Spatial patterns in water quality and source apportionment in a typical cascade development river southwestern China...

Area of Science:

• Environmental Science
• Hydrogeology
• Water Resource Management

Background:

• River cascade development profoundly impacts aquatic environments.
• Understanding cascade development's effect on river hydrochemistry is crucial.
• The Lancang River, China, serves as a typical case for studying these impacts.

Purpose of the Study:

• To investigate the mechanisms by which cascade development affects river hydrochemical components.
• To analyze the spatial variations in hydrochemistry influenced by reservoir development.
• To identify the primary material sources impacting the Lancang River's hydrochemistry.

Main Methods:

• Water Quality Index (WQI) for overall water quality assessment.
• Positive Matrix Factorization (PMF) model for source apportionment.
• Multivariate statistical techniques for analyzing spatial variations and influences.

Main Results:

• River hydrochemistry exhibits distinct spatial variation patterns: irregular (pH, DO), fluctuating decreasing (Na+, Cl-, SO42-, HCO3-), and multi-peak (TN, TDN, NO3--N, NH4+-N).
• Upstream areas show higher hydrochemical concentrations due to reservoir retention, despite less human activity.
• Source apportionment revealed rock weathering, sewage/soil nitrogen, and fertilizer as key contributors, with their relative importance shifting downstream.

Conclusions:

• Cascade reservoir development significantly alters river hydrochemical composition and spatial distribution.
• Reservoir retention effects are notable, influencing upstream vs. downstream hydrochemistry.
• Findings offer insights for controlling eutrophication and guiding sustainable cascade reservoir construction.