Urban Water Cycle

This new research field started on the 1st January 2011 with the project : “Forgotten connections between urban fluxes: Geological, historical and isotopic approaches towards a sustainable development of Brussels”.

Below, the summary of this study that is financially supported by the Brussels Capital Region – InnovIris.

Objectives

This project focuses on the interactions between the different water fluxes present in urban environment (drink-water, groundwater, sewer-water, run-off...), using Brussels as a case study. The study localizes and quantifies exchanges and/or mixing between urban waters fluxes of different origin, quality and usage, such as sewer leakages, groundwater infiltrations, floods, etc. These water connections are well documented in natural environments but they are extremely complex and much more difficult to understand in a densely urbanized city. They fluctuate with seasons, intensity and frequency of precipitations, degree of urbanization, impermeabilization of surfaces, public work and city spreading. Furthermore, forgotten rivers and resurgences could still be functioning, hidden under the urban cover.

A great deal of information is required to complement and better constrain the new plan for water management developed by the Brussels Capital Region. A multidisciplinary team of researchers (in geology, hydrology, history and engineering) from different universities (ULB, VUB, UCL, Université de Montréal) is involved in this project. Ultimately, the results will contribute to a new and better management of urban water cycles, with for example as possible consequence a decrease in the frequency of intensity of floods, and a more sustainable development of the Brussels Capital Region. The scientific approach will eventually be applicable to other cities.

Program

The research is divided into three parts:

• The main part of the research consists of a study of the urban water cycles occurring within Brussels. It includes literature reviews, characterization of the geology, geomorphology and hydrogeology of the area, collection of data (topography, piezometric levels..).
• The second part implies the development of stable isotopes methodologies (O, H, C, N) specifically designed to trace and identify urban water fluxes, using samples localized in one or two micro-catchments (that will be determined within the distribution area of the “Callois” tap-water reservoir). The goal is to distinguish different water sources (precipitation, sewer etc) and their degree of mixing in specific urban environments.
• The third part comprises the compilation of data, conclusions from the first two parts and the development of cartographic tools. These include maps or databases that will be made available for administrations and contractors involved in real-estate development, urban infrastructure constructions, river-restoration and flood mitigation.

Applicability and Perspective

A better knowledge of urban water cycles is indispensable for Water Management and Planning in the Brussels Capital-Region. The objectives of this study support many of the operational measures of this planning, such as:
i) Evaluation of groundwater contribution in urban floods;
ii) Quantification of fresh water (groundwater, rainwater) in sewage and treatment plants;
iii) Promotion of a separated blue-network fed by sustainable waters.

The stable isotopes analyses will be used to evaluate infiltration and leakage into/of the sewage. It will determine the potential of these analytical methods for sewer management (repairs, floods..) in application in Brussels, other cities in Belgium or abroad.

The cartographic tools will help administrations and private contractors to improve the management of water fluxes and reduce geotechnical risks. The data collected on the physical environment (soil infiltration, localization of resurgences,..) could also be useful for construction projects, in a context of sustainable development and optimal management of water resources within the city.