The variations in runoff amounts exhibited a pattern similar
to the pattern of rainfall during the three wheat seasons (Fig. 5).
Apparently, precipitation was the main factor governing the runoff.
However, the runoff events were not completely synchronized with
each rainfall event, but tended to happen immediately after successive
rainfall events and heavy rainfall events (Fig. 5). 44–57%
of the seasonal rainfall during the three wheat seasons was lost via
drainage in the wheat fields (Table 4). This fact implied the potential
contribution of precipitation to N runoff to water systems.