Tim Callahan, Professor

Department Chair

Address: SSMB 224C
E-mail: callahant@cofc.edu


New Mexico Institute of Mining and Technology
Ph.D. Earth and Environmental Science (with Dissertation in Hydrology), 2001

New Mexico Institute of Mining and Technology, Socorro
M.S. Geochemistry, 1995

University of St. Thomas, St. Paul, Minnesota
B.A. Geology, 1991

Research Interests

Hydrology and Water Resources

Courses Taught

EVSS 639 Wetlands and Watersheds

GEOL 438/EVSS 538 Hydrogeology and Lab

GEOL 364/240 Field Studies: Water Resources and Pollution in the Developing World (Abroad Course in India)

GEOL 291/291L Water Resources

GEOL 105 Earth History

HONS 155 Honors Geology I


Amatya, D.M., A. Walega, T.J. Callahan, A. Morrison, V. Vulava, D.R. Hitchcock, T. M. Williams, and T. Epps. 2022. Storm event analysis of four forested catchments on the Atlantic coastal plain using a modified SCS-CN rainfall-runoff model. Journal of Hydrology 608: 127772. DOI:10.1016/j.jhydrol.2022.127772.

Locatis Prochaska, A., A. Watson, T. Callahan, and K. Stewart. 2021. Lowcountry landowners’ wetlands knowledge and perceptions and the impacts of land management actions on isolated wetlands. Journal of South Carolina Water Resources 8(2): 16-29.

Brown, C.E. and T.J. Callahan. 2020. Modeling tidal characteristics in a creek-marsh drainage system: implications for stormwater management. Journal of South Carolina Water Resources 7: 3-19. DOI:10.34068/JSCWR.07.01.

Muwamba, A. D.M. Amatya, G.M. Cheschier, J.E. Nettles, T. Appleboom, E.W. Tollner, H. Ssegane, M.A. Youssef, F. Birgand, and T. Callahan. 2020. Response of drainage water quality to fertilizer applications on a switchgrass intercropped coastal pine forest. Water 12: 1265. DOI:10.3390/w12051265.

Beckingham, B., T. Callahan, and V. Vulava. 2019. Stormwater ponds in the southeastern U.S. coastal plain: hydrogeology, contaminant fate, and the need for a social-ecological framework. Frontiers in Environmental Science. DOI:10.3389/fenvs.2019.00117.

Trettin, C.C., D.M. Amatya, A.H. Gaskins, C.F. Miniat, A. Chow, and T. Callahan. 2019. Watershed response to longleaf pine restoration – application of paired watersheds on the Santee Experimental Forest. in Latimer, James S.; Trettin, Carl C.; Bosch, David D.; Lane, Charles R., eds. 2019. Working watersheds and coastal systems: research and management for a changing future-Proceedings of the Sixth Interagency Conference on Research in the Watersheds. July 23-26, 2018, Shepherdstown, WV. e-Gen. Tech. Rep. SRS-243. Asheville, NC: U.S. Department of Agriculture Forest Service, Southern Research Station. 211 p.

Vulava, V., B. Beckingham, and T. Callahan. 2019. Environmental Factors and Design Features that Control Stormwater Transport and Contaminant Fate in Ponds. Ch. 2 in Cotti-Rausch, B.E., Majidzadeh, H., and DeVoe, M.R. (eds.), Stormwater Ponds in Coastal Souoth Carolina: 2019 State of Knowledge Full Report. S.C. Sea Grant Consortium, Charleston S.C. SCSGC-T-20-02. https://www.scseagrant.org/stormwater-ponds-in-south-carolina-state-of-knowledge-report/

Wallover, C.G., T.J. Callahan, A.E. Scaroni, and K.C. Morganello. 2019. Rerouting Water: Understanding and Managing Urban Hydrology in Historic Charleston. In: Chadwick, J. and S.C. Jaume (eds.), Field Excursions in the Carolinas: Guides for the 2019 GSA Southeastern Section Meeting. Geological Society of America Field Guide 53: 9-17. DOI:10.1130/2019.0053(02).

Amatya, D.M., Muwamba, A., Panda, S.S. Callahan, T.J., Harder, S.V., and C.A. Pellett. 2018. Assessment of spatial and temporal variation of potential evapotranspiration estimated by four methods for South Carolina. Journal of South Carolina Water Resources 5(1): 3-24. DOI:10.34068/JSCWR.05.01.

Sitta, K.A., M. Reed, R. Mortensen, C. Doll, T. Callahan, and D.I. Greenfield. 2018. The influences of nitrogen form and zooplankton assemblages in two coastal southeastern systems. Limnography and Oceanography 63: 2523–2544. DOI:10.1002/lno.10957.

Beckingham, B.A., M. Shahin, K. Ellis, and T.J. Callahan. 2017. Polycyclic aromatic hydrocarbons and suspended materials in a semi-urbanized tidal creek after an historic flood event and implications for water quality monitoring. J. South Carolina Water Resources 4 (1): 5-13. DOI:10.34068/JSCWR.04.01.

Ellis, K.K., T. Callahan, D.I. Greenfield, D. Sanger, J. Robinson, and M. Jones. 2017. Measuring and modeling flow rates in tidal creeks: a case study from the central coast of South Carolina. J. South Carolina Water Resources 4 (1): 21-39. DOI:10.34068/JSCWR.04.03.

Wynne, A., V.M. Vulava, H. Qirko, P. Nieves, and T.J. Callahan. 2017. A community-based approach to solid waste management for riverine and coastal resource sustainability in the Philippines. Ocean and Coastal Management. DOI:10.1016/j.ocecoaman.2017.10.028.

Callahan, T.J., D.M. Amatya, and P.A. Stone. 2017. Coastal forests and groundwater: using case studies to understand the effects of drivers and stressors for resource management. Sustainability 9: 447. DOI:10.3390/su9030447.

Amatya, D., T. Callahan, W. Hansen, C. Trettin, A. Radecki-Pawlik, and P. Meire. 2015. Turkey Creek watershed – A case study of forest hydrology and watershed management on low-gradient Atlantic Coastal Plain, U.S.A. Journal of Water Resource Protection 7: 792-814. DOI: 10.4236/jwarp.2015.710065.

Kassabian, R.L.A., T.J. Callahan, and S. Upchurch. 2015. Water budget of a shallow aquifer in the lower coastal plain: ACE Basin, SC. Journal of South Carolina Water Resources 2(1):93-104. DOI:10.34068/JSCWR.02.11.

Griffin, M.P., T.J. Callahan, and V.M. Vulava. 2014. Influence of soil type and antecedent soil moisture conditions on storm-event flow pathways in lower coastal plain watersheds of the southeastern United States. Water Resources Research 50(10): 8265-8280. DOI: 10.1002/2014WR015941.

Garrett, C.G., V.M. Vulava, T.J. Callahan, and M.L. Jones. 2012. Groundwater-Surface Water Interactions in a Lowland Watershed: Source Contribution to Stream Flow. Hydrological Processes 26: DOI: 10.1002/hyp.8257.

Callahan, T.J., V.M. Vulava, M.P. Passarello, and C.G. Garrett. 2011. Estimating groundwater recharge in lowland watersheds. Hydrological Processes 26. DOI:10.1002/hyp.8356.

La Torre-Torres, I.B., D.M. Amatya, G. Sun, and T.J. Callahan. 2011. Seasonal rainfall–runoff relationships in a lowland forested watershed in the southeastern USA. Hydrological Processes 25: DOI:10.1002/hyp.7955.

Callahan, T.J., C.G. Garrett, and V.M. Vulava. 2010. The role of groundwater recharge in the water budget of lowland watersheds. Proceedings, 2010 South Carolina Water Resources Conference, October 13-14, 2010, Columbia, SC.

Garrett, C.G., V.M. Vulava, T.J. Callahan, M.L. Jones, and C.L. Ginn. 2010. Using water chemistry data to quatify source contribution to stream flow in a coastal plain watershed. Proceedings, 2010 South Carolina Water Resources Conference, October 13-14, 2010, Columbia, SC.

Amatya, D.M., T.J. Callahan, C.C. Trettin, and A. Radecki-Pawlik. 2009. Hydrologic and water quality monitoring on Turkey Creek watershed, Francis Marion National Forest, SC. Proc., ASABE Int’l Annual Meeting, 21-24 June 2009, Reno, NV. Amer. Soc. Agric. Biol. Engin. Pub. No. 09-5999, St. Joseph, MI.

Beltran, B.J., D.M. Amatya, M. Youssef, M. Jones, T.J. Callahan, R.W. Skaggs, and J.E. Nettles. 2009. Impacts of fertilization on water quality of a drained pine plantation: A worst-case scenario. J. Envir. Qual. 39: 293-303, DOI:10.2134/jeq2008.0506.

Amatya, D.M., T.J. Callahan, A. Radecki-Pawlik, P. Drewes, C. Trettin, and W.F. Hansen. 2008. Hydrologic and Water Quality Monitoring on Turkey Creek Watershed, Francis Marion National Forest, SC. Proceedings, 2008 South Carolina Water Resources Conference, October 14-15, 2008, North Charleston, SC. 

Sun, G., J. Boggs, D.M. Amatya, C.C. Trettin, Z. Dai, J.M. Vose, I.B. LaTorre Torres, and T.J. Callahan. 2008. Hydrologic Processes of Forested Headwater Across a Physiographic Gradient in the Southeastern United States. Proceedings, 2008 South Carolina Water Resources Conference, October 14-15, 2008, North Charleston, SC.

Vulava, V.M., C.G. Garrett, C.L. Ginn, and T.J. Callahan. 2008. Application of geochemical end-member mixing analysis to delineate water sources in a lowland watershed. Proceedings, 2008 South Carolina Water Resources Conference, October 14-15, 2008, North Charleston, SC. 

Pyzoha, J.E., T.J. Callahan, G. Sun, and C.C. Trettin. 2008. A conceptual hydrologic model for a forested Carolina bay depressional wetland on the Coastal Plain of South Carolina, USA. Hydrol. Process. 22 (14):2689-2998. DOI:10.1002/hyp6866. 

Reimus, P.W. and T.J. Callahan. 2007. Matrix Diffusion Rates in Fractured Volcanic Rock at the Nevada Test Site:  Evidence for a Dominant Influence of Effective Fracture Apertures. Water Resour. Res. 43:W07421. DOI:10.1029/2006WR005746.

Reimus, P.W., T.J. Callahan, S.D. Ware, M.J. Haga, and D.A. Counce. 2007. Matrix Diffusion Coefficients in Volcanic Rocks at the Nevada Test Site: Influence of Matrix Porosity, Matrix Permeability, and Fracture Coating Minerals. J. Contam. Hydrol. 93:85-95. DOI:10.1016/j.jconhyd.2007.01.017.

Harder, S.V., D.M. Amatya, T.J. Callahan, C.C. Trettin, and J. Hakkila. 2007. Hydrology and Water Budget for a First Order Forested Coastal Plain Watershed, South Carolina. J. Amer. Water Resour. Assoc. 43(3):563-575. DOI:10.1111/j.1752-1688.2007.00035.x.

Sun, G., T.J. Callahan, J.E. Pyzoha, and C.C. Trettin. 2006. Modeling the climatic and geomorphologic controls on the hydrology of a Carolina Bay wetland, South Carolina, USA. Wetlands 26(2): 567-580. DOI:10.1672/0277-5212(2006)26[567:MTCASS]2.0.CO;2.

Amatya D.M., C.C. Trettin, R.W. Skaggs, M.K. Burke, T.J. Callahan, G. Sun, J.E. Nettles, J.E. Parsons, and M. Miwa. 2005. Five hydrologic studies conducted by or in cooperation with the Center for Forested Wetlands Research, USDA Forest Service. USDA Forest Service Report, Research Paper SRS-40, Asheville, NC.

Dickerson, D. and T.J. Callahan. 2005. Students' Conceptions of Scale Regarding Groundwater. J. Geosci. Educ. 53(4): 374-380. DOI:10.5408/1089-9995-53.4.374.

Sun, G., T.J. Callahan, J.E. Pyzoha, C.C. Trettin, and D.M. Amatya. 2004. Modeling the hydrologic processes of a depressional forested wetland in South Carolina, U.S.A. Proceedings, 6th Int’l. Conf. on Hydrosci. and Engin. (ICHE-2004), 30 May-3 June 2004, Brisbane, Australia.

Callahan, T.J., J.D. Cook, M.C. Coleman, D.M. Amatya, and C.C. Trettin. 2004. Measuring and Modeling Storm Water Runoff and Soil Interflow in a Managed Forest, Upper Coastal Plain of the Southeast US. Proceedings, ASAE/CSAE Annual Int’l. Meeting, 1-4 August 2004, Ottawa, Ontario, Canada.

Reimus, P.W., M.J. Haga, A.I. Adams, T.J. Callahan, H.J. Turin, and D.A. Counce. 2003. Testing and parameterizing a conceptual solute transport model in saturated fractured tuff using sorbing and nonsorbing tracers in cross-hole tracer tests. Journal of Contaminant Hydrology 62-63: 613-626. DOI:10.1016/S0169-7722(02)00185-7.

Callahan, T.J., P.W. Reimus, P.C. Lichtner, and R.S. Bowman. 2002. Multicomponent effects on the transport of cations undergoing ion exchange in fractured media. In: Bridging the Gap Between Measurement and Modeling in Heterogeneous Media (A. N. Findikakis, ed.). Proceedings, Int’l. Groundwater Symposium, Lawrence Berkeley National Laboratory, 25-28 March 2002, Berkeley, California, USA. pp. 523-528.

Callahan, T.J., P.W. Reimus, R.S. Bowman, and M.J Haga. 2000. Using multiple experimental methods to determine fracture/matrix interactions and dispersion of nonreactive solutes in saturated volcanic rock. Water Resour. Res. 36(12):3547-3558. DOI:10.1029/2000WR900212.

(Italics denotes student author.)