Selection of study streams showing an urbanization gradient and monitoring of their physico-chemical and socio-urbanistic parameters at Toulouse


Rivers that flow through cities can exhibit a gradient of urbanization, spanning from appearing almost natural to completely artificial streams. This diversity is likely to have a significant impact on the microbial communities, invasive species, mosquitoes or ticks, amphibians, and consequently, the health of both the ecosystem and humans. Therefore, it was necessary to carefully select research sites that represent this diversity of streams. Maps were primarily used to locate the streams, and on-site investigation was conducted to confirm their suitability. This initial characterization enabled us to identify 24 streams in the Toulouse area that represent the full range of urban rivers (Fig. 1).



                                                                                    Figure 1. Illustration of the variety of urban streams


A second phase of fieldwork will provide a more detailed description of the selected urban streams in terms of hydro-morphological parameters, such as flow types, substrate types in the banks and channel, and the presence of barriers or other artificial builds. Additionally, riverine and riparian vegetation, such as the type of plants, will also be characterized. At a larger scale, maps and Geographic Information System (GIS) analysis will be used to characterize the catchment area and land cover near the sampled streams, including impervious rates, and the presence of natural, agricultural or residential areas.

The Ardour-Garonne water agency in Toulouse has been monitoring the quality of surface water in many streams for several years, including chemical pollutant concentrations. If the monitored sites match the selected study streams, the data collected by the agency could represent a valuable dataset for interpreting the observations made during our study. Additionally, the streams will be characterized in terms of physico-chemical parameters, such as temperature, turbidity, and oxygen concentrations. Temperature will be monitored using data-loggers, which will enable the tracking of temperature fluctuations over several weeks (Fig. 2). The other physico-chemical parameters will be measured on-site during the sampling campaign using a multi-parameter probe.

All of these parameters, whether measured during the OneAquaHealth project or retrieved from databases, will provide a comprehensive characterization and enhance our understanding of the selected research sites.



                                                                                    Figure 2. A datalogger in an urban stream


Author(s): Rayan Bouchali (


Map of Toulouse sampling streams:

Ardour-Garonne water agency:

Keywords: Urban ecology, Research sites, Fieldwork, Urban streams, Land cover surveys, Streams monitoring