Artificial ditching of catchments and brownification-connected water quality parameters of lakes.

ABSTRACT

We studied the connections between lake water quality and the density of artificial ditching in lake catchments. Water color and the concentrations of dissolved organic carbon (DOC) and iron (Fe) in lake water increased with increasing ditch density. Additionally, the water colorDOC ratio increased along a ditch density gradient because ditching had a stronger effect on color than on DOC. This was mainly due to the positive effect of ditching on the Fe concentration in lakes. ColorDOC ratio was strongly dependent on Fe up to Fe concentrations of 1-1.5 mg L-1. Thus, the water color of lakes with Fe concentrations < 1 mg L-1 will respond especially strongly to the effects of catchment ditching. The effects of ditching were strongest in catchments with high peatland coverage due to their high ditch density and high storage of organic carbon and Fe. The long-lasting effects of ditching should be taken into account when studying the factors governing lake brownification.