i-Tree cool river: An open source, freeware tool to simulate river water temperature coupled with HEC-RAS

Area of Science:

• Environmental modeling
• Urban hydrology
• Water resource management

Background:

• Urban development alters natural water systems, often leading to increased river water temperatures.
• Urban greening strategies are explored for their potential to mitigate these thermal impacts.

Purpose of the Study:

• To present the algorithms of the i-Tree Cool River model for simulating river water temperature responses to urban greening.
• To provide a tool for assessing the thermal effects of urban development and restoration on rivers.

Main Methods:

• The model utilizes integrated water and energy budget components.
• It incorporates river inflows from storm sewers and reservoirs, considering their temperatures.
• Energy budget adjustments include riparian shading, evapotranspiration, and downstream temperature propagation.

Main Results:

• The model simulates both warming from urban development and cooling from greening/restoration.
• It accounts for cool groundwater inflows and hyporheic exchange for river cooling.
• Novel features include diurnal shading variations and integration with HEC-RAS model outputs.

Conclusions:

• The i-Tree Cool River model offers a robust method for simulating river thermal dynamics in urban environments.
• The model's open-source code and documentation facilitate its adoption by other research groups.
• It serves as a valuable tool for urban planners and environmental managers aiming to improve river health.