A statistical model for karst spring discharge estimation under extensive groundwater development and extreme climate change

Abstract

To acquire better understanding of spring discharge under extreme climate change and extensive groundwater pumping, this study proposed an extreme value statistical decomposition model, in which the spring discharge was decomposed into three items: a long-term trend; periodic variation; and random fluctuation. The long-term trend was fitted by an exponential function, and the periodic variation was fitted by an exponential function whose index was the sum of two sine functions. A general extreme value (GEV) model was used to obtain the return level of extreme random fluctuation. Parameters of the non-linear long-term trend and periodic variation were estimated by the Levenberg-Marquardt algorithm, and the GEV model was estimated by the maximum likelihood method. The extreme value statistical decomposition model was applied to Niangziguan Springs, China to forecast spring discharge. We showed that the modelled spring discharge fitted the observed data very well. Niangziguan Springs discharge is likely to continue declining with fluctuation, and the risk of cessation by August 2046 is 1%. The extreme value decomposition model is a robust method for analysing the nonstationary karst spring discharge under conditions of extensive groundwater development/pumping, and extreme climate changes.

A Critical Review of Climate Change Impacts on Groundwater Resources: A Focus on the Current Status, Future Possibilities, and Role of Simulation Models

“…Discharge of groundwater takes place whenever water from underground sources is brought to the surface, either by way of an aquifer to a surface water body or by human consumption. Forecasts based on current climatic trends indicate a reduction in discharge from groundwater-fed springs in regions experiencing an increasingly arid climate, such as the southwestern United States [17], the Sikkim Himalaya [18], and Niangziguan Springs in Shanxi, China [19]. The massive groundwater extraction required to fulfil the increasing need for cultivation and other agricultural uses is a significant secondary consequence of climate change.…”

Long-term trends in karst spring discharge and relation to climate factors and changes

“…Karst aquifers are often drained by springs having large discharge volumes (Ford and Williams 2007;Kresic and Stevanovic 2010) that vary long term in response to climate changes and extensive groundwater abstraction (Chen et al 2004;Zhong et al 2016;Hartmann et al 2014). Precipitation generally represents the main input of water to karst aquifers and affects their recharge, by both diffuse and concentrated manner, and the groundwater availability.…”