DO LANDSCAPE INDICATORS CORRELATE WITH GROUNDWATER NITRATE CONCENTRATIONS? A TRANS-BORDER AQUIFER STUDY
The goal of this research was to assess the general patterns and possible correlations between land use practices and groundwater nitrate concentrations within the ASA using landscape indicators (such as percent agriculture and percent forest cover). A seamless cross-border land cover mosaic was created by harmonizing a variety of US and Canadian land use and land cover datasets. More detailed landscape indicators were created using agricultural groupings reflecting likely nutrient loading potentials of different crop types and fertilizer management practices. Nitrate concentrations in groundwater samples were examined from 41 well sites throughout the US and Canada. At each monitoring station, terrestrial zones of influence (aligned with the directional flow of groundwater) were delineated around wells and landscape indicators were calculated within this zone. To link landscape indicators with nitrate concentrations, multiple linear regression was used to test for statistical associations between landscape indicators and mean and median nitrate concentrations. Different agricultural crop types and management regimes showed different strengths of correlations with groundwater nitrate concentrations. A general goal of this work was to determine which landscape indicators could be useful to help inform future trans-boundary water management strategies.