Hidden in the flow of history: ‘Presa’ uncovers the Philippines’ forgotten Spanish colonial dams

They do not command town plazas like centuries-old churches, nor span rivers with the obvious monumentality of historic bridges. Many are concealed by vegetation, tucked behind subdivisions or lying across streams far from roads. Some have been so thoroughly absorbed into the everyday landscape that people may use them without realizing how old they are. Yet water still runs through many of them.

Scattered across Cavite, Laguna and other parts of the Philippines are dams and irrigation works whose origins reach back to the Spanish colonial period. For generations, they impounded rivers and streams, directed water through canals, and helped make agricultural lands productive. Some have fallen into ruin or been altered by development. Remarkably, others continue to perform the work for which they were built more than a century ago.

These inconspicuous structures are the subject of Presa: The History and Heritage of Spanish Colonial Dam Building in the Philippines, 1699-1898, a book by historian, journalist, and heritage advocate Edgar Allan M. Sembrano that brings to light a little-known chapter in Philippine engineering history.

Published by the National Historical Commission of the Philippines (NHCP), Presa was formally launched on 25 June 2026 at the Emilio Aguinaldo Shrine, or NHCP Museo ni Emilio Aguinaldo, in Kawit, Cavite. Derived from Sembrano’s master’s thesis in Cultural Heritage Studies at the University of Santo Tomas, the book focuses principally on Spanish colonial dams and irrigation systems in Cavite and Laguna from the late 17th through the 19th century. His research was partly funded by the National Commission for Culture and the Arts (NCCA) through its research grant program.

Historian and NHCP chairman Regalado Trota José, in his foreword, calls the work “a painstaking recovery of information and documentation on Spanish-era dams and waterways in Cavite and Laguna.” It is an apt description for research that required Sembrano to search for history not only in archives but along rivers, through thickets and across landscapes radically transformed since the dams were constructed.

Following the water

The research began in 2014 when Sembrano joined an ocular inspection of a dam between Las Piñas and Bacoor, later identified in his research as Ligas Dam. Initially, he thought there might be fewer than 10 Spanish-era dams to investigate in Cavite and Laguna. Then the archives began telling him otherwise.

“When I dug deeper into archival records,” Sembrano recalled, “that’s when I realized there are many, many dams built during the Spanish period in Cavite alone.”

A seemingly narrow subject expanded into an investigation of entire systems of water engineering. Archival maps provided clues, but locating the structures presented another challenge.

“Finding these structures is hard, and I had to rely on archival maps and Google Maps,” Sembrano said. “It was a time when drones were not yet widely utilized, so surveying dam sites requires walks — at times long walks — through heat, rain, thickets, inside subdivisions, and in many inaccessible areas.”

Eventually, more than 70 dams were visited during the research. Of the 70 dams accounted for in the book’s summary, 67 were identified as having been constructed during the Spanish colonial period.

The surprise was not simply that so many had existed. It was that many survived.

“These systems are well-planned,” Sembrano said. “The topography, river systems, and canal trajectories were well studied. I must say they were built to last.”

Engineering the landscape

For many Filipinos, Spanish colonial architecture evokes stone churches, convents, fortifications and bridges. Water engineering occupies a far less prominent place in that historical imagination. Presa demonstrates how consequential it was.

Religious orders that established haciendas required reliable water for agricultural production. Dams consequently formed parts of larger systems in which water was captured from rivers and distributed through networks of canals and reservoirs.

The scale can be startling. According to historical sources cited by Sembrano, the Hacienda de Imus alone had 54 dams, 79 water or irrigation canals called zanjas, and 28 reservoirs. The historical estate encompassed present-day Imus, Dasmariñas, Bacoor and portions of Kawit.

Cavite had considerably more dams than neighboring Laguna, a difference Sembrano attributes partly to geography.

“The dammed areas of Cavite are located in many parts of the province that are higher than the plains of the coastal areas,” he explained. “This means that more dams are required in these areas to maximize water for irrigation. Also, Cavite has wider irrigable land compared to Laguna.”

The landscape itself dictated engineering responses. Dams were not simply walls across waterways but components of systems designed around terrain, rivers, gravity and cultivation.

The language of water

History survives in words as well as stones.

The Spanish presa gave rise to local variants such as prinsa, prinza and prenza, while zanja, the Spanish word for a ditch or canal, acquired localized forms. Such terminology became another source of evidence for Sembrano.

“Language is very important in research,” he said. “In fact, in the course of the study, I was able to create a glossary of irrigation-related terms. These are Tagalog words collated in Cavite, Laguna and Bulacan.”

“In reconstructing the history of these water systems, language played a significant role, particularly in identifying dam sites and other irrigation-related places,” he added.

Place names could preserve memories of waterworks even when structures had disappeared, or landscapes had changed.

The story also reaches farther back than Spanish colonization. Sembrano discusses evidence for the precolonial Tagalog word salak for dam and points toward indigenous traditions of water management, particularly the sophisticated systems of the Cordilleras. The book thus raises another avenue for research: how indigenous irrigation technologies might be studied alongside those developed during the colonial period.

Beyond Cavite and Laguna

While Cavite and Laguna constitute the heart of Presa, Sembrano’s findings suggest a much wider geography. The book considers dams in Bulacan and points to other Spanish-era structures across Luzon and farther south.

“Cavite has the most Spanish-era dams, followed by Laguna,” Sembrano said. “There were other dams built in other parts of the country, from Cagayan in the north to Misamis Oriental and Zamboanga del Norte in the south.”

“This study is just a scratch on the surface,” he stressed. “I believe these water engineering projects are extensive, and many still need to be documented.”

The book consequently proposes further archival and field research, including wider investigations in other parts of the Philippines. New technologies such as drones and scanning equipment could make it possible to locate, document, and understand sites that were difficult to investigate during Sembrano’s original fieldwork.

In this sense, Presa is as much an invitation as a conclusion. Its maps and inventories establish a foundation for a much larger history of how Filipinos managed water.

When the fields disappear

But finding the dams is only half the problem. Keeping them is another.

The agricultural landscapes for which many were constructed are rapidly changing. Farms have given way to subdivisions, factories, roads and commercial developments. Some rivers and streams have become polluted. When agricultural land disappears, irrigation systems can lose both their function and the communities that retain knowledge of them.

“Most of these dams are still functioning today, but massive land conversion and industrialization are definitely threatening their existence and continued use,” Sembrano said.

“If these dams are lost, we also lose their histories, and we would fail future researchers who would delve deeper into the study of their materials, construction techniques, etc.,” he stressed.

The concern is echoed in José’s foreword, which calls attention to dams destroyed by development and waterways affected by pollution, and presses for greater recognition and rehabilitation of these structures.

Sembrano, however, does not see conservation and contemporary needs as necessarily opposing forces.

“Heritage and development should go hand in hand,” he said. “They should complement each other.”

The challenge is, then, not to freeze the landscape in time but to recognize significant structures before development obliterates them — and find ways for heritage, changing communities and contemporary land uses to coexist.

From infrastructure to heritage

One obstacle is perceptual. A centuries-old church is readily recognized as heritage. A low stone barrier across a river may simply look like an old dam.

Presa argues that such a distinction deserves reconsideration.

These structures contain evidence of engineering and construction techniques, agricultural history and the ways people shaped rivers and land. Some continue to perform practical functions; others survive as ruins that can still reveal how earlier communities managed one of life’s most essential resources. Some have already received official recognition. The NCCA’s cultural-property database lists several.

Sembrano also cites local initiatives. Biñan, he said, has recognized two Spanish-era dams as local heritage properties, while efforts have been made toward securing stronger recognition for other significant structures.

Growing interest in water heritage is also visible in “Patubig: Cavite’s Heritage Irrigation System,” an exhibition that opened at Museo De La Salle in Dasmariñas in May 2026 and explored the historic irrigation networks that helped shape the province’s agriculture and landscape.

The monuments beneath our feet

Sembrano’s subject ultimately challenges our instinctive image of what a monument should look like. A church announces itself with a façade and bell tower. A municipal building commands a plaza. A fortification was intended to be seen. A dam can almost disappear into its environment. Water runs over it, vegetation grows around it, and generations use it until its antiquity becomes ordinary.

Perhaps that ordinariness partly explains why this heritage has been overlooked.

José closes his foreword with the hope that the book will encourage readers to explore how thoughtfully earlier generations lived off the land and to appreciate the gift of ever-flowing water.

That may also be the most compelling way to regard these old presas. They are not merely ruins left behind by history. Where water still passes through them, and fields still benefit from their engineering, the past has never entirely passed. It is still flowing.