Three adjacent watersheds in the South Umpqua Experimental Forest on Coyote Creek were harvested in summer 1971 after 7 years of pre-treatment stream discharge collection. Data collection was discontinued in 1981 but resumed in 2000. Watershed 1 was was logged as preparation for creating a shelterwood stand, watershed 2 was patch clearcut in 20 small units from 1.6 to 3.3 acres, watershed 3 was cut as one large clearcut, and watershed 4 was left undisturbed as a control.
Harr, R. Dennis; Fredriksen, Richard L.; Rothacher, Jack. 1979. Changes in streamflow following timber harvest in southwestern Oregon. Res. Pap. PNW-249. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Forest and Range Experiment Station. 22 p.
Stream discharge is measured on four small gauged watersheds equipped with sharp-crested, 120 degree v-notch weirs. The records of stage are converted to stream discharge by applying a v-notch flume specific rating curve, which is the same for each of the four watersheds (ln y = lna + b ln x, where y = discharge in cubic feet per second, x= gage height in feet, ln a = 1.4884000 and b=2.4489999). Historically, sites have been visited on a 3-week basis and "check sheets" guide the data collection and maintenance activities for the visit. The instrumentation used to measure and record stream stage has changed through the years in response to changes in data collection technology and data management considerations. Leopold-Stevens A-35 (A-71) chart recorders were the primary collection mechanism from the beginning of record through WY 1985, however, Fischer-Porter punched tape recorders were used in lieu of charts from 1967 to 1975. Stage height measurement was switched to Model 2 Stevens Instruments Position Analog Transmitter (PAT) recorders controlled by a data logger shortly after resuming measurement (~2003). Charts are still maintained to provide a visual backup record on two of the four watersheds (WS 3 and 4) with large enough stilling wells to house both the PAT and the Stephens A-71 chart recorder. The discharge measurement is re-initialized every visit to a reference measurement of stream height taken by a hook gage located in an additional stilling well.
Sediment basin surveys are conducted annually since 2000 to determine annual accumulation of bedload. Basin surveys are designed to build basin profiles that are used to determine a change in average bottom elevation between annual surveys. The basins are cleaned annually and resurveyed to provide a base elevation for the following year. Original survey data are summarized in an attachment (1966-1985). Currently, volumetric measurements made with 5-gallon bucket counts and have been used as the basis for calculation since 2002. Historically, a level and leveling rod were used to measure elevation on a point grid and calculations made from the difference in the empty and full basin surveys. From Craig Creel regarding change to bucket counts from a regular survey: We tried to duplicate the historical survey methods, but the transit endpoints were not monumented so we created new ones based on the old notes. One problem with the elevational surveys was the limited number of survey points due to the small size of the basin. Slope points that are usually not included in the calculations because of the difficulty of surveying the exact point when the basin is empty were included just to have a reasonable number of points used in the calculations rater than just a few when the slope is not included (The basins have a large area of sloping sides.). This was one of the reasons we decided to change methods
