The Jinan karst spring system, discharged by 108 springs in 2.6 km² city center area of Jinan, China, has been suffering lower regional groundwater levels, which threatens the karst springs outflowing and aquatic ecological civilization. For better spring protection, monthly hydrogeochemical and isotopic investigations were conducted in four representative karst springs (Baotu Spring (BTQ), Heihu Spring (HHQ), Zhenzhu (ZZQ), and Wulongtan Springs (WLT)) in 2016. Results showed that the BTQ, WLT, and ZZQ had similar hydrogeochemical and isotopic behaviors, which were different with that of HHQ. By combining the daily water level data with monthly hydrogeochemical and isotopic data of BTQ and HHQ, the hydrogeological processes of the two neighboring karst springs (470 m apart) are distinguished. (a) BTQ is recharged by two sources of precipitation and river water, while HHQ is recharged mainly by precipitation. (b) Hydrogeochemical characteristics of Baotu Spring are mainly controlled by calcite, dolomite, and gypsum dissolution mixture with river water and agricultural activity, while the hydrogeochemical characteristics of Heihu Spring are mainly controlled by calcite, dolomite, and gypsum dissolution in dry season, and dilution in wet season. (c) The discharge component of both springs is storage water by diffuse flow which is pressured by new infiltration rain water. The ratio of rain water is 14% in Baotu Spring and 9% in Heihu Spring calculated by a binary mixture model. Overall, this study puts forward the standpoint that neighboring karst springs with the same geological condition, can show different hydrogeological characteristics, which is a useful evidence for understanding the heterogeneity/complexity of karst aquifers.

The Jinan Karst Spring System in Shandong province, China, has suffered to maintain groundwater level and spring flowing for decades. Recharge of river water to karst aquifer in Jinan is important for the outflowing of four large karst springs in the city center. Field investigations were conducted for two times in May and October, 2015, respectively and water samples were collected for hydrogeochemical and isotopic measurements. Results showed that (a) the water type was predominantly Ca-HCO₃-SO₄ for karst groundwater, and Ca-Mg-SO₄ for river water; (b) the concentration of HCO₃⁻ and NO₃⁻ in karst groundwater were higher than that in river water, in contrast, the concentration of SO₄²⁻ and K⁺ in karst groundwater were lower than that in river water; (c) the δ²H and δ¹⁸O values with average of −51.2‰ and −6.6‰ for river water is more enriched than the values in groundwater samples (−59.1‰ and −8.3‰), in that river experienced evaporation in the upstream reservoir; (d) Based on the distribution pattern of δ¹⁸O, groundwater near river bank was found to be recharged from river water and found a preferential flow path in karst aquifer situated from Dongkema to Manzizhuang near the river bank. This study provides useful information for understanding of the hydraulic connection between river water and karst aquifer, and benefit the protection and management of water resources.

As an important surface water source, the rational water rights allocation of reservoirs plays a crucial role in alleviating the contradiction between water supply and demand in surrounding areas. However, the theoretical framework for water rights allocation mostly focuses on the watershed scale, which is different from water rights allocation of reservoirs. Research on the water rights allocation of reservoirs is relatively scarce and still at a preliminary stage. Therefore, this study developed a two-dimensional method for sectoral and regional allocation of initial water rights of a reservoir, which was applied to Nishan Reservoir in northern China. The reservoir’s utilizable storage capacity, total initial water rights, and water rights of various sectors were determined using the water balance principle and chronological method. Subsequently, based on the constructed system of indices and assessment criteria for the regional allocation of initial water rights, an allocation model for the reservoirs’ initial water rights was established using the matter-element extension theory to subdivide the sectoral water rights allocations into regional initial water rights allocations. The results show that the total initial water rights of Nishan Reservoir are 20.64 million m³, with the water rights allocations for agricultural irrigation, industry/domestic use, and ecological needs at 4.24, 10.4, and 6.00 million m³, respectively. The 6.00 million m³ allocation for ecological water use is solely managed by the prefecture-level administration of Jining City. The remaining allocations of the reservoir’s initial water rights are 9.67 million m³ for Qufu City, 1.63 million m³ for Sishui County, and 3.34 million m³ for Zoucheng City. This allocation scheme has been accepted by all stakeholders of the Nishan Reservoir’s water rights. The method proposed in this study can provide support for the construction of a reservoir water rights allocation system. However, it has a limitation in that it fails to consider the robustness of the allocation scheme and the dynamic adjustment mechanism under future variable conditions, such as extreme hydrological scenarios and changes in water demand. This serves as a direction for future research.

The response and coupling mechanism of the “solar-climate-regional water periodicity” is scientifically significant to the water resource management in semi-arid regions. In this study, the influence of solar activity and the El Niño Southern Oscillation (ENSO) on precipitation, temperature, air pressure, and runoff discharge were investigated in an inland river basin in middle eastern Inner Mongolia. Results show that sunspot activity and ENSO significantly influence hydrometeorological elements in the study area in the periodicities of 2–7 and 11a, respectively, while ENSO has no significant influence on surface runoff. With ENSO as the “medium,” solar motion energy “directly” or “indirectly” changes atmospheric circulation and regional climate in different frequency domains through “Sub-high East Asian monsoon circulation water vapour movement over the Western Pacific,” thus influencing the watershed hydrological process. However, the grassland type inland river basins, such as the study area, have complex underlying surface conditions and diverse surface water and groundwater recharge and transformation mechanisms, which may have formed a unique regional hydrological process, slightly delaying the response periodicity of surface runoff to ENSO.