Rich surface water resources in south China can be utilized as heat source-sink for heat pump systems. A district heating and cooling system that utilizes lake water as heat source-sink of heat pumps has been constructed in Xiangtan. a city in Hunan province in south China. The lake water temperature distribution during continuous operation was simulated before the construction. https://www.roneverhart.com/Grace-Design-M801-MK2-High-Fidelity-p15168/