De aanleg van regenbakken in vroegmodern Deventer

In recent years, many old cisterns for the collection of rainwater have been discovered in Dutch cities, in particular in Amsterdam. Such rainwater cisterns were for centuries an important source of fresh water. Most date from the second half of the sixteenth century onwards. They were especially prevalent in the western provinces, where the ground and surface water were mostly unpotable due to salinization and pollution. However, rainwater cisterns are also known to have existed in the eastern parts of the country. Yet very little is known about the architectural history of these cisterns in the Netherlands, especially for the period prior to the seventeenth century. While there are archaeological reports detailing specific aspects of their construction, the historical literature focuses on the use of rainwater cisterns by households and industry. There is a general lack of written sources describing the construction of cisterns prior to the seventeenth century.   This article highlights one specific historical source that has not been fully studied, namely the accounts left by the stewards of the former ecclesiastical houses in the city of Deventer. After the city became   part of the Dutch Republic in 1591, the ecclesiastical houses were confiscated by the city and extensively refurbished. This included the construction of rainwater cisterns in around 1600. The accounts of these  works contain valuable notes regarding the construction process and maintenance of cisterns, the use of specific materials and the hiring of specialist workmen. The findings from these notes, as presented in this article, can be used to complement recent  archaeological findings and contemporary architectural descriptions, thus providing insights for further research. The notes confirm, for example, that these rainwater cisterns were constructed underground by the same specialist, according to a specific design, using similar materials, such as bricks known as ‘klinkaerts’, and trass to create waterproof mortar. The construction of rainwater cisterns was sometimes accompanied by roof renovations designed to enhance the rainwater collection, as illustrated by an example. Ultimately, the article aims to show the relevance of such historical sources to furthering our knowledge of the construction history of rainwater cisterns in the Netherlands, in particular in the rather underexamined eastern parts of the country. Future research could aim to  synthesize such historical sources with archaeological findings in order to arrive at a more comprehensive view of rainwater cisterns and their history in both the eastern and western Netherlands.