Progress 09/15/05 to 08/31/10
Outputs
OUTPUTS: The use of advanced distributed hydrological modeling, statistical techniques, and the extensive historical data sources available in the watershed allowed detailed analysis of the past present and future trends in phosphorus and sediment pollution as related to BMPs. One finding was that explicit knowledge of runoff producing areas is paramount to better understanding watershed scale hydrodynamics, as well as likely potential P source areas. For instance if we can identify an area producing runoff and we know this is also an area where manure is spread then we can begin to manage these areas more effectively. Since 1990, an extensive flow and chemistry monitoring network has collected detailed data. We coupled these data to a BMP database that included data about when and where BMPs were installed in the watershed. Using these data models were developed to represent baseline conditions in the watershed before any pre-BMP. We developed or modified several hydrologic and water quality model capable of correctly capturing the distribution of critical watershed processes. For instance, the commonly used SWAT model was initially found to be less than adequate in predicting the spatial distribution of runoff and pollutant source areas in the watershed, despite adequate prediction of watershed outflow. Thus we re-conceptualized how SWAT distributes watershed moisture, by incorporating variable source area (VSA) hydrology into the model. This new model better predicted when and where runoff was generated, and as a result was able to capture the distribution of phosphorus (P) source areas in the watershed. In an effort to further improve the physicality of the SWAT model we recoded the runoff algorithms, removing the Curve Number method to predict runoff, and replacing with a physically based landscape water balance, which was then coupled to the VSA version of SWAT to define critical runoff source areas and model BMP performance. We have also developed a model modified from the GWLF model that can simulate the spatial distribution of runoff producing areas over the entire Cannonsville Watershed (1180 km2), and thus delineate target areas for BMP implementation. Currently the model is able to predict saturated areas in the landscape with surprising accuracy. We utilized these two models to analyze BMP efficiency because they employ different means of estimating BMP effectiveness. SWAT uses process based or mechanistic chemistry to predict the outcome of watershed management with respect to nutrients, which requires more expertise on the part of the user, and more detailed input parameters, while GWLF uses an export coefficient approach, which, while simpler provides less information about the impact of watershed management, since these coefficients are often calibrated to observed flow chemistry at the outlet. A Net Present Value analysis was coupled to GWLF, and show that converting ag land into buffers and installing barnyard BMPs are both very effective in decreasing dissolved P loading, but are also costly for the farmer. The time frame over which the BMPs are implemented is very important for the net present value to be positive for the farmer. PARTICIPANTS: Tammo Steenhuis (Biological and Environmental Engineering) served as the overall project lead, directing and guiding long term goals, the completion of the project, and mentoring and advising graduate students. Christine Shoemaker directed several graduate students in Civil and Environmental Engineering working on the application of models. Zachary Easton (Biological and Environmental Engineering) served as the day to day lead on project coordination and lead the modeling effort, supervising several graduate students. Steve Pacenka (Biological and Environmental Engineering) served as a liaison with watershed officials and supported efforts to disseminate research findings through the Science Support Group. The support of Eliot Schneiderman Mark Zion of NYCDEP and John Thurgood and Dale Dewing of the Delaware County Watershed Agricultural Program were instrumental to the success of the project. The Watershed Agricultural Council and the farmers of the Catskills are acknowledges for their willingness to cooperate on research. TARGET AUDIENCES: Ultimately there are several target audiences. Agricultural producers in the New York City Watershed were routinely targeted by the research group as a means of testing ideas on the ground. These producers were invaluable in giving us access to their land and to sensitive data. As a result of their support we regularly presented our findings directly to the producers at formal and informal meetings. The Delaware County Watershed Agricultural Commission and the county cooperative extension agency were also common target audiences, as they direct funding for BMP establishment and interact directly with producers. We did this though direct informal dialogue and by the Watershed Science Support Group, a formal venue to disseminate research findings. The NYC DEP was also targeted to present research findings, both in meetings with their scientists and through the watershed Science Support Group. In order to better direct watershed funding for source control BMPs placement. The Soil and Water Conservation district in the watershed often asked for our results and findings so that they could incorporate them into their work with producers and land owners. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Perhaps the most intriguing outcome of our CEAP project work has been the finding that very small areas of the watershed or periods of time are responsible for the majority to the non-point source pollution. For instance, analysis of phosphorus runoff losses in the Town Brook watershed indicated that the bulk of runoff was generated from relatively defined areas of the basin. Approximately 70% of the runoff was generated on 25% of the land area. Phosphorus loss was even more spatially discrete, with a very small fraction of the watershed (16%) responsible for 85% of the P loss. These results indicate that management of the landscape in agricultural watersheds, such as these, needs to focus on relatively well defined areas that lie at the intersection of hydrologically active areas and pollutant source areas. Delineation of these areas provides critical information to state, regional, and local planners and officials to drive management decisions at the field, farm and watershed scale loss. Nutrient management plans are currently being developed based on these results. The results of our modeling and cost analysis provide a more cost-effective means of determining the relative risk of nutrient transport and non-point source pollution for a given management or development scenario. By incorporating VSA hydrology, model results provide farmers and watershed managers more accurate information regarding different zones within their farms which have a high propensity for P loading, so they can then pinpoint areas on which to focus BMP strategies. In addition to different modeling changes, we analyze different BMP scenarios including manure spreading, crop rotation, and riparian buffers and how different combinations can reduce P loading. Cost analysis explored the impact of farmer decision-making on water quality outcomes, and how this can affect P loading. Our combined results ultimately influence zoning regulations and public policy regarding agricultural environmental management of small and large rural watersheds. The results are expected to provide a more cost-effective means of determining the relative risk of nutrient transport and non-point source pollution for a given management or development scenario. These results will ultimately influence agricultural zoning regulations and public policy. At some point implementing BMPs and/or continuing to remove land from agricultural production will reduce farm profit, and may not have a continued effect on decreasing P export (i.e., diminishing returns). However, critical area protection must be weighed against the risks of P export to water bodies. The results of this study provide planners a framework with which they can analyze both the water quality and economic implications of BMP selection and placement and advise farmers on BMP choice and placement.
Publications
- Collick, A.S., Z.M. Easton, F.A. Montalto, B. Gao, Y.J. Kim, L. Day, and T.S. Steenhuis. 2006. Hydrological evaluation of septic disposal field performance in sloping terrains. J. Environ. Eng. ASCE. 132(10) 1289-1297.
- Dahlke, H.E., Z.M. Easton, D.R, Fuka, M.T, Walter, and T.S. Steenhuis. 2010. A decision support tool to forecasting hydrological sensitive areas: Improving water quality management from sub-field to watershed scale. Environmental Modeling and Software. (Submitterd)
- de Alwis, D.A., Z.M. Easton, H.E. Dahlke, W.D. Philpot, and T.S. Steenhuis. 2007. Unsupervised classification of saturated areas using a time series of remotely sensed images. Hydrology and Earth System Sciences 11:1609-1620.
- Faulkner, J.W., Z.M. Easton, W. Zhang, L.D. Geohring, and T.S. Steenhuis. 2010. Design and risk assessment tool for vegetative treatment areas receiving agricultural wastewater: Preliminary results. J. Environ Manag. 91:1794-1801. DOI: 10.1016/j.jenvman.2010.03.019.
- Flores-Lopez, F. Z.M. Easton, and T.S. Steenhuis. 2010. A multivariate analysis of covariance to determine the effects of near stream best management practices on nitrogen and phosphorus concentrations on a dairy farm in the New York City CEAP watershed. J. Soil Water Conserv. (In Press)
- Lyon, S.W., J. Seibert, A.J. Lembo, M.T. Walter, T.S. Steenhuis. 2006. Geostatistical investigation into the temporal evolution of spatial structure in a shallow water table. Hydrol. Earth Sys. Sci. 10:113-125.
- Lyon, S.W., M. McHale, M.T. Walter, T.S. Steenhuis. 2006. Effect of runoff generation mechanism on estimating land use control of P concentrations. J. Am. Water. Resour. Assoc. 42:793-804
- Lyon S.W., J. Seibert, A.J. Lembo, M.T. Walter, and T.S. Steenhuis. 2008. Incorporating landscape characteristics in a distance metric for interpolating between observations of stream water chemistry. Hydrol. Earth Sys. Sci. 12: 1229-1239.
- White, E.D., Z.M. Easton, D.R. Fuka, A.S. Collick, and T.S. Steenhuis. 2010. Development and application of a physically based landscape water balance in the SWAT model. Hydrol. Proc. (In Press)
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Progress 09/15/08 to 09/14/09
Outputs
OUTPUTS: Perhaps the most intriguing result of our CEAP project work has been the finding that very small areas of the watershed are responsible for the majority to the non-point source pollution. For instance in the Townbrook watershed the bulk of runoff was generated from relatively defined areas of the basin. Approximately 70% of the runoff was generated on 25% of the area. Phosphorus loss was even more spatially discrete, with only 16% of the watershed responsible for 85% of the P loss. These results indicate that management of the landscape needs to focus on relatively well defined areas that lie at the intersection of hydrologically active areas and pollutant source areas. Delineation of these areas provides critical information to planners and officials to drive management decisions at the field, farm and watershed scale. We have utilized these results in conjunction with economic data about watershed management strategies to devise a methodology for choice and placement of the BMPs on a farm. Farms in the basin differ in both physical characteristics such as size, proximity to water bodies, topography, and runoff source areas, as well as management characteristics, such as crop rotation schedules, manure spreading plans and dairy herd size. In addition to physical differences, different costs are associated with specific BMPs and their placement, and these factor into the farmer's decision-making process. We are using the GWLF and SWAT, and cost information gathered from a BMP database, and interviews with farmers and farm planners to explore different policy scenarios, and determine the optimal choice and placement of BMPs on farms to decrease P loading. Much of the above work has focused on the development of the modeling and analysis methodology, and is generally applied and tested at the sub watershed scale (e.g., 1-40 km2). Below we highlight application of the developed methodology to the CEAP watershed as a whole (1200 km2). We have utilized a paired watershed statistical study to evaluate the effect of BMPs. The novel statistical technique was to use the Cannonsville SWAT model (calibrated to data from a pre BMP period) to serve as the pre-BMP estimate of the watershed conditions. These data were paired with the actual watershed data observed after the implementation of BMPs in the basin. The statistical analysis indicated that the BMPs did significantly improve water quality. We have developed two versions of the SWAT model for the Cannonsville watershed. The first version is the conventional SWAT model and the second version incorporates VSA hydrology. We used the comparison of the results of the two models to evaluate the maximum impact on phosphorous loading that could be achieved by relocating corn production out of wet regions and into drier regions of the watershed, something that is not possible with the original SWAT model. We have also done an analysis of the impact of buffer strips and we are currently examining the economic aspect of that option. We are currently examining the impact of future changes in BMPs on phosphorous loadings with both the conventional SWAT model and with the VSA SWAT model. PARTICIPANTS: Not relevant to this project. TARGET AUDIENCES: Not relevant to this project. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
The results of our modeling and cost analysis provide a more cost-effective means of determining the relative risk of nutrient transport and non-point source pollution for a given management or development scenario. By incorporating VSA hydrology, model results provide farmers and watershed managers more accurate information regarding different zones within their farms which have a high propensity for P loading, so they can then pinpoint areas on which to focus BMP strategies. In addition to different modeling changes, we analyze different BMP scenarios including manure spreading, crop rotation, and riparian buffers and how different combinations can reduce P loading. Cost analysis will explore the impact of farmer decision-making on water quality outcomes, and how this can affect P loading. Our combined results ultimately influence zoning regulations and public policy regarding agricultural environmental management of small and large rural watersheds.
Publications
- Rao, N.S., Z.M. Easton, E.M. Schneiderman, M.S. Zion, D.R. Lee, and T.S. Steenhuis. 2010. Protecting critical areas in the New York City source watershed Combining economic and water quality analysis to examine the effectiveness of best management practices. J. Soil Water Conserv.
- Flores-Lopez, F. Z.M. Easton, and T.S. Steenhuis. 2010. A multivariate analysis of covariance to determine the effects of near stream best management practices on N and P concentrations on a dairy farm in the New York City CEAP watershed . J. Soil Water Conserv. (In Press)
- Fuka, D.R., Z.M. Easton, T.S. Steenhuis, M.T. Walter. 2009. Integration of a simple process based snowmelt model into SWAT. In. Proceedings of the 4th Annual SWAT Conference, Boulder, CO.
- Easton, Z.M., M.T. Walter, M. Zion, E.M. Schneiderman, and T.S. Steenhuis. 2009. Integrating source specific chemistry in basin scale models to predict phosphorus export from agricultural watersheds. J. Environ. Eng. ASCE. 135(1): 25-35.
- Woodbury, J., C.A. Shoemaker, D.M. Cowan, and Z.M. Easton, 2009. A comparison of a SWAT model for the Cannonsville watershed with and without variable source area hydrology. In Proceedings of ASCE- Environment and Water Resources Institute Conference.
- Walter, M.T, J.A. Archibald, B. Buchanan, H. Dahlke, Z.M. Easton, R.D. Marjerison, A.N. Sharma, and S.B. Shaw. 2009. A new paradigm for sizing riparian buffers to reduce risks of polluted storm water: A practical synthesis. J. Irrig. Drain. Eng. ASCE. 135(2): 200-209.
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Progress 09/15/07 to 09/14/08
Outputs
OUTPUTS: To date we have collected extensive data on the distribution of saturated and runoff producing areas, the processes controlling terrestrial N and P dynamics, as well as data on the contribution of agricultural areas to ground water P migration. We have also extensively modified/re-conceptualized SWAT and GWLF to correctly capture and model the spatial distribution of runoff and P source areas, allowing us to analyzing the effectiveness of BMPs on the landscape. Results indicate that BMPs, implemented in concert, that protect riparian areas and streams from direct pollutant loading provide the most substantial water quality protection per land taken out of production. Farmers are implementing these practice because subsidies are such that there is a net benefit. Details of our output is given in the manuscripts given in the "Publication" section. PARTICIPANTS: Not relevant to this project. TARGET AUDIENCES: Not relevant to this project. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
Best management practices (BMPs) have proven to be a cost effective means of reducing non-point phosphorus (P) loading to surface waters at the field and farm scale. However, very little research has explored BMPs efficiency at the watershed or basin scale. We are currently evaluating the impact of P BMPs in the Cannonsville Reservoir Watershed, New York. The Cannonsville is the largest of the reservoirs that supplies drinking water to New York City, and is at risk of eutrophication due to P loading from the watershed. In many rural watersheds, agriculture runoff is generally acknowledged to be the major source of P inputs to surface water bodies. BMPs are a commonly accepted management tool to reduce P loading to surface water bodies. In the Cannonsville many BMPs have been and are being implemented during the last twenty years. BMPs being implemented on a whole farm basis include crop rotation and tillage, barnyard improvements, manure management and export, nutrient management, fencing, and filter/buffer strips. Since BMPs were implemented there has been a reduction in the P load observed in the Cannonsville reservoir. The results of our models are expected to provide a more cost-effective means of determining the relative risk of nutrient transport and non-point source pollution for a given management or development scenario. These results will ultimately influence zoning regulations and public policy.
Publications
- de Alwis, D.A., Z.M. Easton, W.D. Philpot, E.M. Schneiderman, and T.S. Steenhuis. 2009. Unsupervised landcover classification using a time series of NVDI values from remotely sensed images. Remote Sensing of Environment. (Submitted).
- Easton, Z.M., M.T. Walter, M. Zion, E.M. Schneiderman, and T.S. Steenhuis. 2009. Integrating source specific chemistry in basin scale models to predict phosphorus export from agricultural watersheds. J. Environ. Eng. ASCE. (In Press).
- Easton, Z.M., P. Gerard-Marchant, M.T. Walter, A.M. Petrovic, and T.S. Steenhuis. 2007. Hydrologic assessment of a urban variable source watershed in the Northeast US. Water Resources Research 43, W03413, doi:10.1029/2006WR005076, 2007.
- Easton, Z.M., P. Gerard-Marchant, M.T. Walter, A.M. Petrovic, and T.S. Steenhuis. 2007. Identifying dissolved phosphorus source areas and predicting transport from an urban watershed using distributed hydrologic modeling. Water Resources Research 43, W11414, doi:10.1029/2006WR005697, 2007.
- Easton, Z.M., and A.M. Petrovic. 2008. Determining nitrogen loading rates based on land use in an urban watershed, p. 19-42, In M. Nett, et al., eds. The fate of nutrients and plant protection chemicals in the urban environment 997. ACS, Washinton DC.
- Collick, A.S., S. Inglis, P. Wright, and T.S. Steenhuis. 2007. Inactivation of Ascaris suum in a biodrying compost system. J. Environ. Qual. 36:1528-1533.
- Dahlke, H.E., Z.M. Easton, D.R. Fuka, N.S. Rao, T.S. Steenhuis. 2009. Developing and testing a semi-distributed model to predict saturated area dynamics in an agriculturally dominated watershed. Ecohydrology. (Submitted).
- Easton, Z.M., and A.M. Petrovic. 2008. Determining phosphorus loading rates based on land use in an urban watershed, p. 43-62, In M. Nett, et al., eds. The fate of nutrients and pesticides in the urban environment, Vol. 997. American Chemical Society, Washington, DC.
- Easton, Z.M., D.R. Fuka, M.T. Walter, D.M. Cowan, E.M. Schneiderman, and T.S. Steenhuis. 2008. Re-conceptualizing the soil and water assessment tool (SWAT) model to predict runoff from variable source areas. J. Hydrol. 348:279 - 291
- Easton, Z.M., M.T. Walter, and T.S. Steenhuis. 2008. Combined monitoring and modeling indicate the most effective agricultural best management practices. J. Eviron. Qual. 37:1798-1809.
- Flores-Lopez, F., Z.M. Easton, and T.S. Steenhuis. 2009. Assessing phosphorus and nitrate transport on a valley farm in the New York City source watersheds, USA. Vadose Zone J. (Submitted).
- Flores-Lopez, F., Z.M. Easton, and T.S. Steenhuis. 2009. Effect of near stream best management practices on soluble reactive phosphorus and nitrate concentrations on a dairy farm stream in a Catskill Mountain valley. J. Environ. Qual. (Submitted).
- Schneiderman, E.M., T.S. Steenhuis, D.J. Thongs, Z.M. Easton, M.S. Zion, G.F. Mendoza, M.T. Walter, and A.L. Neal. 2007. Incorporating variable source area hydrology into the curve number based Generalized Watershed Loading Function model. Hydrol. Proc. 21:3420-3430
- Rao, N.S., Z.M. Easton, E.M. Schneiderman, M.S. Zion, D.R. Lee, and T.S. Steenhuis. 2009. Distributed modeling of agricultural best management practices to reduce phosphorus loading. J. Environ. Mang. 90: 1385-1395.
- Walter, M.T, J.A. Archibald, B. Buchanan, H. Dahlke, Z.M. Easton, R.D. Marjerison, A.N. Sharma, and S.B. Shaw. 2008. A new paradigm for sizing riparian buffers to reduce risks of polluted storm water: A practical synthesis. J. Environ. Eng. ASCE. (In Press).
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Progress 09/15/06 to 09/14/07
Outputs
Research in the past reporting period has focuses on transforming existing models such as SWAT and GWLF to models that can realistically predict spatial location of variable source areas in which runoff is produces by saturation excess. The spatial distribution of these variable source areas is an important consideration in numerous applications, such as water resource planning or siting of management practices. We have submitted a number of manuscripts relating to this topic which are either in press or under consideration for publication. Other manuscripts published this year were related to runoff from semi urban areas One of the main problems in validating models is the delineation of these variable source areas. Remotely sensed data is a source of spatial information and could be used to identify HAAs. The research in past reporting period has developed a methodology that determines the spatial variability of saturated areas using a temporal sequence of remotely
sensed images. The Normalized Difference Water Index (NDWI) was derived from medium resolution Landsat 7 ETM+ imagery collected over seven months in the Town Brook watershed in the Catskill Mountains of New York State and used to characterize the areas susceptible to saturation. We found that within a single land cover, saturated areas were characterized by the soil surface water content when the vegetation was dormant and leaf water content of the vegetation during the growing season. The resulting HAA map agreed well with both observed and spatially distributed computer simulated saturated areas (accuracies from 49 to 79%). This methodology shows that remote sensing can be used to capture temporal variations in vegetation phenology as well as spatial/temporal variation in surface water content, and appears promising for delineating saturated areas in the landscape.
Impacts
The impact statement of the progress report of 2006 was quite extensive and there is no need to repeat it here. For this reporting year we can add that the technique developed by us that can simply and reliably predict the variable source areas for runoff is a powerful tool for scientists and watershed managers tasked with implementing practices to improve water quality.
Publications
- de Alwis, D.A., Easton, Z. M., Dahlke, H. E., Philpot, W. D. and T. S. Steenhuis. 2007. Unsupervised classification of saturated areas using a time series of remotely sensed images. Hydrol. Earth Syst. Sci., 11, 1609-1620,
- Easton Z.M., P. Gerard-Marchant, M.T. Walter and T.S. Steenhuis. 2007. Hydrologic assessment of an urban variable source watershed in the northeast United States Water Resources Research 43 (3): Art. No. W03413 MAR 10 2007.
- Easton Z.M., P. Gerard-Marchant, M.T. Walter, A.M. Petrovic and T.S. Steenhuis. 2007. Identifying dissolved phosphorus source areas and predicting transport from an urban watershed using distributed hydrologic modeling. Water Resources Research, Vol. 43, W11414, doi:10.1029/2006WR005697
- Montalto F.A., J.Y. Parlange and T.S. Steenhuis. 2007.A simple model for predicting water table fluctuations in a tidal marsh Water Resources Research 43 (3): Art. No. W03439 MAR 27 2007.
- Schneiderman, E.M., T.S. Steenhuis, D.J. Thongs, Z.M. Easton, M.S. Zion, G.F. Mendoza, M.T. Walter, and A.L. Neal. 2007. Incorporating variable source area hydrology into the curve number based Generalized Watershed Loading Function model. Hydrol. Proc. 21:3420-3430 DOI: 10.1002/hyp6556.
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Progress 09/15/05 to 09/15/06
Outputs
Impact of Best Management Practices (BMPs) are evaluated to reduce non point source phosphorus (P) loading to surface waters at the field, farm and basin scale in the Cannonsville Reservoir Watershed, New York. Agricultural BMPs are a commonly accepted management tool to reduce P loading to surface water bodies, and we are researching different modeling approaches to determine the extent to which BMPs are responsible for the observed P load reduction in the West Branch of the Delaware River. First, we have developed a model termed VSLF (modified from the GWLF model) that can simulate the spatial distribution of runoff producing areas, called Variable Source Areas (VSAs), over the entire Watershed (1180 km2), and thus delineate target areas for BMP implementation. Second, we are modifying the commonly used Soil and Water Assessment Tool (SWAT) model to predict spatially distributed runoff source areas similar to VSLF. The strengths of SWAT include its ability to run
with readily available inputs that do not require significantly complex data gathering for general initialization, and the process based chemistry, and the simple runoff generating algorithms, the ubiquitous Soil Conservation Service Curve Number (SCS-CN) type found in numerous models. We re-conceptualized the SCS-CN equation and divide the watershed into a series of sub-basins (contiguous areas expected to behave similarly), which may or may not contain VSAs. One option was to define the HRU using land use and an index class (TI for example), which would directly incorporate the VSA hydrology into the SWAT framework. Another, more physically realistic option, was to incorporate the soil characteristics at the index level. There is some evidence that soil variability can be explained by topographic features in glaciated regions. To incorporate soil, we have spatially weighted the SSURGO soils in the Town Brook watershed of New York State and extracted the required properties with the
Soil Topographic Index (STI) for the basin. Delineation of HRUs proceeded similarly to the standard delineation, except that now HRUs are defined by the coincidence of land use and STI. Third, we are combining water quality and economic aspects of watershed management strategies to devise a methodology for choice and placement of the BMPs on a farm, which insures that the farmer is using BMP strategies to reduce P loading in the most cost-effective manner. The area farms differ in both physical characteristics such as size, proximity to water bodies, topography, and runoff source areas, as well as management characteristics, such as crop rotation schedules, manure spreading plans and dairy herd size. In addition to physical differences, different costs are associated with specific BMPs and their placement, and these factors into the farmer's decision-making process. We are using the models (VSLF and SWAT), cost information gathered from a BMP database, and interviews with farmers and
farm planners to explore different policy scenarios, and determine the optimal choice and placement of BMPs on farms to decrease P loading.
Impacts
The results of our modeling and cost analysis are expected to provide a more cost-effective means of determining the relative risk of nutrient transport and non-point source pollution for a given management or development scenario. By incorporating VSA hydrology VSLF and SWAT results will provide farmers and watershed managers more accurate information regarding different zones within their farms which have a high propensity for P loading so they can then pinpoint areas on which to focus BMP strategies. By varying different parameters and delineations, the degree of different potential impacts can be examined. For example, we could arbitrarily divide the STI into 10 equal area intervals ranging from 1 to 10, with index class 1 counting the 10 pct of the watershed area with the lowest STI (i.e. lowest propensity to saturate) and index class 10 containing the 10 pct of the watershed with the highest STI (i.e. highest propensity to saturate). For a more discrete
representation of HRUs the index may be divided into more classes or follow a different distribution (i.e. exponential, log normal, etc). In addition to different modeling changes, we analyze different BMP scenarios including manure spreading, crop rotation and riparian buffers and how different combinations can reduce P loading. Cost analysis will explore the impact of farmer decision-making on water quality outcomes, and how this can affect P loading. Our combined results will ultimately influence zoning regulations and public policy regarding agricultural environmental management of small and large rural watersheds.
Publications
- Gerard-Marchant, P., W.D. Hively and T.S. Steenhuis. 2006. Distributed hydrological modelling of total dissolved phosphorus transport in an agricultural landscape, part I: distributed runoff generation. Hydrol. Earth Sys. Sci.10:245-261.
- Gerard-Marchant, P., M.T. Walter and T. S. Steenhuis. 2005. Simple models for phosphorus loss from manure during rainfall. J. Environ. Qual. 34:872-876
- Hively, W.D., P. Gerard-Marchant and T.S. Steenhuis. 2006. Distributed hydrological modeling of total dissolved phosphorus transport in an agricultural landscape, part II: dissolved phosphorus transport. Hydrol. Earth Sys. Sci.10:263-276.
- Lyon, S.W., A.J. Lembo, M.T. Walter and T.S. Steenhuis. 2006. Defining Probability of Saturation With Indicator Kriging on Hard and Soft Data. Advan. Water Resour. 29:181-93.
- Srinivasan, M.S., P. Gerard-Marchant, T.L. Veith, W.J. Gburek and T.S. Steenhuis. 2005. Watershed scale modeling of critical source areas of runoff generation and phosphorus transport. J. Amer. Water Resou. Assoc. 41:361-375.
- Lyon, S.W., J. Seibert, A.J. Lembo, M.T. Walter and T.S. Steenhuis. 2006. Geostatistical investigation into the temporal evolution of spatial structure in a shallow water table. Hydrol. Earth Sys. Sci. 10:113-125.
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