Assessing threshold values for eutrophication management using Bayesian method in Yuqiao Reservoir, North China.

Area of Science:

• Environmental Science
• Water Resource Management
• Limnology

Background:

• Eutrophication of drinking water sources poses a significant threat to urban water security.
• Phosphorus (TP) is a critical nutrient influencing water quality in northern hemisphere lakes and reservoirs.
• Yuqiao Reservoir's water quality is vital for regional water supply.

Purpose of the Study:

• To model the changing trends of total phosphorus (TP) in Yuqiao Reservoir using 15-year monitoring data.
• To analyze nutrient parameter uncertainty and estimate eutrophication management thresholds.
• To establish specific water quality goals for reservoir management.

Main Methods:

• Application of a Bayesian method with a chemical material balance (CMB) model.
• Analysis of 15-year monitoring records (1990-2004) for Yuqiao Reservoir.
• Utilizing an inverse method to evaluate joint management strategies.

Main Results:

• Yuqiao Reservoir was identified as a phosphorus-controlled (P-controlled) water ecosystem.
• TP concentration correlated significantly with TP loading, hydraulic retention, and bottom water dissolved oxygen (DO).
• Management thresholds were established: highest inflow TP (0.15–0.21 mg L⁻¹) and lowest DO (3.76–5.59 mg L⁻¹) to meet a TP goal of 0.05 mg L⁻¹.

Conclusions:

• Controlling inflow phosphorus concentration and maintaining adequate dissolved oxygen levels are crucial for eutrophication management.
• Adjusting reservoir inflow/outflow and dissolved oxygen are valuable measures to prevent eutrophication.
• The study provides a quantitative framework for managing phosphorus and ensuring water quality in reservoirs.