@article{fernandez_chescheir_skaggs_amatya_2007, title={Application of DRAINMOD-GIS to a lower coastal plain watershed}, volume={50}, DOI={10.13031/2013.22635}, abstractNote={This article reports a case study for applying DRAINMOD-GIS, a DRAINMOD-based lumped parameter watershed model, to Chicod Creek watershed, a 11100 ha coastal plain watershed in North Carolina that is not intensively instrumented or documented. The study utilized the current database of land use, topography, stream network, soil, and weather data available to state and federal agencies. Methods for collecting, evaluating, and formatting watershed data for model input are described. The study demonstrated that the lumped parameter model may be used to characterize the hydrology and water quality of Chicod Creek. Hydrology predictions were within 5% of the measured data. Predicted mean monthly nitrate-nitrogen (NO3-N) loads compared well with the measured data. Mean annual delivery ratios of each field ranged from 81% to 99% with a watershed mean of 90%. Application of the model to evaluate the effects of changing land use is presented.}, number={2}, journal={Transactions of the ASABE}, author={Fernandez, G. and Chescheir, G. M. and Skaggs, R. W. and Amatya, D. M.}, year={2007}, pages={439–447} }
 @article{fernandez_chescheir_skaggs_amatya_2006, title={DRAINMOD-GIS: A lumped parameter watershed scale drainage and water quality model}, volume={81}, ISSN={["1873-2283"]}, DOI={10.1016/j.agwat.2005.03.004}, abstractNote={A watershed scale lumped parameter hydrology and water quality model that includes an uncertainty analysis component was developed and tested on a lower coastal plain watershed in North Carolina. Uncertainty analysis was used to determine the impacts of uncertainty in field and network parameters of the model on the predicted outflows and nitrate–nitrogen loads at the outlet of the watershed. The model, which links DRAINMOD field hydrology and a spatially distributed routing model using a kernel function, accurately predicted the outlet flows and nitrate–nitrogen loads from a lower coastal plain watershed. Model predictions were within 1% of both measured outflows and nitrate–nitrogen loads. Uncertainty analysis indicated that uncertainty in stream velocities, decay coefficient and field exports significantly contributed to the uncertainty in the predicted outlet flows, loads and mean watershed delivery ratio.}, number={1-2}, journal={AGRICULTURAL WATER MANAGEMENT}, author={Fernandez, GP and Chescheir, GM and Skaggs, RW and Amatya, DM}, year={2006}, month={Mar}, pages={77–97} }
 @article{fernandez_chescheir_skaggs_amatya_2005, title={Development and testing of watershed-scale models for poorly drained soils}, volume={48}, DOI={10.13031/2013.18323}, abstractNote={Two watershed-scale hydrology and water quality models were used to evaluate the cumulative impacts of land 
use and management practices on downstream hydrology and nitrogen loading of poorly drained watersheds. Field-scale 
hydrology and nutrient dynamics are predicted by DRAINMOD in both models. In the first model (DRAINMOD-DUFLOW), 
field-scale predictions are coupled to the canal/stream routing and in-stream water quality model DUFLOW, which handles 
flow routing and nutrient transport and transformation in the drainage canal/stream network. In the second model 
(DRAINMOD-W), DRAINMOD was integrated with a new one-dimensional canal and water quality model. The hydrology 
and hydraulic routing components of the models were tested using data from a 2950 ha drained managed forest watershed 
in the coastal plain of eastern North Carolina. Both models simulated the hydrology and nitrate-nitrogen (NO3-N) loading 
of the watershed acceptably. Simulated outflows and NO3-N loads at the outlet of the watershed were in good agreement with 
the temporal trend for five years of observed data. Over a five-year period, total outflow was within 1% of the measured value. 
Similarly, NO3-N load predictions were within 1% of the measured load. Predictions of the two models were not statistically 
different at the 5% level of significance.}, number={2}, journal={Transactions of the ASAE}, author={Fernandez, G. P. and Chescheir, G. M. and Skaggs, R. W. and Amatya, D. M.}, year={2005}, pages={639–652} }
 @article{amatya_chescheir_fernandez_skaggs_gilliam_2004, title={DRAINWAT-based methods for estimating nitrogen transport in poorly drained watersheds}, volume={47}, DOI={10.13031/2013.16100}, abstractNote={Methods are needed to quantify effects of land use and management practices on nutrient and sediment loads at 
the watershed scale. Two methods were used to apply a DRAINMOD-based watershed-scale model (DRAINWAT) to estimate 
total nitrogen (N) transport from a poorly drained, forested watershed. In both methods, in-stream retention or losses of N 
were calculated with a lumped-parameter model, which assumes that N concentration decreases exponentially with residence 
(or travel) time in the canals. In the first method, daily field outflows predicted by DRAINWAT were multiplied by average 
N concentrations to calculate daily loads at the field edge. Travel time from the field edge to the watershed outlet was computed 
for each field for each day based on daily velocities predicted by DRAINWAT for each section of the canal-stream network. 
The second lumped-parameter method was similar but used predicted annual outflow to obtain annual load at the field 
edge. The load was transported to the watershed outlet, and the in-stream N loss was determined by using a constant average 
velocity (obtained by long-term DRAINWAT simulations), independent of season, for the entire canal-stream network. The 
methods were applied on a 2,950 ha coastal forested watershed near Plymouth, North Carolina, to evaluate daily, monthly, 
and annual export of nitrogen for a five-year (1996-2000) period. Except for some late spring and hurricane events, predicted 
daily flows were in good agreement with measured results for all five years (Nash-Sutcliffe coefficient, E = 0.71 to 0.85). 
Estimates of monthly total N load were in much better agreement (E = 0.76) with measured data than were the daily estimates 
(E = 0.19). Annual nitrogen load was predicted within 17% of the measured value, on average, and there was no difference 
(. = 0.05) between measured and estimated monthly and annual loads. The estimates of annual N loads using travel time with 
a daily velocity yielded better results than with the constant average velocity. The estimated delivery ratio (load at the 
outlet/load at the field edge) for total N was shown to vary widely among individual fields depending on their location in the 
watershed and distance from the outlet. Both of the methods investigated can potentially be used with GIS in predicting 
impacts of land management practices on total N loads from poorly drained watersheds.}, number={3}, journal={Transactions of the ASAE}, author={Amatya, D. M. and Chescheir, G. M. and Fernandez, G. P. and Skaggs, R. W. and Gilliam, J. W.}, year={2004}, pages={677–687} }
 @article{fernandez_chescheir_skaggs_amatya_2002, title={Watgis: A GIS-based lumped parameter water quality model}, volume={45}, DOI={10.13031/2013.8822}, abstractNote={A Geographic Information System (GIS)-based, lumped parameter water quality model was developed to estimate the spatial and temporal nitrogen-loading patterns for lower coastal plain watersheds in eastern North Carolina. The model uses a spatially distributed delivery ratio (DR) parameter to account for nitrogen retention or loss along a drainage network. Delivery ratios are calculated from time of travel and an exponential decay model for in-stream dynamics. Travel times from any point in the drainage network to the watershed outlet are obtained from simulations using a combined physically based field hydrology and drainage canal routing model (DRAINMOD-DUFLOW). Nitrogen load from contributing areas in the watershed delivered to the main watershed outlet is obtained as the product of field export with the corresponding delivery ratio. The total watershed load at the outlet is the combined loading of the individual fields. Nitrogen exports from source areas are measured. The lumped water quality model is integrated within a GIS framework with menu interface, display options, and statistical procedures. Within this framework, the model can be used as a screening tool to analyze the effects of different land and water management practices on downstream water quality. A description of the model is presented along with the results from the evaluation of the model to characterize the seasonal and annual export of nitrogen from a drained forested watershed near Plymouth, North Carolina. Results of the study showed that the lumped parameter model can reasonably predict the loads at the outlet of the watershed. Predicted loads for 1997 were highly correlated with the observed loads (correlation coefficients of 0.99, 0.90, and 0.96 for nitrate-nitrogen, TKN, and total nitrogen respectively). Sensitivity and uncertainty analyses indicated that predicted outlet loads were sensitive to field flow predictions and export concentrations. Overall, the results indicate that the lumped parameter model can be an effective tool for describing the monthly nitrogen loads from a poorly drained coastal plain watershed.}, number={3}, journal={Transactions of the ASAE}, author={Fernandez, G. P. and Chescheir, G. M. and Skaggs, R. W. and Amatya, D. M.}, year={2002}, pages={593–600} }
 @inproceedings{fernandez_chescheir_amatya_skaggs_1999, title={GIS-based water quality lumped parameter model}, number={1999}, booktitle={Proceedings of the Mini-Conference, Advances in Water Quality Modeling}, publisher={St. Joseph, MI: ASAE}, author={Fernandez, G.P. and Chescheir, G.M. and Amatya, D.M. and Skaggs, R.W.}, year={1999}, pages={65–70} }
 @inbook{fernandez_skaggs_chescheir_amatya_1999, title={Watershed scale GIS based lumped parameter water quality model}, booktitle={Proceedings of 2nd Inter-Regional Conference on Environment-Water, Emerging Technologies for Sustainable Land Use and Water Management}, publisher={Lausanne, Switzerland: Presses Polytechniques et Universitaries Romandes}, author={Fernandez, G. P. and Skaggs, R. W. and Chescheir, G. M. and Amatya, D. M.}, editor={L. Amusy, S. Periera and Fritsch, M.Editors}, year={1999} }
 @inproceedings{fernandez_chescheir_skaggs_1998, title={DRAINMOD 5.0: A Windows version that considers crop yield, nitrogen and salinity}, 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={Fernandez, G. P. and Chescheir, G. M. and Skaggs, R. W.}, year={1998}, pages={220–226} }
 @inproceedings{amatya_chescheir_skaggs_fernandez_birgand_1998, title={Evaluation of a DRAINMOD based watershed scale model}, 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={Amatya, D. M. and Chescheir, G. M. and Skaggs, R. W. and Fernandez, G. and Birgand, F.}, year={1998}, pages={211–219} }