Sustainable Yield of Hot Springs in Shandong Peninsula, China

Abstract

Shandong Peninsula, located on the eastern coast of China between Beijing and Shanghai, is one of the regions rich in natural hot springs. Most of the hot springs are distributed in the Jiaobei uplift and Jiaonan-Weihai orogenic belt, with fractured geothermal reservoirs controlled by the deep and large faults, as well as convective heat sources. Fifteen natural hot springs were found and of which the temperatures range from 49.7 to 90 °C, TDS range from 0.41 to 16.62 g/L and natural flow rates range from 1.79 to 41.42 cubic meters per hour. Their total production is about 2.11 million in 2008. Due to large-scale exploitation of geothermal water; the water levels have been declining in the last 20 years. Most of the hot springs dry up when exploitation is increased during winter seasons, and only part of them can return to being artesian during the rainy season when the exploitation is decreased. Corresponding to the geothermal water level decrease, the colder surface water and shallow groundwater infiltrate and recharge the the geothermal water, which causes the drop in geothermal water temperature. Yujiatang, one of the 15 hot springs is taken as an example in this paper to explore the sustainable yield. Based on the geological and hydrogeological conditions, the geothermal reservoir conceptual model of Yujiatang geothermal field is formulated, and the numerical model is developed. Finally, the sustainable yield of the Yujiatang geothermal field is evaluated with the prerequisites of its water level being higher than the minimum allowable water level and the water temperature higher than the minimum allowable temperature.