Temporal Variation of Groundwater Levels by Time Series Analysis for NCT of Delhi, India

Abstract

Trend detection in time-series data has received a tremendous amount of attention in the last decade. This study was undertaken to analyse the trends in groundwater levels for nine districts of Delhi, India. Time series of groundwater levels (pre-monsoon and post-monsoon) for the period 1996–2019 for nine districts of Delhi were analysed using three tests, namely the Mann-Kendall test (MK), Sen’s slope estimator and the Innovative Trend Analysis (ITA) method. For the pre-monsoon and post-monsoon groundwater levels, the nine districts had increasing trend as per the MK test and Sen’s slope estimator, indicating that groundwater levels have declined in the study region. The Z statistic as well as the Sen’s slope, Q obtained from these tests have been tabulated, and the trends have been depicted in graphical form. The ITA method also revealed increasing trends for all the districts except Central, West, South and New Delhi. For these four districts, the ITA method revealed a multiple trend structure in the time series. Analysis of the temporal variation in groundwater levels is very helpful, as it provides information about the rise or fall in the water table depths over the years which in turn can help in making the appropriate groundwater management decisions.