Technical Note: Assessing a 24/7 solution for monitoring water quality loads in small river catchments

摘要

Quantifying nutrient and sediment loads in catchments is difficult owing todiffuse controls related to storm hydrology. Coarse sampling andinterpolation methods are prone to very high uncertainties due tounder-representation of high discharge, short duration events. Additionally,important low-flow processes such as diurnal signals linked to point sourceimpacts are missed. Here we demonstrate a solution based on atime-integrated approach to sampling with a standard 24 bottle autosamplerconfigured to take a sample every 7 h over a week according to aPlynlimon design. This is evaluated with a number of other samplingstrategies using a two-year dataset of sub-hourly discharge and phosphorusconcentration data. The 24/7 solution is shown to be among the leastuncertain in estimating load (inter-quartile range: 96% to 110% ofactual load in year 1 and 97% to 104% in year 2) due to the increasedfrequency raising the probability of sampling storm events and point sourcesignals. The 24/7 solution would appear to be most parsimonious in terms ofdata coverage and certainty, process signal representation, potentiallaboratory commitment, technology requirements and the ability to be widelydeployed in complex catchments.