The Central Ground Water Board (CGWB) is the national apex agency for scientific assessment, dissemination, and regulation of India's groundwater resources. A Junior Hydrogeologist conducts hydrogeological surveys, drills and tests exploratory wells, analyzes groundwater quality and quantity data, prepares ground water resource assessments for districts, and issues NOCs for groundwater extraction through Central Ground Water Authority (CGWA) under the Environment Protection Act 1986. CGWB also monitors groundwater levels quarterly and assesses the status of over-exploited, critical, and semi-critical groundwater assessment units across India.

The exam covers general geology (mineralogy, petrology, stratigraphy of Indian geology including Gondwana formations, Deccan Traps, and Indo-Gangetic alluvial plains), structural geology (faults, folds, lineaments and their role in groundwater occurrence), geomorphology and landforms relevant to groundwater, remote sensing for hydrogeological mapping, and engineering geology. For hydrogeology specifically: Darcy's law, aquifer types (confined, unconfined, leaky, perched), pump test analysis (Theis, Cooper-Jacob methods), water quality assessment (BIS groundwater quality standards), and contaminant transport in aquifers.

CGWB enforces groundwater regulation through the Central Ground Water Authority (CGWA), constituted under the Environment Protection Act 1986. Industries and projects abstracting groundwater above 10 cubic meters per hour require NOC from CGWA. EIA Notification 2006 mandates hydrogeological assessment for projects in water-scarce areas. CGWB also advises on groundwater development in areas of arsenic, fluoride, and heavy metal contamination — particularly relevant to East India arsenic belt (Bengal, Bihar, Jharkhand), Rajasthan fluoride belt, and industrial groundwater contamination zones.

Important quantitative topics include Darcy's Law applications, transmissivity and storativity calculations from pump test data, Theis equation and Cooper-Jacob straight-line method for confined aquifers, Boulton method for unconfined aquifers, determination of specific yield, water table fluctuation method for recharge estimation, chemical equilibrium calculations for groundwater quality, preparation of Piper diagrams and Stiff diagrams for hydrochemical facies analysis, and basic hydrogeological cross-section construction from borehole data.

CGWB uses the Ground Water Resource Estimation Methodology (GEC 2015) developed by the Ground Water Estimation Committee to assess groundwater availability at the assessment unit (block/taluka/mandal) level. The methodology involves estimating annual replenishable groundwater resource from rainfall, irrigation return flow, and other recharge sources, deducting natural discharge, and calculating net groundwater availability for future use. Units are then categorized as Over-Exploited (>100% extraction), Critical (90-100%), Semi-Critical (70-90%), or Safe (<70%). This framework is tested in detail in CGWB exams.