Modeling the Sensitivity of Total Phosphorus in an Urban Stream to Climate Variability.

摘要

A study was performed to investigate the sensitivity of river phosphorus loading to changes in precipitation, temperature, and flow rate. This research performs sensitivity analyses using elasticity principles similar to those employed by economists (i.e., price elasticity of demand) to uncover climate-nutrient-loading relationships. Here, the concept of elasticity is implemented in a water quality context to identify the sensitivity of total phosphorus (dissolved and particulate) loading in an urban stream to several climate variables using multivariate approaches. Previous analyses have used single parameter elasticity methods to represent the general relationship between nutrient loading and a variable of interest, but these methods cannot reflect the complicated nonlinear relationships inherent among nutrients, precipitation, temperature, and streamflow. Instead, the multivariate analysis presented in this study relies on the combined interactions among precipitation, temperature, and streamflow to successfully distinguish their individual impacts on nutrient loading. This study presents field data results and develops models that can be used to estimate phosphorus loads while determining the sensitivity of total phosphorus loading to changes in climate variables. It was found that total phosphorus loading at Alewife Brook depends significantly on season, rainfall, combined sewer overflow incidents, and flow rate. These results were significant for the development of a nutrient loading model that predicted a 3.6% to 7.4% increase in total phosphorus loading at Alewife Brook if small increases in precipitation, temperature, flow rate, and combined sewer overflow incidents occur. These results could be useful for developing models to better predict water quality responses to climate variability.