Seston transport variability at different spatial and temporal scales in the Agüera watershed (North Spain)

Abstract

The variability of fine particulate organic matter concentrations in the streams of a moderately disturbed catchment were studied under different spatial and temporal scales. Spatial patterns of FPOM concentrations clearly reflect the effects of disturbances imposed by human settlements and land uses, and recovery processes. Temporal changes are mainly caused by floods which disrupt the spatial variability. These sources of variation may be responsible for the lack of a significant fit between discharge and FPOM concentrations in disturbed reaches. On a diel (throughout the day) scale, FPOM transport rhythms were clear only in undisturbed headwaters. Conventional sampling designs (e.g. annual cycles) should take into account short-term variability scales. The Agüera stream shows important internal processes (e.g. self-purification trends) that mitigate the influences of human settlements and tributaries, and can control FPOM transport under low flow conditions. Examination of different temporal and spatial scales seems to be necessary to detect the main factors that control FPOM transport in streams. This organic parameter could be important in evaluating the effects of intermediate disturbances in fluvial systems.