# Documentation of Reused Data

**Dataset Name:** `Lower Oder River System monthly physicochemical compilation dataset`  
**Version:** `1.0`  
**Description:** `Integrated physicochemical dataset for the Lower Oder River and tributaries, combining monthly and irregular water-quality records from German (LfU Brandenburg) and Polish (GIOS) public monitoring programs, and from research institutes (Leibniz-IGB). 
The dataset includes key physicochemical parameters of surface water (nutrients, ions, oxygen, temperature, and organic matter) harmonized to common units and aggregated to a monthly temporal resolution at each monitoring site between 2005 and 2025.`

## 1\. Source Information

- **Original Sources:** `
- Landesamt für Umwelt Brandenburg (LfU) - Data License Germany – Attribution – Version 2.0,
- Chief Inspectorate of Environmental Protection (GIOŚ),
- Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB).`
- **URL/DOI:** `
- LfU data portal: https://apw.brandenburg.de
- GIOŚ dataset: https://wody.gios.gov.pl/pjwp/publication/367
- IGB dataset: https://doi.org/10.18728/igb-fred-1033.0 `

- **Citation:** `
*original sources*
LfU: Landesamt für Umwelt Brandenburg (LfU)
GIOS: Chief Inspectorate of Environmental Protection (GIOŚ)
IGB: Thomas Rossoll, Tobias Goldhammer (2025) ODER~SO Water Quality. IGB Leibniz-Institute of Freshwater Ecology and Inland Fisheries. Dataset. https://doi.org/10.18728/igb-fred-1033.0 

*Compiled dataset*
Paula Torre Zaffaroni, Tobias Goldhammer (2025). Disentangling compound stress preceding a harmful algal bloom in a lowland river - Data and Code. https://fred.igb-berlin.de/data/package/1032
`

## 2\. Data Collection Details

- **Collection Method:** `In-situ physicochemical measurements performed as part of routine surface-water monitoring programs and research campaigns.`
- **Collection Date(s):** `2024-2025 (ongoing)`
- **Geographic Location:** `Oder River basin, Central Europe; subset of 200km reach along Germany–Poland border reach and tributaries including Lusatian Neisse, and Hohensaaten-Friedrichsthaler Wasserstraße.`
- **Temporal Coverage:** `2005-2025 (ongoing)`

## 3\. Data Structure

- **Data Type:** `Quantitative`
- **Format:** `CSV`
- **File Structure:** `Each row corresponds to a unique site–month aggregated observation. Columns include date, site identifier, data source, position along the river including type of location (main channel or tributary), and river kilometer, and measured or harmonized physicochemical variables, including major nutrients, ions, oxygen concentration and temperature. Variable names and units are defined in the accompanying data_dictionary.csv.`

## 4\. Access and Use Conditions

- **License:** `Creative Commons Attribution 4.0 International (CC-BY-4.0).`
- **Restrictions:** `None beyond citation requirement.`

## 5\. Data Quality and Validation

- **Quality Assurance Procedures:** `Source-level quality flags reviewed prior to harmonization; units were standardized to mg/L and checked for consistency.`

- **Known Issues:** `
- Occasional missing observations across all variables;
- Inconsistent sampling due to changes in protocol directives;
- Potential uncertainty introduced by cross-source instrumental differences.`

## 6\. Contact Information

- **Dataset Curator:** `
Paula Torre Zaffaroni
Department of Ecohydrology and Biogeochemistry. Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB), Berlin, Germany. paula.torre.zaffaroni@igb-berlin.de`

## 7\. Data Provenance

- **Transformations and Analyses:** `
- units were harmonized across sources and variables-all concentrations are reported as mg/L; in some cases, variables were renamed for consistency (e.g. `nitrate-nitrogen` to `NO3.N`);
- "below detection limit" concentrations, often reported as `< LDL` were converted to half of the detection limit value
- when two or more reports were made for one calendar month, values were aggregated to a monthly mean`

- **Record of Changes:** `v1.0 (2025-11-03): Initial release compiled for storage in FRED.`

## 8\. Additional Notes

- `The dataset is subset to reproduce the analyses presented in the manuscript “Compound physicochemical stress preceding a harmful algal bloom in a lowland river” by P. Torre Zaffaroni and T. Goldhammer. 
Please cite both the dataset and manuscript when reusing these data.`

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