New Aquathermal Map for Water Authority HDSR

Why this study was needed

Dutch municipalities are required to draw up a heat programme by the end of 2027 to make the built environment more sustainable. This requires concrete insight into which sustainable heat sources are locally available. On behalf of Hoogheemraadschap De Stichtse Rijnlanden (HDSR), EXTRAQT therefore investigated the potential of aquathermal energy from surface water (thermal energy from surface water, TEO) across HDSR's entire management area.

The existing national aquathermal viewer only provides a rough indication of this potential and does not account for complex hydrological processes such as changing flow directions, cumulative effects between installations, and seasonal variations. As a result, it systematically overestimates the actually available potential.

An integrated, physically grounded methodology

To arrive at a reliable picture, EXTRAQT developed an integrated methodology in which thermal and ecological effects are explicitly modelled using a Digital Twin of the water system. This made it possible to determine precisely how much heat can maximally be extracted from the water without exceeding the thermal or ecological carrying capacity of the waterways.

The results show that cumulative effects play a central role: aquathermal installations influence each other through the water system, meaning cooling effects can accumulate along a waterway. A local intervention can therefore have an impact on much larger parts of the system. In addition, the available source potential depends not only on the characteristics of the waterway itself, but can also be strongly steered by targeting the location of heat demand: when mainly buildings within preferred zones are connected, the effective usability of the available potential increases significantly.

The tool: from source to water energy plan

The study's results are now available through the new Aquathermal Atlas HDSR, accessible at aquathermie-atlas.extraqt.be/hdsr-temperatuur. As with previous EXTRAQT atlases, the tool is built around three main sections:

• Sources – the calculated source potential of waterways within HDSR's management area, including local and cumulative effects.
• Consumers – heat demand and the heat that can effectively be allocated per area.
• Boundary conditions – the factors that determine where aquathermal energy is most feasible and desirable.

Additional background on the methodology is available on the atlas's information page.

Towards a water energy plan

The study underlines the need for water energy plans: a strategic framework that maps, at system level, where and how much aquathermal energy can sustainably be deployed, taking into account cumulative effects and the spatial distribution of heat demand. Such a plan can serve as a basis for permitting, spatial planning, and coordination between the water authority and municipalities.

With this study, EXTRAQT, in collaboration with HDSR, provides a physically grounded and policy-ready basis for deploying aquathermal energy reliably and sustainably within the heat transition.

Explore the results yourself via the Aquathermal Atlas HDSR.