Hydrodynamics of floodplain wetlands
Soil-Water fluxes in macro-porous soils
Hydrology of permeable catchment
Current / recent research
Hydrodynamics of floodplain wetlands
This on-going work seeks to advance ways to investigate the hydrology of lowland floodplain wetlands and includes the modelling of shallow groundwater flows and river-aquifer interaction. Specific research projects have included the modelling of transient water table variations on floodplain wetlands using the USGS groundwater modelling program, MODFLOW (Bradley, 2002). The research has been associated with the use of hydrological data to characterise wetland hydrology, within the context of floodplain / wetland sedimentology. Joint work with David Gilvear (University of Stirling) has investigated the movement of water to and from the water-table at sites in the Insh Marshes, Speyside, using a lysimeter and nests of tensiometers (Gilvear & Bradley, 2000; Gilvear & Bradley, 2009). Other work, recently completed, has included an investigation of the use of stable isotopes to fingerprint water sources from a small headwater wetland in North Shropshire (Clay et al., 2004), and the use of a network of 12 recording tensiometers to identify variations in the direction and rate of water movement through a small upland floodplain wetland near Plynlimon.
Soil – Water fluxes in Macro-porous soils
Many studies of wetland hydrology assume that water fluxes can be estimated using Darcy’s Law. The limitations of this approach have been considered in a number of papers that examine water flow through peat deposits, and, for a cracking clay soil at Brimstone Farm, Oxfordshire. Bradley and van den Berg (2005) describe a novel field experiment to determine the hydraulic conductivity of a herbaceous peat deposit, in which four infiltration experiments were conducted on the same isolated peat column. Bradley et al (2005 & 2007) examined seasonal soil-water dynamics in an instrumented plot, comprising four nests of recording tensiometers, in a cracking clay soil, and investigated the factors contributing to macro-pore flow.
Hydrology of Permeable Catchments
A recently completed project (with Dr Tim Grapes) investigated surfacewater - groundwater interactions in a permeable chalk catchment in the UK (the River Lambourn). The project included the modelling of groundwater flows using an enhanced version of MODFLOW (Groundwater Vistas). An extensive flow accretion survey highlighted characteristic variations in seepage to and from the river, related to catchment topography.
On-going work with Prof. Andy Baker (University of New South Wales) seeks to quantify the uncertainty in stalagmite δ18O that arises specifically as a function of the variation in karst water flow pathways. A lumped hydrological model to summarise the dynamics of water movement and has been successfully applied to karst systems in differing climates (Bradley et al. In Press). Current work seeks to calibrate the model for individual speleothems to compare the sensitivity of stalagmite δ18O to changes in temperature, and precipitation, over various time-scales.
On-going work in the Tern Catchment (North Shropshire) is investigating carbon fluxes from small riparian wetlands, and looking at the connectivity between the river and different floodplain units (Bradley et al. 2007). A further project with A. Milner and J. Crossman seeks to understand the Hydro-ecology of Upwelling Zones in the Denali National Park, Alaska.
Key Publications since 2001
Bradley, C., Baker, A, Jex, C.N., & Leng, M.J. In Press. Hydrological uncertainties in the modelling of cave drip-water δ18O and the implications for stalagmite palaeoclimate reconstruction. Quaternary Science Reviews.
Baker, A., Bradley, C. 2010. Modern stalagmite δ18O: Instrumental calibration and forward modelling. Global and Planetary Change, 71, pp. 201-206.
Hannah, D.M., Malcolm, I.A., & Bradley, C. 2009. Seasonal hyporheic temperature dynamics over riffle bedforms. Hydrological Processes, 23, pp. 2178-2194.
Gilvear, D & Bradley, C. 2009. Hydrological Dynamics II: Groundwater and hydrological connectivity. Chapter 7 in "The Wetlands Handbook", edited by E. Maltby, Wiley, pp. 169-193.
Rosales, J.L., Belmont-Blanco, L. & Bradley C. 2007. Hydrogeomorphological and ecological interaction in the confluence zones of the Orinoco River, Venezuela. In: “Hydroecology and Ecohydrology: Past, Present and Future” Edited by D.M. Hannah, P. Wood & J. Sadler. Wiley, pp. 295-316.
Bradley, C., Baker, A., Cumberland, S., Boomer, I., & Morrissey, I.P. 2007. Dynamics of water movement and trends in dissolved carbon in a headwater wetland in a permeable catchment. Wetlands, 27 (4), pp. 1066-1080.
Bradley, C., Mosugu, M & Gerrard AJ. 2007. Seasonal dynamics of soil-water pressure in a cracking clay soil. Catena, 69, 253-263.
Bradley, C. 2006. Classics Revisited: Lewis 1949: the Pegsdon Dry Valleys. Progress in Physical Geography, 30 (3), 394-398.
Grapes, T, Bradley, C & Petts, GE. 2006. Hydrodynamics of floodplain wetlands in a Chalk catchment: the River Lambourn, UK. Journal of Hydrology. 320, 324-341.
Bradley, C., Mosugu, M, & Gerrard AJ. 2005. Simulation modelling of water movement in a cracking clay soil. Soil Use and Management. 21, 386-395
Bradley, C. & van den Berg, JA. 2005. Infiltration mechanisms in a herbaceous peat: results of an infiltration experiment. Hydrological Sciences Journal, 50 (4) pp. 713-725
Grapes, T, Bradley, C & Petts, GE. 2005. Spatial and temporal dynamics of river - aquifer interaction along a Chalk stream: the River Lambourn, UK. Hydrological Processes. 19, 2035-2053.
Bradley, C. 2002. Simulation of the annual water table dynamics of a floodplain wetland, Narborough Bog, UK. Journal of Hydrology, 261, pp. 150-172