Exploring recent groundwater level changes using Innovative Trend Analysis (ITA) technique over three districts of Jharkhand, India

Abstract

Groundwater is the largest store of available freshwater in the world. With the increasing impact of climate change and human activities, assessment of variations in groundwater levels is essential. This study presents the trend of groundwater levels in three districts (Purbi Singhbhum, Ranchi and Saraikela) of Jharkhand State, India. The depth to groundwater level (DGWL) data from 24 wells over the three districts for 1996–2018 is collected for both pre-monsoon and post-monsoon seasons. The conventional non-parametric trend analysis techniques (e.g., Mann-Kendall, Sen's Slope, Spearman's Rho tests) have several restrictive assumptions, such as Gaussian distributed time series and absence of serial correlation. Innovative Trend Analysis (ITA) technique does not have these restrictive assumptions and therefore, can be effectively used to detect trends in a time series of shorter length. Moreover, ITA is a slope-based technique that provides visual interpretations as well as the statistical significance of trends in a time series, thereby comprehensively acquiring the benefits of multiple conventional methods. Therefore, ITA is employed in this study to investigate the trends in groundwater levels. The results reveal a significantly increasing trend of DGWL for 17 sites in pre-monsoon and 14 sites in post-monsoon seasons. On the other hand, only four and six stations showed negative trends during pre- and post-monsoon seasons, respectively. The increasing DGWL trends at a majority of the sites imply a serious decline in the groundwater levels over the years. This study will be helpful to water resources managers to identify the causes of the declining groundwater levels, take necessary actions to control them, and efficiently manage groundwater at local levels.