Understanding the linkages between seasonal variability and annual trends in groundwater levels in alluvial aquifers of Uttar Pradesh, India

In this study, we analyse the seasonal variability of groundwater table depths (GWTDs) to understand the drivers of annual groundwater trends in the state of Uttar Pradesh (UP), which has the largest groundwater withdrawal in India. We perform the analysis using observations of GWTDs in wells located in shallow aquifers during 2001-2019 without excluding wells with missing observations. We find higher seasonal variability of GWTD in southeast UP as compared to northwest UP due to higher groundwater recharge during monsoon. While there is significant groundwater withdrawal for irrigation in the dry season in both regions, it exceeds the monsoon recharge in northwest UP leading to an increasing trend in GWTD in the region. The groundwater depletion in shallow aquifers of northwest UP has led to a decrease in the number of shallow tubewells and a sharp increase in the number of deep tubewells in the region. There is a smaller increase in GWTDs in southeast UP as compared to northwest UP, as the groundwater abstraction in the non-monsoon season has been balanced by the high recharge received during monsoon. However, there has been a rapid increase in the number of both shallow and deep tubewells in southeast UP, which could accelerate groundwater depletion in the future. We also find that the wells with missing observations have a significant contribution to the depletion trend observed in northwest UP which highlights the importance of incorporating information from wells with missing observations in groundwater assessment studies.