Geochemical-Spatial Model Estimating Phosphorus Load from Septic Systems into the Lake Erie Basin

Session: Poster session

Lauren Oldfield, The University of Western Ontario , [email protected]
Clare Robinson, The University of Western Ontario, Civil & Environmental Eng., [email protected]
Ming Wu, University of Western Ontario, [email protected]

Abstract

The role of phosphorus(P) in the development of harmful algal blooms in the Great Lakes is well known; but unlike wastewater and agricultural sources, the relative importance of septic systems(SS) as a source of P is not well quantified. This is attributed to the complex chemical nature and transport of P in the subsurface, and the limited tools available to reliably estimate P loading at large scales. To address this uncertainty, a geospatial model specific to conditions in the Lake Erie Basin was developed. This model, based on an extensive review of geochemical and hydrologic conditions controlling P mobility, uses a two-part approach. Initially, Hydrus with PHREEQC is used to estimate the percentage transport of P from septic tile bed to groundwater; following this, ArcGIS is used to simulate the movement of P through ground water to surface waters.

Preliminary results from a pilot test of two sub-watersheds in the Lake Erie Basin indicate that SS P loadings provide a small but consistent source of the annual loadings into the lake. This model will be used to improve estimates of P loadings in the Lake Erie Basin, and to better inform regulatory decisions regarding P loading from SS.

1. Keyword
GIS

2. Keyword
Lake Erie

3. Keyword
phosphorus

4. Additional Keyword
HABs