4. Waters and dams


4. Waters and dams

Underwater Tales

The Bormida Valley includes an extensive territory that stretches from the Ligurian Apennines in the hinterland of Savona up to southern Piedmont. These are the places that have given rise to Atlas Bormida: a collection of stories, a choral work of revelation, a space where visions and documents, sound experiences and stories strike sparks off one another.
Necessarily partial and subjective just like any work of fiction, Atlas Bormida does not focus on the best known places, the most popular images, and the official histories. It is consistent with the land where it was born: a complex, polycentric, and contradictory valley. Those who wander through these places and discover other stories will continue this opus.
by Alessandro Sciaraffa
28 audio tracks, recordings of a world
undeclared but real. Experience sound
literally immersive that can be chosen,
turned on and off. To change tracks
click on the sound player in the top right.
Osiglia Dam. Alberto Momo, Laura Cantarella and WPA

Enrico Del Vasto: the North Star
and the five red stripes

Gemma Del Carretto (interview transcript)

Enrico Del Vasto, the progenitor of the Del Carretto family, lived in the twelfth century and participated in the Second Crusade (1147-1148). In 1162, Frederick Barbarossa assigned a feud to “Henry the Brave”, a nickname which he had acquired during the crusade, of vast territories stretching between Savona and the Bormida Valley up to the Langhe area, thus giving rise to the dynasty of the Marquises Del Carretto. He was chancellor and advisor to the Emperor and, as his plenipotentiary, negotiated the Peace of Constance with the Lombard League.

Enrico del Vasto, the progenitor of the Del Carretto family, fought in the Holy Land where he was involved, surely not willingly, in a battle. In fact, he was in those lands to better administer the Liguriancommercial affairs. Wthout having recognized him, he fought with his best friend, Prince Tosbeo, who had saved him from robbers in the Holy Land, and killed him. As he was dying, the prince took off his helmet and asked him for help: Enrico pressed his five bloodstained fingers on his coat and when he returned to his estates, he wanted to remember that brutal fact: thus, his coat of arms was five red stripes on a gold background.

Nevertheless, his remorse was great for having done what he would never have wanted to do to that friend who had saved him from death so many times. He arrived in these his lands and asked himself: "What should I do?". He started down a road and came upon the Bormida river, and heard a bell ringing: it was precisely that of the abbey of San Quintino, whose bells were heard when the monks went to pray at about seven o'clock in the evening. He knelt down, took his sword and threw it into the river: "I will never fight again, I do not want to know anything more about fighting or death, and as long as I shall live, peace will reign." But looking up at the darkened sky, he saw the North Star that indicates the right way to sailors and wayfarers and addressing it, said: "What can I do? You who indicate the right way to everyone, indicate it to me too." At that moment, he saw the Little Dipper: “Behold! The del Carrettos' coat of arms will be golden with five red stripes and the emblem of Little Dipper.”

Enrico I Del Carretto. With Gemma Del Carretto and Pietro Merlo, Mombaldone. Alberto Momo, Laura Cantarella and WPA

Osiglietta Dam

Tirreno Power data sheet

The Osiglietta dam, built between 1937 and 1939, is located in the municipality of Osiglia in the Osiglietta river valley, a tributary of the Bormida river. It is classified as a masonry dome dam, as it is has a double-arch, spanning both vertically and horizontally from bank to bank.

The work was constructed of reinforced concrete with two rows of vertical and horizontal rods placed at 20 cm from the vestments. The upstream façade is concrete is covered by a layer 3 cm thick of gunite (sprayed cement), while the downstream façade is made of exposed concrete.

The dam has 16 radial joints and a perimeter joint: its holding strength is made up of a butt strap beam superimposed on bituminized felt and a copper plate towards upstream and an iron plate in the downstream direction; inside it, clogging injections were made after the withdrawal of the concrete.
The foundation is a dosseret connected to the dam body by means of a perimeter joint.
The dam is provided with a surface drainage system, a bottom drainage duct, and an exhaust duct.

The House at the Bottom of the Lake, Andrea Botto | Osiglia

Dam height: 70,70 m
Catchment area: 20,50 km2
Volume of reservoir: 13.040.000 m3
Maximum reservoir quota: 638,60 slm
Maximum regulation quota: 637,00 m slm
Dam crest development: 224 m
Maximum outflow capacity: 675 m3/s
Maximum derivable flow: 10 m3/s
Power stations fueled: Cairo and Spigno through auction; Millesimo

The disconcerting speed
of the flying lure

From Graig A. Spolek, The mechanics of flycasting: The flyline
Mechanical Engineering Department, Portland State University, 1985.

In many recreational activities the participant is re- quired to launch an object either for distance, accuracy, or both; examples of such objects are a baseball, javelin, rifle bullet, golf ball, ski jumper, discus, and arrow. Once the object is launched with its initial speed and direction, the only major forces that affect its path ofmotion are the body force due to gravity and air friction or viscous drag. In most cases, the factor that limits performance is air friction. Its minimization is the target ofphysical technique and equipment design. As examples, the ski jumper strives to maintain aerodynamic orientation of the skis and body, and a golfball is dimpled to cause the air boundary layer to trip from laminar to turbulent to reduce the drag coefficient. In all cases, however, air friction diminishes the horizontal component of the object's velocity throughout its flight.

The casting offishing lures is quite similar to the launch- ing of the objects just described except that an additional force acts on the cast lure. The lure is tethered to the angler via the fishing line, ostensibly to allow the angler to reel in the fish but more realistically to allow retrieval of the empty lure.

When the lure is cast with the aid ofthe fishing rod, the lure's motion is resisted by air friction and is also re- tarded by the force necessary to payout the line. Hence, its horizontal velocity decreases at even a greater rate than ifit were in free flight. It is easy to visualize that as the fishing lure becomes progressively lighter with a large drag coefficient, it will become virtually impossible to launch it as a projectile for any useful distance. That is precisely the problem that faces the angler who uses artificial flies as lures.

Fishing flies are designed to imitate floating insects. They are very light with a relatively large volume offeath- ers and fur so the surface tension acting on the large surface area can "float" the fly. Because of the large surface area, the fly's motion during a cast is easily dominated by air friction. For example, to cast a typical fishing fly horizon- tally 20 m from a height of 1.5 m, and no line were even attached to it, an initial velocity in excess of 140 mls (3l3 mph) would be required, a prohibitive condition indeed.

The flying lure, Andrea Botto

The solution to the flyfisher's dilemma is to cast a rather massive line to which the fly is attached and allow the fly to go along for the ride. As a result of this symbiotic relation- ship between line and fly, the fly (as the launched object) demonstrates a behavior during flight that is unique from all others: it accelerates horizontally. While this effect may be intuitively disconcerting, the predicting physics are quite straightforward.

Anatomy of a Dam. With Pietro Merlo and Alessia Stivala, Osiglia. Alberto Momo, Laura Cantarella and WPA


Locations, routes and directions

Lake Osiglia. Alberto Momo, Laura Cantarella and WPA