Publication Date
5-2020
Abstract
Karst waters from a mountainous recharge area drains toward basin and emerges at the edge of the basin after encountering quaternary sediments. The flow paths are partly covered by Quaternary sediments or other sedimentary rocks, which makes the spring acts as an artesian spring. The spring is more vulnerable to human activities and climate change than the classic confined karst spring. Weakly confined spring is typical in faulted karst basin. Heilongtan Springs are located at the foothills of Wulao Mountains in the northern suburb of Kunming City. They consist of Qingshuitan (QST), Hun-shuitan (HST) and Xiaoshuitan (XST) springs. Spring water appears clear and muddy in QST and HST Spring, respectively, even though they share a common outlet at the southern end of QST Spring pool. From 2010 to 2012, a comprehensive hydrochemical study has been performed in Heilongtan Springs. In coincidence, the study area experienced continuously severe droughts in Yunnan Province, China, which offered an opportunity to better understand the impact of global climate change on such weakly confined karst springs. Both concentra-tions of hydrochemical parameters at high-resolution (every 15 min) and weekly measured data during March 2010–December 2012 covering two complete hydrologic years were used to investigate the response of hydrochemical changes to prolonged and severe droughts in Yunnan from 2010 to 2012. During the drought, in addition to the decline of water table, the EC of spring decreased progressively from 319.5 μS/cm (yearly average, ranging from 294.0 to 339.1 μS/cm) in 2010 to 299.2 μS/cm (ranging from 248.9 to 323.3 μS/cm) in 2011 and 277.6 μS/cm (ranging from 237.4–311.4 μS/cm) in 2012. At the same time, instead of the tendency of temperature to decrease, pH values increased. In 2010, the ratio of Ca/Mg was constantly increasing from May, but in 2011 and 2012, Ca/Mg ratios fluctuated greatly, which highlights the rapid responses of spring to precipitation. All the evidence has shown that as the drought went on, the water from the karstic aquifer kept draining out and the residence time of water got shorter. Meanwhile the water quality of the spring was more sensitive to the rain events. With a small to medium amount of precipitation, the concentrations of Cl- and NO3- of the spring water started to increase a few hours after the rain, which would last 7 to 14 days. In summary, this study has shown the high sensitivity and variability of a weakly confined karst spring to environmental changes.
Rights Information
DOI
https://doi.org/10.5038/9781733375313.1043
The hydrochemical response of Heilongtan springs to the 2010-2012 droughts of Yunnan Province, Kunming, China
Karst waters from a mountainous recharge area drains toward basin and emerges at the edge of the basin after encountering quaternary sediments. The flow paths are partly covered by Quaternary sediments or other sedimentary rocks, which makes the spring acts as an artesian spring. The spring is more vulnerable to human activities and climate change than the classic confined karst spring. Weakly confined spring is typical in faulted karst basin. Heilongtan Springs are located at the foothills of Wulao Mountains in the northern suburb of Kunming City. They consist of Qingshuitan (QST), Hun-shuitan (HST) and Xiaoshuitan (XST) springs. Spring water appears clear and muddy in QST and HST Spring, respectively, even though they share a common outlet at the southern end of QST Spring pool. From 2010 to 2012, a comprehensive hydrochemical study has been performed in Heilongtan Springs. In coincidence, the study area experienced continuously severe droughts in Yunnan Province, China, which offered an opportunity to better understand the impact of global climate change on such weakly confined karst springs. Both concentra-tions of hydrochemical parameters at high-resolution (every 15 min) and weekly measured data during March 2010–December 2012 covering two complete hydrologic years were used to investigate the response of hydrochemical changes to prolonged and severe droughts in Yunnan from 2010 to 2012. During the drought, in addition to the decline of water table, the EC of spring decreased progressively from 319.5 μS/cm (yearly average, ranging from 294.0 to 339.1 μS/cm) in 2010 to 299.2 μS/cm (ranging from 248.9 to 323.3 μS/cm) in 2011 and 277.6 μS/cm (ranging from 237.4–311.4 μS/cm) in 2012. At the same time, instead of the tendency of temperature to decrease, pH values increased. In 2010, the ratio of Ca/Mg was constantly increasing from May, but in 2011 and 2012, Ca/Mg ratios fluctuated greatly, which highlights the rapid responses of spring to precipitation. All the evidence has shown that as the drought went on, the water from the karstic aquifer kept draining out and the residence time of water got shorter. Meanwhile the water quality of the spring was more sensitive to the rain events. With a small to medium amount of precipitation, the concentrations of Cl- and NO3- of the spring water started to increase a few hours after the rain, which would last 7 to 14 days. In summary, this study has shown the high sensitivity and variability of a weakly confined karst spring to environmental changes.
