At all stream sites water samples for chemical analysis are collected monthly, whereas lake sites, because water chemistry fluctuates less, are sampled on a quarterly basis. All dip samples are collected in acid-rinsed bottles.
The chemical determinands recorded at each site are those recommended by the Acid Waters Review Group (Warren et al. 1986). Accuracy requirements were established in accordance with Water Research Centre (WRc) recommendations and UK water industry practice. The UK UWMN laboratories regularly participate in ICP Waters international water chemistry intercalibration exercises (eg. Hovind H., 2004; Hovind H., 2005; Hovind H., 2006; Hovind H., 2007; Hovind H., 2009; Dahl I. and Hagebo E., 2011; Dahl I., 2012; Escudero-Onate C., 2013; Escudero-Onate C., 2014; Escudero-Onate C., 2016).
A range of laboratories used to contribute chemical analyses. Today, most analysis is performed by the analytical chemistry facility at the UK Centre for Ecology & Hydrology, Lancaster. To maintain temporal consistency, determinands considered to require particularly prompt analysis (pH, Gran Alkalinity and electrical conductivity) in samples from sites in Wales are analysed at the UK Centre for Ecology & Hydrology, Bangor. The tables below summarise the methods utilised and detection limits for the analysis of each determinand. The freshwater laboratory at Marine Scotland, Pitlochry, used to provide analysis for a significant proportion of the network, and continues to provide analysis for the Baddoch Burn.