An automated #ow data collection system was installed in a subsurface drainage system to determine discharge volumes and drainage #ow rates. An experimental site was established by installing a subsurface drainage system on 36 plots, each of 0)4 ha, to measure subsurface drain #ows and collect drain water samples for water quality analysis. Subsurface drains from individual plots were intercepted at the end of plots and routed to individual sumps to collect drain water. Flowmeters connected to individual sump pumps measured the volume of water pumped from these sumps. Electronic outputs of the #owmeters were recorded with data loggers, and readings of the analog registers were recorded manually. The data loggers recorded the time when each sump pump started and stopped pumping water. Data collected by data loggers were used to calculate drain discharge volumes and drain #ow rates. This monitoring system was evaluated by comparing the drain volume rates between #owmeter readings and the data collected by data loggers for some rain events.
Subsurface drain #ow measured by the data logger system was not signi"cantly di!erent from the manual readings taken by the #owmeters. The data logger system was an e!ective method for measuring changes in subsurface drain #ow rates over short time periods and drain #ow response to individual rainfall events. This automated system was also used to monitor the movement of nitrate}nitrogen (NO }N) to subsurface drain water.