@article{johnson_burchell_evans_osmond_gilliam_2013, title={Riparian buffer located in an upland landscape position does not enhance nitrate-nitrogen removal}, volume={52}, ISSN={0925-8574}, url={http://dx.doi.org/10.1016/j.ecoleng.2012.11.006}, DOI={10.1016/j.ecoleng.2012.11.006}, abstractNote={Relatively narrow (<50 m) riparian buffers strategically reestablished in correct landscape positions have been shown to significantly reduce agricultural non-point source pollution to streams. Because of this, conservation programs have been established to encourage landowners to enroll lands near surface waters to improve water quality. Former cropland enrolled in a conservation program was evaluated to determine its effectiveness in reducing nitrate-nitrogen (NO3−-N) in shallow groundwater. This conservation buffer (CB) was up to 80 m wide and was planted with loblolly pine (Pinus taeda). It was situated upslope of an existing 30–60 m wide riparian hardwood forest buffer (EHB) located within the floodplain of an intermittent stream. Shallow groundwater NO3−-N, groundwater hydrology, total organic carbon, and soil redox potential were measured throughout both the CB and the EHB for 18 months. Groundwater NO3−-N concentrations, often 5–15 mg L−1 within the CB, were not significantly reduced from concentrations that entered from the agricultural field edge. However, a decrease in NO3−-N concentration was observed within the EHB (17–83%). The hydrology of the CB coupled with relatively low organic carbon contributed to a low denitrification potential and lack of NO3−-N reduction compared with the EHB. While the CB enrollment likely provided additional habitat benefits it did not appear to provide treatment of groundwater NO3−-N. It is our conclusion that landscape position is a more important defining variable for buffer site selection than buffer width if NO3−-N reduction is a primary goal.}, journal={Ecological Engineering}, publisher={Elsevier BV}, author={Johnson, Sara R. and Burchell, Michael R., II and Evans, Robert O. and Osmond, Deanna L. and Gilliam, J. Wendell}, year={2013}, month={Mar}, pages={252–261} }
 @article{jarzemsky_burchell_evans_2013, title={The impact of manipulating surface topography on the hydrologic restoration of a forested coastal wetland}, volume={58}, ISSN={["1872-6992"]}, DOI={10.1016/j.ecoleng.2013.06.002}, abstractNote={A wetland, converted to agriculture in the mid-1970s, was restored to re-establish a non-riverine wet hardwood forest community in eastern North Carolina. Three surface techniques were implemented during construction to determine their effect on successfully restoring target wetland hydrology. The surface treatments, replicated within a randomized complete block design, were: plugging field ditches without altering the land surface (PLUG), plugging the field ditches and roughening the surface (ROUGH), and plugging the field ditches and removing the field crown (CR). Hydrologic conditions for the restoration and a nearby reference site were evaluated based on three years of monitoring data. Daily water table depths between the restoration and reference were within 11 cm on average. An initial evaluation found inconsistencies of treatment effect between blocks, and an as-built survey later confirmed surface elevations within Block 3 deviated from the intended design and was excluded from further analysis. Water table and outflow conditions for the remaining treatment plots and the reference were evaluated using several hydrologic criteria. The CR treatment was found to produce the wettest surface conditions and exported the lowest volume of outflow. For the majority of criterion considered, CR also produced significantly wetter conditions than the reference. The PLUG and ROUGH treatments produced similar hydrologic conditions and tracked closely with the median hydrologic conditions in the reference. Based on the results of this study and several others in low lying coastal areas, plugging pre-existing field ditches may be adequate to restore jurisdictional wetland hydrology and match reference hydrologic conditions. However, surface roughening is low cost method to increase surface storage and introduce microtopographic diversity. For many areas, the removal of existing field crown may be cost-prohibitive and produce wetter than desired conditions. Crown removal should be reserved for sites which have borderline historic wetland hydrologic characteristics.}, journal={ECOLOGICAL ENGINEERING}, author={Jarzemsky, Robert D. and Burchell, Michael R., II and Evans, Robert O.}, year={2013}, month={Sep}, pages={35–43} }
 @article{skaggs_fausey_evans_2012, title={Drainage water management}, volume={67}, ISSN={["1941-3300"]}, DOI={10.2489/jswc.67.6.167a}, abstractNote={This article introduces a series of papers that report results of field studies to determine the effectiveness of drainage water management (DWM) on conserving drainage water and reducing losses of nitrogen (N) to surface waters. The series is focused on the performance of the DWM (also called controlled drainage [CD]) practice in the US Midwest, where N leached from millions of acres of cropland contributes to surface water quality problems on both local and national scales. Results of these new studies are consistent with those from previous research reported in the literature that DWM can be used to reduce N losses (primarily in the nitrate nitrogen [NO3-N] form) from subsurface drained fields. The measured impact varied over a wide range (18% to more than 75% reduction in N loss to surface waters), depending on drainage system design, location, soil, and site conditions. Crop yields were increased by DWM on some sites and not on others, with the year-to-year impacts of DWM on yields dependent on weather conditions, as well as the above factors. Papers reporting advances in the development of datasets and models to predict the impact of drainage intensity and DWM on hydrology and water quality at watershed and…}, number={6}, journal={JOURNAL OF SOIL AND WATER CONSERVATION}, author={Skaggs, R. Wayne and Fausey, Norman R. and Evans, Robert O.}, year={2012}, pages={167A–172A} }
 @article{liu_grabow_huffman_osborne_evans_2012, title={Factors affecting uniformity of irrigation-type manure application systems}, volume={28}, DOI={10.13031/2013.41285}, abstractNote={Liquid manure is usually treated through application to agricultural land using irrigation systems. Land application of liquid manure needs to follow established guidelines in order to achieve economic goals as well as to protect the environment. Guidance at the time of this study in North Carolina suggested calibration of land application equipment be performed once every three years by the catch can method, a time- and labor-consuming method. The goals of this project were to investigate the relationship between liquid manure application uniformity by using data from historical uniformity assessment trials and from additional trials conducted during the study, and to use the results to provide guidance in developing a simplified field method for uniformity assessment. Trials were performed to test the liquid manure application uniformity for different irrigation system types, sprinkler types and models, nozzle types, nozzle diameters, and nozzle pressures. Wind speed during the trials was monitored. Different sprinkler overlaps were achieved by superposition, thereby allowing for assessment of multiple sprinkler spacings for each trial. Regression models were constructed using historic and study-period trial data and a process of main effect selection, collinearity checking, interaction term and quadratic term selection, parameter estimation, and normality testing of model residuals. The model for stationary systems performed well with an adjusted R2 of 0.72 and predicted application uniformity showed the expected tendencies with changes in predictive factors. The model for traveling gun systems did not perform as well as that for stationary systems; the adjusted R2 was only 0.33. The results of this study were used to amend uniformity assessment requirements to a simple procedure requiring measurement of sprinkler nozzle pressure, wetted diameter, and sprinkler spacing.}, number={1}, journal={Applied Engineering in Agriculture}, author={Liu, Z. and Grabow, G. L. and Huffman, R. L. and Osborne, J. and Evans, R. O.}, year={2012}, pages={43–56} }
 @article{grabow_huffman_evans_2011, title={SDI Dripline Spacing Effect on Corn and Soybean Yield in a Piedmont Clay Soil}, volume={137}, ISSN={["1943-4774"]}, DOI={10.1061/(asce)ir.1943-4774.0000277}, abstractNote={A subsurface drip irrigation (SDI) system was installed in the Piedmont of North Carolina in a clay soil in the fall of 2001 to test the effect of dripline spacing on corn and soybean yield. The system was zoned into three sections; each section was cropped to either corn (Zea mays L.), full-season soybean [Glycine max (L.) Merr.], or winter wheat (Triticum aestivum) double cropped to soybean representing any year of a typical crop rotation in the region. Each section had four plots; two SDI plots with dripline spacing at either 1.52 or 2.28 m, an overhead sprinkler irrigated plot, and an unirrigated plot. There was no difference in average corn grain yield for 2002–2005 between dripline spacings or between either dripline spacing and sprinkler. Irrigation water use efficiency (IWUE) was greater for sprinkler irrigated corn than for either SDI treatment and there was no difference in IWUE in soybean. Water typically moved laterally from the driplines 0.38 to 0.50 m. SDI yield and IWUE increased relative t...}, number={1}, journal={JOURNAL OF IRRIGATION AND DRAINAGE ENGINEERING}, author={Grabow, G. L. and Huffman, R. L. and Evans, R. O.}, year={2011}, month={Jan}, pages={27–36} }
 @article{skaggs_youssef_gilliam_evans_2010, title={Effect of controlled drainage on water and nitrogen balances in drained lands}, volume={53}, DOI={10.13031/2013.35810}, abstractNote={Field studies have shown that subsurface drainage systems can be managed to conserve water and reduce losses of nitrogen (N) to surface waters. The practice, called controlled drainage (CD) or drainage water management (DWM), is a viable alternative for reducing N loads from drained cropland, including millions of acres in the Midwest. This article reviews past studies on the effect of CD on drainage volumes and N losses for a wide range of soils and climatological conditions and uses simulations to examine mechanisms affecting the practice. Results published in the literature show that CD has reduced drainage volumes and N losses in drainage waters by 17% to over 80%, depending on soil properties, crops, drainage intensities, control strategies, and location. This study resulted in the following conclusions. CD reduces subsurface drainage and raises water tables, while increasing ET, seepage, and surface runoff. Seepage, which depends on soil properties and site conditions, is an important factor that often governs the effectiveness of CD. Experiments to determine the effect of CD on drainage volumes and N losses should be conducted on the field or watershed scale so that impacts of seepage are properly represented. Increases in ET in response to CD are important but are rarely greater than 10%. The effect of this increase in water use on drainage water loss is also less than 10% for most locations. CD reduces N losses in drainage water by about the same percentage as its effect on subsurface drainage volume in most cases. The effect of CD on N loss to surface waters depends on denitrification, both in the profile and in reduced zones along seepage paths. For soils that do not develop reduced zones, the effect of CD on N loss may be substantially less than its effect on drainage volume.}, number={6}, journal={Transactions of the ASABE}, author={Skaggs, R. W. and Youssef, M. A. and Gilliam, J. W. and Evans, R. O.}, year={2010}, pages={1843–1850} }
 @article{hathaway_cook_evans_2010, title={Nutrient removal capability of a constructed wetland receiving groundwater contaminated by swine lagoon seepage}, volume={53}, DOI={10.13031/2013.30079}, abstractNote={Seepage from waste lagoons has the potential to leach into underlying groundwater systems. Groundwater flow can transport this nutrient-rich lagoon seepage to surrounding surface waters where water quality degradation may occur. Groundwater contaminated by lagoon seepage can be removed from the shallow aquifer by pumping, but the pumped water must still be treated before discharge into surface waters. Constructed wetlands have been successfully implemented to attenuate nitrogen and phosphorus in wastewaters. A constructed wetland receiving groundwater contaminated by swine lagoon seepage was monitored for four years during this study. Wetland effluent concentrations were variable but were on average substantially lower than influent concentrations. During the four-year study, the wetland assimilated between 76% and 84% of the influent total nitrogen and between 22% and 42% of the influent total phosphorus, or 520 to 575 kg of total nitrogen per hectare per year and 83 to 158 kg of total phosphorus per hectare per year. Residence time likely played a major role in nutrient assimilation within the wetland.}, number={3}, journal={Transactions of the ASABE}, author={Hathaway, J. M. and Cook, M. J. and Evans, R. O.}, year={2010}, pages={741–749} }
 @article{lindow_fox_evans_2009, title={Seepage erosion in layered stream bank material}, volume={34}, ISSN={["1096-9837"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-70349884157&partnerID=MN8TOARS}, DOI={10.1002/esp.1874}, abstractNote={Abstract}, number={12}, journal={EARTH SURFACE PROCESSES AND LANDFORMS}, author={Lindow, Nick and Fox, Garey A. and Evans, Robert O.}, year={2009}, month={Sep}, pages={1693–1701} }
 @article{cook_hathaway_evans_2008, title={The impact of swine lagoon seepage on shallow groundwater quality: Groundwater remediation through lagoon closure and pumping}, volume={51}, DOI={10.13031/2013.24528}, abstractNote={Anaerobic lagoons have been used extensively since about 1960 to temporarily store and partially treat livestock waste from concentrated animal production facilities. An earlier study characterized an unlined swine lagoon located in the Middle Coastal Plain of North Carolina and detected elevated mineral nitrogen concentrations (nitrogen as both nitrate and total ammoniacal nitrogen) 38 m down gradient from the lagoon. As this site was shown to be a potential source of nonpoint-source pollution, further study was needed to characterize the aerial extent of the seepage plume and remediate the contaminated groundwater. Hydrologic and water quality monitoring of the site was conducted from March 1999 to September 2004, a period during which the lagoon went from being semiactive to completely closed out. Analysis of data collected prior to lagoon closure indicated that seepage from the lagoon traveled to a nearby channelized stream. Total ammoniacal nitrogen (TAN = NH3-N + NH4-N) concentrations from monitoring wells installed between the lagoon and the channelized stream averaged 121 mg L-1 of TAN, with the highest concentrations exceeding 170 mg L-1. TAN concentrations in the stream 150 m down gradient from the lagoon ranged from 10 to 25 mg L-1. Monitoring of groundwater levels and subsurface water quality continued following the closure of the lagoon in March 2001, as well as through the installation of a groundwater pumping system and construction of a wetland that received and treated the contaminated groundwater. The average hydraulic gradient decreased from 0.0033 m m-1, prior to the activation of a groundwater pumping system (Mar. 1999 to Jan. 2000) to 0.0010 m m-1 after pumping was initiated (Sept. 2000 to Sept. 2004). Although the direction of groundwater flow was unaffected by the addition of the pumping system and water control structure, the average hydraulic gradient was reduced by 70%. Since the installation of the pumping system, approximately 17,900 m3 of subsurface water has been pumped, removing 1200 kg of TN from the groundwater plume. TAN concentrations steadily declined from 120 mg L-1 at the onset of pumping in September 2000 to less than 6 mg L-1 by September 2004.}, number={3}, journal={Transactions of the ASABE}, author={Cook, M. J. and Hathaway, J. M. and Evans, R. O.}, year={2008}, pages={891–900} }
 @article{madramootoo_johnston_ayars_evans_fausey_2007, title={Agricultural drainage management, quality and disposal issues in North America}, volume={56}, ISSN={["1531-0353"]}, DOI={10.1002/ird.343}, abstractNote={The North American continent, comprising Canada and the United States of America, has a wide range of climatic, soils and cropping conditions. Surface and subsurface drainage is required to remove excess soil water in the wetter regions of the continent, as well as to maintain a favorable salt and water balance in the crop root zone in the drier irrigated regions. Drainage and water table management practices are essential for the production of food and fiber. However, these practices may sometimes cause third‐party impacts, which are largely of a water quality nature. Drainage practices have therefore evolved from removal of water for increased crop productivity, to a method of environmental control. Consequently, much effort over recent years has been in designing and installing drainage systems, which have multiple objectives. A very recent notable institutional development is the formation of the Agricultural Drainage Management Systems (ADMS) Coalition, comprised of farmers, drainage contractors and the drainage industry, government advisors, and water management and agricultural specialists, to promote research, education and adoption of drainage water management as a practice that can reduce the delivery of pollutants to streams. This paper describes the need, extent and status of drainage in North America, including water quality issues, drainage water management and disposal problems. Copyright © 2007 John Wiley & Sons, Ltd.}, journal={IRRIGATION AND DRAINAGE}, author={Madramootoo, Chandra A. and Johnston, William R. and Ayars, James E. and Evans, Robert O. and Fausey, Norman R.}, year={2007}, month={Dec}, pages={S35–S45} }
 @article{evans_bass_burchell_hinson_johnson_doxey_2007, title={Management alternatives to enhance water quality and ecological function of channelized streams and drainage canals}, volume={62}, number={4}, journal={Journal of Soil & Water Conservation}, author={Evans, R. O. and Bass, K. L. and Burchell, M. R. and Hinson, R. D. and Johnson, R. and Doxey, M.}, year={2007}, pages={308–320} }
 @article{dukes_evans_2006, title={Impact of agriculture on water quality in the North Carolina Middle Coastal Plain}, volume={132}, DOI={10.1061/(ASCE)0733-9437(2006)132:3(250)}, abstractNote={Water quality in the Middle Coastal Plain of North Carolina has been impacted by agriculture; however, the water quality impacts in these areas over time have not been studied in detail. The surface water quality of several streams in the Neuse River Watershed along the Middle Coastal Plain of North Carolina was monitored for approximately five years, while shallow groundwater in cropped fields and adjacent to drainage ditches was monitored for three years. Surface water samples were collected biweekly and analyzed for nitrate nitrogen (N O3 -N) , ammonium nitrogen (N H4 -N) , total Kjeldahl nitrogen, orthophosphate (P O4 -P) , total phosphate, and total suspended solids, and approximately monthly groundwater samples were collected from wells and analyzed for N O3 -N . Trends relating to seasonal changes in stream water quality as a function of land use and soil type were analyzed, as well as long term changes. Generally, upstream sampling points showed low levels of all constituents. Nutrient and sedimen...}, number={3}, journal={Journal of Irrigation and Drainage Engineering}, author={Dukes, M. D. and Evans, R. O.}, year={2006}, pages={250–262} }
 @article{grabow_huffman_evans_jordan_nuti_2006, title={Water distribution from a subsurface drip irrigation system and dripline spacing effect on cotton yield and water use efficiency in a coastal plain soil}, volume={49}, DOI={10.13031/2013.22303}, abstractNote={A subsurface drip irrigation (SDI) system was installed in 2001 in the Coastal Plain of North Carolina. Initially, four zones were installed, each with 0.91 m dripline spacing. In 2002, a fifth zone with 1.82 m dripline spacing was added. This system irrigated a cotton (Gossypium hirsutum L.) and peanut (Arachis hypogea L.) rotation on a Norfolk sandy loam soil. Seed cotton yield data was collected from 2001 to 2004. In addition to SDI, overhead sprinkler irrigation was applied to cotton plots from 2001 to 2003. This study was concurrent with another study that evaluated the effect of irrigation system type, cotton growth regulator (mepiquat chloride), herbicide (glyphosate) treatment, and planting date on lint yield and quality. Although the soil is classified as a sandy loam, water moved laterally to the midpoint of the 1.82 m spaced dripline; this was likely due to the pan layer found at about 0.3 m just below the dripline depth of 0.23 m. There was no difference in lateral water movement between the two dripline spacings. Seed cotton yield and irrigation water use efficiency was not statistically different between irrigation system type or dripline spacing over all years in the study. Seed cotton yield averaged 3.44 Mg ha-1 for the 0.91 m dripline spacing and 3.22 Mg ha-1 for the 1.82 m spacing for the three-year period 2002-2004 compared to an unirrigated average of 2.58 Mg ha-1 for the same period. Average irrigation water use efficiency was greater for the 0.91 m dripline spacing but not statistically different from the 1.82 m spacing. For 2001-2003, when sprinkler-irrigated plots existed, seed cotton yield averaged 3.55 Mg ha-1 for the 0.91 m dripline spacing, 3.35 Mg ha-1 for the sprinkler-irrigated plots, and 2.56 Mg ha-1 for the unirrigated plots. Drought conditions existed in 2002, when 258 mm of rain occurred between planting and final irrigation. The other growing seasons received relatively high amounts of rainfall: 524, 555, and 643 mm in 2001, 2003, and 2004, respectively.}, number={6}, journal={Transactions of the ASABE}, author={Grabow, G. L. and Huffman, R. L. and Evans, R. O. and Jordan, D. L. and Nuti, R. C.}, year={2006}, pages={1823–1835} }
 @article{ha_evans_luo_skaggs_2004, title={Modification and use of DRAINMOD to evaluate a lagoon effluent land application system}, volume={47}, DOI={10.13031/2013.15869}, abstractNote={Traditionally, lagoon design has considered waste inflow, sludge accumulation, individual event rainfall 
associated with the 25-year, 24-hour storm, and sufficient temporary storage to handle excess rainfall during non-irrigation 
periods. Excess rainfall was defined as the “average” or “normal” rainfall in excess of evaporation during the non-irrigation 
(drawdown) period. North Carolina experienced a series of tropical storms and hurricanes in 1995 that resulted in several 
lagoon overtoppings; however, none of the storms individually satisfied the 25-year, 24-hour criterion. These storms raised 
questions as to whether the 25-year, 24-hour criterion presented the appropriate design constraint to prevent lagoon 
overtopping or whether the cumulative impact of prolonged rainy periods (referred to herein as “chronic” rainfall) was a 
greater threat. To evaluate the validity of existing lagoon design criteria and emergency action measures proposed by the 
North Carolina Soil and Water Conservation Commission, the irrigation component of the field hydrology model DRAINMOD 
was modified to consider animal waste lagoon constraints of chronic rainfall, crop nitrogen utilization, and emergency lagoon 
operational measures. The modified DRAINMOD was used to evaluate lagoon design and operational guidelines in effect 
in eastern North Carolina at the time of the 1995 lagoon breaches and the proposed 1999 emergency measures. Model 
simulation results showed that prolonged wet periods in the winter that result in high moisture surplus are the most likely cause 
of excessively high lagoon stage or overflow. To minimize the occurrence of elevated lagoon stage and eliminate the risk of 
overflow, model results also showed that the design temporary storage criterion should be increased to account for chronic 
rainfall excess between drawdown periods. Intense storms with short durations, such as the catastrophic design (25-year, 
24-hour) storm, mainly occurred in the summer and usually posed no risks to lagoon overflow because these events typically 
occurred at a time when lagoons were traditionally drawn down to their lowest allowable stage. Using a constant average 
nitrogen concentration for lagoon wastewater resulted in fewer irrigation applications, which in turn resulted in more 
frequent high lagoon stage and more overflows. Lagoon spills resulting from extreme weather conditions could be avoided 
by applying wastewater more frequently and temporarily suspending the crop nitrogen limit in wet years without exceeding 
soil hydraulic limits.}, number={1}, journal={Transactions of the ASAE}, author={Ha, Z. and Evans, R. O. and Luo, W. and Skaggs, R. W.}, year={2004}, pages={47–58} }
 @article{dukes_evans_gilliam_kunickis_2003, title={Interactive effects of controlled drainage and riparian buffers on shallow groundwater qaulity}, volume={129}, DOI={10.1061/(ASCE)0733-9437(2003)129:2(82)}, abstractNote={As a result of recent surface water quality problems in North Carolina, riparian buffers and controlled drainage are being used to reduce the loss of nonpoint source nitrogen from agricultural fields. The effect of controlled drainage and riparian buffers as best management practices to reduce the loss of agricultural nonpoint source nitrogen from the middle coastal plain has not been well documented. The middle coastal plain is characterized by intensive agriculture on sandy soils with deeply incised or channelized streams. A 2-year study was conducted to determine the effectiveness of controlled drainage, riparian buffers, and a combination of both in the middle coastal plain of North Carolina. It was hypothesized that raising the water table near the ditch would enhance nitrate-nitrogen reduction through denitrification. On the sandy soils studied, controlled drainage did not effectively raise the water table near the ditch to a greater degree than observed on the free drainage treatment. Due to random treatment location, the free drainage treatment was installed along a ditch with a shallower impermeable layer compared to the impermeable layer on the controlled drainage treatments (2 m versus 3- to 4-m deep). This resulted in a perched or higher water table on the free drainage treatment. Over 17 storm events, the riparian buffer (free drainage) treatment had an average groundwater table depth of 0.92 m compared to 0.96 and 1.45 m for the combination (riparian buffer and controlled drainage) and controlled drainage treatments, respectively. Nitrate concentration decrease between the field wells and ditch edge wells averaged 29% (buffer only), 63% (buffer and controlled drainage), and 73% (controlled drainage only). Although apparently more nitrate was removed from the groundwater on the controlled drainage treatments, the controlled drainage treatment water table near the ditch was not raised closer to the ground surface compared to the free drainage treatment. Nitrate removal effectiveness was attributed to local soil and landscape properties, such as denitrification in deeper reduced zones of the soil profile.}, number={2}, journal={Journal of Irrigation and Drainage Engineering}, author={Dukes, M. D. and Evans, R. O. and Gilliam, J. W. and Kunickis, S. H.}, year={2003}, pages={82–92} }
 @article{dukes_evans_2003, title={Riparian Ecosystem Management Model: Hydrology performance and sensitivity in the North Carolina Middle Coastal Plain}, volume={46}, DOI={10.13031/2013.15645}, abstractNote={A riparian buffer installed along streams is one alternative that can be used to reduce the delivery of nitrogen, 
phosphorus, and sediment to the stream. The Riparian Ecosystem Management Model (REMM) has been developed to 
simulate surface and subsurface riparian buffer hydrology, sediment transport, litter and sediment interactions, vegetation 
growth, and soil carbon, nitrogen, and phosphorus dynamics. For this model to accurately simulate transport and fate of 
nutrients in the shallow groundwater beneath a riparian buffer, the subsurface hydrology component must be verified. Two 
years of field data were utilized to evaluate and test the sensitivity of the hydrology component of REMM in the North Carolina 
Middle Coastal Plain. Daily simulated water table depth was compared to observed water table depths across a 15 m wide 
buffer. The simulated water table depth was sensitive to hydrologic parameters such as groundwater inputs from the upland 
into zone 3, stream depth, and buffer slope. Average absolute errors between simulated and observed water table depth were 
found to be 0.35 to 0.36 m, while relative errors ranged from 0.12 to 0.15 m. Simulated evapotranspiration (ET) was higher 
in zone 3 compared to zones 1 and 2, although all three zones were parameterized alike. Flow into the buffer from the stream 
is not simulated by REMM, although it occurred frequently during data collection. Estimates of ET should be improved for 
herbaceous and grass vegetation types to improve water table depth predictions. Also, for conditions where the stream 
contributes flow to the groundwater, an additional component in REMM is necessary.}, number={6}, journal={Transactions of the ASAE}, author={Dukes, M. D. and Evans, R. O.}, year={2003}, pages={1567–1579} }
 @article{dukes_evans_gilliam_kunickis_2002, title={Effect of riparian buffer width and vegetation type on shallow groundwater quality in the Middle Coastal Plain of North Carolina}, volume={45}, DOI={10.13031/2013.8528}, abstractNote={The effect of riparian buffer width and vegetation type on shallow groundwater quality has not been evaluated 
in the Middle Coastal Plain of North Carolina. Four riparian buffer vegetation types and no–buffer (no–till corn and rye 
rotation or pasture) were established at 8 and 15 m widths as follows: cool season grass (fescue), deep–rooted grass (switch 
grass), forest (pine and mixed hardwood), and native vegetation. Nested groundwater monitoring wells were installed at the 
field/buffer edge and the stream edge in the middle of each riparian buffer plot at three depths. Most deep, mid–depth, and 
shallow wells were 3.0 m, 1.8 m, and 0.6 m deep from the ground surface to the top of the 0.6 m perforated section, respectively. 
Wells were sampled for 23 months beginning July 1998. Although the ditch well nitrate–nitrogen concentrations at the middle 
well depth were significantly lower in the 15 m wide plots compared to the 8 m plots over half the monitoring period, extreme 
flooding as a result of a hurricane in the middle of the study confounded the results. The effect of vegetation was not significant 
at any time, including the no–buffer cropped and fertilized plots. The effect of vegetation was minimized because at the early 
stage in the buffer vegetation establishment, vegetative cover and root mass were not fully developed, the hurricane–induced 
flooding forced the re–establishment of several vegetation types (forest and fescue), and there was likely some mixing of 
groundwater flowing toward the vegetation plots. Establishment of buffers along streams where groundwater flowed away 
from the stream did not result in lower groundwater nitrate levels.}, number={2}, journal={Transactions of the ASAE}, author={Dukes, M. D. and Evans, R. O. and Gilliam, J. W. and Kunickis, S. H.}, year={2002}, pages={327–336} }
 @article{tweedy_evans_2001, title={Hydrologic characterization of two prior converted wetland restoration sites in Eastern North Carolina}, volume={44}, DOI={10.13031/2013.6441}, abstractNote={Wetland losses resulting from conversion to agriculture and other land uses has generated considerable interest 
in wetland restoration. Increased federal and local regulations have mandated that wetland areas must be protected, and when 
loss is unavoidable, mitigation and restoration efforts are required. Establishing appropriate hydrologic functions will 
inherently influence wetland restoration success. This research involved a three–year field study to develop guidelines for 
restoring wetland hydrologic function to drained agricultural fields. Two field sites (9.2 ha and 10.4 ha) located in Beaufort 
and Craven Counties, North Carolina, were instrumented and monitored to evaluate the effectiveness of the restoration 
treatments used. Experimental treatments included two levels of water table management (high outlet control at 15 cm above 
average land surface and low outlet control at 15 cm below average land surface) and two types of surface contouring (smooth 
and rough) to control runoff. The restoration treatments imposed at the Beaufort County site created a range of wet conditions. 
The high water table management, rough microtopography treatment displayed the most consecutive and total number of days 
with the water table less than 30 cm deep, while the low water table management, smooth microtopography treatment 
displayed the driest conditions. The restored wetland status of the Craven County site was marginal. Due to both lateral 
seepage and seepage around the water control structures, the intended levels of water table management at the Craven County 
site could not be maintained. Roughing of the soil surface reduced the amount of outflow from restoration treatments by 
approximately 30% compared to the smooth microtopography treatments. Rough microtopography also reduced peak outflow 
rates and increased the duration of outflow events.}, number={5}, journal={Transactions of the ASAE}, publisher={St. Joseph, Michigan: American Society of Agricultural Engineers}, author={Tweedy, K. L. and Evans, R. O.}, year={2001}, pages={1135–1142} }
 @inproceedings{smith_evans_1998, title={Evaluation of BMPs to improve drainage water quality from agricultural land irrigated with swine lagoon effluent}, booktitle={Drainage in the 21st century: Food production and the environment: Proceedings of the seventh International Drainage Symposium}, publisher={St. Joseph, Michigan: American Society of Agricultural Engineers}, author={Smith, J. T. and Evans, R. O.}, year={1998}, pages={9–16} }
 @article{breve_skaggs_gilliam_parsons_mohammad_chescheir_evans_1997, title={Field testing of DRAINMOD-N}, volume={40}, DOI={10.13031/2013.21360}, abstractNote={This study was conducted to evaluate the performance of DRAINMOD-N, a nitrogen fate and transport model 
for artificially drained soils, based on a comparison between predicted and observed hydrologic and nitrogen variables 
for an experimental site in eastern North Carolina. The site consisted of six plots drained by subsurface drain tubes 
1.25 m deep and 23 m apart. Each plot was instrumented to measure water table depth, subsurface drainage, surface 
runoff and subirrigation rates. There were two replications of three water management treatments: conventional 
drainage, controlled drainage and subirrigation. Crops were winter wheat followed by soybean. Results showed the 
model did a good job in describing the hydrology of the site. On average the predicted daily water table depths were 
within 0.13 m of observed during the 14-month study period. Differences between predicted and observed cumulative 
subsurface drainage and surface runoff volumes were less than 0.10 and 0.09 m, respectively, for all treatments. 
Predictions for the movement and fate of nitrogen were also in good agreement with measured results. Simulated nitratenitrogen 
(NO3-N) losses in subsurface drainage water were within 1.5 kg/ha of the observed values for the 14-month 
period. Differences between simulated and observed total NO3-N losses (subsurface drainage plus surface runoff) were 
within 3.0 kg/ha. 
Results of this study indicated DRAINMOD-N could be used to simulate nitrogen losses in poorly drained soils with 
artificial drainage. The model, however, needs to be tested for longer periods of time and under different climatic 
conditions and soil types, before it can be recommended for general use.}, number={4}, journal={Transactions of the ASAE}, author={Breve, M. A. and Skaggs, R. W. and Gilliam, J. W. and Parsons, J E. and Mohammad, A. T. and Chescheir, G. M. and Evans, R. O.}, year={1997}, pages={1077–1085} }
 @article{evans_skaggs_sneed_1991, title={Stress day index models to predict corn and soybean relative yield under high water table conditions}, volume={34}, DOI={10.13031/2013.31829}, abstractNote={ABSTRACT High water table conditions reduce crop yields. This study developed com and soybean relative yield models for high water table conditions. The relative yield models were based on Stress-Day-Index (SDI) relationships using SEW30 (0.3-m water table depth) to describe the high water table stress criteria and normalized SDI crop susceptibility (CS) factors. The normalized crop susceptibility (NCS) factors were determined from previous studies conducted in North Carolina. The models were developed using existing field data for SDI and crop yield from Ohio. The resulting com model was tested against data from India and North Carolina and explained 69% of the relative yield variance for the pooled data. The soybean model explained 66% of the variance in relative yield for six years of soybean data from Ohio. The models developed should improve relative yield estimates using DRAINMOD, a water table management simulation model.}, number={5}, journal={Transactions of the ASAE}, author={Evans, R. O. and Skaggs, R. W. and Sneed, R. E.}, year={1991}, pages={1997} }
 @article{evans_skaggs_sneed_1990, title={Normalized crop susceptibility factors for corn and soyabean to excess water stress}, volume={33}, DOI={10.13031/2013.31452}, abstractNote={ABSTRACT Crop susceptibility factors for plants stressed by excessive soil water conditions (wet stress) are presented for five growth stages based on four years of experimental data for com and five years of data for soybean. Com was most susceptible to wet stress just prior to tasseling and soybean was most susceptible during the pod filling stage. A normalizing approach is presented that reduces the sensitivity of the crop susceptibility factor to the level of stress imposed. Evidence is presented based on data from three independent studies on com to show that use of the normalized crop susceptibility (NCS) factor reduces its dependence on stress duration.}, number={4}, journal={Transactions of the ASAE}, author={Evans, R. O. and Skaggs, R. W. and Sneed, R. E.}, year={1990}, pages={1153} }