Fig. 3. Observed values of daily rainfall (a), runoff recorded at the outlet of the no-till field (b) and tilled field (c), and average concentrations in diuron (d) and simazine (e) during runoff events on the no-till and tilled fields, 1997. Dashed line indicates the analytical limit of detection. Concentrations under this detection limit were set to 0.025 µg L^-1 for graphical representation.