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Isotope Hydrology Section


Isotope Hydrology: Tools to unlock waters secrets

Water resources are being increasingly stressed by multiple factors, including growing population, grater food production, irrigated agriculture, energy production and climate variability and change. One billion people around the world currently have no access to safe drinking water and only about 15% of the worlds population enjoy relative abundance.

A key requirement for assuring adequate water supplies and their sustainable management is to improve the assessment of water resources. Such assessments are severely lacking in most of developing countries. The greatest proportion of the earths available fresh water is located underground, and this vital resource is often poorly understood and poorly managed.

Only with precise information on the availability and renewability of water resources can country makes sound decisions about sustainable water resources management. Isotopes provide unique information about water resources characteristics in a cost efficient, accurate and easy-to-use way. Isotopes are waters fingerprints. They provide information on the age, origin and renewal rate of groundwater, its dynamics, as well as the vulnerability to source of pollution, salt water intrusion and climate change.

Applications of Isotope Techniques in Water Management and Dam Safety

Isotope techniques allow rapid understanding of hydrological systems that may otherwise require years or decades of monitoring. Therefore it is cost effective. In some cases it is unique.

Isotopes are commonly employed to investigate:

  • Recharge Mechanism of groundwater:
    • Identification of groundwater recharge sources
    • Recharge areas
    • Mixing of different water sources
  • Groundwater Dating:
    • Identification of modern recharge
    • Groundwater movement and residence time
    • Infiltration rates in unsaturated zone
    • Identification of paleowaters
    • Delineation of protection zones
  • Groundwater pollution and salinization:
    • Identification of pollution sources
    • Origin of nitrates
    • Origin of groundwater salinity
    • Microbial denitrification processes
    • Mixing of sea water
  • Surface water/groundwater relationship and interconnection between aquifers
  • Dam safety & sustainability:
    • Leakage /seepage problems
    • Effect of dam reservoir on surrounding areas
  • Investigation of geothermal resources:
    • Source of thermal waters
    • Residence time
    • Subsurface history (rock-water interaction, mixing with fresh water)
    • Estimation of reservoir temperature

Most commonly used isotopes are 2H1 , 3H1 , 18O8 , 13C6 ,  14C6 , 15N7 and 34S16

Further Reference

Analytical Capabilities

Isotope Hydrology Laboratory of the Atomic Energy Authority is equipped with following equipments for water isotope measurements and wet chemical analysis.

a. Liquid Water Isotope Analyzer-LWIA (Laser Mass Spectrometer) for stable isotopes (18O and 2H) measurements in water.

LWIA- Model- LGR -24d � DLT 100

Auto Sampler
LWIA- Model- LGR -24d � DLT 100   Auto Sampler

b. Liquid Scintillation Counter (LSC) for radioactive isotope (3H) measurements in water.
This includes electrolysis enrichment of 3H in natural waters.

Electrolysis Enrichment

LSC -Packard-TriCarb 3170 TR/SL
Electrolysis Enrichment  LSC -Packard-TriCarb 3170 TR/SL

c. Spectrophotometers / Digital Titrators for wet chemical analysis (major ions) of water and basic water quality measuring kits for field measurements of pH, EC, DO etc in water.


Isotope Hydrology Section

Mr. Viraj Edirisinghe (M.Sc. in Nuclear Science),
Deputy Director,
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Ms. K. S. G. S. Priyadarshanee [B.Sc.(Hons)-Sp(Geology)]
Scientific Officer,
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Ms. J. D. C. Gunasekara [B.Sc.(Hons)-Sp(Environmental Science and Natural Resources Management)]
Scientific Officer
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Mr. R. A. P. Mahesh Maduwantha
Laboratory Assistant


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