Data belonging to: Monitoring the unknown: A citizen science approach assessing the ecological quality of Dutch ditches and ponds

This data set combines citizen-science (CS) measurements of surface water quality, the participants’ effort, and independent validation measurements, collected in the Vang de Watermonsters project in 2022 and 2023. It also includes a separate nutrient sampling test (2021) that assessed whether the citizen-science sampling protocol gives results comparable to standard (control) sampling. The data support the analyses of participant effort, comparison of CS and validation measurements, total nitrogen (TN) and total phosphorus (TP) per ecosystem representation, and the share of locations scoring good, moderate or poor status (WFD-based). Components 1. Citizen-science data, 2022-2023 (Watermonsters_20141011_CitizenScience_data_2022_2023_anoniem.xlsx)Anonymised measurements submitted by participants per location and year. According to the analysis scripts, this includes: Secchi depth (water clarity)Total N and total P (TN and TP; quality-control (QC) flags are used and validators are excluded)Abundance scores for duckweed, floating rooted plants, submerged plants and floating algae (FLAB)Ecosystem representation (for example duckweed dominated, turbid, or clear water with diverse submerged plants)Number of locations visited per participant per yearTraining type of the participant (Training, Webinar or Experienced) 2. Participant metadata, 2022 and 2023 (Watermonsters_20241011_CitizenScience_data_2022_metadata_en_ruwedata.xlsx and the 2023 equivalent)Raw metadata used only to identify unique participants (via e-mail addresses). These files contain personal data and are not publicly available. 3. Validation data (Watermonsters_20250423_Validatie_koppeling_burger_codes_2022_2023.csv)A linking table that connects validation measurements to the corresponding CS measurements. It covers Secchi depth (2022, 2023), TN and TP (2022), and the plant abundance scores, which are compared between CS and validation observers. 4. Nutrient sampling test (20210318_TestNP_Sven.xls and 20210422_TestN_Sven.xlsx) TestNP: TN and TP in control (standard) versus CS sampling, with 5 replicates per method.TestN: TN after 3 versus 6 days between sampling and analysis, for control and CS samples (n = 4 per group).