[Water environmental capacity calculation model for the rivers in drinking water source conservation area]

Area of Science:

• Environmental Science
• Water Resource Management
• Ecosystem Modeling

Context:

• Drinking water source conservation areas (DWSCA) require integrated water environmental capacity (WEC) assessments for rivers and reservoirs.
• Existing models face challenges due to differing water quality standards and hydrological conditions between riverine and reservoir environments.
• The Laohutan reservoir in southeast China serves as a case study for this integrated approach.

Purpose:

• To develop a novel WEC model for river-reservoir systems within DWSCA.
• To establish a unified water quality control target for upstream rivers based on downstream reservoir demands.
• To address discrepancies in water quality standards (e.g., for total phosphorus (TP) and total nitrogen (TN)) and hydrological assumptions between river and reservoir WEC estimations.

Summary:

• A new one-dimension WEC model integrates river and reservoir systems in DWSCA, using the reservoir's water quality demand to set river targets.
• This method simplifies WEC estimation by resolving conflicting standards and hydrological conditions.
• Case study results for Laohutan reservoir show WEC for TN and TP are 65.05 t/a and 5.05 t/a, respectively, indicating a need for significant TN reduction.

Impact:

• Provides a more accurate and unified approach to WEC assessment in connected water bodies.
• Facilitates effective water quality management and pollution control in DWSCA.
• Applicable to continuous water systems with varying water quality targets, particularly where downstream requirements are more stringent.