Green energy and its high-efficiency utilization model of surface karst springs in karst plateau mountainous area

To solve the problem of water shortage in karst plateau mountainous area, this study on the model of development and utilization of surface karst water is conducted. The karst mountainous area in east border of Luxi basin isa typical cluster-peak depression region with an average altitude from 2,100-2,300 m. Depressions and sinkholes are developed there. Outcrops in this area are mailnly composed of limestone and dolomite in sections a, c, d and e of Gejiu formation (T₂g), and partially composed of T₂g b mudstone, calcareous mudstone, stacked siltstone with marlstone and limestone. The area is generally a monoclinal structure. Detailed hydrogeology research shows that there are 13 exposed epikarst springs with the flow of 0-67.53 L·s⁻¹ due to precipitation. The water leakage in this area is fast, and drought and water shortage are very severe. Thus, surface karst water becomes a very valuable natural resource. This article summarizes a green, high-efficient method of development and utilization of surface karst water as "spring-pool(cellar)-reservoir" optimal management model. In karst concave depression area with siltstone, the grouting with anti-seepage curtain was conducted at the grouting depth of 1.9-16.3 m. An earth dam was built at an anti-seepage foundation and a reservoir with a total storage of 140,000 m³ was constructed to reserve surface water and surface karst water to supply the downstream villages. Below the nozzles of epikarst springs with large flows in Wanbankong depression area, two 1,500-square-meter storage ponds were built to connect the current water supply network for downstream villages. This model of development and utilization of surface karst water is called "spring-pond-cellar" linkage model with an exploitation quantity of around 73,000 m³·a⁻¹. The distance between Aobushan Reservoir and Wanbankong epikarst spring is around 4 km and the reservoir is around 100 m higher than the Wanbankong spring. The flow of the Wanbankong epikarst spring is quite big but very unstable and cannot be reserved. Most of the water in rain season (around 493,700 m³·a⁻¹ accounting for 81.4% of the annual volume) enters to the underground through sinkhole and cannot be utilized. To make the most of reservoir regulation function from surface karst water against rainfall, a pump station and a photovoltaic power plant have been bulit near the Wanbankong epikarst spring. In the rainy season-water stable period with large flows, electric power is generated from the photovoltaic power plant and the pump station will draw surface karst water (around 40,000 m³·a⁻¹) to the upstream Aobushan reservoir. Thus, the reservoir capacity increases from 140,000 m³ to 180,000 m³ under the condition that the reservoir cannot be expanded. In this case, the water supply capacity will increase in dry season. The surface water and underground water are regulated optimally and the total volume of surface spring water and surface water is up to 253,000 m³·a⁻¹. This model may solve the problem of over 13,000 people’s domestic and production water demand, as well as the water demand from seedling over 10,000 Mu in the dry season.