Identification and genetic mechanism of recharge sources in groundwater-rich area of Changxiao karst water system in Jinan City

[Objective] In order to identify the recharge sources and reveal the water-rich mechanism in the karst groundwater rich area of Jinan Changxiao Karst water system, [Methods] Hydrochemical method and self-organized neural network (SOM-KM) coupling method were used to reveal the recharge sources and spatial distribution of karst groundwater in the study area, and the contribution ratio of karst groundwater recharge sources in the karst groundwater rich area was quantitatively calculated by using the end-element mixed model. The enrichment mechanism of karst groundwater is explored in combination with topography, geological structure, stratigraphic lithology and catchment conditions. [Results] The results showed that the karst groundwater in the catchment drainage area was similar to the water chemistry of the southern recharge area, the karst groundwater in the lateral runoff area and the Yellow River, and the hydraulic relationship was close, indicating that the karst groundwater in the catchment drainage area was charged by the three sources of the southern mountain area, the karst groundwater in the lateral runoff area and the Yellow River. The contribution ratios of the three components were 75.09%, 21.02% and 3.89%, respectively. [Conclusions] Carbonate rocks are widely distributed and fissure karst develops in the accumulation and discharge area, especially in the Maji - Xiaoli - Guide area. In addition, karst groundwater recharge sources are abundant in this area. In the process of karst groundwater runoff from southeast to northwest, the groundwater is blocked by sandstone mudstone in the north, and the groundwater accumulates in the contact zone between soluble rock and non-soluble rock. Formation block type karst underground water-rich structure. [Research significance] By revealing the enrichment mechanism of karst groundwater in Changxiao Karst water system, it can provide scientific support for accurate calculation of recoverable resources and water supply of Baoquan in Jinan. Key words: Jinan; Changxiao karst water system; Karst groundwater; Supply source identification; Water enrichment mechanism.