The hydrology of a floodplain wetland, Narborough Bog, Leicestershire.

A combination of fieldwork and numerical modelling is used to examine the hydrology of a floodplain wetland, Narborough Bog in Leicestershire. The hydrogeological conditions which maintain floodplain wetlands are considered by describing floodplain hydrostratigraphies and deriving a simplified model of wetland hydrology. The hydrological processes which provide water inflow and outflow to a wetland system are reviewed. The mathematics of subsurface water flow are described to provide the background for application of a full groundwater model to the site. The processes are considered by reviewing studies on wetland hydrology. Regular monitoring of field water tables was undertaken, from November 1990 to June 1993; and the spatial and temporal relationship of these records to rainfall, evapotranspiration and river stage are described. Regression models and a response function are used to quantify the relationship of water tables to meteorological parameters, and also to examine the extent of temporal variations in model explanation. Experiments investigating water flow through in-situ peat deposits and alluvial sediments are described. These included an artificial flood experiment and the study of infiltration through an isolated peat column. The results enable approximate values for hydraulic parameters to be estimated for organic and alluvial deposits. The groundwater model MODFLOW was used to develop a calibrated transient model, the ability of which to replicate water table responses to isolated recharge and evapotranspiration events was examined. The results enable an assessment of the significance of influent and effluent water flows, and the contribution of overbank water flow to Narborough Bog. Suggestions for further refinement to the model are advanced. The model is used to derive approximate water budgets for 1991 and 1992 to demonstrate the sensitivity of Narborough Bog to periods of drought, and examine the current significance of the river to site hydrology.