Goodwater Creek Experimental Watershed Research Articles

Validating the Soil Vulnerability Index for a claypan watershed

Assessment studies of conservation efforts have shown that best management practices were not always implemented in the most vulnerable areas where they are most needed. While complex computer simulation models can be used to identify these areas, resources needed for using such models are beyond reach for most water resources managers. Soil and water conservationists need simple, spatially explicit tools such as the USDA-NRCS's Soil Vulnerability Index (SVI) to evaluate the inherent vulnerability of soils and the risk they pose to water quality when used for row crop agriculture. In this study, the SVI was evaluated in the Goodwater Creek Experimental Watershed (GCEW), a claypan watershed in Missouri, using three methods: professional judgment, comparison to the Conductivity Claypan Index (CCI) developed specifically for claypan soils, and comparison to model results. Factors affecting the critical areas identified by each method were assessed and classified areas were compared. Slope and depth to claypan had the most variability in GCEW and were found to be influential in determining area classification by each index. While the original definition of SVI included the soil type representative slope from the USDA SSURGO database, slope values provided by a Digital Elevation Model (DEM) improved the index usefulness by classifying visibly degraded and non-degraded areas in different categories. High and moderately high vulnerability areas identified with SVI, CCI and model results with DEM slopes were consistent and matched professional judgment. Additional testing of SVI is recommended in areas characterized by soils of different permeability and under different climates.

Controls on nitrate‐N concentrations in groundwater in a Missourian claypan watershed

AbstractNitrogen (N) fertilizer applications have resulted in widespread groundwater nitrate‐N (NO3‐N) contamination in the U.S. Corn Belt. Goodwater Creek Experimental Watershed (GCEW) is an agricultural watershed in the claypan soil region of northeastern Missouri with a network of 96 wells at depths of 2.7–15.7 m. The objectives of this study were to (1) inspect the spatial and temporal variations of NO3‐N concentrations in GCEW's groundwater, particularly with well depth at scales ranging from individual well, well nest, and field to the entire watershed during the period 1991 to 2004; (2) understand the processes controlling the variability of NO3‐N concentrations in groundwater at various scales within GCEW; and (3) compare groundwater NO3‐N concentrations in GCEW to other agricultural watersheds in the U.S. Nitrate‐N concentrations were determined in more than 2000 samples collected from 1991 to 2004. Despite the low hydraulic conductivity of the claypan soils, considerable NO3‐N contamination of the glacial till aquifer occurred, with 38% of the wells exceeding 10 mg L−1. Groundwater recharge by preferential pathways through the claypan appeared to be the primary mechanism for NO3‐N movement to the aquifer. Changes in concentration with depth steadily increased to 8.5–10 m and then decreased with further depth. This pattern was consistent with decreased hydraulic conductivity in the Paleosol layer at 8.5–10 m, denitrification below this layer, and mixing of recent contaminated water with older uncontaminated water in the lowest strata. Only 19–23% of sampled wells exceeded 10 mg L−1 in nonclaypan agricultural watersheds over the continental U.S., suggesting that groundwater in GCEW was more susceptible to NO3‐N contamination than nonclaypan watersheds. These results demonstrated that preferential flow through the soil and hydraulic conductivity of the subsurface strata controlled NO3‐N transport in this claypan watershed.

Long-term agroecosystem research in the central Mississippi river basin: dissolved nitrogen and phosphorus transport in a high-runoff-potential watershed.

Long-term monitoring data from agricultural watersheds are needed to determine if efforts to reduce nutrient transport from crop and pasture land have been effective. Goodwater Creek Experimental Watershed (GCEW), located in northeastern Missouri, is a high-runoff-potential watershed dominated by claypan soils. The objectives of this study were to: (i) summarize dissolved NH-N, NO-N, and PO-P flow-weighted concentrations (FWC), daily loads, and yields (unit area loads) in GCEW from 1992 to 2010; (ii) assess time trends and relationships between precipitation, land use, and fertilizer inputs and nutrient transport; and (iii) provide context to the GCEW data by comparisons with other Corn Belt watersheds. Significant declines in annual and quarterly FWCs and yields occurred for all three nutrient species during the study, and the decreases were most evident for NO-N. Substantial decreases in first- and fourth-quarter NO-N FWCs and daily loads and modest decreases in first-quarter PO-P daily loads were observed. Declines in NO-N and PO-P transport were attributed to decreased winter wheat ( L.) and increased corn ( L.) production that shifted fertilizer application from fall to spring as well as to improved management, such as increased use of incorporation. Regression models and correlation analyses indicated that precipitation, land use, and fertilizer inputs were critical factors controlling transport. Within the Mississippi River Basin, NO-N yields in GCEW were much lower than in tile-drained areas, but PO-P yields were among the highest in the basin. Overall, results demonstrated that reductions in fall-applied fertilizer and improved fertilizer management reduced N and P transport in GCEW.

Long-term agroecosystem research in the central Mississippi river basin: introduction, establishment, and overview.

Many challenges currently facing agriculture require long-term data on landscape-scale hydrologic responses to weather, such as from the Goodwater Creek Experimental Watershed (GCEW), located in northeastern Missouri, USA. This watershed is prone to surface runoff despite shallow slopes, as a result of a significant smectitic clay layer 30 to 50 cm deep that restricts downward flow of water and gives rise to a periodic perched water table. This paper is the first in a series that documents the database developed from GCEW. The objectives of this paper are to (i) establish the context of long-term data and the federal infrastructure that provides it, (ii) describe the GCEW/ Central Mississippi River Basin (CMRB) establishment and the geophysical and anthropogenic context, (iii) summarize in brief the collected research results published using data from within GCEW, (iv) describe the series of papers this work introduces, and (v) identify knowledge gaps and research needs. The rationale for the collection derives from converging trends in data from long-term research, integration of multiple disciplines, and increasing public awareness of increasingly larger problems. The outcome of those trends includes being selected as the CMRB site in the USDA-ARS Long-Term Agro-Ecosystem Research (LTAR) network. Research needs include quantifying watershed scale fluxes of N, P, K, sediment, and energy, accounting for fluxes involving forest, livestock, and anthropogenic sources, scaling from near-term point-scale results to increasingly long and broad scales, and considering whole-system interactions. This special section informs the scientific community about this database and provides support for its future use in research to solve natural resource problems important to US agricultural, environmental, and science policy.

Long-term agroecosystem research in the central Mississippi river basin: goodwater creek experimental watershed and regional nutrient water quality data.

We document the 20-yr-long research effort to study the transport of N and P to surface and groundwater in Goodwater Creek Experimental Watershed. We also document related efforts in nearby claypan watersheds and watersheds with contrasting soil and hydrologic conditions across the northern Missouri-southern Iowa region. Details of the analytical methods, instrumentation, method detection limits, and quality assurance program used to generate the data are described along with a brief overview of significant findings. Nutrient concentrations in streams were in the range associated with nuisance algal growth and presumed loss of aquatic invertebrate diversity. Incorporation of fertilizers was shown to be the most effective practice for reducing nutrient transport in runoff. Despite the claypan soils, NO leaching was a major fate for fertilizer N, and significant contamination of the glacial till aquifer has occurred when long-term fertilizer and manure N inputs exceeded crop N requirements. A key finding of these studies was that field areas with the poorest crop growth were also the most vulnerable to nutrient as well as sediment and herbicide transport.

Long-term agroecosystem research in the central Mississippi river basin: goodwater creek experimental watershed and regional herbicide water quality data.

Goodwater Creek Experimental Watershed (GCEW) has been the focus area of a long-term effort to document the extent of and to understand the factors controlling herbicide transport. We document the datasets generated in the 20-yr-long research effort to study the transport of herbicides to surface and groundwater in the GCEW. This long-term effort was augmented with a spatially broad effort within the Central Mississippi River Basin encompassing 12 related claypan watersheds in the Salt River Basin, two cave streams on the fringe of the Central Claypan Areas in the Bonne Femme watershed, and 95 streams in northern Missouri and southern Iowa. Details of the analytical methods, periods of record, number of samples, study locations, and means of accessing these data are provided. In addition, a brief overview of significant findings is presented. A key finding was that near-surface restrictive soil layers, such as argillic horizons of smectitic mineralogy, result in greater herbicide transport than soils with high percolation and low clay content. Because of this, streams in the claypan soil watersheds of northeastern Missouri have exceptionally high herbicide concentrations and relative loads compared with other areas of the Corn Belt.

Long-Term Agroecosystem Research in the Central Mississippi River Basin: Goodwater Creek Experimental Watershed Weather Data

Knowledge of weather, particularly precipitation, is fundamental to interpreting watershed and hydrologic processes. The long-term weather record in the Goodwater Creek Experimental Watershed (GCEW) complements hydrologic and water quality data in the region. The GCEW also is the core of the Central Mississippi River Basin (CMRB) node of the Long-Term Agroecosystem Research network. Our objectives are to (i) describe the climatological context of the GCEW and CMRB settings, (ii) document instrumentation and the data collection, quality assurance, and reduction processes; (iii) provide examples of the data obtained and descriptive statistics; and (iv) document the availability of and access methods to obtain the data from the web-based data access portal at . These objectives support an overall goal to make these long-term data available to the public for use in further analyses and modeling in support of research and public policy on watershed management.

Long-term agroecosystem research in the central Mississippi river basin: goodwater creek experimental watershed flow data.

Flow monitoring in Goodwater Creek Experimental Watershed started in 1971 at three nested watersheds ranging from 12 to 73 km. Since then, runoff or stream flow has been measured at 14 plots, three fields, and 12 additional stream sites ranging from 0.0034 to 6067 km in the Central Mississippi River Basin. Long-term data sets are important to document the changes resulting from anthropogenic and natural drivers. The data set presented here documents discharge across a range of catchment sizes in an area known for its high runoff potential. It constitutes the flow database of the Central Mississippi River Basin site of the Long-Term Agricultural Research network. Like the other sites of this network, data are accessible through the STEWARDS web interface (). Here we (i) describe the data collection methods, (ii) document the data available at plot, field, and watershed scales, and (iii) provide the main characteristics of discharge. General characteristics of discharge per unit area for different cropping system management systems show that in this claypan soil setting, management and tillage of row crop systems do not affect surface flow during the growing season (April-October). Data from fields and stream sites show the dampening of peak flow values and lengthening of storm hydrographs caused by mixed land uses and longer times of concentration. Overall, stream flow accounts for a third of the precipitation, of which 80% is from surface runoff and 20% is from groundwater.

Incorporating Pesticide Transport into the WEPP Model for Mulch Tillage and No Tillage Plots with an Underlying Claypan Soil

<abstract><title><italic>Abstract.</italic></title> Best management practice (BMP) tools that provide site-specific water quality assessment with limited input data are needed to assist soil and water managers as they work to target BMP placement and reduce dissolved and sediment bound pesticide loss from agricultural landscapes. BMP effectiveness largely depends on accurate characterization of dominant regional hydrologic processes. However, most BMP tools are region specific in their characterization of hydrology (e.g., most models capture either infiltration excess runoff or saturation excess runoff but cannot predict a combination of the two). In this study, we develop and couple a pesticide transport module with the Water Erosion Prediction Project (WEPP) model (v2012.8). The WEPP model realistically simulates infiltration excess and saturation excess runoff as well as dissolved pesticide loss from hillslopes in the Goodwater Creek Experimental Watershed (GCEW) in northeastern Missouri. Simulated runoff and dissolved atrazine concentrations were compared to observed data from mulch till (MT) and no till (NT) plots in the GCEW. The timing of runoff predicted by WEPP coincided well with observed events and simulated flow magnitudes were between minimum and maximum observations for replicate plots. Event-based Nash-Sutcliffe Efficiencies (NSE) are 0.84 and 0.79 for MT and NT runoff simulations, respectively. Both simulations and observations showed little difference in total growing season (planting to harvest) runoff between MT and NT. Event-based dissolved atrazine loads are well predicted for MT and NT with NSEs of 0.59 and 0.71, respectively. Consistent with observations, seasonal NT atrazine losses were greater than losses from MT plots. While this study only focuses on dissolved pesticide transport from the base of hillslopes using MT and NT conservation practices, the WEPP pesticide transport module is capable of predicting both dissolved and sediment bound pesticide loss from each section of the hillslope (i.e., top-slope, mid-slope, and toe-slope) for a wide range of BMPs. However, further field data are needed to evaluate these aspects of the model.

A simple index explains annual atrazine transport from surface runoff-prone watersheds in the north-central USA

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.

Assessing Watershed Transport of Atrazine and Nitrate to Evaluate Conservation Practice Effects and Advise Future Monitoring Strategies

Continued public support for U.S. taxpayer funded programs aimed at reducing agricultural pollutants depends on clear demonstrations of water quality improvements. The objective of this research was to determine if implementation of agricultural best management practices (BMPs) in the Goodwater Creek Experimental Watershed (GCEW) resulted in changes to atrazine and nitrate (NO(3)-N) loads during storm events. An additional objective was to estimate future monitoring periods necessary to detect a 5, 10, 20, and 25% reduction in atrazine and NO(3)-N event load. The GCEW is a 73km(2) watershed located in northcentral Missouri, USA. Linear regressions and Akaike Information Criteria were used to determine if reductions in atrazine and NO(3)-N event loads occurred as BMPs were implemented. No effects due to any BMP type were indicated for the period of record. Further investigation of event sampling from the long-term GCEW monitoring program indicated errors in atrazine load calculations may be possible due to pre-existing minimum threshold levels used to trigger autosampling and sample compositing. Variation of event loads was better explained by linear regressions for NO(3)-N than for atrazine. Decommissioning of upstream monitoring stations during the study period represented a missed opportunity to further explain variation of event loads at the watershed outlet. Atrazine requires approximately twice the monitoring period relative to NO(3)-N to detect future reductions in event load. Appropriate matching of pollutant transport mechanisms with autosampling protocols remains a critical information need when setting up or adapting watershed monitoring networks aimed at detecting watershed-scale BMP effects.

Herbicide Transport in Goodwater Creek ExperimentalWatershed: I. Long-Term Research on Atrazine1

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 Abstract: 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 km2 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.

Herbicide Transport in Goodwater Creek Experimental Watershed: II. Long-Term Research on Acetochlor, Alachlor, Metolachlor, and Metribuzin1

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 Abstract: 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.