Physiographic Environment Classification: a Controlling Factor Classification of Landscape Susceptibility to...

Area of Science:

• Environmental Science
• Hydrology
• Geoscience

Background:

• Spatial variations in climate, geomorphology, and lithology influence water quality.
• Land use pressures alone do not fully explain differences in water quality issues.
• The Physiographic Environment Classification (PEC) framework categorizes landscapes by contaminant loss susceptibility.

Purpose of the Study:

• To assess the contribution of PEC classes and land use to spatial variation in water quality contaminants.
• To compare the explanatory power of landscape factors versus land use on contaminant concentrations.
• To validate the conceptual model of hydrochemical maturation using real-world data.

Main Methods:

• Developed a multi-level PEC classification using climatic, topographic, and geological data in New Zealand.
• Applied variance partitioning analysis to national surface water monitoring data (810 stations).
• Quantified the influence of PEC classes and land use on various water quality contaminants (NNN, TKN, DRP, PP, E. coli, Turbidity).

Main Results:

• PEC explained more variation in Dissolved Reactive Phosphorus (DRP), Particulate Phosphorus (PP), E. coli, and Turbidity (TURB) than land use.
• Overall, PEC accounted for 2.1 times more variation in riverine contaminant concentrations than land use.
• Significant differences in contaminant concentrations between PEC classes were observed, aligning with hydrochemical maturation concepts.

Conclusions:

• Physiographic Environment Classification (PEC) is a robust tool for understanding the underlying causes of contaminant loss.
• PEC provides valuable insights for targeted land management strategies to improve water quality.
• Landscape factors, as classified by PEC, play a critical role in determining water quality outcomes.