A review of low-grade weirs as an agri-environmental best management practice in the Elginfield Municipal Drain watershed, Ontario, Canada

Abstract

R ecent algae blooms in Lake Erie are projected to worsen with continued anthropogenic climate and land use changes. Agricultural systems have evolved from being net phosphorus (P) sinks, where crop production is P-limited, to being P sources, with net P export from most farms (McElmurray et al. 2013; Scavia 2014). In 2012, the International Joint Commission established the Lake Erie Ecosystem Priority in response to growing lake-wide changes related to problems of P runoff from agricultural fields, compounded by the influence of climate change on winter hydrology and extreme rainfall event statistics (International Joint Commission 2014). These changes have resulted in impaired water quality, with impacts on ecosystem health, drinking water supplies, fisheries, recreation and tourism, and waterfront property values. Agricultural runoff is the major source of nonpoint inputs of P in the Lake Erie basin. The basin receives 44% of the total P (TP) load entering the Great Lakes from agricultural activities, more than any other individual Great Lake in the system (Rucinski et al. 2014; Dolan and Chapra 2012). Commercial fertilizers account for the majority of agriculturally applied P in most locations. In Ohio, 84% of P applied to agricultural land in the Lake Erie basin originates from…