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As environmental data are increasingly recognized as important, increased attention is focused on data quality. A critical component of quality assurance and quality control (QA/QC) is implementing tests for problems like missing data, outliers, and changes that might be too abrupt or too slow to be real, and most implementations involve coding the combinational logic of tests in if-then-else constructs to arrive at outcomes or actions depending on the inputs. Herein we propose two alternative implementation methods that avoid if-then-else logic and therefore can be used to perform more complex QA/QC screens on data from stations with one or more sensors. The objectives of this technical note are to describe the methods and to demonstrate their performance using realistic examples with existing data. Both new methods use truth tables to express and implement logic; the first method expands a truth table with N tests to all 2N possible combinations and uses that as a lookup table, while the second method matches test patterns in the truth table using its original unexpanded form. The if-then-else method and the two new methods are illustrated with a simple example of air temperature measurement for scenarios with one, two, or three (redundant) sensors. The relative advantages and disadvantages of each method are discussed. Scalability of the new methods is illustrated using measurements from a local weather station. If provided both the test results and either the expanded truth table (for the lookup method) or the original truth table (for the pattern-match method), the core code was general. The flexibility of these methods should increase the power of QA/QC programs for environmental or other time series data. [ABSTRACT FROM AUTHOR]

Spatial irrigation of agricultural crops using site-specific variable-rate irrigation (VRI) systems is beginning to have widespread acceptance. However, optimizing the management of these VRI systems to conserve natural resources and increase profitability requires an understanding of the spatial crop responses. In this research, we utilize a recently developed spatially explicit analysis model to reanalyze spatial corn yield data. The specific objectives of this research were to (1) calculate a suite of estimates (estimated yield, rainfed yield, maximum yield, and irrigation at maximum yield) and provide credible intervals (measures of uncertainty) around these estimates for comparing with the previous analysis, and (2) examine whether the conclusions from this rigorous re-analysis were different from the prior analysis and if the results would force any modifications to the conclusions obtained with the prior analyses. The spatially explicit analysis was achieved using a mixed model formulation of bivariate penalized smoothing splines and was implemented in a Bayesian framework. This model simultaneously accounted for spatial correlation as well as relationships within the treatments and had the ability to contribute information to nearby neighbors. The model-based yield estimates were in excellent agreement with the observed spatial corn yields and were able to estimate the high and low yields more accurately than the previous analysis. Credible intervals were calculated around the estimates, and the majority encompassed the observed yields. After calculating estimates of yield, we then calculated estimates of other response variables, such as rainfed yield, maximum yield, and irrigation at maximum yield. These estimated response variables were then compared with previous results from a classical statistical analysis. Our conclusions supported the original analysis in identifying significant spatial differences in crop responses across and within soil map units. These spatial differences were great enough to be considered in irrigation system design and management. The major improvement in the 2014 re-analysis is that the model explicitly considered spatial dependence in calculating the estimated yields and other variables and thus should provide improved estimates of the impact of spatial differences for use in irrigation system design and management. [ABSTRACT FROM AUTHOR]

Streamflow monitoring typically relies on the establishment of a rating curve that describes the relationship between stage and streamflow. This rating curve is based on direct and indirect measurements of discharge at various stages and application of open-channel hydraulics principles. Potential measurement errors increase with out-of-bank flow conditions because of difficulties in measuring flow velocity and flow depth during increased stages. With increasing frequency of large rain events attributed to climate change, it becomes critical to have an accurate rating curve for flood flows. This article presents techniques that, when used concurrently, can help identify errors and reduce uncertainty in the rating curve. They include commonly used techniques such as comparison of mean annual discharge per unit drainage area with those from nearby watersheds having similar characteristics. In addition, new techniques are proposed based on the hydrologic budget of a storm event and the analysis of the change inflow relative to time and stage. The methodology was tested using flow data from the 72 km2 Goodwater Creek Experimental Watershed in northeast Missouri. Results showed that the original rating curve overestimated flow values by 30% for out-of-bank conditions. A revised rating curve was proposed based on channel conveyance. This revised rating curve satisfied the requirements of water balance and change inflow relative to time and stage. The resulting annual flows were reduced by up to 30%, better matching those of nearby watersheds. These techniques are useful for retrospective analysis of flow data series and for identifying rating curve inconsistencies. [ABSTRACT FROM AUTHOR]

Year-to-year dynamics in weather affect both the timing of application and the potential hydrologic transport of pesticides. Further, the most commonly used pesticides dissipate in the environment during the growing season. Interactions among these factors - hydrology, timing of application and dissipation kinetics - hinder the detection of temporal trends in transport. It is increasingly important to be able to discern such trends, to judge effectiveness of management practices or to determine whether observed changes were caused by management or weather. In previous work, a cumulative vulnerability index was developed to account for these three factors. It explained 63% of annual variation in atrazine load in the Goodwater Creek Experimental Watershed (GCEW). The objectives of the current work were (i) to generalize the cumulative vulnerability index to explicitly account for variation in watershed size, area treated with atrazine and average application rate; (ii) to test the overall performance on watersheds showing such variation; and (3) to test whether the generalized index properly accounted for the additional input parameters. The generalized index was tested using data from GCEW (73.7 km2) and seven additional watersheds in the northeast Missouri claypan region that varied in size from 212 to 1180 km2 and from 4% to 23% of watershed area planted to corn or sorghum. Across 32 site-years, the generalized index explained 84% of variation in annual atrazine load. Further, tests of residuals showed no dependence on either watershed area or fraction of area planted to corn and sorghum, indicating that these parameters were properly integrated into the index. The performance of the index supports the conclusion that data obtained from GCEW is representative of the Mark Twain Lake Basin and likely the entire Central Claypan Major Land Resource Area. Published 2012. This article is a U.S. Government work and is in the public domain in the USA. [ABSTRACT FROM AUTHOR]

Lerch, R.N., E.J. Sadler, K.A. Sudduth, C. Baffaut, and N.R. Kitchen, 2010. Herbicide Transport in Goodwater Creek Experimental Watershed: I. Long-Term Research on Atrazine. Journal of the American Water Resources Association (JAWRA) 1-15. DOI: 10.1111/j.1752-1688.2010.00503.x Atrazine continues to be the herbicide of greatest concern relative to contamination of surface waters in the United States (U.S.). The objectives of this study were to analyze trends in atrazine concentration and load in Goodwater Creek Experimental Watershed (GCEW) from 1992 to 2006, and to conduct a retrospective assessment of the potential aquatic ecosystem impacts caused by atrazine contamination. Located within the Central Claypan Region of northeastern Missouri, GCEW encompasses 72.5 km of predominantly agricultural land uses, with an average of 21% of the watershed in corn and sorghum. Flow-weighted runoff and weekly base-flow grab samples were collected at the outlet to GCEW and analyzed for atrazine. Cumulative frequency diagrams and linear regression analyses generally showed no significant time trends for atrazine concentration or load. Relative annual loads varied from 0.56 to 14% of the applied atrazine, with a median of 5.9%. A cumulative vulnerability index, which takes into account the interactions between herbicide application, surface runoff events, and atrazine dissipation kinetics, explained 63% of the variation in annual atrazine loads. Based on criteria established by the U.S. Environmental Protection Agency, atrazine reached concentrations considered harmful to aquatic ecosystems in 10 of 15 years. Because of its vulnerability, atrazine registrants will be required to work with farmers in GCEW to implement practices that reduce atrazine transport. [ABSTRACT FROM AUTHOR]

Lerch, R.N., E.J. Sadler, C. Baffaut, N.R. Kitchen, and K.A. Sudduth, 2010. Herbicide Transport in Goodwater Creek Experimental Watershed: II. Long-Term Research on Acetochlor, Alachlor, Metolachlor, and Metribuzin. Journal of the American Water Resources Association (JAWRA) 1-15. DOI: 10.1111/j.1752-1688.2010.00504.x Farmers in the Midwestern United States continue to be reliant on soil-applied herbicides for weed control in crop production, and herbicide contamination of streams remains an environmental problem. The main objective of this study was to analyze trends in concentration and load of acetochlor, alachlor, metolachlor, and metribuzin in Goodwater Creek Experimental Watershed (GCEW) from 1992 to 2006. A secondary objective was to document the effects of best management practices (BMPs) implemented within GCEW on herbicide transport trends. Median relative herbicide loads, as a percent of applied, were 3.7% for metolachlor, 1.3% for metribuzin, 0.36% for acetochlor, and 0.18% for alachlor. The major decrease in alachlor use and increase in acetochlor use caused shifts in flow-weighted concentrations that were observed over the entire concentration range. The smaller decrease in metolachlor use led to a consistent decreasing time trend only for the upper end of the concentration distribution. Metribuzin also showed moderate decreases in concentration with time since 1998. Annual loads were generally correlated to second quarter discharge. Despite extensive education efforts in the watershed, conservation BMPs within GCEW were mainly implemented to control erosion, and therefore had no discernable impact on reducing herbicide transport. Overall, changes in herbicide use and second quarter discharge had the greatest effect on trends in flow-weighted concentration and annual load. [ABSTRACT FROM AUTHOR]

Variability in soil landscapes and their associated properties can have significant effects on erosion and deposition processes that affect runoff and transport of pesticides. Simulation models are one way in which the effects of landscapes on these processes can be assessed. This simulation study evaluated the effects of variations in landscape position on runoff and dissolved atrazine utilizing a calibrated farm- and field-scale Agricultural Policy/Environmental eXtender (APEX) model. Twelve agricultural plots (18 m x 189 m) in the Goodwater Creek watershed, a 7250 ha agricultural area in north-central Missouri, were simulated. Plots were treated with three tillage and herbicide management systems for two grain crop rotations. Each plot contained three landscape positions (summit, backslope, and footslope) along with two transition zones. Runoff was measured and samples were collected from 1997 to 2002 during the corn year of the crop rotations. Runoff samples were analyzed for dissolved atrazine. The model was calibrated and validated for each plot with event data from 1997 to 1999 and from 2000 to 2002, respectively. APEX reasonably simulated runoff and dissolved atrazine concentrations, with coefficients of determination (r²) values ranging from 0.52 to 0.98 and from 0.52 to 0.97, and Nash-Sutcliffe efficiency (NSE) values ranging from 0.46 to 0.94 and from 0.45 to 0.86 for calibration and validation, respectively. The calibrated model was then used to simulate variable sequencing of landscape positions and associated soil properties as well as variable lengths of landscape positions. Simulated results indicated that the runoff and the atrazine load at the plot outlet increased when the backslope length increased while keeping the steepness constant. The maximum simulated runoff among different sequences of landscape positions occurred when the backslope position was located adjacent to the outlet. Results from this study will be helpful to managers in placement of conservation practices on sensitive landscapes for improvement in water quality. [ABSTRACT FROM AUTHOR]

A web-based, data retrieval application was developed (Sustaining the Earth's Watersheds, Agricultural Research Data System, or STEWARDS) as part of the USDA-ARS Conservation Effects Assessment Project (CEAP) to increase the availability and accessibility of scientific data to the research community. The STEWARDS application is GIS-based and couples temporal and spatial aspects of data collected from each site within a watershed. The STEWARDS database and software design accommodates research data with heterogeneous characteristics and format, and captures rich descriptive information that is important to understand the data from complex, dynamic research programs. The database includes soil, water, climate, land management, and socio-economic data from multiple watersheds across the U.S. and can provide data commonly needed for hydrologic modeling and assessments. The release of STEWARDS marks an advance in the research capacity for the ARS research watershed network by improving access to well-documented and consistently organized data and is becoming the prototype of additional data and software designs for other ARS research projects. [ABSTRACT FROM AUTHOR]

The MarkTwain Lake/Salt River Basin was selected as one of the USDA Agricultural Research Service benchmark watersheds for the Conservation Effects Assessment Project because of documented soil and water quality problems and broad stakeholder interest. The basin is located in northeastern Missouri within the Central Claypan Region, and it is the source of water to Mark Twain Lake, the major public water supply in the region. At the outlet to Mark Twain Lake, the basin drains 6,417 km² (2,478 m²), including 10 major watersheds that range in area from 271 to 1,579 km² (105 to 609 m²). The basin is characterized by flat to gently rolling topography with a predominance of claypan soils that result in high runoff potential. The claypan soils are especially. vulnerable to soil erosion, which has degraded soil and water quality throughout the ,basin, and to surface transport of herbicides. Results from cropping system best management practice studies showed that no-till cropping systems did not reduce surface runoff compared to tilled systems, and no-till led to increased transport of soil-applied herbicides. A major challenge is the need to develop cropping systems that incorporate herbicides yet maintain sufficient crop residue cover to control soil erosion. Results of the Soil and Water Assessment Tool model simulations showed that the model was capable of simulating observed long-term trends in atrazine concentrations and loads and the impact of grass waterways on atrazine concentrations. Current and future research efforts will continue to focus on best management practice studies, development of needed tools to improve watershed management, and refinements in the calibration and validation of the Soil and Water Assessment Tool model. [ABSTRACT FROM AUTHOR]

Presents a study on ammonia volatilization from marsh-pond-marsh constructed wetlands treating swine wastewater in Greensboro, North Carolina. Rates of volatilization; Determination of the dominant nitrogen removal mechanism; Preference for continuous marsh systems.

Examines the impact of site-specific crop management with a center pivot irrigation system on water conservation, plant stress reduction and fertilizer loss reduction in the American Coastal Plains. Modifications on conventional center pivot systems; Requirements for site-specific management of crop production; Features of the water application and irrigations systems.