Abstract
Water chemistry deterioration has become increasingly evident at mire pools with agricultural development occurring in pool catchment areas. Improvement of hydrochemical conditions is urgently necessary for the conservation of such mire pools' ecosystems. We investigated the hydrological and chemical budgets of Lake Miyajimanuma, a Ramsar Convention wetland, which is surrounded by paddy fields in Ishikari Peatland, northern Japan, during its ice-free period in 2007-2008. Surface water inflow and outflow via ditches dominate its hydrological budget, respectively constituting 88 % of total input and 78 % of total output. Similarly, chemical budgets including Ca2+, total nitrogen, and total phosphorus were dominated by ditch inflow and outflow. Chemical constituents of the ditch inflow were derived from mineral-rich and nutrient-rich river water supplied to paddy fields as irrigation water. Therefore, the input fluxes of Ca2+, total nitrogen, and total phosphorus were much greater than those of a pristine mire pool. Increased input fluxes of chemical constituents induced by irrigation changed the hydrological and chemical budgets of mire pools, which degraded the water chemistry through eutrophication and other processes.
