Quantification of the water budget and nutrient loading in a small peatland

Few water budgets exist for specific types of wetlands such as peatlands, e ven though such information provides the basis from which to investigate li nkages between wetlands and upland ecosystems. In this study, we first dete rmined the water budget and then estimated nutrient loading from an upland farm field into a 1.5 ha, kettle-block peatland. The wetland contains highl y anisotropic pest and has no distinct, active layer of groundwater flow. W e estimated the depth of the active layer using Fick's law of diffusion and quantified groundwater flow using a chemical mass balance model. Evapotran spiration was determined using MORECS, a semi-physical model based on the P enman-Monteith approach. Precipitation and surface outflow were measured us ing physical means. Groundwater provided the major inflow, 84 percent (44,4 18 m(3)) in 1993 and 88 percent (68,311 m(3)) in 1994. Surface outflow repr esented 54 percent (28,763 m(3)) of total outflows in 1993 and 48 percent ( 37,078 m(3)) in 1994. A comparison of several published water budgets for w etlands and lakes showed that error estimates for hydrologic components in this study are well within the range of error estimates calculated in other studies. Groundwater inflow estimates and nutrient concentrations of three springs were used to estimate agricultural nutrient loading to the site. D uring the study period, nutrient loading into the peatland via groundwater discharge averaged 24.74 kg K ha(-1), 1.83 kg total inorganic P ha(-1), and 21.81 kg NO3-N ha(-1).