SPATIAL AND DOWNSTREAM VARIABILITY OF BASEFLOW NUTRIENT RUNOFF IN THE LITTLE CHAZY RIVER, NORTHEASTERN NEW YORK

Nutrient loadings for total P, total N, phosphate and nitrate to Lake Champlain are based on chemical and streamflow data from gaging stations near the mouths of major tributaries. The lack of spatial resolution in nutrient data from the watershed however, limits the ability of these studies to identify the locations and relative magnitudes of different nutrient sources to the lake. The objective of this study was to use a closely spaced stream gage network and high-resolution water-sampling regime to relate spatial and downstream nutrient loads to land management practices in a predominantly agricultural, 6 km reach of the Little Chazy River (basin area = 142 km²) in northeastern New York. The reach includes several small tributaries (basin area <10 km²) and tile-drain outflows that contribute high nutrient concentrations but relatively small nutrient loads to the main channel. Two mid-reach sections that exhibit substantial loss of discharge and decrease in nutrient loads interrupt the general downstream increase in baseflow nutrient loadings. Nutrient losses in these sections may be explained by biological uptake, adsorption onto reactive mineral surfaces in the hyporheic zone or losses to groundwater. High-resolution nutrient loading studies illustrate the complexity of natural river systems and may provide a better understanding processes controlling fate and transport of non-point source pollutants.