Santee Experimental Forest, Watershed 77: streamflow, water chemistry, water table, and weather data: 2nd edition

This data publication contains streamflow, water chemistry, water table and weather data measured at the Watershed 77 (WS77) on the Santee Experimental Forest near Cordesville, South Carolina from 1964 to 2022. The major treatments imposed on this watershed over its history have been forest thinning and prescribed fire. Watershed 77 also suffered major damage during Hurricane Hugo in September 1989 (as did the control Watershed 80), which is reflected in the measurement periods. Daily streamflow records are provided from 1964-1981, November 1989-2000, and 2003-2022 as well as 10- or 15-minute streamflow from 2003-2022. Approximately weekly water chemistry samples were collected upstream of the Watershed 77 weir from 1976-1982 and 1989-1994. From 2003-2022 stream water samples were collected during periods of active flow by an automated sampler on a flow-proportional basis, and starting in 2006 additional water quality parameters were measured in situ on an approximately weekly basis. Well water levels were monitored manually approximately every two weeks from 1964-1971 (in a network of 24 non-recording wells) and 1992-1995 (in a network of 42 non-recording wells) on Watershed 77. Hourly well water levels were electronically recorded from 2005-2022. Daily precipitation was recorded manually from 1963-1984 at five different gauges near WS77. Daily precipitation was recorded manually at the Met 5 station from 1963-1966 and electronically from 1989-1997. Daily temperatures were recorded at the Met 5 station from 1996-2000. From September 2001 through 2022 hourly air temperature, soil temperature, and rainfall were recorded at the Met 5 station. In 2020 a major new, long-term project was initiated to convert most of the watershed area from an existing loblolly pine to a longleaf pine dominated system. Harvesting operations in each of three treatment areas (Regeneration, Group Selection, and Thinning) began in April 2020 and continued, with lengthy delays resulting from wet site conditions, until November 2021. An initial site preparation prescribed burn was conducted on March 13, 2022.
The purpose of Watershed 77, when established in 1963, was to provide a site for research on understanding runoff and evapotranspiration processes and the water balance. Since then, research has been conducted on the effects of management treatments such as thinning and periodic prescribed burns (taking place since 1976) as well as natural disturbances (such as Hurricane Hugo in 1989) on the hydrology, water quality, carbon dynamics, soils and vegetation of low gradient, poorly drained forested watersheds in the South Carolina Coastal Plain. One of the approaches adopted in the new longleaf pine restoration project is to use a paired watershed approach (with Watershed 80 serving as the control watershed) of monitoring to examine the short and long-term effects of the restoration on watershed hydrology and carbon dynamics. This is being backed up by process-based modeling approaches as well.
* This metadata applies to the raw data available through the full data publication download. Summary data available through the online query are calculated based on user selections and should be carefully interpreted. These data are a newer edition of Amatya and Trettin (2019, https://doi.org/10.2737/RDS-2019-0033). This second edition includes the addition of data from 2020-2022, but it also includes some data corrections. Streamflow measurements from 2003-2020 were recalculated based on a discovery made concerning the added metallic weir plate to the concrete V-notch weir infrastructure likely sometime later in 1991 after Hurricane Hugo in 1989. So this same concern applies to the streamflow data from 1992-2002 also; however, the process to correct these data is very time-consuming and these older data have not yet been corrected so instead have been set to missing. Many days of data from this 1992-2002 (11-year) period were already missing, anyway, for various reasons, including the extreme drought affecting SC between 1999 and 2002. For example, only 2328 days, or some 58% of the possible total days (for the 11-year period), are available. In fact, data from most of 1995, half of 1999, most of 2000 and all of 2001 are missing. This data package will be updated and those corrected values added as soon as they are available (the first edition contains the uncorrected data also from 1992-2002 if it were actually needed for some reason). There were also some corrections to a few water quality measurements because of errors that were discovered in the original data prepared at the Coweeta Analytical Laboratory. Data updates are fully described in the process steps section. For more information about the Santee Experimental Forest go to: https://www.fs.usda.gov/research/srs/forestsandranges/locations/santee