed to two different underground canal each of which circled half of the peristyle. Evidently they had been used for irrigation.
The first half and exactly the western part of it which we studied was very interesting. The canal which ran 60 cm underground had lost its upper part and now lay down exposed to our research. Thus we could see that, from time to time, at its bottom there were some square cuts which evidently let water flow into the garden soil and, looking on the other side of the peripheral pits, we could see that the same cuts and in the same positions were there; moreover they perfectly corresponded to the bottom of the trenches which crisscrossed the area.
The first two cuts in the upper southern part were set at the same height of the trenches’ bottoms and flowed directly in them. What was more difficult to explain was that, starting from there, a drainage canal went sloping toward north and, becaming more deep, it cut all the trenches’ bottoms and severed all connections through them and the cuts in the flowerbeds walls.
There was no discussion on the fact that the canal in question was a drainage. It had been made in the proper way and its bottom was strewn with rubble. Then a question arose and troubled me: it was evident that the connection between the cuts and the trenches had been important and that all this system had been studied to let water flow in the garden, but why had they immediately destroyed this possibility creating the drainage canal?
This question vexed me deeply and some time passed while I was trying to find an explanation for it. It was only when later on I decided to have a look at the rubble set down in the drainage canal that I solved everything: the rubble was made with the ruins of the Piazza d’Oro buildings. Now it is evident that you never have ruins at disposition when a building is brand new. Ergo the canal was a modern one which had nothing to do with the Hadrianic system and had been cut when the owner of the area decided to cultivate the plot, a fact which had also been set to light by the work that had been made at the time. often destroying the clear cut and perfectly done Hadrianic trenches with roughly made and large implanting holes.
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The trenches crossed all the garden passing under the euripus, but with the passing of the centuries and nobody to care for the garden, the soil under the euripus transformed itself in “cappellaccio”, a sort of tufa, and rainwater, which didn’t have any way out, accumulated in this kind of basin and transformed it in a swamp. Of course you could not plant olive trees in a swamp, so the first task to do was to drain the area and this had been done with a canal excavated between the 1830, (year in which Penna did draw the Piazza d’Oro garden as a barren area without not even a bush), and the first year of the 1900 when a photo of it shows to us a well grown olive grove with at least twenty or thirty years trees.
What had happened was now clear. Here the irrigation worked by capillarity. At the beginning of the canal a sluice, which regulated the afflux of water, was kept open only for the time necessary to form the water reserve. It created a very moist filter bed at the canals’ bottoms and kept there all the water the soil could absorb. Then when the surface of the garden’s soil dried the capillarity pushed up the water and irrigated the plants’ roots.
The other canal worked as a normal kind of irrigation one, and watered the plants which didn’t receive the infiltrated water. As the first part of its vault had caved in this canal was open to inspection. We immediately saw that from time to time there were some small pits beginning with one just at the euripus corner. We followed them up to the extreme eastern part of this section, there the canal was covered and the only thing that we could see was some irregular hole breaking the vault and set roughly where the little pits would have been. It was an old system that we find also in the Persian garden of Pasagardae: enough water to make possible pumping it collected in these pits. Evidently bronze pumps were set over the vault and after the fall of the Roman Empire the people who came to pillage this residence wrenched them from their places leaving the on the vault the sign of this vandalism for us to see.


Bibliography
1. E. SALZA PRINA RICOTTI -Villa Adriana: il sogno di un imperatore, L’Erma di Bretschneider, Rome, 2001.
2. W. F. JASHEMSKI ed E. SALZA PRINA RICOTTI, I giardini di Villa Adriana: rapporto preliminare , in RPAA, Vol. LX., 1987-88, pp. 145-169
3. E. SALZA PRINA RICOTTI - Il sistema di irrigazione della Piazza d'Oro in RPAA, LXII 1989-1990, pp 121-150
4. W. F. JASHEMSKI ed E. SALZA PRINA RICOTTI,, Preliminary excavations in the gardens of Hadrian's Villa: The Canopus and the Piazza d'Oro in AJA 96 , 1992, pp. 121-157
5. E. SALZA PRINA RICOTTI, Adriano: architettura del verde e dell’acqua in Horti Romani, Rome , 1995, pp. 363-399.