The Migliaro “Chiavica” – The Migliaro water-diversion structure for irrigation The Migliaro Chiavica is the 4th of the 7-water diversion structure for irrigation, built in 1868. We have chosen Migliaro as a symbol of that public work. It is composed of a sluice-gate and a building structure inserted into the river embankment to allow water-diversion from the “Po di Volano” river to the countryside. The technique of constructing buildings to close and open the canals was known to the ancient Romans. Initially, they constructed gates for controlling drainage of the countryside into natural waterways. The same terminology then extended to the control of derivation, which - vice versa – diverts water from natural watercourses: the direction of water flow is the opposite, but the hydraulic control function remains. The overflow water was initially regulated by a cataract in wooden planks, placed one above the other, as a barrier, fixed at a level lower than the water in the river. The derivation took, therefore, place by gravity and the flow rate was discharged into a culvert (which crosses the embankment) and then conveyed and distributed along a branched canalization, to be available to a large surface of cultivated agricultural land. The building structure consists of:

• a small brick cabin, inside which – in the past - the operator raised and lowered the gates in wooden planks
• a culvert, at the base of the embankment, built-in bricks with a vaulted section
• 4 brick structures, inside the embankment, with anti-siphoning function

The structure dates back to 1868, as witnessed by a walled tombstone. It was built by the 2nd District Consortium (a Drainage Board of that period, now united with other Districts in the “Consorzio di Bonifica Pianura di Ferrara”). Thanks to the “Migliaro Chiavica” about 2.750 ha were and still are under irrigation.

The flow rate varies from 150 to 300 l/s: in the last 4 years, the average total flow is around 1.8 MCM. The maintenance has slightly changed the structure, i.e., the tiled roof is now a terrace; the barrier in wooden planks has later been replaced with a steel gate; and to reduce the risk of infiltration, the “Consorzio di Bonifica Pianura di Ferrara” built a barrier with a new steel sluice-gate, detached from the old structure.

The water diversion takes place by gravity but now the flow is beneath the gate, under free condition. It is a simple but very important structure if we consider the period in which it was built - the second half of the 1800s – when Ferrara was, first of all, worried about drainage and land reclamation than about irrigation, but the enlightened and far-sighted mind of that time technicians has allowed the growth of agriculture in the province.

Water Heritage

The structure represents a milestone / turning points in the development of irrigated agriculture and bears exceptional testimony to the development of agriculture and an increase in food production along with the improvement of the economic condition of farmers;

In Italy, after the Risorgimento Independence War ended, in 1861 the Unitary State of Italy was born. In the first years of peace society focused on agricultural development: political and social authorities intended to help the agricultural economy and achieve food security. The territory of Ferrara, flat, crossed by many rivers (The Po, Reno and Panaro rivers) and occupied by vast wetlands, was above all concentrated on drainage and reclamation of submerged areas: the first pumping plant for land reclamation goes back to 1862. Despite this priority, the old 2nd District Consortium understands the importance of the water supply for agricultural need and plans 7 water-diversion structures, the first in the province of Ferrara for the summer water supply to the cultivated countryside.

The structure made outstanding contribution to enhancing food production, livelihood opportunities, rural prosperity, and poverty alleviation in a region;

The “maceri” were small artificial basins similar to rectangular pools, about 2 meters deep, large 1.000 – 2.000 m2, built in the most depressed areas of the countryside. The surface drainage waters flowed into them and their water guaranteed to water for livestock and small water supplies for the vegetable gardens. For the elaboration of hemp, it was important to have water in the “maceri” in summer. Thus, territorial characteristics, agrarian settlements, productive economy and local entrepreneurship intertwined, supporting themselves in the characteristic balance of land and water that has always characterized the province of Ferrara.

The structure was innovative in its ideas at the time of its construction;

At the decrease of hemp’s economic importance in the middle of the 20th century, other cultivations took over and water became the main production tool for fruit-growing, another important sector of the Ferrara agricultural economy. Today, the need for irrigation water is everywhere widespread and essential: for all fruit crops (pears, apples, peaches), field-scale vegetables (tomatoes, carrots, onions, garlic, potatoes, salad) and rice fields (6,000 ha in the province of Ferrara). Water is a guarantee of production and income. The Migliaro water diversion sluice-gate represents the other 6 and deserves to be reminded and emphasized – although old - because it’s still existing and fully functioning. It was only renovated in the external body - today lower and with a terrace instead of the tiled roof - and the old wooden gates replaced by steel gates. But its heart, the culvert crossing the embankment body, is original, in brick with a vaulted section. The structure is still functioning and continues to meet the needs of the territory and its constructive simplicity has proved to be a guarantee of durability.

The structure is an example of attention to environmental aspects in its design and construction;

Although around the middle of the 19th century, steam-driven machines and mechanical tools were spreading, the designer paid special attention to energy saving as explained in old writings.

Present State of Conservation

The Migliaro water diversion structure serves 2.750 ha, providing an average of 1,8 million cubic meters of water each year. Its maintenance is constant, above all to the mechanisms of the sluice gate. To avoid the risk of infiltration into the embankment, in 1993, the Water Board realized a barrier, detached from the building: on it was installed a new gate that regulates the flow. Although in 2012 the Ferrara area was affected by earthquakes, there were no damages.

The “Chiavica di Migliaro” is a small, simple structure, but with a great value for the territory. Around it, there have been changes. For example, on the top of the embankment, an asphalted road exists from many years: on it, there is discrete traffic, even of heavy vehicles. The structure’s design and its construction were therefore excellent: it still exists and resists the aggression of time.