The map below provides trend information and summary statistics for a variety of parameters collated by the ICP Waters programme.
- Use the layers menus at the top-right corner of the map to select a base map and parameter of interest (TOC is selected by default)
- Click on any location to display summary statistics for that site
- See the notes below for further details on the data presented
Data summaries are presented for 1990 to 2016, but note that not all sites have complete data records for this period. To check the amount of data available, see the Number of years with data entry in the information boxes (see below).
Acid neutralising capacity (ANC) and all parameter names beginning with the letter “E” (for equivalents) are expressed in micro-equivalents per litre (μeq/l). The units for Al and TOC are μg/l and mg-C/l respectively.
Having selected a parameter of interest, clicking on any site will show a pop-up information box containing summary statistics. The following quantities are reported:
- ICPW ID, ICPW code and NFC code. Various unique site identifiers used by the ICPW project
- Number of years with data. The number of years within the period from 1990 to 2016 for which measurements are available. Note that when this value is less than about 10, estimates of statistical significance may be unreliable
- Median. The median of annual medians within the period of interest
- Standard deviation. The standard deviation of annual medians within the specified period
- Mann-Kendall p-value. Results from the Mann-Kendall trend test (a non-parametric method for identifying monotonic trends)
- Trend. Whether the Mann-Kendall test identified a statistically significant increasing or decreasing monotonic trend in the data series of annual medians (at the 95% confidence level; p < 0.05)
- Theil-Sen slope. The average rate of change of the selected parameter (in units/year e.g. μeq/l/yr), obtained using the Theil-Sen robust line estimator. The median slope and intercept have been calculated using SciPy’s theilslopes function
- Time series plot. A plot showing the annual median values for each year (in blue) with the fitted Theil-Sen robust line superimposed (in black).