Detecting defects of groundwater:

Atomic Energy Authority ready with indigenous expertise

By Dhaneshi Yatawara

An array of problems are rising in several parts of the country on the condition of the ground water reserves. Over extraction of groundwater through tube wells set up irregularly in several parts of the country has lead to water drying up.

Checking with isotope hydrology meter

Collecting data from wells

From tube wells

Groundwater is recharged from, and eventually flows to, the surface naturally; natural discharge often occurs at springs and seeps, and can form oases or wetlands. Groundwater is also often withdrawn for agricultural, municipal and industrial use by constructing and operating extraction wells.

Groundwater is an important part of the water cycle. Groundwater is the part of precipitation that seeps down through the soil until it reaches rock material that is saturated with water. Water in the ground is stored in the spaces between rock particles. Groundwater slowly moves underground, generally at a downward angle and may eventually seep into streams, lakes, and oceans.

Groundwater makes up about twenty percent of the world's fresh water supply, which is about 0.61 percent of the entire world's water, including oceans and permanent ice. Global groundwater storage is roughly equal to the total amount of freshwater stored in the snow and ice pack, including the north and south poles. This makes it an important resource which can act as a natural storage that can buffer against shortages of surface water, as in during times of drought. Groundwater can be a long-term 'reservoir' of the natural water cycle, as opposed to short-term water reservoirs like the atmosphere and fresh surface water.

With research done over period of time it has come to the knowledge of the scientists that ground water of the country needs to be evaluated soon for the benefit of the people. This could lead to unsolved problems in human health issues like the Chronic Kidney disease that continue to make farmers of the North Central Province suffer.

Addressing all these issues the Atomic Energy Authority has come forward with a state of the art technology to study the ground water quality and movements with the use of a separate science called 'isotope hydrology'. "We are in fact developing the isotope hydrology laboratory at the Atomic Energy Authority ready to be a service provider," said Atomic Energy Authority Chairman Dr. Ranjith Wijewardane.

"We knew that for a long time that there are so many applications using isotope hydrology. This is one of the peaceful nuclear applications. In Sri Lanka there are many fields that need the assistance of isotope hydrology which in most cases we seek expertise from foreign professionals spending huge amounts of funds," said Dr. Wijewardane.

According to Dr. Wijewardane, the Atomic Energy Authority started developing isotope hydrology laboratory around 2005.

As the AEA's Senior Scientific Officer Viraj Edirisinghe said this isotope hydrology will give the opportunity to study specially the recharge process of ground water - where the ground water originating from - we can trace that path. Along with Viraj Edirisinghe three other scientists are involved in the experiment.

"In order to get the details of the groundwater we need data of rain water from different locations of the country. The reason is the composition of oxygen isotope in rain water is different from place to place. Water under ground should have the same percentage if the source is solely rain water," he said.

These isotopes work as the fingerprint of the ground water by examining a sample of water we can identify where the water is taken from.

"If the groundwater has different mixture of isotopes than the rain water of the immediate area we can identify the other sources of water by testing large water bodies in the close proximity," he said.

If the water is polluted Isotope hydrology can find the source of contamination as well. Using this technology we can protect the ground water resources.

"Knowledge gathered by the isotope testing is very important for policy makers in water sector departments. How much water can be extracted from particular areas can be decided by recharging source and recharging areas," Edirisinghe said.

"Normally the ground water is recharged regularly - meaning it continuously gets water from its source. But there are other groundwater reserves where there is no recharging source and water is very old," he said.

Accordingly extracting water from such reserves can lead to drying up of water reserve eventually effecting the the soil moisture.

"At present we are collecting data in certain parts of the North Central Province. Our concern for the dry zone is because most of the water related problems are in the dry zone. Concerned people of these areas are assisting us to collect rain water in order for us to test and get information," he said.

With the existing data the scientists who are conducting the testing have already started to find connections between certain water tanks and ground water reserves that supply water through tube well to several villages. "we have collected data of water from tube wells within 3 - 4 kilometre radius of Kandalama and Kalawewa tanks that showed the tube well water had isotopes found in the tanks.

Though the main recharge source of groundwater is rain tanks and such large water reserves can act as recharge sources as well.

"This is only once case of the there other areas we are slowly starting to study groundwater - areas like Jaffna peninsula and Puttlam area. In these two areas studies are done in collaboration with the water resources board," said Edirisinghe explaining their overall study area.

As they further said this is only one form of usage in isotopes. "Another main area this technology can be used is detecting leakages in dams. The Atomic Energy Authority has successfully found the leakage point of the Samanala wewa tank after several attempts by foreign scientists spending millions of money," he said.

What happens when there is a leakage in a dam is that it cannot be filled up to the maximum level. Thus effecting the electricity power generation using the water flow. "The most important and difficult issue is locating the leakage.

When it is identified the relevant authorities can take proper action to rectify the matter avoiding the low electricity power generation and possible risks," he said.

In order to create a network among the relevant authorities, the AEA is planning to have interactive sessions with them, thus saving millions of rupees that is unnecessarily spent on areas that needs the technology of isotope hydrology.

*************

Isotopes

Isotopes are forms of the same element that have variable numbers of neutrons in their nuclei. Isotope hydrology is a field of hydrology (study of water) that uses isotopic dating to estimate the age and origins of water and of movement within the hydrologic cycle. Water molecules carry unique fingerprints, based in part on differing proportions of the oxygen and hydrogen isotopes that constitute all water. The isotope hydrology program at the International Atomic Energy Agency works to aid developing states and to create a detailed portrait of Earth’s water resources. An arsenic pollution crisis in Bangladesh that the World Health Organisation calls the “largest mass poisoning of a population in history” has been investigated using this technique.

*************