Change in mountainous stream water chemistry after passage through the wetland-like topography formed by a small sabo-dam.

Abstract

Change in mountainous stream water chemistry after passing through the pile of accumulated sand formed by a small sabo-dam was evaluated. In this passage, pH and the concentrations of Na⁺, K⁺, Ca⁺, Si, SO₄^2--S, NO₃^--N : p< 0.001), while Cl- concentration increased (p< 0.05). The concentrations of Na⁺, Si, Ca²⁺, SO₄^2--S, and NO₃^--N and pH decreased more with lower water level at the sand pile. In lower water level at the sand pile, lower flow rate of stream water and its longer contact time with the sand pile were thought to have caused the larger change in stream water chemistry. It was suggested that the change in stream water chemistry could have been caused by the mixture with the dilute and low pH soil solution at the parts of the soil subject to humus formation on the surface of the sand pile.