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Accurate groundwater level (GWL) prediction can contribute to sustaining reliable water supply to domestic, agricultural and industrial uses as well as ecological services, especially in arid and semi-arid areas. In this paper, a regional GWL modeling framework was first presented through coupling both spatial and temporal clustering techniques. Specifically, the self-organizing map (SOM) was applied to identify spatially homogeneous clusters of GWL piezometers, while GWL time series forecasting was performed through developing a stepwise cluster multisite inference model with various predictors including climate conditions, well extractions, surface runoffs, reservoir operations and GWL measurements at previous steps. The proposed modeling approach was then demonstrated by a case of an arid irrigation district in the western Hexi Corridor, northwest China. Spatial clustering analysis identified 6 regionally representative central piezometers out of 30, for which sensitivity and uncertainty analysis were carried out regarding GWL predictions. As the stepwise cluster tree provided uncertain predictions, we added an AR(1) error model to the mean prediction to forecast GWL 1 month ahead. Model performance indicators suggest that the modeling system is a useful tool to aid decision-making for informed groundwater resource management in arid areas, and would have a great potential to extend its applications to more areas or regions in the future., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

In Northern China, karst systems in widely distributed carbonate rocks are one of the most important water supplies for local inhabitants. Constrained by the specific geological and geomorphological conditions, most karst water in this region is discharged as individual or groups of springs. This paper summarizes the characteristics, chemistry, and environmental quality of these karst systems in Northern China. Five structural models of karst water systems were identified based on the relationships between the karst geological strata and karst groundwater flow fields. These specific structural models may closely relate to the attendant environmental geological issues and consistent risks from pollution. Over the past 40 years, the karst water systems in Northern China have suffered from various environmental problems, including deteriorating water quality, the drying up of springs, a continuous decline in the level of karst water, and so on. Based on the field investigation and previous data, a preliminary summary is provided of the environmental problems related to the development and evolutionary trends of karst water in this region. The results highlight the significant challenges associated with karst water, and it is essential that all segments of society be made aware of the situation in order to demand change. In addition, the study provides a scientific basis for the management, protection, and sustainable utilization of karst water resources. [ABSTRACT FROM AUTHOR]