Stream flow and ground water recharge from small forested watersheds in north central Minnesota

In hydrologic studies of forested watersheds, the component of the water balance most likely to be poorly defined or neglected is deep seepage. In the complex glaciated terrain of the northern Lake States, subsurface water movement can be substantial. On the Marcell experimental forest (MEF) in north-central Minnesota, ground water table elevations measured in observation wells in recharge areas were used to calculate rates of ground water recharge. In northern Minnesota winters, precipitation is stored on the surface as snow and ground water recharge ceases. Water table elevations in recharge areas decline over winter at calculable rates. Deviations from these rates during other times of the year are due to ground water recharge. On 10–50 ha watersheds on the MEF, ground water recharge varies among watersheds but constitutes about 40% of the total water yield. Annual ground water recharge amounts were found to vary linearly with precipitation. Even in high precipitation years, the infiltration capacity of the watersheds was not exceeded. Regression equations were developed relating yearly ground water recharge, stream flow, and total water yield, to seasonal precipitation amounts, summer and autumn precipitation during the previous year, and non-winter air temperature.