Groundwater and stream water exchange revealed by water chemistry in a hyporheic zone of agricultural area

Abstract

Groundwater–stream water exchange and mixing in a hyporheic zone were examined using the water chemistry data and multivariate statistical analyses. The study area was the Munsan stream of agricultural area in Paju, Korea. Three rounds of water samplings (August, September, and November, 2008) were conducted for five monitoring nests along the stream flow, with each having three different-depth piezometers in the streambed, one surrounding groundwater well and one stream water point. The chemical compositions of hyporheic water were controlled by those of the groundwater and stream water. The factor analysis identified four main factors that explain 67 % of total variance of the water chemistry data and also revealed that the parameters responsible for water quality variances were mainly related to rainfall, anthropogenic activities, and dissolution of carbonate minerals. The cluster analysis produced a few different groups in August (3 groups), September (4 groups), and November (4 groups), respectively, which showed that the water quality parameters of the three water bodies were very different and the hyporheic water showed a different mixing of the stream water and groundwater at each monitoring point.