For the 2005 water year the project will include continuation of the surface water, water quality, and ground water data collection network as well as specific enhancements to the program.
Surface Water
The surface-water component of the study includes water level and streamflow monitoring on Johnson Creek at Gresham, Sycamore, and Milwaukie. A monitoring station is also located at the mouth of Kelley Creek (a tributary to Johnson Creek at RM 10.4). Streamflow data from these stations are valuable in both a real-time and historic context. Real time data are used to provide warning of flooding events. Historic data are used to identify and document changes in flow conditions in response to land use changes, as well as to provide the necessary data for flow frequency analyses.Water Quality
Water quality monitoring consists of continuous stream temperature and turbidity. Both of these parameters are indicators of watershed health.Stream temperature gages are located on Johnson Creek at the Gresham, Sycamore, and Milwaukie sites, and on Kelley Creek. In addition, two stream temperature monitors are located on Crystal Springs Creek: at Bybee Street and at Clatsop Street near the mouth. Urban-type development typically increases stream temperature during warm-weather periods due to reduced shading, and rapid runoff from unshaded areas such as rooftops and roads. In contrast, reducing the rapid delivery of runoff to the stream, increased shading from tree and shrub canopy, and provision for infiltration of runoff to the ground-water system can result in cooling of the stream. Stream temperature monitoring at multiple locations will help identify baseline conditions and trends over time.
Two turbidity sensors are located on Johnson Creek.These are located at the Gresham and Milwaukie gages. Turbidity can be used as a surrogate for suspended sediment in the water, which in turn can be related to the presence of certain pesticided in the water. Differences in turbidity between the upper basin (representd by the Gresham gage), and the lower basin (represented by the Milwaukie gage) may be able to be related to land use.
Ground Water
Data collection and analysis in this study continues to build upon the work done in the Portland Basin Ground-Water Study allowing a better understanding of the interaction between the aquifer system, springs, and Johnson Creek. Water levels in 19 wells is measured on a quarterly schedule, adequate to provide water- level hydrographs that represent seasonal climatic changes. The water-level data are useful in predicting the timing of inundation of the low-lying Holgate Lake area and increased flow of Crystal Springs Creek due to a rising water table.Five wells are instrumented with continuous water-level recorders, of which one is equipped with telephone telemetry. Continuous recording allows detection of water-level changes that occur in response to specific precipitation (recharge) events and that may result in increased discharge to springs.
Data collected from observation wells will be plotted both in hydrographs (change in water level with time) and as aerial water-level maps. The hydrographs will be helpful in studying trends related to climatic events and the aerial water-level maps will allow an understanding of changes of ground-water gradients and flow directions as a result of changes in recharge. This recharge includes infiltration of precipitation, septic systems, discharge to drywells, and seepage from streams.
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Last modified: Thu Jan 23 15:01:23 PST 2003URL:http://oregon.usgs.gov/jcrk/htmls_dir/approach.html