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Pu J.-B.,Chongqing Three Gorges University | Pu J.-B.,Karst Dynamics Laboratory | Pu J.-B.,International Karst Research Center Auspices of UNESCO | Yuan D.-X.,Chongqing Three Gorges University | And 7 more authors.
Huanjing Kexue/Environmental Science | Year: 2011

In order to thoroughly reveal the karst groundwater system in response to the external environment, multi-index high-resolution auto-monitoring instruments were used to research the hydrogeochemistry variations of Qingmuguan subterranean stream. The monitoring indicators were pH value, electrical conductivity (EC), water level, rainfall and NO3 -. In the observed 6 times rainfall events, the pH value was mainly controlled by acid rain and EC was impacted by the rain chemistry, physical dilution effect of rainfall and agricultural wastewater. NO3 - derived from agricultural activities was less impacted by rain chemistry; and its variations were mainly affected by physical dilution effect of rainfall and agricultural wastewater. Under the influences of the R1 rainfall, the rapid changes of EC and NO3 - were contrary in generally, but pH value decreased due to the acid rain. In the R2, R3, R4 and R6 rain events, the water level was positively response to the rainfall and the pH value decreased due to the acid rain; however both of the EC and NO3 -decreased due to the dilution effect. With the afflux of agricultural wastewater, both of the EC and NO3 - were rapidly changed in synchronization within the shortest of 5 h of and the longest of only 27 h and the pH value showed accelerated decline. During the R5 torrential rain events, water level abruptly increased and all of the pH value, EC and NO3 - sharply decreased as a result of dilution effect. The groundwater quality was changed because the afflux of agricultural wastewaters in the entire rainfall periods. According to the National Groundwater Quality Standard, P. R. China (GB/T 14848-9), the groundwater quality of the QSS showed the following order in the entire rainfall events: Grade III → Grade IV → Grade V → Grade IV → Grade V → Grade IV → Grade V → Grade IV → Grade III. As a important drinking water source around local inhabitants, the groundwater quality of Qingmuguan subterranean stream was deteriorated to Grade V in rain-fertilize periods. However, the sampling methods in field did show a simple variation curve. Consequently, the results from the research illustrate the need to redesign hydrochemical sampling methods for karst hydrology system, especially under the impact of human activities.


Pu J.,Southwest University | Pu J.,Karst Dynamics Laboratory | Pu J.,International Karst Research Center auspices of UNESCO | Yuan D.,Southwest University | And 6 more authors.
Environmental Earth Sciences | Year: 2011

Abstracts: Globally, it is possible that up to 25% of the world's population depends on karst water supplies. In karst areas, a high degree of groundwater and surface water linkage often results in the direct recharge of groundwater with polluted run-off following rainfall. In order to reveal the hydrochemical variations after rainfall, especially real-time variation of pollutants, high-resolution auto-monitoring techniques were used at the outlet of Qingmuguan subterranean stream (QSS), which is influenced by agricultural activities. In addition to rainfall, high-resolution measurements of pH, water level, electrical conductivity (Ec) and NO3 - concentration were recorded in the monsoon season and fertilizer application period using a data logger with time intervals of 15 min. In the six observed rainfall events, the pH value was mainly controlled by acidic rainfall inputs. The pH showed sharp decline after the rainfall event, and then increased. The Ec was impacted by the rainfall chemistry, dilution effect of rainfall and agricultural wastewater. NO3 - derived from agricultural activities was less impacted by rain chemistry; and its variations were mainly affected by the dilution effect of rainfall and agricultural wastewater. Under the influences of the R1 rainfall, the rapid changes of Ec and NO3 - were opposite in direction. As the rain continued, both the Ec and NO3 - rapidly changed in synchronization within the shortest period of 5 h and the longest of 27 h because of the impact of the agricultural wastewater. The groundwater quality changed due to the influx of agricultural wastewater over the entire monitoring period. According to the National Groundwater Quality Standard, People's Republic of China (GB/T14848-9), the groundwater quality of the QSS moved through the following grades during the monitoring period: Grade III → Grade IV → Grade V → Grade IV → Grade V → Grade IV → Grade V → Grade IV → Grade III. Traditional sampling methods did not reveal accurate hydrochemistry changes of the QSS, and even generated misleading results. Consequently, the high-resolution auto-monitoring technique is necessary for the future protection and sustainable use of karst aquifer in Southwest China. © 2011 Springer-Verlag.


Pu J.-B.,Southwest University | Pu J.-B.,International Karst Research Center Auspices of UNESCO | Yuan D.-X.,Southwest University | Yuan D.-X.,Karst Dynamics Laboratory | And 4 more authors.
Shuikexue Jinzhan/Advances in Water Science | Year: 2010

The subterranean karst stream services as an important water source to the groundwater supply system in the karst areas. There are approximately 380 subterranean karst streams that supply groundwater to the areas of Chongqing municipalities. The hydrogeochemistry is studied for 61 subterranean karst streams in Chongqing. The result shows that the solutes are mainly originated from the dissolution of carbonate rocks through the water-rock interaction process. The groundwater chemistry is found to be of Ca-HCO3 type or Ca(Mg)-HCO3 type. However, the Na+Ca-HCO3, Na+Ca-SO4, Na+Ca-Cl or Ca-SO4+HCO3 type water have been detected in some of subterranean karst streams due to the influence of human activities. The impacts of agriculture activities and city sewages on hydrogeochemistry are more common than that of industrial and mining activities. The groundwater temperature gradually decreases with the increase of elevations. For the same geological setting, the presence of Ca2+, Mg2+, HCO3 - exhibits significant regionality due to the discrepancy of karst processes in different areas. The same regionality is also found in the distribution of K+, Na+, SO4 2-, NO3 -, Cl- because of human activities. The study concludes that the hydrogeochemical condition of Chongqing karst subterranean streams is deteriorating due to the industrial and agricultural activities as well as the discharge from the city sewage system.


Chang Y.,Nanjing University | Chang Y.,Institute of Karst Geology | Chang Y.,International Karst Research Center Auspices of UNESCO | Wu J.-C.,Nanjing University | And 4 more authors.
Shuili Xuebao/Journal of Hydraulic Engineering | Year: 2012

Many closed depressions distribute in peak cluster area. The overland flow occurring in the closed depression enters the conduit though sink holes during storms and finally becomes a part of karst spring. In this paper, the typical peak cluster depression landscape-Yaji experimental site was selected to study the role of overland flow in discharge and hydrochemistry of karst spring though monitoring the quantity of overland flow and tracer experiment. The monitoring results of runoff plot show that overland flow occurred when rainfall was more than 64.4 mm/day with low discharge in 2010. The overland flow coefficients were between 0.48% and 0.71%. The rainfall-runoff process of 19 May was chose to do water balance and ions mass conservation. Though the water balance analysis of catchment of Spring S31, overland flow only accounted for 0.63% of total discharge of spring. Overland flow could hardly influence the discharge of karst spring. The results of ions mass conversation model show that the variation of electrical conductivity of spring S31 was caused mainly by fracture water. The overland flow contains abundant rainwater, but the effect to electrical conductivity is very limited. Because of high rainfall needs and low proportion of overland flow, we can ignore the impact of overland flow on the variation of discharge and hydrochemistry of karst spring under appropriate rainfall conditions.


Karst aquifers are commonly simulated based on conceptual models. However, most karst conceptual models hardly consider the function of turbulent conduits. The conduit network acts as the main draining passage of the karst aquifer and may also have a strong influence on the hydrological processes, especially during storm events. A conceptual model with a nonlinear reservoir and a turbulent pipe (representing the conduit system) in series is proposed according to the basic structure of a typical karst aquifer, to simulate the karst spring. The model indicates whether the spring discharge is influenced by the turbulent pipe; this not only depends on the parameters of the nonlinear reservoir and turbulent pipe, but also depends on the volume of spring discharge itself. Even though the spring discharge is strongly influenced by the turbulent pipe during the storm, this influence decreases with the rainfall intensity and volume of spring discharge. In addition, an ‘evapotranspiration store’ is used to consider the moisture loss through evapotranspiration and to calculate the effective rainfall on the proposed model. Then, this simple conceptual model is used to simulate a karst spring (named S31) near Guilin city, China, with satisfactory results, especially with respect to discharge peaks and recession curves of the spring under storm conditions. The proposed model is also compared with the Vensim model of similar complexity, which has been applied to the same spring catchment. The comparison shows the superiority and better performance of the nonlinear reservoir-pipe model. © 2015, Springer-Verlag Berlin Heidelberg.

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