The Niangziguan Spring is one of the largest karst springs in northern China and water in this spring area is the main water-supply source for people in Yangquan City for daily life, industrial processes and agricultural production. However, decreasing groundwater levels and growing waterpollution issues have been observed recently. Therefore, the objective of this study was to conduct a systematic analysis of water-flow reduction and water-quality deterioration of the Niangziguan Spring. The results show that various wastewater sources upstream of the spring, such as coal mining, and urban industrial and domestic effluents, have contributed to the deterioration of the Niangziguan Spring water quality. A mathematical model known as the one-order one-variable grey differential equation model GM(1,1) was employed to evaluate the contribution of climate change versus human activities potentially affecting the reduction of spring-water flow. The calculations for the period from 1979 to 2006 suggest that a contribution of human activities to water-flow reduction was 2.5 times greater than those that can be attributable to climate change. The research results obtained as presented in this paper can provide a scientific basis for rational exploitation of karst-water resources and environmental protection in this karst area of northern China.