Landscape controls of hydrologic function and phosphorus dynamics in two pond-wetland complexes on the mixedwood boreal plain

The dominant hydrologic and phosphorus (P) fluxes were measured in two pond-peatland complexes in the Boreal Plain of Northern Alberta: one moraine pond-peatland (topographic high) and one clay plain pond-peatland (topographic low). During 1999--2000, both locations were groundwater recharge zones to underlying flow systems. At both pond-peatlands, hydrometric, geochemical and isotopic measurements determined that precipitation and evaporation dominated the water balance, and local groundwater fluxes were seasonally variable. The periphery of the moraine pond exhibited local groundwater flow reversals: recharge during dry periods, discharge during wet periods. The clay plain complex was a groundwater flow-through system for most of the study, but reversed to discharge during high rainfall (spring 2000). Although [P] were high in surface and groundwater of both complexes ([TDP] = 30--3000 mugl -1), concentrations were consistently greater at the clay plain. Groundwater [P] was most strongly correlated to low DO, mid-range pH, and high water table. Shallow groundwater accounted for ∼50% of TDP and SRP loading to ponds, and groundwater flow reversals influenced pond [P]. Therefore, shallow groundwater is a small flux in the water balance, but an important control on surface water chemistry. Complex groundwater-phosphorus interactions may have important implications for forest disturbance in the Boreal Plains.