coupling rural and urban CEC's emissions in THE dutch hydrological network

The sub-project “Integration” deals with coupling contaminants of emerging concerns (CECs) emission sources from rural and urban areas into rivers. Rural area sources are considered diffuse sources mainly originated from manure dispersed on lands, while urban area sources are considered as point sources from waste water treatment plants (WWTPs). Figure 1 provides the full flowchart of CEC's in the SUSPECt project.

The goal is to provide spatial and temporal hazard information for risk assessment and management, predicting the concentration of CECs in rivers at Dutch country scale.

Figure 1 - the flowchart of CEC's flow in the SUSPECt project.

 To integrate the rural and urban routes, we selected the Landelijk Waterkwaliteitsmodel - LWKM 2.4 (WEnR/Deltares, 2019), a water quality model tool which relies on the national hydrological model Landelijk Hydrologisch Model – LHM 4.0 (Deltares, 2019). The main model output is the seasonal contaminant concentration due to diffuse and point sources.

We have selected the Eem River basin in the Velue een Vallei water board as a test area (Figure 2). However, the methodology will be applicable elsewhere in the Netherlands. An overview of the river network, WWTPs and monitoring and measurement points is depicted in figure 2. 

Figure 2 - The Eem Basin test area and the available information on water infrastructures and measurements.

 We run a test with fipronil as tracer compound. We took the hydrological year 2015, a urban constant source of fipronil along the year and a seasonally variable source of fipronil from rural areas. We assumed that Spring and Summer have double crop effluent concentration with respect to Winter and Fall. This is because manure and pesticides are mostly applied in spring and summer. Results per seasons are reported in figures 3, while figure 4 shows the mean tracer concentration for 2015. This exercise has been done in order to preliminary test the selected model methodology and show its capability with a tracer compound. The fipronil consumption input was arbitrary and the resulting concentrations depicted in figures 3 and 4 do not reflect a validated prediction.