Modeling of Riparian Buffers in North Carolina

Introduction

Riparian buffer are known to mitigate non-point sources of pollution such as nitrogen and phosphorus from urban and agricultural settings by acting as sinks for these pollutants and thus improving the water quality (Peterjohn and Correll, 1984; Fennessy and Cronk, 1997; Lowrance, 1997; Naiman and Decamps, 1997). Riparian zones are known to be sinks for non-point source pollutions like the groundwater nitrate which has been actively studied by many researchers (Hill, 1996; Haycock and Pinay, 1993).

Most of the buffer studies that have been carried out are short term field studies generally extending for 4-5 years (Pinay and Decamps, 1988; Osborne and Kovacic, 1993; Jordan et al., 1993; Puckett and Hughes, 2005; Robertson et al., 2006). There also have been numerous field, microcosms and mesocosms studies (Lowrance 1992; Lowrance, 1997; Groffman et al., 1992 and Gold et al., 1998) carried out.

Figure 1: Cross-section of Riparian Buffers

Modeling objectives: There have been no long term studies describing the attenuation capacity of the riparian buffers for reducing pollutants such as nitrate-nitrogen, especially in the groundwaters. Researchers have shown that groundwater hydrology plays an important role in success of these riparian buffers (Hill, 1996; Puckett, 2004; Angier et al., 2005).

Due to spatial and temporal nature and the seasonally changing riparian buffer hydrology, it has become increasingly difficult to predict the nitrate-nitrogen attenuation capacity of riparian buffers. Short term field studies coupled with highly variable hydrology will make it difficult to predict the nitrate-nitrogen attenuation capacity of riparian buffers. There is need for computer model which can describe the various components of physical system, explore and analyze the inter-relationship of these various components (Allison et al., 2006).

REMM: REMM stands for “Riparian Ecosystem Management Model” designed and developed at USDA-ARS in Tifton GA by (Lowrance et al., 2000) to quantify the water quality benefits achieved by riparian buffers. The model is designed to simulate the physical, chemical and biological process of riparian buffers at field scale (Inamdar et al., 1999I). REMM has been calibrated, validated and tested on five year field study conducted at Gibbs Farm site in Tifton GA for the hydrology and nutrient dynamics (Inamdar et al., 1999I; Inamdar et al., 1999II).

Figure 2: REMM model interface

REMM modeling in North Carolina: Two riparian buffer sites site 2 and site 3 will be modeled using the REMM model. The two buffer sites are located in Halifax County North Carolina and detailed description of buffer sites is given in the riparian buffer field studies section.

Modeling Research Objectives

1. To calibrate/validate the model on riparian buffer sites in North Carolina enrolled in the Conservation Reserve Enhancement Program.
2. Test the model extensively with the five year field data set on two riparian buffers sites located in Halifax County NC
3. Quantify the hydrology and nitrate dynamics at two riparian buffers making both short term and long term predictions.
4. Simplify the model to be used by field personal such as the North Carolina Conservation Reserve Enhancement Program to make a quick assessment of riparian buffers for nitrate attenuation.
5. Provide them with simple model as a tool to evaluate various factors based on the site hydrology, topography, climate and types of soils.

Results

The 4 year field data sets from two buffers in Halifax County NC (2005-2008) using REMM were used to simulate the buffer hydrology and water quality to obtain the un-calibrated results. Calibrated is in progress and some representative results will be on the website after calibration with some results comparing field and modeled data.

 

References

Angier J., G McCarty and Prestegaard K.L. 2005. Hydrology of first order riparian zone and stream, Mid-Atlantic coastal plain, Maryland Journal of Hydrology 309:149-166

Allison B.E., Fatula S.M and Wolanski D.P. 2006. Evaluating Riparian Buffers for Non-Point Source Pollution Control in an Urban Setting using the Riparian Ecosystem Management Model, REMM. Hydrology and Management of Forested Wetlands, Proceedings of International Conference ASABE, pg 8-12

Fennesey, M. S. and J. K Cronk. 1997. The effectiveness and restoration potential of riparian ecotones of management of non-point source pollution, particularly nitrate. Critical review environmental science technology 27:285-317

Gold A. J., P.A Jacinthe, P. M Groffman and R.H Puffer.1998.Patchiness in groundwater nitrate removal in riparian forest. Journal of environmental quality 27:146-155.

Groffman P.M., A. J Gold and R. C. Simmons. 1992. Nitrate dynamics in riparian forest: Microbial studies. Journal of environmental quality 21:666-671.

Haycock, N.E. and G. Pinay. 1993: Groundwater nitrate dynamics in grass and poplar vegetated riparian buffer strips during the winter. Journal of environmental quality 22:273-278.

Hill, A.R. 1996. Nitrate removal in stream riparian zones. Journal of environmental quality 25:743-755.

Inamdar S. P., J. M Sheridan, R. R Lowrance, R. G Williams, D.D Bosch, L.S Altier, D.L Thomas. 1999: Riparian Ecosystem Management Model (REMM) I: Testing of Hydrology component for costal plain riparian system ASAE 42(6): 1679-1689.

Inamdar S. P., J. M Sheridan, R. R Lowrance, R. G Williams, D.D Bosch, L.S Altier, D.L Thomas. 1999. Riparian Ecosystem Management Model (REMM) II: Testing of Water quality and nutrient cycling component for costal plain riparian system ASAE 42(6): 1691-1707.

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Lowrance R, 1997. The potential role of riparian forests as buffer zones 128-133, In: N. Haycock, T. Burt, K. Goulding, and G. Pinay (eds.), Buffer Zones: Their Processes and Potential in Water Protection. Quest Environmental Publication Harpenden, UK.

Lowrance R 1992. Groundwater nitrate and denitrification in a coastal plain riparian forest Journal of environmental quality 21:401-405.

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NRCS, 1995.Riparian Forest Buffer, 392; NRCS Watershed Science Institute, Seattle WA

Osborne L.L. and Koviac D.A. 1993: Riparian vegetated buffer strips in water quality restoration and stream management. Fresh Water Biology, 29:243-258.

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Puckett L.J. 2004. Hydrogeologic controls on transport and fate of nitrate in groundwater beneath riparian buffer zones, results from thirteen studies across United States. Water Science Technology 49:47-53.

Puckett L.J. and W.B Hughes 2005. Transport and Fate of nitrate and pesticides; Hydrogeology and Riparian zone processes. Journal of Environmental Quality 34: 2278-2292

Robertson W. D., P. W. van Driel and L Craig Merkley. 2006. Up flow Reactors for Riparian zone denitrification, Journal of environmental quality 35:412-420

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