Phosphorus retention patterns along the Tisza River, Hungary

Area of Science:

• Environmental Science
• Hydrology
• Water Quality Management

Background:

• Large rivers play a crucial role in nutrient cycling and sediment transport.
• Understanding in-stream nutrient retention is vital for effective water resource management.
• The Tisza River, a significant European watercourse, faces challenges related to water quality and flow dynamics.

Purpose of the Study:

• To quantify in-stream retention of suspended solids (SS) and total phosphorus (TP) in the Tisza River under low flow conditions.
• To analyze the influence of river morphology and flow dynamics on SS and TP transport and retention.
• To investigate the impact of storage reservoirs on longitudinal nutrient retention patterns.

Main Methods:

• Conducted a longitudinal water quality survey along the Hungarian section of the Tisza River (approx. 600 km).
• Collected manual water samples for SS and TP analysis and utilized on-line turbidity data for SS concentration estimation.
• Employed a 1D hydrodynamic model to calculate the velocity field and applied a first-order equation to model SS transport and TP retention.

Main Results:

• Total phosphorus (TP) retention reached 42% along the studied section of the Tisza River at a flow rate of 110 m(3) s(-1).
• Storage reservoirs significantly altered the longitudinal retention pattern, with net TP retention of 73% upstream of Dam II.
• The downstream section of the river acted as a source of TP, indicating complex nutrient dynamics.

Conclusions:

• The Tisza River exhibits substantial in-stream TP retention, particularly influenced by reservoir structures.
• Flow velocity and riverbed characteristics are key factors governing SS and TP transport and deposition.
• Effective management strategies for the Tisza River should consider the role of reservoirs in nutrient retention and potential downstream TP release.