Suggestions for Further Study


Additional information is needed to quantify small gains and losses relative to streamflow. In particular, more information is needed to identify the uncertainty of streamflow measurements and understand the relation of near-stream groundwater level to stream level. 


Multiple streamflow measurements at a given location, as well as measurements a short distance upstream and downstream, could justify a narrowing of the uncertainty ratings typically assigned to streamflow measurements. For example, corroboration of streamflow at a given location from one hour to the next, as well as from one location to locations 1–2 channel widths upstream and downstream, could provide insight into the “true” streamflow. This could be accomplished by streamflow measurements at a subset of sites selected from the 2006 study. For this approach, measurements could be made at the Estacada, Barton, Carver, Clackamas, and Oregon City sites (6, 13, 22, 25, and 28, respectively). 


High nutrient concentrations observed in near‑stream wells and springs (Carpenter, 2003) suggest that the Clackamas River might be receiving nutrients from groundwater discharge by way of springs and/or seepage. Little is known, however, about the seasonal fluctuation of groundwater levels near the river and the relation of these water levels to stream level. A network of groundwater observation wells coupled with periodic stream-level measurements could provide an indication of the timing and spatial distribution of the groundwater contribution to the lower Clackamas River, which could facilitate an assessment of nutrient loading to the stream. 


First posted November 28, 2011