<p> The period of observation necessary to obtain representative mean monthly values for precipitation, temperature, and streamflow is about fifteen years. At present there is a paucity of meteorological and streamflow records of such length. This makes hydrological investigations in northern Ontario difficult. </p> <p> River regimes of northern Ontario are found to exhibit general characteristics. More specifically, runoff peaks occur in spring due to snowmelt, and secondary fall peaks occur due to rainfall. The regimes can be classified into four types based upon qualitative comparisons of annual flow response patterns. River regimes in northern Ontario exhibit spatial variation. Rivers to the northwest have lower flow magnitude due to decreased precipitation, and tend to have flow "buffered" by the many small lakes located there. Rivers to the southeast have more pronounced spring melt peaks resulting from greater winter snow accumulation. Fall contributuion to total annual runoff increases to the northwest. The colder winter conditions of northern Ontario is reflected in a tendency of winter contribution to annual yield to decrease towards the northwest. </p> <p> Seasonal runoff is affected by meteorological conditions. Temperature has a marked effect on spring streamflow as rising temperature causes snowmelt. Summer flow reflects the effects of both temperature and precipitation. Precipitation has a pronounced effect on fall runoff. Winter runoff is dominated by baseflow only as temperatures are low and precipitation is snow which accumulates until spring. </p> <p> An attempt to produce equations for predicting seasonal monthly flow was unsuccessful. Meteorological stations are too sparsely distributed to provide representive data necessary for producing such equations. There is a need to increase the meteorological and streamflow station network in northern Ontario to enable a more comprehensive study of the hydrologic processes. / Thesis / Candidate in Philosophy