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IS 9640:1980 is the Indian Standard (BIS) for field methods of geohydrological investigations. This code provides guidelines for conducting field geohydrological investigations to assess aquifer characteristics like transmissivity and storativity. It details procedures for various tests including pumping tests, recuperation tests, tracer studies, and geophysical methods to understand groundwater availability and movement.
Lays down field methods for geohydrological investigations, including drilling, pumping tests, and water level measurements.
Overview
Status
Current
Usage level
Specialized
Domain
Geotechnical — Surveying and Geotechnical Investigation
! Ensure pumped water is discharged far enough away to prevent recirculation into the aquifer, which can skew test results.
! Achieving true steady-state conditions for equilibrium tests can be time-consuming, especially in low-permeability formations; non-equilibrium methods are often more practical.
! Geophysical survey results are indirect and should always be correlated with direct data from boreholes or pumping tests for accurate interpretation.
A comprehensive code for all ground investigations, with significant sections covering geohydrological testing and methods.
ISO 14686:2003ISO, International
HighCurrent
Hydrometric determinations — Pumping tests for water wells — Considerations and performance of tests
Focuses specifically on the planning, performance, and interpretation of pumping tests, a core component of IS 9640.
ASTM D4043-16ASTM International, USA
HighCurrent
Standard Guide for Selection of Aquifer-Test Method in Determining Hydraulic Properties by Well Techniques
Provides guidance on selecting appropriate aquifer testing methods, aligning with the 'code of practice' nature of the Indian Standard.
ISO 22282-1:2012ISO, International
HighCurrent
Geotechnical investigation and testing — Geohydraulic testing — Part 1: General rules
Establishes general principles and rules for conducting geohydraulic tests, mirroring the foundational guidance in IS 9640.
Key Differences
≠IS 9640:1980 is a single, all-encompassing document, whereas ASTM and ISO provide a suite of highly specific standards for individual test types (e.g., slug tests, constant-rate tests, packer tests).
≠The Indian Standard is from 1980 and has not been updated, while international standards are regularly reviewed (typically every 5-10 years) to incorporate modern techniques, equipment (like data loggers), and computer-aided analysis methods.
≠Modern international standards like BS 5930 place a much stronger and more explicit emphasis on health, safety, and environmental (HSE) management throughout the investigation process compared to the implicit guidance in IS 9640.
≠International standards provide more detailed, performance-based criteria for test termination (e.g., stabilization of drawdown rate on a log-log plot), whereas IS 9640 often suggests fixed durations (e.g., 72 hours).
Key Similarities
≈All standards recognize the fundamental importance of conducting step-drawdown tests to determine well efficiency and select an appropriate rate for the main constant-rate test.
≈The core hydrogeological principles and analytical methods, such as the Theis non-equilibrium and Cooper-Jacob straight-line methods for data interpretation, are common across all standards.
≈All standards recommend a similar logarithmic time schedule for manual water level measurements, especially during the early stages of a pumping test, to capture the initial rapid drawdown.
≈There is a shared emphasis on the necessity of using dedicated observation wells in addition to the pumping well to accurately determine aquifer parameters (Transmissivity and Storativity) rather than just well performance.
Parameter Comparison
Parameter
IS Value
International
Source
Pumping Test Duration (Aquifer Performance)
Generally recommends a duration of 72 hours.
No fixed duration; continue until drawdown trends are clear for the chosen analytical method or boundaries are detected.
ISO 14686:2003
Step-Drawdown Test Step Duration
Recommends steps of equal duration, typically 100 minutes each.
Recommends steps of equal duration, long enough to approach steady-state, but no specific time is mandated.
ISO 14686:2003
Number of Steps in Step-Drawdown Test
Recommends 3 to 5 steps.
Recommends at least three, preferably four or five, steps.
ISO 14686:2003
Recovery Measurement Criteria
Measure until water level has recovered to 95% of the pre-pumping static level.
Measure for a period at least as long as the pumping period or until residual drawdown is negligible.
ISO 14686:2003
Observation Well Placement
General guidance (e.g., 'within 30 m', 'between 30 and 150 m').
Recommends placement based on aquifer characteristics, often at logarithmic spacing from the pumping well.
ASTM D4043-16
Data Logging
Prescribes a schedule for manual readings.
Strongly recommends using electronic data loggers in addition to manual readings for higher data density and accuracy.
BS 5930:2015+A1:2020
Well Development Completion Criteria
Primarily based on visual clarity (water being 'sand-free').
Based on stabilization of key water quality parameters (pH, conductivity, turbidity) in addition to sediment removal.
ASTM D5521-13 (Standard Guide for Development of Ground-Water Monitoring Wells)
⚠ Verify details from original standards before use
Key Values0
No quick reference values available for this code yet.
Key Formulas
Theis's Non-Equilibrium Formula: s = (Q / 4πT) * W(u) — For determining transmissivity (T) and storativity (S) from drawdown (s) over time.
Thiem's Equilibrium Formula: T = [Q / (2π(s1-s2))] * ln(r2/r1) — For determining transmissivity (T) under steady-state conditions using drawdown at two observation wells.
Slichter's Formula: K = (πr²/A(t2-t1)) * ln(s1/s2) — For determining hydraulic conductivity (K) from a recuperation test.
To determine the hydraulic properties of an aquifer, such as transmissivity (T) and storativity (S), by analyzing the drawdown response to pumping (Clause 3).
What is a recuperation test used for?+
It's a single-well test to get a quick estimate of the hydraulic conductivity of the formation immediately around the well by measuring the rate of water level recovery after a rapid change (Clause 4).
What is a tracer test used for in geohydrology?+
To determine the velocity and direction of groundwater flow, and parameters like effective porosity and dispersivity by introducing a substance (e.g., dye, salt) and monitoring its movement (Clause 5).
Which geophysical method is most common for groundwater exploration?+
The electrical resistivity method is widely used to map subsurface variations, identify freshwater/saline water interfaces, and delineate aquifer boundaries (Clause 6.2).