DOI: 10.5281/zenodo.16994619
title: Dilution factor of perennial and non-perennial European rivers

description: This dataset is supplement to the article published in Water Research: "Impacts of climate change on the dilution capacity of perennial and non-perennial European rivers"by Margot Sepp, Mahdi Abbasi, Petra Döll, Anna Freixa, Rafael Marcé, and Sergi Sabater.Rivers provide ecosystem services, such as water purification and drinking water supply, which depend on the river’s capacity to dilute effluents from wastewater treatment plants (WWTPs). There are no large-scale analyses of the dilution capacity of rivers that take into account the differences between perennial and non-perennial river reaches, even though more than half of the world’s river and stream reaches are estimated to be non-perennial. We evaluated the actual and future capacity of perennial and non-perennial river reaches in Europe to dilute WWTP effluents. Future (2071–2100) climatic conditions were compared to reference (1985–2014) conditions, considering average and extreme streamflow conditions (i.e., driest months or years). The dilution factor (DF), i.e., the ratio of streamflow to cumulated upstream WWTP discharge, was annually, on average, 4.6 times lower in non-perennial than in perennial reaches under reference conditions, and decreased up to 10.8 times lower in August. Annual DF is projected to decrease significantly in two-thirds of the reaches under the high emissions scenario (corresponding to Representative Concentration Pathway RCP8.5). Reaches in the Mediterranean and semi-arid regions of Europe have low dilution capacity and are the most vulnerable to WWTP discharges. Therefore, they are particularly sensitive to climate change-induced streamflow decreases, which will further reduce DF. In contrast, under the low emissions scenario (corresponding to RCP2.6), DF will remain largely unchanged, highlighting the importance of emissions reductions in preserving the dilution capacity of the European rivers.
description: This dataset includes two main folders: "HR monthly streamflow" and "Map layers with calculated DF".Folder "HR monthly streamflow" includes the average values of the high-resolution (HR) monthly time series of streamflow for the 110,889 river reaches in the European river network used in the study. Word file "Explanation of column headers" explains the column names used in all files in this folder. File "Q_present.csv" includes the average streamflow values for the reference period 1985–2014. Dataset includes average annual streamflow values, average streamflow values for every calendar month, and streamflow values for extreme climatic conditions (driest month, driest years). Subfolder "Future predictions" includes streamflow data for future period (2071–2100) under two contrasting greenhouse gas emissions scenarios, the Representative Concentration Pathways (RCPs) RCP2.6 (low emissions scenario) and RCP8.5 (high emissions scenario), considering the output of five global climate models (GCMs): GFDL-ESM4, IPSL-CM6A-LR, MPI-ESM1-2HR, MRI-ESM2-0, and UKESM1-0-LL. The estimates of streamflow for the future period were used to calculate the future changes in the dilution factor (DF). For the comparison, we used the estimates of streamflow from five GCMs for reference period (1985–2014) as well as for the future period (2071–2100) under two greenhouse gas emissions scenarios (RCP2.6 and RCP8.5). Therefore, there is a folder "Reference period", which includes five csv files (one for every GCM), folder "2071-2100", which includes two subfolders "RCP2.6" and "RCP8.5", both including five files (one for every GCM).Folder "Map layers with calculated DF" includes three shapefiles: "DF_present", "DF_change", DF_snr", and a Word file "Description of attributes" explaining the names of the attributes used on the map layers . "DF_present" inlcudes the current dilution factor (DF) values for 110,889 river reaches used in the study. "DF_change" includes the calculated future changes in DF. "DF_snr" includes the signal-to-noise ratio (SNR) values, which characterize the uncertainty in the median change in the DF by stemming from the differences among the five GCMs.