| Groundwater is a principal pathway of nutrient fluxes to the coastal zone. In a two year study, five methods of quantifying freshwater flux from a shallow coastal embayment were examined for their utility in coastal marine ecological studies of nutrient cycling and eutrophication of shallow embayments. Four methods were in good agreement (chloride mass balance, inlet blocking, Darcian methods, water budget). Inflation of volumetric tidal results was caused by tidal irregularities caused by wind and barometric changes. Use of a single method can lead to errors, and the use of at least two independent methods (e.g. chloride mass balance, Darcian flow analysis, water balance), will improve confidence in the results while increasing the understanding of the system. Estimates of embayment zones of contribution using topographic delineation or poorly constrained water table maps may lead to significant errors when used for water budgets or nutrient loading models.;Aquifer parameters (water table configuration, hydraulic conductivity, porosity, thickness, areal extent) were examined using field and laboratory methods. Five methods for determining hydraulic conductivity (K) (tidal transmissivity, tracer, slug, permeameter, grain size), were compared in both upland and nearshore areas. K in the nearshore zone was significantly lower than upland sites. Probable causes of the lower near-shore K values were: peat layers from relict fringing marshes; incorporation of allochthonous organic matter into bay sediments; formation of iron precipitates in discharge zones at bay margins; and variations in sediment sorting. Methods which measured K over greater distances (tracer, tidal transmissivity) were found to be preferable, while smaller scale measurements were often easier to obtain and repeat. Grain size results were equation specific and were varied for the same sediment sample. Permeameter results were depressed by about one-third to one-half of other methods.;Embayment morphology and relationship to regional morphology affected groundwater flow. When mean tide levels increased, groundwater was diverted from the embayment. During random blockage of the inlet the normal groundwater flow pattern was altered: as embayment elevation increased, water within the embayment began to flow into the aquifer, groundwater flow diverged from the embayment, altering the zone of contribution and the nutrient load. |
