You should park in Lot #2 of White Clay Creek Preserve (39d 44.974 75d 46.303).
Follow the trail to the published coordinates and you should be on a small gravel beach at the junction of the East and West Branches of White Clay Creek. You need to look at how the two streams come together because you will have to estimate which has the greater flow. This is also a good place to take your required picture. As you look upstream (north), the West branch comes in from your left and the East branch comes in from the north. You can see how the beach has been made by deposits from previous very high water flows.
Now proceed to gaging station (39D 44.840 and 75D 46.237) and you are looking for a small concrete building that houses the Strickersville Hydrologic Unit, commonly called a gaging station. This unit continuously monitors the stream flow, called stream discharge, measuered in cubic feet per second (a cubic foot is equal to 7.48 gallons). The unit is a part of the nationwide US Geological Survey that monitors and reports stream flow for 8,500 rivers and streams.
The gaging station is actually measuring very accurately the depth of water in the stream above a datum point. When the station was initially calibrated, the actual stream flow was measured. A detailed stream cross section was measured and split into grid points. For each of the grid point the actual stream velocity was measured. This was used to calculate the stream flow in cubic feet per second (or CFS). This process had to be done for many different gage heights to develop a rating curve--A drawn curve showing the relation between gage height and discharge of a stream at a given gaging station. This rating curve needs to be periodically verified (especially after very severe flood), since changes in the stream bed can effect the curve.
Look at the stream bank and you can see two pipes going into the bottom of the stream from the gaging station. There is a water filled chamber in the station connected by the pipes that is at the exact height of the stream and this is measured to an accuracy of 0.01 inches. The unit automatically reports its gage height and stream discharge to the USGS. All of this information is available to the public and free. The link for the Strickersville station is: http://waterdata.usgs.gov/nwis/uv?cb_00065=on&cb_00060=on&cb_00045=on&format=gif&period=7&site_no=01478245 And the link for the entire network is: http://waterdata.usgs.gov/nwis/rt
Walk downstream about 100 feet to (39D 44.828 and 75d 46.240) where you will see a very small rapids. Its easy to see why increased stream discharge would raise the gage height to flow past this point.
To claim your cache you need to:
1. Take your picture with your GPS at the posted coordinates. (river junction) This is now an optional requirement per GC.com guidelines
2. Answer following questions
A. What gage level (in feet) would occur if the stream completely filled its banks. (Flood stage is when the stream overflows its banks.)
B. What is the current gage height (look at the field gage at edge of stream)
3. Estimate what you think the stream flow is.
A. First estimated the distance across the stream and the depth to get the stream cross sectional area.
B. Next select a distance on shore at stream bank of ten feet.Time a floating twig or leaf for how many seconds it takes to go that distance Figure the velocity in feet/second.
C. Now calculate the flow. You must show me your calculation.
4. When you get home, go on line and access the Strickersville Gaging station and report what the “Official“ flow is and see how close it is to your estimated flow. The gaging station can give you the stream discharge and gage height for up to the past 31 days. By looking at the past months flow, do you think you can tell when there has been any rain?