THE USE OF STABLE ISOTOPE TRACERS FOR THE ESTIMATION OF THE DIRECTION OF GROUNDWATER-FLOW

Spatial variation in the stable isotopic composition of groundwater is indicative of mixing of waters of different stable isotopic content. Infiltration losses from a river or lake are examples which result in a positive correlation with distance from the source of infiltration to the groundwater. This technical note describes a method for determining the direction of groundwater flow. The regression is determined of either 18O or deuterium against distance along the X-coordinate of each sampling location. This computation is made for given intervals, for example 5 degrees, of rotation of the axes through 180 degrees. The angle of rotation which results in the maximum value of the correlation coefficient determines the direction of groundwater flow. This approach is applied to field studies in Ecuador and the Republic of Korea. In the latter case the estimated direction of flow agreed with the resultant of the two flow vectors obtained from water level contours. © 1990.