The LOIS river monitoring network: strategy and implementation

The large-scale, highly integrated, multidisciplinary nature of the LOIS rivers programme mean that certain measurements were common to many LOIS research projects (including water discharge, suspended sediment concentrations, pH, conductivity) or depended upon routine weekly or flood-related sampling (eg. for nutrients, metals and organics). This paper describes the underlying strategy which led to the design of the major observational programme in LOIS rivers and provides information on siting of sample points, field sampling methods, instrumentation and associated chemical analyses. There was a need for field measurements to reflect the full range of river flows and to identify critical points for measurement of flux from, and within, the large-scale study river basins. Tests of manual sampling runs against the time series of river flows indicate good representation of both low to moderate flows and extreme flood events in the LOIS rivers field data. Field and analytical methods for sampling the wide range of chemical determinands (major and minor elements, trace metals, nutrients, inorganic and organic carbon and micro-organic pollutants) are outlined. The first LOIS chemical harmonisation assessment, designed to investigate the comparability and accuracy of the chemical and analytical techniques used by the LOIS community is also reported.