Kohji Muraoka

Streamwater chemistry during rainfall events in a forested basin

Abstract The hydrochemistry of streams has been measured during two water cycles in an experimental forested basin of 67.5 ha area. An itemized list of the water quality parameters includes pH, specific conductance (SC), Cl − , NH + 4 -N, NO − 2 -N, NO − 3 -N, PO 3− 4 -P, SO 2− 4 , K + , Na + , Ca 2+ , Mg 2+ , and SiO 2 . The chemical changes of streamwater measured during four rainfall runoff events allow to distinguish two types of solute element behavior. Until the peak flow, the concentration of each element decreases, due to a dilution effect by the surface runoff water. Whereas during the recession period the concentrations increase, following two major modes: (1) Type I, which shows approximately the same concentrations around the end of the runoff period as the baseflow level prior to the runoff event and (2) Type II, which overshoots the baseflow level. Type I includes SiO 2 , SC, Cl − , Na + ; and Type II, NO − 3 -N, K + , Ca 2+ , Mg 2+ . During the recession period, the streamwater might be originating mainly from interflow, probably associated with surface soil water, therefore the soil water chemistry has been analyzed. SiO 2 , originating from soil and bedrock showed nearly uniform concentration in the downward direction, and NO − 3 -N concentration near soil surface was greater than that of deep soilwater and streamwater. Then two results correspond respectively to the runoff characteristics of Type I and Type II. The materials classified into Type II are revealed to be major essential elements closely involved in the metabolic activity of forest soil ecosystem and those of Type I to be minor or nonessential elements.

On the box model for prediction of water quality in eutrophic lakes

Abstract Using the box model, a method of prediction of water quality in eutrophic lakes is discussed. As to the box segmentation of the lake concerned, three subjects are emphasized: box number, locations of partition, and accuracy or error of the model. The box model is one of approximations deduced from the advection-dispersion differential equations, and comparing the moment of concentration pattern between model and theory, the reasonable box model is proposed for shallow and eutrophic lakes, of which the physical parameters, Peclet number and the biochemical parameter, and the ratio of reaction rate and advection ratio are given. This model applied to Lake Kasumigaura, a typical eutrophic lake in Japan, has good coincidence with the result of field survey, and applicability for other shallow lakes was also confirmed.

Assesment on Development of Golf Links in terms of Headwater Conservation Function

This study investigates the assesment on the development of golf links in terms of the headwater conservation function. Mathematical runoff model developed by authors are applied to a virtual basin based upon Shirakawadani experimental basin in Tokushima prefecture, and simulates the change of daily runoff discharge in various conditions concerned with the infiltration and water retention capacities. The reduction of the capacities by the development of golf links cause the accelerative decrease of daily runoff discharge.

Experimental Study on Turbulence Properties of Particle Plume

The purpose of this investigation is to clarify the turbulence properties of particle plumes which are generated by relatively coarse and nearly monodisperse particles (the particle diametersare 1 and 3mm) falling with constant volume fluxes in the stagnant water bath. The main results are as follows: In the case that 1mm diameter particles are used, the mean and turbulence properties are quite similar to that of the single phase plume or jet. In the case of 3mm diameter particles, the flow properties are chiefly dominated by vortex shedding of each particle.