Division of karst water protection areas based on analysis of hydrogeologic conditions

This paper discussed the division of water source protection zones in karst areas with complex hydro-geological conditions. Taking the Baiquan karst water system of Xingtai City, Hebei Province as an example, we analyzed the historical evolution characters of the groundwater flow field of the karst system influenced by human activities, and forecasted the variation of this field in ten years under the conditions of over exploitation by the numerical modeling method. It is found that "the artificial watershed of the Shahe River" has formed due to water drainage from mines in the spring areas, which is moving north rapidly, indicative of the seriousness of water resource shortage in the Baiquan karst area. We suggested that under complex karst hydro-geological conditions, if the protection zone is divided using the calculation flow method, it can result in waste of the protected area and the non-protection of the recharge area with carbonate exposure. On the premise of water quality protection and sustainability of water resources, we analyzed the protective capability of overlying strata of the water source and the influence on the water source of drainage from mines in the recharge area with carbonate exposure. Such recharge area should be attributed to a secondary protection zone, which breaks the traditional pattern of "the primary protection zone enclosed by the second protection zone". The overall water level of the Baiquan karst water system has increased for nearly 30 m in two years since the adjustment of the protection area, which proves that the quality and sustainability of the water source with a relatively small protection zone is guaranteed by the new division method and that the hydrogeological condition analysis is important for the division of water source protection zones in complicated areas.