Water quality data produced from rainfall, throughfall and stemflow samples collected within a beech stand at Black Wood in Hampshire, and an ash stand at Old Pond Close in Northamptonshire. Two studies were carried out in the early 1990s to examine water quality in relation to hydrological and pollution changes. Chemical analysis involved a combination of electrometric (pH), inductively-coupled plasma emission spectroscopy (most major, minor and trace elements), atomic absorption spectroscopy (potassium), ion chromatography (major anions and fluorine) and colourimetry (ammonium and silicon).