The map below provides trend information and summary statistics for a variety of parameters collated by the ICP Waters programme.
- Use the drop-down lists at the bottom-left of the map to select your time period and parameter of interest
- Click on any location to display summary statistics for that site
- See the notes below for further details on the data presented
Four time periods are available: 1990 to 2004, 1990 to 2012, 1998 to 2012 and “all data”. Care should be taken when comparing values between sites for the “all data” period, as the summary statistics may be calculated over different time periods in different locations.
Not all sites have complete data records, so selecting e.g. “1990-2004” does not necessarily mean all the stations will have complete time series spanning this period. To check the amount of data available, compare the Data period and Number of years with data entries in the information box (see below) with the time period you have selected.
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 time period and 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
- Data period. The first and last years for which the station has data within the specified period of interest
- Number of years with data. The number of years within the period of interest for which measurements are available. Note that when this value is less than about 10, estimates of statistical significance may be unreliable
- Mean. The mean of annual means within the period of interest
- Median. The median of annual medians within the period of interest
- Standard deviation. The standard deviation of annual medians within the specified period
- Normalised Mann-Kendall statistic, 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).