Over the last 40 years, declining spring water flow rates have become a typical feature of karst springs in Northern China. Wavelet analysis, the Mann-Kendall trend test and the mutation test were used to analyze dynamic monitoring data of groundwater levels and atmospheric precipitation in the Jinan karst spring area, from 1956 to 2013, to study hydrological responses to atmospheric precipitation over one-year periods. Results from this analysis show that: (1) Atmospheric precipitation and the spring water level displayed multi-scale change characteristics, having two very similar cycles of change of 16 and 12 years. This finding shows that atmospheric precipitation generates a direct impact on the level of spring water. (2) From 1956 to 2013, the groundwater level in the Jinan spring area had a significant downward trend (0.65 m/10a). Precipitation recorded an increasing trend (12.65 mm/10a), however this was not significant. The weight of the influencing factors of the spring dynamic therefore changed due to the influence of human factors. (3) A mutation of atmospheric precipitation occurred in 1999, after which annual precipitation increased. Results for the mutation of the groundwater level showed an initial change in 1967. After this change the water level continued to decrease before rapidly increasing after 2004. The future trend of the spring water level should be maintained with consistent precipitation (having an upward trend), indicating that atmospheric precipitation is not the only factor affecting the dynamics of the spring. (4) Different periods were identified on the multiple regression model. The main influencing factors on groundwater level over the past 58 years were identified as a transition from precipitation to artificial mining. These results also validate the suitability and reliability of using wavelet analysis and the Mann-Kendall test method to study groundwater dynamics; these results provide a reference for the future protection of the Jinan City spring.

Pore water in inland plain areas, generally having poor water quality, contain complex hydrochemical properties. In order to examine groundwater chemical composition formation characteristics, groundwater in the Jiyang area of Lubei Plain was studied using stratified monitoring of drilling, analysis of water level and water quality, isotope analysis, ion ratio coefficient and isothermal adsorption experiments, hydrochemical characteristics, and analysis of variations in different shallow depths. Results show that: (1) Numerous hydrochemistry types are present in the diving. Along with the direction of groundwater flow, total dissolved solids (TDS) of diving in the study area generally increases and the hydrochemical type changes from the HCO 3 type to the HCO 3 •SO 4 type, Cl•HCO 3 type and the Cl•SO 4 type. (2) Shallow brackish water and freshwater in the horizontal direction are alternately distributed, and shallow brackish water is distributed in the area between old channels, showing sporadic spots or bands, whose hydrochemistry type is predominantly Cl•SO 4-Na•Mg•Ca. (3) Affected by the sedimentary environment, hydrodynamic conditions and other factors; diving, middle brackish water and deep freshwater are vertically deposited in the study area. The dynamics of middle brackish water quality are stable due to the sedimentary environment and clay deposits. The hydrochemistry types of middle brackish water are mainly Cl•SO 4-Mg•Na and SO 4 •Cl-Na•Mg, while the deep confined water is dominated by HCO 3. (4) The optimal adsorption isotherms of Na + , Ca 2+ and Mg 2+ in groundwater from clay, with a thickness raging from 6-112 m, conformed to the Henry equation and the Langmuir equation. The retardation of Na + , Ca 2+ and Mg 2+ in groundwater differed with differing depths of the clay deposit. The trend of change in retardation strength correlates strongly with the TDS of groundwater. Groundwater in the inland plain area is affected by complicated hydrogeochemical processes; in addition, leaching, cation exchange, evaporative concentration and clay retardation have an important influence on the horizontal and vertical zonation of groundwater chemical components.

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In order to reveal the hydrodynamic characteristics of the karst aquifer system, the water temperature dynamic data of a hydrological year in the direct recharge area of Jinan spring area were analyzed using the temperature tracer method, and the runoff intensity of karst water was estimated. The results revealed that, affected by the regional groundwater flow, the vertical temperature profile of the study area consists of four types, a gradual cooling type, a gradual heating type, a temperature‐increasing type, and “S” type. Based on these four geothermal types, three heat transfer models adapted to the region were developed. The inflection point method is used to discriminate the horizontal runoff channels of the three depth segments in the Ordovician strata in the recharge area, and the shallow groundwater horizontal runoff intensity is greater than the deep. According to the calculation of the thermal transport model, the Ordovician limestone in the direct recharge area of the spring area is shallow (at a depth of 100 m), and the vertical flow velocity of the groundwater is around 1.28 × 10−7–3 × 10−6 cm/s, and the flow rate is slow. Based on the field tracer test, the visual flow of the karst water system was found to range between 29.41 and 115.02 m/day, indicating that the karst water is dominated by horizontal motion. Since the method of temperature measurement in the hole is relatively simple, the temperature change signal could be used to reveal the seepage characteristics of the groundwater.

In order to increase understanding of the hydrogeochemical effects that influence changes in the quality of salt water, we investigated the distribution of saline and fresh water in an inland plain area and, in particular, the scarcity of fresh water resources. Taking the inland plain in Jiyang County as a specific case study, samples of undisturbed clay and underground saline water from different depths were collected to examine hydrogeological changes. A wide variety of methods was used to analyze the blocking effect of clay on the chemical characteristics of the groundwater. These include real-time monitoring for field water quality, tests for isothermal adsorption, a factor analysis model, physiochemical analysis, and correlation analysis. Our results show that the optimal adsorption isotherm of clay for Na+, Ca2+ and Mg2+ in groundwater conform to the established Henry and Langmuir equations for adsorption isotherms. The influence of clay mineral types and content on the blockage of Na+, Ca2+ and Mg2+ in groundwater samples were evident at different depths, with the clay adsorption capacity increasing in line with increases in the clay mineral content. Clay at different depths was found to have the strongest blocking effect on Na+ in groundwater, being systematically greater than its effect on Ca2+ and Mg2+. It is believed that the blocking effect of clay has an important influence on the hydrochemical zoning of groundwater in inland plains and the formation of saline water in groundwater systems. This study therefore provides concrete evidence in support of this supposed effect.