Novel quantification of coupled natural and cross-sectoral water and nutrient/pollutant flows for environmental management.

Human water use and anthropogenic water pollution and ecosystem deterioration have increased so much that it is now a strategic challenge to maximize benefits from various possible water uses, while ensuring that basic human needs are met and the environment is protected. We propose and develop a novel use of input-output flow analysis as a relatively simple, compact and powerful tool for quantification of coupled natural and cross-sectoral flows of water, nutrients, and pollutants in catchments. The tool quantifies implications of various environmental regulation and management scenarios for both natural water systems and engineered-economic systems and sectors that use and impact natural waters for meeting human needs. Specific case study application to water and nitrogen flows in the Swedish Norrström drainage basin indicates considerable nitrogen load contributions to surface and coastal waters from slow groundwater flow paths and legacies of accumulated nitrogen in subsurface and immobile water pools. This implies that effective nitrogen load abatement cannot focus only on active sources but must also include downstream measures, which can capture and abate nitrogen/pollutant loading from different types of known and yet unknown point and diffuse sources within associated catchments.