Source: NORTH CAROLINA STATE UNIV submitted to
EFFECTS OF AFFORESTATION ON HYDROLOGY AND DRAINAGE WATER QUALITY
Sponsoring Institution
National Institute of Food and Agriculture
Project Status
NEW
Funding Source
Reporting Frequency
Annual
Accession No.
0216277
Grant No.
(N/A)
Project No.
NC02301
Proposal No.
(N/A)
Multistate No.
(N/A)
Program Code
(N/A)
Project Start Date
Oct 1, 2008
Project End Date
Sep 30, 2013
Grant Year
(N/A)
Project Director
Skaggs, R. W.
Recipient Organization
NORTH CAROLINA STATE UNIV
(N/A)
RALEIGH,NC 27695
Performing Department
BIOLOGICAL & AGRICULTURAL ENGINEERING
Non Technical Summary
This project will investigate the hydrologic and water quality effects of afforestation on pasture, abandoned cropland and native grassland in Uruguay, and of the production of energy crops including those interplanted in forest plantations in North Carolina. Growing trees and other crops to produce forest and energy products is a promising method of improving local economies and contributing to energy security, with the added potential of sequestering CO2, reducing the effects of climate change. However, introduction of trees and improved crops may have high impact on water yield due to higher transpiration rates. While studies reaching this conclusion have typically been conducted in water-limited environments, afforestation is expected to have some effect on water yield, regardless of location. Water availability and water quality decline have increasingly become a worldwide issue as human population rises. The proposed project will expand an existing paired watershed loblolly pine-pasture study in Uruguay, adding both eucalyptus and biomass crop treatments. It will also include long-term watershed studies in North Carolina to determine the environmentally related effects of producing both biomass crops and forestry crops for energy. Paired watershed studies will be used in both Uruguay and North Carolina to determine hydrologic and water quality effects of afforestation and other land use changes. A well-instrumented existing study at La Corona near Tacuarembo, Uruguay will be expanded to include eucalyptus and a biomass crop. Two watersheds are currently being used to evaluate the hydrologic response to afforestation with loblolly pine, as compared to pasture, which is the traditional land use in most of Uruguay. Two additional watersheds, roughly 50 to 75 ha in area will be instrumented to evaluate the long-term effects of eucalyptus and energy crop production on hydrology and water quality. Studies will also be conducted on another site located about 150 km from La Corona. This site will consist of three or four watersheds with the same land uses (native pasture, pine, eucalyptus, and a biomass crop for energy) as at La Corona, but will allow evaluation of the effects of changing land use on hydrology and water quality for different soils and geologic conditions. In North Carolina, studies to determine the hydrologic and water quality impacts of producing and harvesting forestry and biomass crops for energy production will be conducted on the Carteret 7 research site. The site consists of three 25 ha artificially drained (1 m deep parallel ditches 100 m apart) and well-instrumented watersheds. Studies at both locations will provide long-term data and a direct evaluation of the effects of land use and management practices on hydrology and water quality. The data collected will be used to test and further develop simulation models which can be applied to evaluate the effects for other soils, crops, and climatological conditions.
Animal Health Component
65%
Research Effort Categories
Basic
35%
Applied
65%
Developmental
(N/A)
Classification

Knowledge Area (KA)Subject of Investigation (SOI)Field of Science (FOS)Percent
1020320205010%
1110320205010%
1110210205010%
1310210205020%
1250210205020%
1110611205010%
1310699205010%
1310320107010%
Goals / Objectives
The goal of the project is to quantify the impacts of forestry and biomass crop production on hydrology and drainage water quality in both Uruguay and North Carolina. Specific objectives are: 1. Determine the hydrologic and water quality effects of afforestation of grass lands in Uruguay by conducting long-term paired watershed studies. 2. Determine impacts of land use, including managed forestry, biomass crops for energy and managed forests with interplanted biomass crops on hydrology, water yield, and drainage water quality in Uruguay and North Carolina. 3 Develop and test models to predict the hydrology and water quality impacts of land use and management practices including afforestation and biomass crop production on lands that were historically in pasture, native grassland,or poorly drained agricultural lands. 4. Incorporate the information derived from this research into useable concepts and materials for stakeholders leading to improved management of forest land, biomass crop land, and pasture land.
Project Methods
Paired watershed studies will be used in both Uruguay and North Carolina to determine hydrologic and water quality effects of afforestation and other land use changes. An existing study established at La Corona near Tacuarembo, Uruguay is one of the few current paired-watershed studies in South America. Two watersheds are being used to evaluate the hydrologic response to afforestation with loblolly pine. Instrumentation on the existing watersheds includes a weather station, an automatic rain gauge, four manual rain gauges, and six water table elevation recorders. Outflows from the two experimental watersheds are continuously measured with HL flumes at the outlet. Two new watersheds will be added at the existing La Corona project site. One will be planted to eucalyptus and the other will be planted with a biomass crop. The new watersheds will be monitored in an untreated condition for three years to establish the relationship between these new sites and the existing reference watershed. Pre-treatment measurements on the new watersheds will begin in early 2009, with planting in 2012; monitoring will continue through the duration of the eucalyptus rotation (about 15 years). A new paired watershed site will be established in another area of Uruguay to determine effects of land use changes on different soils and site conditions. The new site will be located about 200 km east of La Corona and will include three or four watersheds, each about 100 ha in area with similar soils, topography and drainage configuration. The watersheds will be monitored in their existing land use (pasture) for three years. Treatments will then be applied to two or more of the watersheds (eucalyptus, pine, and/or a biomass crop). One watershed will be left in pasture to serve as a reference. After planting, the watersheds will be monitored through the entire forest rotation, which will include multiple planting and harvesting cycles for the biomass crop. North Carolina studies will be conducted on the Carteret 7 forest hydrology research site in Carteret County. The objective of this part of the study is to determine the hydrologic and water quality impacts of producing and harvesting forestry and biomass crops for energy production. We will consider as treatment alternatives, the most promising scenarios for the production of forestry and biomass crops for energy. The site consists of three 25 ha artificially drained watersheds, used for long-term hydrologic and water quality studies since 1988. The watersheds are instrumented to continuously record outflows using V-notched weirs at the outlets, water table elevations, rainfall and meteorological data. Watershed D2 was planted to Loblolly pine in 1997 and will serve as the control watershed for this study. The other two watersheds will be harvested and planted to either Loblolly pine with conventional practices, or Loblolly pine with a biomass energy crop, such as switch grass, interplanted between the rows. Other treatment alternatives, including the instrumentation of additional watersheds, will be considered.

Progress 10/01/11 to 09/30/12

Outputs
OUTPUTS: OUTPUTS: Data collection continued for the twelfth year at the afforestation study watersheds near Tacuarembo, Uruguay. Data for outlet flow rates, weather parameters, water table depths, and water quality were compiled and analyzed for the eighth and ninth years after treatment on the pine watershed and the pasture watershed, and for the second and third pretreatment years on the eucalyptus and biomass watersheds. Data collection continued at the three paired watershed study sites to study the hydrological and water quality impact of bioenergy crop production in forested landscapes. Data for outlet flow rates, weather parameters, water table depths, and water quality were compiled and analyzed for the first and second pretreatment years on the one mature pine and 4 young pine watersheds at each of the Calhoun County, MS and Green County, AL sites. Watershed treatments were installed in 2012 that include: (1) mature pine reference, (2) young pine with standard forestry practice, (3) young pine with switchgrass planted between rows. (4) newly planted (2012) pine with switchgrass planted between rows, and (5) switchgrass only. At the third site, Carteret County, NC, watershed treatments were installed in 2011 that include: (1) mature pine reference, (2) young pine with standard forestry practice, (3) young pine with switchgrass planted between rows, and (4) Switchgrass only. Hydrology and water quality data were compiled and analyzed for the first year after treatment. Data collection continued for the second and third year after treatment to quantify hydrology and in-situ nutrient dynamics at the existing plot-scale research site in Lenoir County, NC, which includes replicate plots of three different experimental treatments: switchgrass interplanted with pine trees, switchgrass only, and traditional pine plantation. The DRAINMOD-FOREST model, which predicts hydrology, soil C and N cycles, and tree growth in drained forests under various climate conditions and silvicultural practices, was evaluated using the 21-year dataset collected from the intensively managed loblolly pine plantations at the Carteret County, NC site. The model accurately predicted annual, and monthly drainage, as well as annual and monthly nitrate export values. A new routine was developed for DRAINMOD-FOREST that enabled it to accurately predict dissolved organic nitrogen dynamics and export. Our paired watershed research sites have facilitated the development of several collaborative studies that include wildlife, plant diversity, aquatic biology, soil productivity and sustainability, regional scale modeling, biofuel life cycle analysis, economics BMP guidance, and safety. PARTICIPANTS: The following individuals worked on the project: Dr. R.W. Skaggs, W. N. Reynolds and University Distinguished Professor, Dr. G.M. (Chip) Chescheir, Associate Research Professor; Dr. Mohamed A. Youssef, Associate Professor; Dr. Francois Birgand, Assistant Professor; Dr. Tim Appelboom, Research Associate, Dr. S. Tian, Post Doctoral Research Associate, Mr. Brian Phillips, Research Associate (all at the Dept of Biological and Agricultural Engineering, N. C. State University), and Dr. Devendra Amatya, US Forest Service, Charleston, SC. Graduate students working on the project are Elizabeth E. Allen, Erin H. Bennett, and Julian Cacho. We collaborate with Weyerhaeuser Company (Dr. Jami Nettles, Dr Zakyia Leggett, and Dr. Bob Bilby) in the studies on drained pine plantations in Carteret and Lenoir Counties, NC, Calhoun County, MS, Green County, AL and in Uruguay. We also collaborate with the Agronomy Faculty at the Universidad de la Republica de Uruguay and with the Instituto Nacional de Investigacion Agropecuaria in Uruguay. TARGET AUDIENCES: Our target audiences include the general public, government and nongovernment agencies, private firms and organizations interested in the hydrologic and water quality effects of afforestation and bioenergy crop production in forested lands. Our target audiences also include State, Federal, and International Agencies who need results of our research as a basis for developing incentive programs, regulations, guidelines and methods to conserve water and natural resources and reduce nutrient losses to surface and ground waters. We also target students, and practicing engineers and scientists who need information to enable them to address design and manage issues related water quantity and water quality. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
The paired watershed study in Uruguay has documented the hydrologic impacts of converting grass land to managed loblolly pine forests. For the last five years of the nine year treatment period, measured outflow from the pine watershed has ranged from 20 to 237 mm lower than the expected outflow if the watershed had been in pasture. The percent reduction due to afforestation has ranged from 8% to 50% of expected outflow. Annual water yield reductions varied from year to year depending on weather patterns with the greatest reductions occurring during wet years that follow dry conditions. Afforestation reduced event peak outflow rates and total outflow, while increasing time to peak for individual storm events and generally changed the distribution of flow from the planted watershed to be less flashy. The DRAINMOD-FOREST model has been well documented and validated, and can be utilized to comprehensively predict water, C and N dynamics in drained forest ecosystems under intensive management practices. DRAINMOD-FOREST will be a valuable tool in our future research.

Publications

  • Sampson, D.A., D.M. Amatya, C.D. Lawson, and R.W. Skaggs. 2011. Leaf area index (LAI) of loblolly pine and emergent vegetation following a harvest. Transactions ASABE 54(6): 2057-2066.
  • Tian, S. M.A. Youssef, R.W. Skaggs, D.M. Amatya, and G.M. Chescheir. 2012. Temporal variations and controlling factors of nitrogen export from an artificially drained coastal forest. Environmental Science and Technology. 46:9956-9963
  • Tian, S. M.A. Youssef, R.W. Skaggs, D.M. Amatya, and G.M. Chescheir. 2012. DRAINMOD-FOREST: Integrated Modeling of Hydrology, Soil Carbon and Nitrogen Dynamics, and Plant Growth for Drained Forests, J. Environmental Quality 41:764-782.
  • Tian, S. M.A. Youssef, R.W. Skaggs, D.M. Amatya, and G.M. Chescheir. 2012. Modeling water, carbon, and nitrogen dynamics for two drained pine plantations under intensive management practices. Forest Ecology and Management 264:20-36.
  • Kim, H., D.M. Amatya, G.M. Chescheir, R.W. Skaggs, and J.E. Nettles. 2012. Hydrologic effects of size and location of fields converted from drained pine forest to agricultural cropland. Journal of Hydrologic Engineering; posted ahead of print January 2, 2012.
  • Skaggs, R.W. 2012. Effects of the growing season on the hydrologic criterion for wetland hydrology. Wetlands 32:1135-1147.
  • Francois Birgand, Timothy W. Appelboom, George M. Chescheir and R. Wayne Skaggs. 2011. Measured nutrient loads in forested watersheds of the lower coastal plain: uncertainties associated with infrequent sampling. Transactions ASABE 54(6):2099-2110.
  • D. M. Amatya, K.R. Douglas-Mankin, T.M. Williams, R.W. Skaggs, and J.E. Nettles. 2011. Advances in forest hydrology: Challenges and opportunities. Transactions ASABE 54(6):2049-2056.
  • Skaggs, R. W., B. D. Phillips, G. M. Chescheir, C. C. Trettin. 2011. Effect of Minor Drainage on Hydrology of Forested Wetlands. Transaction ASABE 54(6): 2139-2149.
  • Skaggs, R.W., G. M. Chescheir, G. P. Fernandez, D. M. Amatya, J. Diggs. 2011. Effects of land use on soil properties of drained coastal plains watersheds. Transactions of the ASABE, 54(4):1357-1365.
  • Amatya, D.M. and R.W. Skaggs. 2011. Long-term hydrology and water quality of a drained pine plantation in North Carolina. Transactions ASABE 54(6): 2087-2098.
  • Caldwell, P.V., M. J. Vepraskas, J. D. Gregory, R. W. Skaggs, and R. L. Huffman. 2011. Linking plant ecology and long-term hydrology to improve wetland restoration success. Transaction ASABE 54(6): 2129-2137.


Progress 10/01/09 to 09/30/10

Outputs
OUTPUTS: Data collection continued for the tenth year at the afforestation study watersheds near Tacuarembo, Uruguay. Data for outlet flow rates, weather parameters, water table depths, and water quality were compiled and analyzed for the seventh year after treatment on the pine watershed and the pasture watershed, and for the first pretreatment year on the eucalyptus and biomass watersheds. Installation of instrumentation was completed and data collection was initiated at the three paired watershed sites to study the hydrological and water quality impact of bioenergy crop product in forested landscapes. Data for outlet flow rates, weather parameters, water table depths, and water quality were compiled and analyzed for part of the first pretreatment year on the one mature pine and 4 young pine watersheds at each of the Calhoun County, MS and Green County, AL sites. Similar data were compiled and analyzed at the third site, Carteret County, NC, where pine trees were planted in the beginning of 2010 on three watersheds and one mature pine watershed remained as a reference stand. Installation of instrumentation was completed and data collection was initiated to measure in-situ nutrient dynamics at the existing plot-scale research site in Lenoir County, NC. Data for weather parameters, water table depths, and groundwater quality were compiled and analyzed on replicate plots of three different experimental treatments: switchgrass interplanted with pine trees, switchgrass only, and traditional pine plantation. The DRAINMOD-FOREST model was developed by linking a forest growth model to the DRAINMOD and DRAINMOD-NII models and by incorporating a revised Gash rainfall interception algorithm and the Penman-Monteith equation into the DRAINMOD hydrology model. The new model can predict hydrology, soil C and N cycles, and tree growth in drained forests under various climate conditions and silvicultural practices. Our paired watershed studies have facilitated the development of several collaborative studies. A collaborative proposal was prepared and submitted to US-DOE that incorporates our biofuel studies with studies on wildlife, plant diversity, aquatic biology, soil productivity and sustainability, regional scale modeling, biofuel life cycle analysis, economics BMP guidance, and safety. The project, which was ultimately funded by DOE, includes researchers from Weyerhaeuser Company, NCASI, Virginia Tech University, Mississippi State University, and the US Forest Service. PARTICIPANTS: The following individuals worked on the project: Dr. R.W. Skaggs, W. N. Reynolds and University Distinguished Professor, Dr. G.M. (Chip) Chescheir, Associate Research Professor; Dr. Mohamed A. Youssef, Assistant Professor; Dr. Francois Birgand, Assistant Professor; Dr. Tim Appelboom, Research Associate, Mr. Brian Phillips, Research Associate; Mr. Wilson Huntley, Technican; (all at the Dept of Biological and Agricultural Engineering, N. C. State University), and Dr. Devendra Amatya, US Forest Service, Charleston, SC. We collaborate with Weyerhaeuser Company (Dr. Jami Nettles, Dr Zakyia Leggett, and Dr. Bob Bilby) in the studies on drained pine plantations in Carteret and Lenoir Counties, NC, Calhoun County, MS, Green County, AL and in Uruguay. We also collaborate with the Agronomy Faculty at the Universidad de la Republica de Uruguay and with the Instituto Nacional de Investigacion Agropecuaria in Uruguay. This project has produced research opportunities for 3 graduate students and one post-doc. TARGET AUDIENCES: Our target audiences include State, Federal, and International Agencies who need results of our research as a basis for developing incentive programs, regulations, guidelines and methods to conserve water and natural resources and reduce nutrient losses to surface and ground waters. We also target students, and practicing engineers and scientists who need information to enable them to do address design and management issues related water quantity and water quality PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
The paired watershed study in Uruguay further documented the hydrologic impacts of converting grass land to managed loblolly pine forests. Rainfall for the last year was 2146 mm (662 mm above normal) and was the highest recorded since the pretreatment period. Outflow from the pine watershed (763 mm) was 237 mm lower than the expected outflow if the watershed had been in pasture; this reduction was the greatest absolute annual reduction observed during the treatment period. The percent reduction (24 %) was not as great as those (28% and 36%) observed in two previous years. The very wet year occurred after a very dry period which is consistent with previous observations that the greatest reductions occur during wet years that follow dry conditions. Outflows observed this past year were very consistent with our hypotheses developed from modeling studies. Those hypotheses are: reductions in absolute annual outflow volume increase as average annual precipitation increases, while the percent reductions in outflow decrease with increased precipitation; and the greatest annual reductions occur during years when a dry period is followed by a wet period. The DRAINMOD-FOREST model was calibrated and validated using the 21-year data collected from the intensively managed loblolly pine plantations at the Carteret County, NC site. The model accurately predicted annual, and monthly drainage, as well as daily water table fluctuations. The model also predicted annual and monthly nitrate export values and annual and monthly dissolved organic nitrogen export value that were in good agreement with measured values. DRAINMOD-FOREST model can be utilized to comprehensively predict water, C and N dynamics in drained forest ecosystems under intensive management practices and will be a valuable tool in our future research.

Publications

  • Skaggs, R.W. M.A. Youssef., R.O. Evans and J.W. Gilliam. 2010. Effect of controlled drainage on water and nitrogen balances in drained lands. Trans of the ASABE 53(6):1843-1850.
  • Appelboom, T.W., G.M. Chescheir, F. Birgand, R.W. Skaggs, J.W. Gilliam, and D. Amatya. 2010. Temperature coefficient for modeling denitrification in surface water sediments using the mass transfer coefficient. Trans ASABE, 53(2):465-474.
  • Phillips, B.D., R.W. Skaggs, and G.M. Chescheir. 2010. A method to determine lateral effect of a drainage ditch on wetland hydrology: field testing. Trans of ASABE, 53(4):1087-1096.
  • Beltran, B.J., D.M. Amatya, M. Jones, M.A. Youssef, T.J. Callahan, R.W. Skaggs, and J. E. Nettles. 2010. Impacts of fertilization on water quality of a drained pine plantation: A worst case scenario. J. Environmental Quality, 39: 293-303.
  • Sun, G., A. Noormets, M.J. Gavazzi, S.G. McNulty, J.Chen, J.-C Domec, J.S. King, D.M. Amatya, and R.W. Skaggs. 2010. Energy and water balance of two contrasting loblolly pine plantations on the lower coastal plain of North Carolina, USA. Forest Ecology and Management, 259:1299-1310.
  • Skaggs, R.W., M.A. Youssef, and G.M. Chescheir. 2010. Methods to estimate effects of drainage water management on annual nitrogen losses to surface waters. In: G.M. Chescheir and M.A. Youssef (Eds.), Proceedings of the ASABE's 9th International Drainage Symposium, Quebec City, Canada, June 13-17. (non refereed)
  • Chescheir, G.M., F. Birgand, S. Tian, M.A. Youssef, and D.M. Amatya. 2010. The effect of sampling frequency on the accuracy of nitrogen load estimates from a drained loblolly pine plantation in eastern North Carolina. In: G.M. Chescheir and M.A. Youssef (Eds.), Proceedings of the ASABE's 9th International Drainage Symposium, Quebec City, Canada, June 13-17. (non refereed)
  • Tian, S., M.A. Youssef, R.W. Skaggs, D.M. Amatya, and G.M. Chescheir. 2010. Field evaluations of a forestry version of DRAINMOD-NII model. In: G.M. Chescheir and M.A. Youssef (Eds.), Proceedings of the ASABE's 9th International Drainage Symposium, Quebec City, Canada, June 13-17. (non refereed)


Progress 10/01/08 to 09/30/09

Outputs
OUTPUTS: Two research watersheds were added to the paired watershed study near Tacuarembo, Uruguay. The new watersheds were instrumented to measure outflow rates, weather parameters, water table depths, and to collect water samples for water quality analyses. One watershed is 80 ha and will be planted to eucalyptus. The other watershed is 36 ha and will be planted to a biomass crop. As with the existing loblolly pine watershed (107 ha), the hydrology and water quality of the new watersheds will be studied in their current pasture condition for a three year pretreatment period before they are planted to their new land use. The existing pasture watershed (69 ha) will continue serving as a control for the treatment watersheds. Data collection continued for the ninth year at the two existing paired watersheds. Our paired watershed study in Uruguay has facilitated the development of several collaborative studies with local researchers. Studies conducted by researchers from the Agronomy Faculty at the Universidad de la Republica de Uruguay include water quality, soil quality, and tree physiology. Researchers from the Instituto Nacional de Investigacion Agropccuaria are conducting collaborative studies on pasture and cattle health. Two new paired watersheds studies have been established to determine the hydrologic and water quality effects of the production of energy crops inter-planted in forest plantations in the southeastern US. One study is located in Calhoun County, MS and the other study is in Green County, AL. Five watersheds in each site have been instrumented to measure outflow rates, weather parameters, and to collect water samples for water quality analyses. At each study site, four of the watersheds have been planted to loblolly pine within the last three years and the fifth watershed contains a mature loblolly forest. All of the watersheds will be monitored in their current condition for a two year pretreatment period. Bioenergy crops will be planted in various configurations on three of the four young pine watersheds after the pretreatment period. The other young pine watershed will remain as a control with typical pine forest management and the mature forest watershed will serve as a reference. One new research watershed was added to the three existing research watersheds at the paired watershed study site in Carteret County, NC. The resulting four watershed research site will become the third site in the study to determine the hydrologic and water quality effects of inter-planted energy crops in forest plantations. A nutrient dynamics study has been initiated on an existing plot-scale research site in Lenoir County, NC. The site has multiple 1 ha plots with various replicated configurations of switch grass interplanted with loblolly pine trees. Groundwater quality sampling wells and continuous recording water table wells were installed on replicate plots of three different experimental treatment: switchgrass interplanted with pine trees, switchgrass only, and traditional pine plantation. Information from these wells along with in-situ nutrient dynamic experiments will be used to test the water quality model DRAINMOD-NII. PARTICIPANTS: The following individuals worked on the project: Dr. R.W. Skaggs, W. N. Reynolds and University Distinguished Professor, Dr. G.M. (Chip) Chescheir, Associate Research Professor; Dr. Mohamed A. Youssef, Assistant Professor; Dr. Francois Birgand, Assistant Professor; Dr. Tim Appelboom, Research Associate, Mr. Brian Phillips, Research Associate; Mr. Wilson Huntley, Technican; (all at the Dept of Biological and Agricultural Engineering, N. C. State University), and Dr. Devendra Amatya, US Forest Service, Charleston, SC. We collaborate with Weyerhaeuser Company (Dr. Jami Nettles, Dr Zakyia Leggett, and Dr. Bob Bilby) in the studies on drained pine plantations in Carteret and Lenoir Counties, NC and in Uruguay. We also collaborate with the Agronomy Faculty at the Universidad de la Republica de Uruguay and with the Instituto Nacional de Investigacion Agropccuaria in Uruguay TARGET AUDIENCES: Our target audiences include State, Federal, and International Agencies who need results of our research as a basis for developing incentive programs, regulations, guidelines and methods to conserve water and natural resources and reduce nutrient losses to surface and ground waters. We also target students, and practicing engineers and scientists who need information to enable them to do address design and management issues related water quantity and water quality. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
The paired watershed study in Uruguay has documented the hydrologic impacts of converting grass land to managed loblolly pine forests. The conversion of grass land to forest lands reduced the water yield of the treatment watershed. Reductions in annual water yields varied from year to year depending on weather patterns. Annual changes in water yields ranged from a 3% increase in the third year to a 37% reduction in the sixth year after tree planting. Changes in absolute water yields ranged from an 8 mm increase in the third year to a 134 mm decrease in the fourth year. The greatest yield reduction occurred in a year characterized by a very dry period followed by a very wet period, while lower water yield reductions occurred during years that began with wet periods and ended with dry periods. The yield reduction calculated during a period of time that began and ended with similar soil water conditions was 18%. The conversion of grassland to forest also changed the time distribution of flow from the watershed. Afforestation reduced total storm flows by more than 50% and peak flow rates by more than 70%. Afforestation also reduced the flashiness index of the watershed. While afforestation reduced the amount of water draining from the watershed as storm flow, it did not reduce the baseflow from the watershed. A hydrologic modeling study was conducted using DRAINMOD to predict the impact of converting pasture land to managed forest land in 10 different climate regions ranging from Sweden to Malaysia. The study showed that the percent reduction in outflow was strongly correlated to the ratio of rainfall to potential evapotranspiration. The reduction in outflow volume increased as average annual precipitation increased, while the percent reduction in outflow decreased with increased precipitation. Predicted reductions in outflow were very consistent with the field study observations in that the year to year variability in the percent reductions were great and the greatest reductions occurred during years when a dry period was followed by a wet period. The results of these studies have been presented to international audiences of scientists and policy makers at the XIII World Forestry Congress in Buenos Aries, Argentina, the 2nd International Conference on Forests and Water in a Changing Environment in Raleigh NC, and the ASABE Annual International Meeting in Reno. NV. Results of these studies have been presented to local scientists and policy makers in Uruguay and Argentina at the XXIII Jornadas Forestales de Entre Rios in Concordia, Argentina and at various local meeting in Montevideo and Tacuarembo, Uruguay.

Publications

  • Chescheir, G.M., Skaggs, R.W., and Amatya, D.M. 2009. Quantifying the Hydrologic Impacts of Afforestation in Uruguay: A Paired Watershed Study. Proc. XIII World Forestry Congress, Buenos Aries, Argentina. http://www.cfm2009.org/es/programapost/resumenes/uploads/Quantifying_ FD.pdf