Research on Groundwater Level Warning for karst collapse of covered karst areas in Tai’an City

Research on Groundwater Level Warning (GLW) is helpful for the regulation of groundwater resources development and the protection of the geological disaster of karst collapses in covered karst areas in northern China. This paper proposed a method for the delineation of karst GLW. Specific steps include, (1) establish the criterion of GLW based on statistical analysis of groundwater level monitoring data and plot the minimum,5th,25thand 75th percentile curve of water level; (2) establish the criterion of GLW for karst collapse in line with the threshold value of water level fluctuation around roof of bedrock and beneath the roof when collapse happened; (3) firstly,establish the comprehensive judgment criterion model to determine the GLW of a single observation well ,and determine the GLW divisions based on observation wells cluster finally. This method was verified in the Chengqu-Jiuxian karst system of Taian City in Shandong Province. According to the comparison of warning result of single observation well and GLW divisions between 2015 and 2016, the method was proved to meet the actual conditions and was reliable to be promoted.