U.S. Department of Agriculture Agricultural Research Service ...

WATER RESOURCES RESEARCH, VOL. 47, W08701, doi:10.1029/2010WR010056, 2011

U.S. Department of Agriculture Agricultural Research Service Mahantango Creek Watershed, Pennsylvania, United States: Physiography and history Ray B. Bryant,1 Tamie L. Veith,1 Gary W. Feyereisen,2 Anthony R. Buda,1 Clinton D. Church,1 Gordon J. Folmar,1 John P. Schmidt,1 Curtis J. Dell,1 and Peter J. A. Kleinman1 Received 29 September 2010; revised 31 May 2011; accepted 8 July 2011; published 20 August 2011.

The 420 km2 Mahantango Creek Watershed, within the Northern Appalachian Ridges and Valleys Province, is a subwatershed of the Susquehanna River, which flows to the Chesapeake Bay. Research on agricultural management and hydrologic processes controlling nonpoint source nutrient loss is conducted within a 7.3 km2 subwatershed designated WE‐38. The physical watershed description and history of monitoring and research activities contained herein and the data discussed in three companion papers are intended to facilitate the use and interpretation of archived databases on the U.S. Department of Agriculture Agricultural Research Service’s Sustaining the Earth’s Watersheds—Agricultural Research Data System (STEWARDS) Web site. Sources for regional geospatial data not maintained on STEWARDS are also identified.

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Citation: Bryant, R. B., T. L. Veith, G. W. Feyereisen, A. R. Buda, C. D. Church, G. J. Folmar, J. P. Schmidt, C. J. Dell, and P. J. A. Kleinman (2011), U.S. Department of Agriculture Agricultural Research Service Mahantango Creek Watershed, Pennsylvania, United States: Physiography and history, Water Resour. Res., 47, W08701, doi:10.1029/2010WR010056.

1. Introduction [2] Long‐term experimental watersheds were instrumented by the U.S. Department of Agriculture (USDA) Agricultural Research Service (ARS) regional watershed research centers in the late 1960s. With reorganization of ARS into national programs in 1976, research to determine major hydrologic factors affecting runoff and erosion was expanded to address issues of water quantity and water quality [Pionke and Weaver, 1977]. Each watershed center addresses specific research needs within its respective major land resource area, as defined by Natural Resources Conservation Service (NRCS) [2006], to meet the national objective of “enhancing watersheds’ capabilities to deliver safe and reliable fresh water” [ARS, 2007]. [3] In response to a congressional mandate, the Conservation Effects Assessment Project (CEAP) was initiated in 2002 to quantify environmental benefits of conservation practices and to provide an accounting of the value of public expenditures for conservation programs [Richardson et al., 2008]. Partners in CEAP include the USDA’s NRCS, the National Institute of Food and Agriculture (NIFA), formerly called the Cooperative State Research, Education, and Extension Service (CSREES), ARS, and other federal agencies. Researchers responsible for existing long‐term experi1 Pasture Systems and Watershed Management Research Unit, Agricultural Research Service, USDA, University Park, Pennsylvania, USA. 2 Soil and Water Management Research Unit, Agricultural Research Service, USDA, St. Paul, Minnesota, USA.

This paper is not subject to U.S. copyright. Published in 2011 by the American Geophysical Union.

mental watersheds were charged with providing detailed data on water quality and conducting research on the effects of specific conservation practices on watershed scale water quantity and quality. In support of CEAP objectives, the Sustaining the Earth’s Watersheds—Agricultural Research Data System (STEWARDS), a digital repository for long‐term watershed monitoring data, has been developed and is publically available at http://www.ars.usda.gov/Research/docs. htm?docid=18622 [Sadler et al., 2008; Steiner et al., 2008]. [4] The Mahantango Creek Watershed was selected in 1966 as a USDA ARS experimental watershed in part because of the presence of a USGS stream gauge, which was established at the watershed outlet (USGS 01555500 East Mahantango Creek near Dalmatia, Pennsylvania; http:// waterdata.usgs.gov/nwis/nwisman/?site_no=01555500) in 1930 [Gburek, 1977]. From 1967 to 1976, a network of up to 43 rain gauges, 8 meteorological sites, and 6 stream gauging stations provided uniform coverage across this 420 km2 watershed. In response to the 1976 reorganization of ARS, the decision was made to cease monitoring the entire Mahantango Creek Watershed and focus resources on a 7.3 km2 watershed designated WE‐38. [5] The objective of this paper is to provide physiographical and historical information on the 420 km2 Mahantango Creek Watershed and the WE‐38 subwatershed. The WE‐38 watershed has been the focus of intensive research on impacts of agriculture on water quality, effectiveness of conservation practices in protecting water quality, and development of new management and conservation practices. This paper describes geographic information system (GIS) data layers available for WE‐38 through STEWARDS and other public‐access data repositories. Historical hydrologic data are available for WE‐38 on STEWARDS and are discussed

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BRYANT ET AL.: DATA AND ANALYSIS NOTE

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Figure 1. Topography (in meters above mean sea level) and instrumentation site locations in the WE‐38 watershed and the location of WE‐38 within the Mahantango Creek and Chesapeake Bay watersheds. in three companion papers. By documenting these long‐term databases, this series of papers provides natural resource and environmental professionals with informed access to data from an area that is representative of the physiography and land use of a significant proportion of the Chesapeake Bay Watershed.

2. Mahantango Creek Watershed [6] Mahantango Creek Watershed drains to the Susquehanna River, which accounts for 48% of the annual river flow to the Chesapeake Bay. Located approximately 48 km north of Harrisburg in Northumberland County, Pennsylvania, Mahantango Creek Watershed encompasses two agricultural valleys bounded by three long forested ridges (Figure 1) and is generally representative of major land resource area (MLRA) 147, the Northern Appalachian Ridges and Valleys Province [NRCS, 2006]. Resistant sandstones and conglomerate bedrock primarily compose Mahantango Creek Watershed’s ridge crests (350–510 m elevation), while

valleys (125–300 m elevation) are underlain by less resistant shales and siltstones. Limestone and associated karst topography, which is common throughout the MLRA, is absent from the valley floors. The resulting simplified hydrology of Mahantango Creek Watershed was one reason for originally selecting it as a research watershed. Mature forest covers the dominant ridge to the north, while cropland and pasture dominate the rolling hills of the watershed interior. Total area is approximately 44% cropland or pasture, 55% forested, and 1% urban and residential. [7] Soils on steep side slopes and ridge tops are well‐ drained, medium‐textured Dystrudepts [Urban, 1977]. Periglacial activity during the most recent glacial periods is evidenced by multiple colluvial deposits on lower foot slopes and valley floors. Soils in these landscape positions are medium‐ to fine‐textured Hapludults, Fragiudults, and Paleudults formed in residuum or colluvium derived from sandstones, siltstones, and shales [NRCS, 2006]. Soils with fragipans are associated with colluvial deposits on gentle slopes adjacent to valley bottoms and frequently give rise to

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perched water tables and saturation excess runoff. Well‐ drained to poorly drained medium‐ and fine‐textured soils are found in alluvium on floodplains along drainage ways. [8] The climate is temperate and humid. Mean annual precipitation is 1080 mm; 760 mm annual snowfall contributes to approximately 10% of this total precipitation [Gburek, 1977]. Evapotranspiration is approximately 560 mm per year. Average annual runoff from Mahantango Creek Watershed is approximately 46% of annual precipitation (500 mm), with base flow comprising approximately 70% of total streamflow. An unconfined, highly transmissive, highly fractured, shallow bedrock layer with low storativity controls subsurface flow. Hydrologically active groundwater zones are considered limited to 60 m depth [Pionke and Weaver, 1977]. [9] From 1967 to 1972, a network of 6 stream gauging stations, 8 meteorological sites, and 40 rain gauges were located and monitored to give uniform coverage of the Mahantango Creek Watershed. The system, which used Fisher and Porter digital punch paper tape rain gauges recording at 5 min intervals to the nearest 2.5 mm, is described by Carr [1973]. Ten rain gauges were removed in 1972, and 10 more rain gauges were removed in 1973. In 1976, ARS established National Programs, and research objectives in the Mahantango Creek Watershed became more sharply focused on water quality. In response to this change, resources and research activities were largely consolidated within the 7.3 km2 WE‐38 subwatershed.

3. WE‐38 Experimental Watershed [10] The WE‐38 Experimental Watershed is a headwater catchment located in the north central portion of Mahantango Creek Watershed (Figure 1). The name WE‐38 is derived from nomenclature that identifies the monitoring category and grid location within Mahantango Creek Watershed and carries no local meaning or recognition, but this designation is used in research publications. Tributary 17302 to Little Mahantango Creek drains WE‐38 from the crest of the northern ridge (503 m elevation) southward to a compound weir (215.6 m elevation) at 40°42′16″N, 76°35′ 16″W. The physiography and land use are representative of the larger Mahantango Creek Watershed. [11] Two bedrock formations of Late Devonian‐Early Mississippian age occur in WE‐38. The predominantly shale Trimmers Rock formation outcrops at the watershed outlet in a near‐horizontal position. The younger, overlying Catskill formation consists of interbedded shales, siltstones, and sandstones coarsening to a relatively pure quartz‐sandstone‐ conglomerate outcrop at the ridge crest to the north. The dip of the Catskill strata increases from almost horizontal near the valley floor to approximately 30° northward at the ridge top.

4. Geospatial Data [12] Light detection and ranging (lidar) data and color orthophotography for WE‐38 Watershed were collected on 26 March 2007 at horizontal and vertical resolutions of 0.5 and 0.15 m, respectively. A digital elevation model (DEM), also known as digital terrain model (DTM), was obtained by using the ArcGIS 9.3 software developed by Environmental Systems Research Institute, Inc. (http://www.esri.com/), to resample the submeter lidar data into a 5 m horizontal res-

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olution. After logging on to STEWARDS with an email address, the 5 m DEM is available through direct ftp download or by selecting it as an additional option when saving data from a specific query. The DEM layer is projected in NAD83 UTM 18N, and elevations range from 212 to 506 m with a mean of 294.8 m. Catchment boundaries and streams were delineated from both the lidar and 5 m DEM using a basic eight‐directional‐flow algorithm through ArcGIS 9.3. The resulting GIS layers were reconciled and ground truthed to create the WE‐38 watershed boundary and stream network data layers that are available on STEWARDS and accessible in the same manner as the DEM. [13] Agricultural land throughout the watershed is visually surveyed every year by on‐site USDA ARS technicians for changes in land use, management, and boundaries, with farmer interviews conducted as needed. This proprietary information is maintained strictly within the ARS unit for research purposes on the effects of land management on the environment. However, a wealth of data is publically available online. For example, USDA National Agricultural Statistics Service (NASS) currently provides Pennsylvania Cropland Data Layers (CDL) for 2002, 2008, and 2009 through the USDA NRCS Geospatial Data Gateway (http:// datagateway.nrcs.usda.gov). These GIS raster layers contain categorized, georeferenced land cover information that has been produced from satellite imagery and ground truthed. Additionally, USGS funded a 4 year, 30 m resolution, land cover data series for Chesapeake Bay (1984, 1992, 2001, and 2006), which is publically available through Pennsylvania Spatial Data Access (PASDA) (http://www.pasda.psu.edu). On the basis of these data, WE‐38 has experienced virtually no change in land cover in the past 20 years and is divided into 2.3% developed area, 39.6% woodlands, 3.2% pasture, and 54.9% cultivated land. [14] The Soil Survey Geographic (SSURGO) database, created and maintained by the USDA NRCS, is available directly through the USDA NRCS Web Soil Survey (http:// websoilsurvey.nrcs.usda.gov) as well as through both the USDA NRCS Geospatial Data Gateway and PASDA. This database contains georeferenced spatial layers and relational tabular attribute information at the county‐level survey scale. Numerous other data layers, including DEMs, orthophotoimagery, and special interest databases, are also publically available through the USDA NRCS Geospatial Data Gateway or PASDA.

5. Mahantango Creek Watershed Data Reports [15] Mahantango Creek Watershed data reports are intended to facilitate use and interpretation of archived databases in STEWARDS by documenting methods and describing data characteristics. Four types of basic data that were collected within WE‐38 are discussed in the accompanying series of data reports. Collection details and a discussion of precipitation are provided by Buda et al. [2011b]. Detailed descriptions of the outlet weir, instrumentation, chronology of measurement, discharge data, and examples of data use are described by Buda et al. [2011a]. Methods for sample collection and water quality analysis, a discussion of concentrations and loads, and implications for management effects on nonpoint sources of contaminants are presented by Church et al. [2011]. Databases are available from STEWARDS at http://www.ars.usda.gov/Research/docs.

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htm?docid=18622. Guidelines for navigating STEWARDS are provided within the system’s interface by Sadler et al. [2008] and at http://www.ars.usda.gov/Research/docs. htm?docid=18644. A descriptive list of data available for the Mahantango Creek Experimental Watershed and WE‐38, access information for these data, and relevant links are available at http://www.ars.usda.gov/Services/docs.htm?docid=21452.

[18] Acknowledgments. The existence, accuracy, and consistency of the Mahantango Creek Watershed data are a testament to the dedication of numerous past and present USDA–ARS employees. This study is a contribution from the USDA–ARS Pasture Systems and Watershed Management Research Unit with collaboration and financial support from the USDA–NRCS. All programs and services of the U.S. Department of Agriculture are offered on a nondiscriminatory basis without regard to race, color, national origin, religion, sex, age, marital status, or disability. Mention of trade names does not imply endorsement by the USDA.

6. Research in the WE‐38 Experimental Watershed

References

[16] Since 1976, when streamflow and water quality monitoring were focused within WE‐38, a number of different types of hydrologic and water quality research studies have been conducted. These studies have largely focused on improving our understanding of nutrient transport to better guide nutrient management planning in the Chesapeake Bay and throughout the United States. Some examples of recent research conducted in WE‐38 include (1) determining subsurface pathways and travel times [Gburek and Urban, 1990; Gburek and Folmar, 1999a, 1999b; Gburek et al., 1999], (2) determining nutrient export mechanisms [Gburek et al., 1986; Pionke et al., 1996; Lindsey et al., 2001], (3) describing surface runoff generation mechanisms during storm events [e.g., Needelman et al., 2004; Gburek et al., 2006; Buda et al., 2009a], (4) characterizing phosphorus losses in surface runoff using rainfall simulation on field plots [e.g., McDowell and Sharpley, 2002; Sharpley and Kleinman, 2003; Kleinman et al., 2006; Srinivasan et al., 2007] or packed soil boxes [e.g., Kleinman et al., 2004; Bechmann et al., 2005; Shigaki et al., 2007], (5) characterizing phosphorus losses in subsurface flow [e.g., McDowell and Sharpley, 2001; Kleinman et al., 2003, 2005; Bechmann et al., 2005], (6) determining controls of phosphorus release to runoff from land‐applied manure [e.g., Kleinman et al., 2002a, 2002b; Kleinman and Sharpley, 2003], (7) quantifying phosphorus losses at a hillslope scale [e.g., Needelman et al., 2004; Buda et al., 2009b], (8) quantifying phosphorus losses at the watershed scale [e.g., Gburek and Heald, 1974; Sharpley et al., 1999, 2008a], (9) identifying critical source areas of phosphorus in runoff using monitoring [e.g., Gburek and Sharpley, 1998; Weld et al., 2001; Gburek et al., 2002] and modeling [e.g., Srinivasan et al., 2005; Veith et al., 2005] techniques, (10) developing, testing, and refining nutrient management indices for phosphorus [e.g., Gburek et al., 2000; Sharpley et al., 2001, 2008b; Weld et al., 2002] and for phosphorus and nitrogen [McDowell et al., 2002], (11) testing novel agricultural amendments to reduce the mobility of phosphorus in soils [e.g., Stout et al., 1998, 2000; Callahan et al., 2002], and (12) parameterizing water quality models and evaluating the impact of land use change in conjunction with CEAP [Van Liew et al., 2007; Veith et al., 2008, 2011]. These studies provide insight into physical characteristics and landscape processes that control hydrology, streamflow, and nutrient export from the watershed. [17] The public availability of monitoring data for the WE‐38 watershed provides new opportunities for scientists to contribute to the existing body of knowledge within the watershed and expand the utility of these data through comparative studies across multiple watersheds. Data users are encouraged to contact the lead author for collaborative assistance with analyzing and interpreting these data.

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