A watershed's water quality is infl uenced by contaminanttransport pathways unique to each landscape. Accurate information on contaminant-pathways could provide a basis for mitigation through well-targeted approaches. Th is study determined dynamics of nitrate-N, total P, Escherichia coli, and sediment during a runoff event in Tipton Creek, Iowa. Th e watershed, under crop and livestock production, has extensive tile drainage discharging through an alluvial valley. A September 2006 storm yielded 5.9 mm of discharge during the ensuing 7 d, which was monitored at the outlet (19,850 ha), two tile-drainage outfalls (total 1856 ha), and a runoff fl ume (11 ha) within the sloped valley. Hydrograph separations indicated 13% of tile discharge was from surface intakes. Tile and outlet nitrate-N loads were similar, verifying subsurface tiles dominate nitrate delivery. On a unit-area basis, tile total P and E. coli loads, respectively, were about half and 30% of the outlet's; their rapid, synchronous timing showed surface intakes are an important pathway for both contaminants. Flume results indicated fi eld runoff was a signifi cant source of total P and E. coli loads, but not the dominant one. At the outlet, sediment, P, and E. coli were reasonably synchronous. Radionuclide activities of 7 Be and 210 Pb in suspended sediments showed sheet-and-rill erosion sourced only 22% of sediment contributions; therefore, channel sources dominated and were an important source of P and E. coli. Th e contaminants followed unique pathways, necessitating separate mitigation strategies. To comprehensively address water quality, erosioncontrol and nitrogen-management practices currently encouraged could be complemented by buff ering surface intakes and stabilizing stream banks.
A comprehensive set of soil characteristics were examined to determine the effect of soil on the transport of agrichemicals to ground water. This paper examines the relation of local soil characteristics to concentrations and occurrence of nitrate, atrazine (2‐chloro‐4 ethylamino‐6‐isopropylamino‐s‐trazine), and atrazine residue [atrazine + deethylatrazine (2‐amino‐4‐chloro‐6‐isopropylamino‐s‐triazine) + deisopropylatrazine (2‐amino‐4‐chloro‐6‐ethylamino‐s‐triazine)] from 99 wells completed in unconsolidated aquifers across the midwestern USA. The occurrence and concentrations of nitrate and atrazine in ground water were directly related to soil characteristics that determine the rate of water movement. The substantial differences in the relations found among soil characteristics and nitrate and atrazine in ground water suggest that different processes affect the transformation, adsorption, and transport of these contaminants. A multivariate analysis determined that the soil characteristics examined explained the amount of variability in concentrations for nitrate (19.0%), atrazine (33.4%), and atrazine residue (28.6%). These results document that, although soils do affect the transport of agrichemicals to ground water, other factors such as hydrology, land use, and climate must also be considered to understand the occurrence of agrichemicals in ground water.
Abstract:To support the USDA Agricultural Research Service Conservation Effects Assessment Project, a publicly available Web-based watershed data system, named Sustaining the Earth's Watersheds-Agricultural Research Data System (STEWARDS), was developed to provide data search, viewing, and downloading capabilities. The objectives of this paper are to (1) describe the data within STEWARDS, (2) describe the process of accessing watershed data and (3) provide an overview of the system management. STEWARDS is a data delivery system with a geographic information system interface, using space, time, and topic as key fields for searching an extensive database of soil, water, climate, land management, and socio-economic data from multiple long-term research watersheds. STEWARDS facilitates (1) researchers in obtaining USDA Agricultural Research Service historic watershed data for hydrological studies; (2) modelers in retrieving measured data over extensive time periods for model calibration and validation in watershed assessments to support CEAP; and (3) watershed managers, partners, and stakeholders in accessing long term data to support decisionmaking for selecting effective conservation practices. Key words: Conservation Effects Assessment Project (CEAP)-database access and usedatabase operation-database structure-Sustaining the Earth's Watersheds-Agricultural Research Data System (STEWARDS)The Sustaining the Earth's WatershedsAgricultural Research Data System (STEWARDS) database was developed to organize, store, and provide Web-based access to data from USDA Agricultural Research Service (ARS) benchmark watersheds associated with the Conservation Effects Assessment Project (CEAP) Cropland component and eventually other national projects. The CEAP network currently includes 14 instrumented long-term watersheds having, in some cases, more than 60 years of potentially available data. These watershed studies are spread over a range of geophysical contexts and were initiated independently by researchers studying problems at specific locations. Consequently, the data collected vary, the methods for collecting and storing the data vary, and insufficient (and variable) effort has been expended to store, organize, or deliver the data at the national level. As a result, data that are critical for the success of CEAP, or other hydrologic analyses, are not consistently available to users (Steiner et al. 2003).Recognizing that data embodied in this network are now increasingly relevant to the CEAP, a team of researchers and information technology staff within CEAP was requested to create a database system capable of delivering the long-term USDA ARS watershed data for research purposes. This team is represented in the author list, and team operations necessary to achieve the objectives are described in Steiner et al. (2008). Here, our objectives are to (1) describe the data within STEWARDS, (2) describe the process of accessing watershed data and (3) provide an overview of the system management. Objectives 1 and 2 are necessaril...
The USDA Agricultural Research Service has supported watershed research since the 1930s. Data from USDA Agricultural Research Service watersheds have been disseminated independently at each location, hindering multi-site analyses. A virtual team spanning diverse organizational units developed a web-based system, Sustaining the Earth's WatershedsAgricultural Research Data System (STEWARDS) that allows users to search, visualize, and download soil, water, climate, management, and economic data from Conservation Effects Assessment Project benchmark watersheds. The objective of this paper is to provide an overview of STEWARDS and discuss challenges that were met to deliver STEWARDS on time, according to requirements, and within available resources. The information technology specialists had to understand that vague and changing requirements are reasonable for a system to support loosely coupled research across diverse watersheds. Researchers and data managers had to learn to communicate clearly about their data. Open communication, respect for perspectives and constraints of others, and a shared commitment to the goal provided the basis for trust. Anticipated benefits of STEWARDS include data preservation, increased data use, and facilitation of hydrological research.
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