@article{amatya_tian_marion_caldwell_laseter_youssef_grace_chescheir_panda_ouyang_et al._2021, title={Estimates of Precipitation IDF Curves and Design Discharges for Road-Crossing Drainage Structures: Case Study in Four Small Forested Watersheds in the Southeastern US}, volume={26}, ISSN={["1943-5584"]}, DOI={10.1061/(ASCE)HE.1943-5584.0002052}, abstractNote={AbstractWe compared precipitation intensity-duration-frequency (PIDF) curves developed for four small forested watersheds to spatially interpolated estimates from the National Oceanic and Atmospher...}, number={4}, journal={JOURNAL OF HYDROLOGIC ENGINEERING}, author={Amatya, D. M. and Tian, S. and Marion, D. A. and Caldwell, P. and Laseter, S. and Youssef, M. A. and Grace, J. M. and Chescheir, G. M. and Panda, S. and Ouyang, Y. and et al.}, year={2021}, month={Apr} }
 @article{skaggs_amatya_chescheir_2020, title={Effects of Drainage for Silviculture on Wetland Hydrology}, volume={40}, ISSN={["1943-6246"]}, DOI={10.1007/s13157-019-01202-6}, number={1}, journal={WETLANDS}, author={Skaggs, R. Wayne and Amatya, Devendra M. and Chescheir, George M.}, year={2020}, month={Feb}, pages={47–64} }
 @article{muwamba_amatya_chescheir_nettles_appelboom_tollner_ssegane_youssef_birgand_callahan_2020, title={Response of Drainage Water Quality to Fertilizer Applications on a Switchgrass Intercropped Coastal Pine Forest}, volume={12}, ISSN={["2073-4441"]}, DOI={10.3390/w12051265}, abstractNote={The objectives of this study were (1) to test the hypothesis that fertilizer applications do not increase nutrient fluxes on a switchgrass/pine forest (IC) when compared to a mature pine forest (MP) and (2) to evaluate post-fertilization (post-fert, 2014–2016) fluxes of nitrogen (N) and phosphorus (P) on IC and compare them to those observed during switchgrass growth prior to fertilization (pre-fert, 2012–2014) and site preparation for switchgrass establishment (site prep, 2009–2012). Nitrogen and P were applied to IC, a paired pure switchgrass site (SG), and MP, each about 25 ha in size, in June 2014, and again in June 2015 for the IC and SG sites only. Nitrogen and P concentrations were measured biweekly and rainfall and drainage outflow were measured continuously. During post-fert, the mean N concentrations and total loads were lower (p < 0.05) in IC than in SG and MP. The mean NO3-N concentration and loads in IC were lower during post-fert than during site prep. The post-fert phosphate concentrations in IC were lower than they were during pre-fert and site prep. Frequent N and P applications in IC did not significantly (α = 0.05) increase N and P fluxes, likely due to plant uptake and sorption on the acidic site.}, number={5}, journal={WATER}, author={Muwamba, Augustine and Amatya, Devendra M. and Chescheir, George M. and Nettles, Jamie E. and Appelboom, Timothy and Tollner, Ernest W. and Ssegane, Hebert and Youssef, Mohamed A. and Birgand, Francois and Callahan, Timothy}, year={2020}, month={May} }
 @article{muwamba_amatya_ssegane_chescheir_appelboom_nettles_tollner_youssef_walega_birgand_2020, title={Response of Nutrients and Sediment to Hydrologic Variables in Switchgrass Intercropped Pine Forest Ecosystems on Poorly Drained Soil}, volume={231}, ISSN={["1573-2932"]}, DOI={10.1007/s11270-020-04808-3}, number={9}, journal={WATER AIR AND SOIL POLLUTION}, author={Muwamba, Augustine and Amatya, Devendra M. and Ssegane, Herbert and Chescheir, George M. and Appelboom, Timothy and Nettles, Jamie E. and Tollner, Ernest W. and Youssef, Mohamed A. and Walega, Andrzej and Birgand, Francois}, year={2020}, month={Aug} }
 @article{amatya_williams_nettles_skaggs_trettin_2019, title={COMPARISON OF HYDROLOGY OF TWO ATLANTIC COASTAL PLAIN FORESTS}, volume={62}, ISSN={["2151-0040"]}, DOI={10.13031/trans.13387}, abstractNote={Abstract. This article compares the short-term and long-term hydrology of two typical forests in the humid Atlantic Coastal Plain, including a relatively undisturbed forest with natural drainage in South Carolina (SC) and a drained pine plantation in North Carolina (NC), using monitoring and modeling approaches. Highly dynamic outflow (O) from both of these systems is driven by the water table (WT) position, as influenced by rainfall (R) and evapotranspiration (ET). The annual runoff coefficient (ROC) varied from 5% in dry years to 56% in wet years, depending on the soil water storage (SWS), with a significantly higher average value for the NC site despite its deeper WT, on average, than the SC site. Although both sites behaved similarly in extreme climate conditions, the change in SWS above the WT influenced the annual RO, ROC, and ET. The 17-year average annual ET of 1114 mm (R – O, assuming annual balanced SWS) for the SC site was significantly higher (p = 0.014) than the ET of the drained NC site (997 mm) despite the SC site’s lower mean annual R of 1370 mm, compared to 1520 mm for the NC site. This may be due to both the higher potential ET (PET) and soil water-holding capacity of the SC site. The SC site had higher frequency and duration of WT near the surface during winter, deeper summer WT, and higher correlation of annual ET to annual R (r2 = 0.90 vs. 0.15), suggesting that the SC site was often moisture-limited, particularly during the growing season. Most of the streamflow in these systems occurred during winter, with low ET demands. However, summer periods with tropical storms also resulted in large RO events, generally with higher frequency and longer durations at the drained NC site. These results are similar to an earlier short-term comparison with an unstable behavior period at the SC site after Hurricane Hugo (1989). This study highlighted (1) the differences in hydrology between coastal forests drained for silvicultural production and undrained natural forests managed only for restoration, (2) the importance of long-term monitoring and the effects of regeneration as well as vegetation management on flow regime, and (3) the application and limitations of two widely used models (MIKESHE and DRAINMOD) in describing the hydrology of these forests. Long-term studies can be a basis for testing new hypotheses on water yield, stormwater management, wetland hydrology, vegetation restoration, bioenergy production, and climate change, in addition to applications of proper models for assessing the eco-hydrologic impacts of land use and climate change on freshwater coastal forests linked with downstream riparian rivers and estuaries affected by tidal fluxes and sea level rise.}, number={6}, journal={TRANSACTIONS OF THE ASABE}, author={Amatya, D. M. and Williams, T. M. and Nettles, J. E. and Skaggs, R. W. and Trettin, C. C.}, year={2019}, pages={1509–1529} }
 @article{panda_amatya_muwamba_chescheir_2019, title={Estimation of evapotranspiration and its parameters for pine, switchgrass, and intercropping with remotely-sensed images based geospatial modeling}, volume={121}, ISSN={["1873-6726"]}, DOI={10.1016/j.envsoft.2019.07.012}, abstractNote={Intercropping switchgrass (Panicum virgatum) with pine can increase bioenergy feedstock production without land opportunity costs but can potentially alter water budgets. Measuring evapotranspiration (ET) and its parameters (stomatal conductance (gs), leaf area index (LAI), canopy temperature (Tc), and soil moisture (SM)) across cropping systems is costly and time-consuming. However, interpretation of remotely-sensed data can facilitate the effective assessment of relative ET demands among competing forest landuses. This study develops and tests geospatial models informed by a normalized difference vegetation index (NDVI), soil adjusted vegetation index (SAVI), vegetation vigor index (VVI), and other spectral information to estimate ET and its parameters, which are measured on experimental watersheds with young pines and natural understory (YP), switchgrass only (SG), and young pine intercropped with switchgrass (IC). The treatment watersheds were replicated on three sites located across the Southeastern U.S. in Carteret, NC; Calhoun, MS; and Greene, AL. Despite the growth inconsistency for the SG only treatment, remote modeling estimation of ET parameters yielded an acceptable R2 > 0.70, and the ET model yielded R2 of 0.50 and a standard error of prediction of 0.94. However, ET and ET parameter model estimation for the IC performed somewhat less satisfactorily, with an R2 of 0.47, 0.59, 0.56, 0.81, and 0.57 for ET, LAI, gs, Tc, and SM, respectively, potentially due to inconsistencies in Landsat image pixel size and landuse homogeneity. Moreover, ET parameter models for the YP site performed rather poorly, with R2 = 0.28, 0.63, and 0.76 for LAI, gs, and Tc, respectively. Additionally, image analysis automation was created with Python scripting and geospatial models. The findings from this study suggest that inclusion of more spatial variability, sound data mining, ultra-high resolution imagery and advanced image processing approaches to account for potential modeling uncertainties can enhance the predictive capability of models to remotely estimate environmental parameters including ET. Radial Basis Function Network (RBFN) based models provided promising results for estimating ET and ET parameters using remotely-sensed digital information when they are prepared with advanced data mining, but it is likely that laypersons may find these models difficult to use. However, forest managers with access to neural network software can use our devised RBFN training models for estimating those forest hydrologic parameters with better accuracy.}, journal={ENVIRONMENTAL MODELLING & SOFTWARE}, author={Panda, Sudhanshu Sekhar and Amatya, Devendra Man and Muwamba, Augustine and Chescheir, George}, year={2019}, month={Nov} }
 @article{panda_amatya_jackson_sun_noormets_2018, title={Automated Geospatial Models of Varying Complexities for Pine Forest Evapotranspiration Estimation with Advanced Data Mining}, volume={10}, ISSN={["2073-4441"]}, DOI={10.3390/w10111687}, abstractNote={The study goal was to develop automated user-friendly remote-sensing based evapotranspiration (ET) estimation tools: (i) artificial neural network (ANN) based models, (ii) ArcGIS-based automated geospatial model, and (iii) executable software to predict pine forest daily ET flux on a pixel- or plot average-scale. Study site has had long-term eddy-flux towers for ET measurements since 2006. Cloud-free Landsat images of 2006−2014 were processed using advanced data mining to obtain Principal Component bands to correlate with ET data. The regression model’s r2 was 0.58. The backpropagation neural network (BPNN) and radial basis function network (RBFN) models provided a testing/validation average absolute error of 0.18 and 0.15 Wm−2 and average accuracy of 81% and 85%, respectively. ANN models though robust, require special ANN software and skill to operate; therefore, automated geospatial model (toolbox) was developed on ArcGIS ModelBuilder as user-friendly alternative. ET flux map developed with model tool provided consistent ET patterns for landuses. The software was developed for lay-users for ET estimation.}, number={11}, journal={WATER}, author={Panda, Sudhanshu and Amatya, Devendra M. and Jackson, Rhett and Sun, Ge and Noormets, Asko}, year={2018}, month={Nov} }
 @article{tian_youssef_skaggs_amatya_chescheir_2012, title={Modeling water, carbon, and nitrogen dynamics for two drained pine plantations under intensive management practices}, volume={264}, ISSN={["1872-7042"]}, DOI={10.1016/j.foreco.2011.09.041}, abstractNote={This paper reports results of a study to test the reliability of the DRAINMOD-FOREST model for predicting water, soil carbon (C) and nitrogen (N) dynamics in intensively managed forests. The study site, two adjacent loblolly pine (Pinus taeda L.) plantations (referred as D2 and D3), are located in the coastal plain of North Carolina, USA. Controlled drainage (with weir and orifice) and various silvicultural practices, including nitrogen (N) fertilizer application, thinning, harvesting, bedding, and replanting, were conducted on the study site. Continuous collection of hydrological and water quality data (1988–2008) were used for model evaluation. Comparison between predicted and measured hydrologic variables showed that the model accurately predicted long-term subsurface drainage dynamics and water table fluctuations in both loblolly pine plantations. Predicted mean and standard deviation of annual drainage matched measured values very well: 431 ± 217 vs. 436 ± 231 mm for D2 site and 384 ± 152 vs. 386 ± 160 mm for D3 site. Nash–Sutcliffe coefficients (NSE) were above 0.9 for drainage predictions on annual and monthly basis and above 0.86 for predictions of daily water table fluctuations. Compared to measurements in other similar studies, the model also reasonably estimated long-term dynamics of organic matter pools on forest floor and in forest soil. Predicted mean and standard deviation of annual nitrate exports were comparable to measured values: 1.6 ± 1.3 vs. 1.5 ± 1.5 kg ha−1 for D2 site, and 1.4 ± 1.3 vs. 1.3 ± 1.1 kg ha−1 for D3 site, respectively. Predicted nitrate export dynamics were also in excellent agreement with field measurements as indicated by NSE above 0.90 and 0.84 on annual and monthly bases, respectively. The model, thus successfully tested, was applied to predicted hydrological and biogeochemical responses to drainage water management and silvicultural practices. Specifically, the model predicted reduced rainfall interception and ET after clear cutting, both of which led to increased water yield and elevated water table, as expected. The model also captured temporary changes in nitrogen transformations following forest harvesting, including increased mineralization, nitrification, denitrification, and decreased plant uptake. Overall, this study demonstrated that DRAINMOD-FOREST can predict water, C and N dynamics in drained pine forests under intensive management practices.}, journal={FOREST ECOLOGY AND MANAGEMENT}, author={Tian, Shiying and Youssef, Mohamed A. and Skaggs, R. Wayne and Amatya, Devendra M. and Chescheir, George M.}, year={2012}, month={Jan}, pages={20–36} }
 @article{kim_amatya_broome_hesterberg_choi_2012, title={Sensitivity analysis of the DRAINWAT model applied to an agricultural watershed in the lower coastal plain, North Carolina, USA}, volume={26}, ISSN={["1747-6585"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84857111286&partnerID=MN8TOARS}, DOI={10.1111/j.1747-6593.2011.00283.x}, abstractNote={Abstract}, number={1}, journal={WATER AND ENVIRONMENT JOURNAL}, author={Kim, Hyunwoo and Amatya, Devendra M. and Broome, Stephen W. and Hesterberg, Dean L. and Choi, Minha}, year={2012}, month={Mar}, pages={130–145} }
 @article{sun_noormets_gavazzi_mcnulty_chen_domec_king_amatya_skaggs_2010, title={Energy and water balance of two contrasting loblolly pine plantations on the lower coastal plain of North Carolina, USA}, volume={259}, ISSN={["1872-7042"]}, DOI={10.1016/j.foreco.2009.09.016}, abstractNote={During 2005–2007, we used the eddy covariance and associated hydrometric methods to construct energy and water budgets along a chronosequence of loblolly pine (Pinus taeda) plantations that included a mid-rotation stand (LP) (i.e., 13–15 years old) and a recently established stand on a clearcut site (CC) (i.e., 4–6 years old) in Eastern North Carolina. Our central objective was to quantify the differences in both energy and water balances between the two contrasting stands and understand the underlining mechanisms of environmental controls. We found that the LP site received about 20% more net radiation (Rn) due to its lower averaged albedo (α) of 0.25, compared with that at the CC (α = 0.34). The mean monthly averaged Bowen ratios (β) at the LP site were 0.89 ± 0.7, significantly (p = 0.02) lower than at the CC site (1.45 ± 1.2). Higher net radiation resulted in a 28% higher (p = 0.02) latent heat flux (LE) for ecosystem evapotranspiration at the LP site, but there was no difference in sensible heat flux (H) between the two contrasting sites. The annual total evapotranspiration (ET) at the LP site and CC site was estimated as 1011–1226 and 755–855 mm year−1, respectively. The differences in ET rates between the two contrasting sites occurred mostly during the non-growing seasons and/or dry periods, and they were small during peak growing seasons or wet periods. Higher net radiation and biomass in LP were believed to be responsible to the higher ET. The monthly ET/Grass Reference ET ratios differed significantly across site and season. The annual ET/P ratio for the LP and CC were estimated as 0.70–1.13 and 0.60–0.88, respectively, indicating higher runoff production from the CC site than the LP site. This study implied that reforestation practices reduced surface albedos and thus increased available energy, but they did not necessarily increase energy for warming the atmosphere in the coastal plain region where soil water was generally not limited. This study showed the highly variable response of energy and water balances to forest management due to climatic variability.}, number={7}, journal={FOREST ECOLOGY AND MANAGEMENT}, author={Sun, G. and Noormets, A. and Gavazzi, M. J. and McNulty, S. G. and Chen, J. and Domec, J. -C. and King, J. S. and Amatya, D. M. and Skaggs, R. W.}, year={2010}, month={Mar}, pages={1299–1310} }
 @inproceedings{appelboom_chescheir_skaggs_gilliam_amatya_2008, title={Nitrogen balance for a plantation forest drainage canal on the North Carolina coastal plain}, volume={51}, DOI={10.13031/2013.25239}, abstractNote={Human alteration of the nitrogen cycle has led to increased riverine nitrogen loads, contributing to the eutrophication of lakes, streams, estuaries, and near-coastal oceans. These riverine nitrogen loads are usually less than the total nitrogen inputs to the system, indicating nitrogen removal during transport through the drainage network. A two-year monitoring study quantified the ammonium, nitrate, and organic-N inputs, outputs, and inferred in-stream processes responsible for nitrogen transformations and removal in a 1900 m reach of a drainage canal located in a managed pine plantation. Total nitrogen inputs to the canal section were 527.8 kg in 2001 and 1422.7 kg in 2002. Total nitrogen discharge at the outlet was 502 kg in 2001 and 1458 kg in 2002. The mass balance of nitrogen inputs and outputs indicated a loss of 25.8 kg (5.1%) of total nitrogen from the system in 2001, and a gain of 35.3 kg (2.4%) of total nitrogen to the system in 2002. Variability in the input and output estimates was high, especially for groundwater exchange. Different hydrologic and nitrogen inputs and outputs were identified and quantified, but measurement variability obscured any potential nitrogen removal from the system.}, number={4}, booktitle={Transactions of the ASABE}, author={Appelboom, T. W. and Chescheir, G. M. and Skaggs, R. W. and Gilliam, J. W. and Amatya, D. M.}, year={2008}, pages={1215–1233} }
 @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{stackelberg_chescheir_skaggs_amatya_2007, title={Simulation of the hydrologic effects of afforestation in the Tacuarembo River basin, Uruguay}, volume={50}, DOI={10.13031/2013.22636}, abstractNote={The Soil and Water Assessment Tool (SWAT) was used to simulate the hydrology of two small paired catchments in northern Uruguay. The control and treatment catchments (69 and 108 ha, respectively) were monitored for a three-year pretreatment period during which the land use was grassland with livestock grazing. Subsequently, the treatment catchment was planted (57% afforested) with loblolly pine (Pinus taeda). The objectives of the modeling study were to simulate the hydrologic response of the two catchments during the pretreatment period and predict the hydrologic effects of converting the native pasture to pine plantation. SWAT models of the two catchments were calibrated and validated using data measured during the pretreatment period. The model predicted outflows from the catchments reasonably well as compared to observed outflows during the years with above average rainfall (5% to -13% error). Model efficiency (E) for daily outflow volumes was greater than 0.71, indicating a good fit between simulated and observed results. A 33-year continuous simulation was performed on three land uses: grassland with livestock grazing, grassland without grazing, and pine treatment. The conversion of the catchments from the baseline pasture condition with grazing resulted in a predicted reduction in average annual water yield from the catchments of 15% for native grassland without grazing, and 23% for pine trees. A maximum predicted hydrologic effect was estimated by maximizing the model parameter that increases the ability of pine trees to withdraw water from the ground. For this condition, the model predicted a 30% reduction in mean annual water yield from the afforested catchment.}, number={2}, journal={Transactions of the ASABE}, author={Stackelberg, N. O. and Chescheir, G. M. and Skaggs, R. W. and Amatya, D. M.}, year={2007}, pages={455–468} }
 @article{amatya_skaggs_gilliam_hughes_2003, title={Effects of orifice-weir outlet on hydrology and water quality of a drained forested watershed}, volume={27}, number={2}, journal={Southern Journal of Applied Forestry}, author={Amatya, D. M. and Skaggs, R. W. and Gilliam, J. W. and Hughes, J. H.}, year={2003}, pages={130–142} }
 @book{chescheir_lebo_amatya_hughes_gilliam_skaggs_herrmann_2003, title={Hydrology and water quality of forested lands in eastern North Carolina}, publisher={Raleigh, N.C. : N.C. Agricultural Research Service, N.C. State University}, author={Chescheir, G. M. and Lebo, M. E. and Amatya, D. M. and Hughes, J. and Gilliam, J. W. and Skaggs, R. W. and Herrmann, R. B.}, year={2003} }
 @article{sun_mcnulty_amatya_skaggs_swift_shepard_riekerk_2002, title={A comparison of the watershed hydrology of coastal forested wetlands and the mountainous uplands in the Southern US}, volume={263}, ISSN={["0022-1694"]}, DOI={10.1016/S0022-1694(02)00064-1}, abstractNote={Hydrology plays a critical role in wetland development and ecosystem structure and functions. Hydrologic responses to forest management and climate change are diverse in the Southern United States due to topographic and climatic differences. This paper presents a comparison study on long-term hydrologic characteristics (long-term seasonal runoff patterns, water balances, storm flow patterns) of three watersheds in the southern US. These three watersheds represent three types of forest ecosystems commonly found in the lower Atlantic coastal plain and the Appalachian upland mountains. Compared to the warm, flat, and shallow groundwater dominated pine flatwoods on the coast, the inland upland watershed was found to have significantly higher water yield, Precipitation/Hamon's potential evapotranspiration ratio (1.9 for upland vs 1.4 and 0.9 for wetlands), and runoff/precipitation ratio (0.53±0.092 for upland vs 0.30±0.079 and 0.13±0.094 for wetlands). Streamflow from flatwoods watersheds generally are discontinuous most of the years while the upland watershed showed continuous flows in most years. Stormflow peaks in a cypress–pine flatwoods system were smaller than that in the upland watershed for most cases, but exceptions occurred under extreme wet conditions. Our study concludes that climate is the most important factor in determining the watershed water balances in the southern US. Topography effects streamflow patterns and stormflow peaks and volume, and is the key to wetland development in the southern US.}, number={1-4}, journal={JOURNAL OF HYDROLOGY}, author={Sun, G and McNulty, SG and Amatya, DM and Skaggs, RW and Swift, LW and Shepard, JP and Riekerk, H}, year={2002}, month={Jun}, pages={92–104} }
 @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} }
 @article{sun_mcnulty_shepard_amatya_riekerk_comerford_skaggs_swift_2001, title={Effects of timber management on the hydrology of wetland forests in the southern United States}, volume={143}, ISSN={["0378-1127"]}, DOI={10.1016/s0378-1127(00)00520-x}, abstractNote={The objectives of this paper are to review the hydrologic impacts of various common forest management practices that include harvesting, site preparation, and drainage. Field hydrological data collected during the past 5–10 years from ten forested wetland sites across the southern US are synthesized using various methods including hydrologic simulation models and Geographic Information Systems. Wetland systems evaluated include red river bottoms, black river bottoms, pocosins, wet mineral flats, cypress domes, and pine flatwoods. Hydrologic variables used in this assessment include water table level, drainage, and storm flow on different spatial and temporal scales. Wetland ecosystems have higher water storage capacity and higher evapotranspiration than uplands. Hydrologic impacts of forest management are variable, but generally minor, especially when forest best management practices are adopted. A conceptually generalized model is developed to illustrate the relative magnitude of hydrologic effects of forest management on different types of wetlands in the southern US. This model suggests that in addition to soils, wetland types, and management practice options, climate is an important factor in controlling wetland hydrology and the magnitude of disturbance impacts. Bottomland wetlands, partial harvesting, and warm climate usually offer conditions that result in low hydrologic impact.}, number={1-3}, journal={FOREST ECOLOGY AND MANAGEMENT}, author={Sun, G and McNulty, SG and Shepard, JP and Amatya, DM and Riekerk, H and Comerford, NB and Skaggs, W and Swift, L}, year={2001}, month={Apr}, pages={227–236} }
 @article{amatya_skaggs_2001, title={Hydrologic modeling of a drained pine plantation on poorly drained soils}, volume={47}, number={1}, journal={Forest Science}, author={Amatya, D. M. and Skaggs, R. W.}, year={2001}, pages={103–114} }
 @article{sun_amatya_mcnulty_skaggs_hughes_2000, title={Climate change impacts on the hydrology and productivity of a pine plantation}, volume={36}, ISSN={["1752-1688"]}, DOI={10.1111/j.1752-1688.2000.tb04274.x}, abstractNote={ABSTRACT:  There are increasing concerns in the forestry community about global climate change and variability associated with elevated atmospheric CO2. Changes in precipitation and increases in air temperature could impose additional stress on forests during the next century. For a study site in Carteret County, North Carolina, the General Circulation Model, HADCM2, predicts that by the year 2099, maximum air temperature will increase 1.6 to 1.9°C, minimum temperature will increase 2.5 to 2.8°C, and precipitation will increase 0 to 10 percent compared to the mid‐1990s. These changes vary from season to season. We utilized a forest ecosystem process model, PnET‐II, for studying the potential effects of climate change on drainage outflow, evapotranspiration, leaf area index (LAI) and forest Net Primary Productivity (NPP). This model was first validated with long term drainage and LAI data collected at a 25‐ha mature loblolly pine (Pinus taeda L.) experimental watershed located in the North Carolina lower coastal plain. The site is flat with poorly drained soils and high groundwater table. Therefore, a high field capacity of 20 cm was used in the simulation to account for the topographic effects. This modeling study suggested that future climate change would cause a significant increase of drainage (6 percent) and forest productivity (2.5 percent). Future studies should consider the biological feedback (i.e., stomata conductance and water use efficiency) to air temperature change.}, number={2}, journal={JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION}, author={Sun, G and Amatya, DM and McNulty, SG and Skaggs, RW and Hughes, JH}, year={2000}, month={Apr}, pages={367–374} }
 @article{amatya_gregory_skaggs_2000, title={Effects of controlled drainage on storm event hydrology in a loblolly pine plantation}, volume={36}, ISSN={["1093-474X"]}, DOI={10.1111/j.1752-1688.2000.tb04258.x}, abstractNote={ABSTRACT:  A paired watershed approach was utilized to study the effects of three water management regimes on storm event hydrology in three experimental watersheds in a drained loblolly pine (Pinus taeda L.) plantation in eastern North Carolina. The regimes were: (1) conventional drainage, (2) controlled drainage (CD) to reduce outflows during spring fish recruitment, and (3) controlled drainage to reduce outflows and conserve water during the growing season. Data from two pit‐treatment years and three years of CD treatment with raised weirs at the watershed outlet are presented. CD treatment resulted in rises in water table elevations during the summer. But the rises were small and short‐lived due to increased evapotranspiration (ET) rates as compared to the spring treatment with lower ET demands. CD treatment had no effect on water tables deeper than 1.3 m. CD treatments, however, significantly (α= 0.05) reduced the stoning outflows for all events, and peak outflow rates for most of the events depending upon the outlet weir level. In some events, flows did not occur at all in watersheds with CD. When event outflows occurred, duration of the event was sharply reduced because of reduced effective ditch depth. Water table depth at the start of an event influenced the effect of CD treatment on storm event hydrology.}, number={1}, journal={JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION}, author={Amatya, DM and Gregory, JD and Skaggs, RW}, year={2000}, month={Feb}, pages={175–190} }
 @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} }
 @inproceedings{sun_amatya_mcnulty_skaggs_hughes_1999, title={Potential impact of climate change on the hydrology and productivity of a drained loblolly pine plantation in North Carolina}, booktitle={Proceedings: Specialty Conference on Potential Consequences of Climate Variability and Change to Water Resources of the United States: May 10-12, 1999, Atlanta, Georgia  (American Water Resources Association technical publication series ; TPS-99-1).}, publisher={Herndon, VA: American Water Resources Association}, author={Sun, G. and Amatya, D. M. and McNulty, S. G. and Skaggs, R. W. and Hughes, J. H.}, year={1999}, pages={403–408} }
 @inproceedings{amatya_chescheir_fernandez_skaggs_1999, title={Testing of a watershed scale hydrologic/water quality model for poorly drained soils}, number={1999}, booktitle={Proceedings of the Mini-Conference, Advances in Water Quality Modeling}, publisher={St. Joseph, MI: ASAE}, author={Amatya, D. M. and Chescheir, G. M. and Fernandez, G. P. and Skaggs, R. W.}, year={1999}, pages={33–39} }
 @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} }
 @article{amatya_gilliam_skaggs_lebo_campbell_1998, title={Effects of controlled drainage on forest water quality}, volume={27}, ISSN={["0047-2425"]}, DOI={10.2134/jeq1998.00472425002700040029x}, abstractNote={Abstract}, number={4}, journal={JOURNAL OF ENVIRONMENTAL QUALITY}, author={Amatya, DM and Gilliam, JW and Skaggs, RW and Lebo, ME and Campbell, RG}, year={1998}, pages={923–935} }
 @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} }
 @article{amatya_skaggs_gregory_1997, title={Evaluation of a watershed scale forest hydrologic model}, volume={32}, ISSN={["0378-3774"]}, DOI={10.1016/S0378-3774(96)01274-7}, abstractNote={A watershed scale hydrologic model (DRAINWAT) for drained forested lands was developed by coupling DRAINLOB, a field scale forestry version of DRAINMOD and the ditch and channel routing model section of FLD and STRM. The simulation model was tested with 5 years (1988–1992) of data collected on a 340 ha watershed located near Beaufort in eastern North Carolina. Testing of the model included comparison of observed and simulated daily, monthly, and annual outflows and hourly event hydrographs by three different evapotranspiration (ET) methods. Two of which (Teskey form and GS HR form) are based on the Penman-Monteith method and the third one on the Thornthwaite method. The average absolute deviation in observed and predicted daily outflows for a 5 year period was 0.94 mm day−1, when the Penman-Monteith methods were used to predict ET. The average absolute deviation in cumulative outflow when ET was predicted by the Thornthwaite method was, respectively, 23% and 50% higher compared with the values obtained with both forms of the Penman-Monteith method. Based on coefficient of determination (R2), coefficient of efficiency (E), and root mean square error (RMSE), Teskey and GS HR forms of the Penman-Monteith method performed better than the Thornthwaite method in predicting both daily and monthly outflows. However, the average daily deviations by all three methods were not significantly different at 5% level. Prediction errors in simulating monthly outflows were reduced compared with daily outflows. The predicted mean annual outflow volumes when the GS_HR and Thornthwaite methods were used for ET were in closest agreement with observed data. Statistics showed that errors resulting from use of the Thornthwaite method, with correction factors, were usually within acceptable limits given the large input data required by the Penman-Monteith ET methods. Model prediction of event hydrographs was satisfactory based on different statistical and graphical comparisons. Deviations in predicted and observed results are attributed to errors in both. Errors in the measured outflows occurred for some larger events due to weir submergence. Errors in the simulations resulted from errors in rainfall inputs, and from uncertainties in drainable porosity, hydraulic conductivity and estimates of ET due to a number of factors including approximations of leaf area index (LAI) and stomatal conductance parameters. The model performance as a whole was satisfactory given the complexity of the model, limitations of input data for the watershed, measurement errors in outflow and rainfall, and the fact that the model was not calibrated.}, number={3}, journal={AGRICULTURAL WATER MANAGEMENT}, author={Amatya, DM and Skaggs, RW and Gregory, JD}, year={1997}, month={Mar}, pages={239–258} }
 @article{amatya_skaggs_gregory_herrmann_1997, title={Hydrology of a drained forested Pocosin watershed}, volume={33}, ISSN={["0043-1370"]}, DOI={10.1111/j.1752-1688.1997.tb03530.x}, abstractNote={ABSTRACT:  In order to assess the effects. of silvicultural and drainage practices on water quality it is necessary to understand their impacts on hydrology. The hydrology of a 340 ha artificially drained forested watershed in eastern North Carolina was studied for a five‐year period (1988–92). Effects of soils, beds and changes in vegetation on water table depth, evapotranspiration (ET) and drainage outflows were analyzed. Total annual outflows from the watershed varied from 29 percent of the rainfall during the driest year (1990) when mostly mature trees were present to as much as 53 percent during a year of normal rainfall (1992) after about a third of the trees were harvested. Annual ET from the watershed, calculated as the difference between annual rainfall and outflow, varied from 76 percent of the calculated potential ET for a dry year to as much as 99 percent for a wet year. Average estimated ET was 58 percent of rainfall for the five‐year period. Flow rates per unit area were consistently higher from a smaller harvested block (Block B ‐ 82 ha) of the watershed than from the watershed as a whole. This is likely due to time lags, as drainage water flows through the ditch‐canal network in the watershed, and to timber harvesting of the smaller gaged block.}, number={3}, journal={JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION}, author={Amatya, DM and Skaggs, RW and Gregory, JD and Herrmann, RB}, year={1997}, month={Jun}, pages={535–546} }
 @article{amatya_skaggs_1997, title={Predicting effects of orifice/weir structures at the outlets of drained pine forests}, number={972096}, journal={Paper (American Society of Agricultural Engineers)}, author={Amatya, D. M. and Skaggs, R. W.}, year={1997}, pages={5} }