Dynamics in groundwater and surface water quality : from field-scale processes to catchment-scale monitoring

Clean water is essential for our existence on earth. In areas with intensive agricultural land use, such as The Netherlands, groundwater and surface water resources are threatened. The leaching of agrochemicals from agricultural fields leads to contamination of drinking water resources and toxic algae blooms and loss of biodiversity in surface waters. Water quality managers are responsible for the detection of water quality problems and for taking appropriate measures. Therefore, a lot of their effort and resources goes into the monitoring of groundwater and surface water quality. Despite all measurements, the detection of the effects of measures is often still problematic. Human-induced changes in water quality are often concealed by the large weather-induced variations surface water and upper groundwater quality. In addition, the common measurement intervals of 1 month for surface water and 1 year for groundwater are not sufficient to capture the highly dynamic behaviour of solute concentrations in surface water and upper groundwater. This thesis is about dynamics in groundwater and surface water quality. The main research question: What are the processes behind the dynamics in water quality and what are the implications for monitoring, modeling, and managing water quality? The general objective of this thesis was to improve the efficiency of water quality monitoring by applying recent developments in measurement techniques and data processing.