  Citation: Niranjannaik, M.; Kumar, A.; Beg, Z.; Singh, A.; Swarnkar, S.; Gaurav, K. Groundwater Variability in a Semi-Arid River Basin, Central India. Hydrology 2022, 9, 222. https://doi.org/10.3390/ hydrology9120222 Academic Editor: Tommaso Caloiero Received: 18 October 2022 Accepted: 3 December 2022 Published: 7 December 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). hydrology Article Groundwater Variability in a Semi-Arid River Basin, Central India M. Niranjannaik , Amit Kumar , Zafar Beg, Abhilash Singh , Somil Swarnkar and Kumar Gaurav * Department of Earth and Environmental Sciences, Indian Institute of Science Education and Research, Bhopal 462066, India * Correspondence: kgaurav@iiserb.ac.in Abstract: The Betwa River basin, a semi-arid catchment that has been classified as a major hotspot of groundwater depletion in Central India. The rainfall and streamflow intermittency have affected agricultural practices due to the variability of groundwater availability for irrigation. This study evaluates the spatial and temporal variations of groundwater level (GWL) in the last 25 years (1993–2018) in the catchment. We applied a nonparametric Seasonal Trend decomposition based on the Loess (STL) method to decompose the GWL time series into the seasonal, trend, and remainder components. We observed that the GWL in the northeastern regions of the basin has depleted about 3–5 mbgl in the last two decades. During the same period, the basin has experienced a reduction in the rainfall magnitude (2.07 mm/yr). We observed that the overexploitation of groundwater for irrigation and rainfall variability have greatly impacted the GWL condition in the study area. Further, if the groundwater extraction continues at present rates, the Betwa River basin may experience severe depletion in the future. Keywords: groundwater level; trend analysis; semi-arid region; Betwa River basin 1. Introduction Groundwater is a natural freshwater resource that directly or indirectly affects millions of people living in drought-prone regions. Over-extraction of groundwater for domestic, agricultural, and industrial purposes has resulted in immense stress and a rapid decline in the groundwater level (GWL). Groundwater depletion has been severe, particularly in the arid and semi-arid regions [1]. Consequently, ecological and socioeconomic developments in these regions have been severely impacted [2]. Several studies have been conducted to assess groundwater depletion in the current and future scenarios [1,3–5]. For example, over- exploitation of GWL in the Middle East [6], North-East Pakistan, North-West India [7–9], United States of America [10], and North-East China [11] is responsible for the major hotspot of groundwater depletion in the world. If such a situation persists for a prolonged period, it may lead to the irreversible loss of groundwater resources in many of these regions. Additionally, frequent hydrological drought events due to warming climates are expected to intensify groundwater depletion in future [12–15]. The rapid rate of urbanisation and population growth have put imminent pressure on groundwater resources to meet the water demand for industrial and domestic pur- poses [16]. After the “Green revolution” in the 1960s, India experienced a significant change in landuse/landcover and an increase in groundwater consumption for irrigation. The forests were cut down for infrastructural developments and agriculture production, which has greatly altered the landuse/landcover pattern [17]. The change in landuse/landcover is an essential driver of the regional climate and hydrology [18–20]. It directly impacts hydrological processes such as infiltration, groundwater recharge, and runoff [19]. In India, about 230 billion m 3 of groundwater is extracted annually for irrigation [21,22]. Particularly, the northwestern states such as Punjab, Haryana, Rajasthan, and the northern state of Uttar Pradesh have formed as the major hotspot of groundwater depletion [7]. The precipitation intensity is strongly linked with groundwater recharge [23]. Rainfall contributes about Hydrology 2022, 9, 222. https://doi.org/10.3390/hydrology9120222 https://www.mdpi.com/journal/hydrology