This paper presents the results of a project in which the seasonal changes in the chemistry of groundwater in dipwells at Wicken Fen National Nature Reserve were investigated for the first time. Thirteen dipwells arranged in two roughly perpendicular transects across Wicken Fen were sampled for groundwater on a monthly basis between April 2010 and April 2011. Surface water from a drainage ditch (Gardiner’s Drain) and groundwater from a further location (dipwell 17) were also sampled at the same interval. The water samples were analysed for pH, electrical conductivity (EC), major solutes (Ca, Na, Mg, S), nutrients (N, P, K) and trace elements (Al, Fe, Mn) in the laboratory. Measurements of pH and electrical conductivity were also taken from the soil at the fourteen dipwell locations. The results of these analyses are compared to borehole data, groundwater levels and precipitation data to form a new conceptual model of the spatial and temporal variations in groundwater chemistry at Wicken Fen, which have important implications for future hydrological and vegetation management regimes.