Assessment of trends and multi-decadal changes in groundwater level in parts of the Malwa region, Punjab, India

Abstract

Due to spatial unevenness in rainfall, groundwater dependency for irrigation has increased exponentially, which poses a challenge for its sustainability. Hence, the long-term behaviour of groundwater level (GWL) fluctuations needs to be understood for better management of water resources and formulating a new action plan. Due to semi-arid climatic condition, most of the agricultural lands in Malwa region of Punjab in India depend on the groundwater for irrigation. The present study focuses on multi-decadal trend estimation and spatio-temporal variations of GWL changes using geostatistics and analyzing the groundwater fluctuations using the standardized depth to water level index (SDWLI) method over the Malwa region. For this study, GWL data for 90 observation wells/piezometers for 21 years (1997–2018) were analyzed. The wells were classified into different clusters according to the fluctuation rate using hierarchical cluster analysis. The trend for each well's GWL changes was analyzed with the Modified Mann–Kendall (MMK) test and Sen's slope. The trend analysis results show that most of the wells over the Malwa region possess a significantly declining trend of GWL during 1997–2018. The spatio-temporal variation maps reveal that more than 30 % of tubewells in the eastern part of the study region have seen an average depletion rate of about 40 cm/year in both seasons (pre- and post-monsoon). In contrast, GWL in southwestern part of the Malwa region shows an evident rise in water level during the last two decades; this rising water level causes severe waterlogging problems during the monsoon period. Over 21 years, we observed that more than 20 % of wells had increased GWL in the southwestern part of the Malwa region. The present study's result raises concern about groundwater resources' future in the highly groundwater-dependent Malwa region.