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Using oxygen isotopic ratio and humidity, a new simple method of measurement for an evaporation rate in a lake is proposed. The oxygen isotopic ratio of the Inawashiro Lake is thought to have increased from-10.3‰ to-9.3‰ estimating from river flow rates and lake and river oxygen isotopic ratios. As a result of some evaporation experiments, the relation between evaporation ratio, initial oxygen isotopic ratio and humid was analyzed and then the evaporation ratio in the Inawashiro Lake was estimated 5.6 % from the relation and oxygen isotopic ratios. The evaporation in the Inawashiro Lake is calculated about 560 mm per year from 5.6 % evaporation ratio, lake inflow and lake area and is in agreement with that estimated by Jacob equation.

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Flow and fluid forces acting on several kind of trees in large scale wind tunnel were measured by using wind flow velocity meter and load cell. Drag coefficient of drag forces acting on a tree decreased with increase of Reynolds number because projected frontal area of tree canopy in still air decreased with increase of incident flow velocity. The reverse flow was not found at down stream region of tree under the influence of the flow passing through the tree canopy. The recovery of flow velocity in the wake of tree was more slow compare to that of circular cylinder in uniform flow. The impulsive forces acting on a pine tree were also measured.