Water resource exploitation from big karst spring by flow narrowing-water pressure adjusting-water table raising -- A case in Pijiazhai spring, Luxi county, Yunnan

Water resource and energy resource are in short supply at present, so it is valuable to exploit more hydropower from ascending spring. This paper is to offer an effective demonstration to the exploitation of karst ascending spring. The Pijiazhai big karst spring is an ascending spring of 1 072.75～1 957.5L/s in discharge. Its outflow point is at a flat karst valley bottom in the upper part of the Luxi karst basin. The outflow point and runoff way are lower in elevation than the fields and the villages. According to the particular hydrogeologic and engineering geologic conditions, the original engineer technique program by narrowing flow, adjusting water pressure and is designed for the exploitation of the spring. The engineer design takes benefits of favorable conditions such as the higher confining water table, the weak permeable karst zone at the lower reaches and the superjacent impermeable soil layer around the spring outflow point. The engineer made up of the seepage-proof grouting curtain and the flow narrowing, water pressure adjusting tank. The water level is adjusted by opening and closing the lock gate on the tank to realize raising the water table and transporting the water to higher elevated area, and as a result enabling the spring an artesian irrigation source. The demonstration engineer now has replaced the former 17 pumping stations and eliminated the water logging hazards at the area downstream Pijiazhai spring.