Reappraisal Hydrogeological Surveys (RHS) are undertaken to appraise and assess the status of ground water regime periodically form an important activity of CGWB. These surveys bring out the changes and behaviours of dynamic ground water system both in terms of its quality and quantity consequent to variations in the input and in the output components. Thus the objectives of the RHS can be summed up as follows:

• To depict the ground water regime in terms of quality and quantity as on the date.

• Ascertaining the factors influencing the ground water scenario.

• Identification of problems and issues pertaining to ground water and provide suitable object oriented strategy for implementation.

• To Assess the social and economic aspects of ground water utilisation and the role of various agencies, panchayat Raj, NGOs and VO etc., in ground water development, conservation and management.

• To update the existing database on ground water regime.

• To demarcate the ground water worthy and unworthy areas.

• To recommend suitable follow up action/ remedial measures/ administrative and technical measures for the specific problems.

Reappraisal Hydrogeological Studies, earlier known as 'District Ground Water Management Study' are carried out on a routine basis. The target area is slected and the work is carried out within a field season. Recently Central Ground Water Board has laid down the revised guidelines for Reappraisal Hydrogeological Studies which was prepapared bya group of scientists headed by a scientist from CGWB,NCCR Shri D S Thambi, Scientist 'D'. The broad modus operandi as suggested in the guidelines is given below.

• The basic information of the detailed study area should be recorded on base map/ topo sheet on 1: 50,000 scale. The observation on soil, cropping pattern, irrigation practices, stream flow, discharge measurement of ground water structures, springs, water conservation structures, recharge structures, water logged areas, scarcity areas, command areas etc., should be recorded explicitly.

• The well inventory form should be used to record the base line details.

• Interaction with people at the core of the problem, areas/ issues to be addressed in an informal way to understand the actual problems and also to make the villagers and also to make the villagers / inhabitants aware of the solutions. A brief write up of the same may be incorporated in the RHS report highlighting the issues.

• The information / statistics should be collected from various agencies including NGO, VO etc., and proformas given may be used to standardises the database at HQ and CHQ level.

• Pumping tests should be carried out to determine the aquifer parameters of representative hydrogeological units.

• Field photography adds an unique impression in the mind of user and readers of the report. Efforts should be made to take number of photographs of the field areas reflecting ground ground water features and issues and should be reproduced in the report also.

• The need of infiltration tests, soil moisture test, auger hole drilling, geophysical studies, should be worked out and field assists from Chemists, Hydro meteorologist, Hydrologist, Geophysicist and Survey should be planned in advance for the necessary arrangement.

• Necessary field data as required in the guidelines for the ground water resource evaluation in vogue ( Presently GEC 1997) shall be collected in the field. The officer shall compute the ground water resources as per the methodology and compare with the values and figures available with the office. Based on the data collected he shall recommend changes if any required in the input values wherever needed with justification for future use. A brief write up has to be included under this item,

• He may identify suitable number of monitoring stations for future monitoring if needed in the problem areas and suitable recommendations be given in this regard.