The Effects of Environmental Pollution on Lakes in Manitoba

Several fascinating research topics were presented by the visiting scientists from Canada on the symposium’s final day of professional discussions. One of the most problematic sources of pollution in the State of Manitoba is the residue that is discharged from the copper, nickel and zinc mines operating throughout the state. They have produced some 20 million tons of discharge over the past 25 yea

January 20, 2010 15:26

WNEW15. (photo credit: KKL)


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One of the intriguing sidelights at the recently held Israel-Manitoba symposium on water was the announcement that leading water scientists in Israel are considering the possibility of recommending to government decision-makers that an additional desalination plant be set up on the Mediterranean coast, from which all the desalinated water produced by this facility would flow into ....Lake Kinneret (the Sea of Galilee).  This would also make it possible to divert greater quantities of water from the southern part of the River Jordan for agricultural use in the Bet She’an Valley.  The input of desalinated water to could improve the quality of its water and lessen its salinity, while reducing its dependency on the caprices of weather and rainfall to sustain its level.

Several fascinating research topics were presented by the visiting scientists from on the symposium’s final day of professional discussions. One of the most problematic sources of pollution in the State of is the residue that is discharged from the copper, nickel and zinc mines operating throughout the state. They have produced some 20 million tons of discharge over the past 25 years, which lies exposed to the elements, so that rain sweeps the metallic oxides away with it.  In certain places, such as river beds and shallow lakes, almost one gram of nickel oxide per litre of water has been officially measured. 

Among the topics addressed by environmental researcher Michael McKernan was deciding what is the desirable upper risk threshold for the discharge of such elements into ’s enormous water systems.  In the discussion, McKernan described how the metallic oxides in the rivers are monitored by installations containing local clams as a means of measurement: the various metallic oxides accumulate in the clams’ bodies, thereby serving as a model for how these dangerous substances affect other forms of life in the water and its surroundings.

The ongoing monitoring activity checks primarily for concentrations of copper oxides in the clams at their various stages of development.  Since copper oxide is ten times more toxic than other metallic oxides such as nickel, zinc or aluminium, it is possible to determine from the aggregate data what target should be aimed for in lowering the pollution level, in order to prevent injury to the animals (and, of course, to people).  As part of his research, fish populations in the rivers within the mines’ catchment basins have also been studied, showing that the number of fish species is decreasing in the more polluted bodies of water, when compared with the number of species in unpolluted rivers and bodies of waters.   These findings, McKernan explained, provide the basis for determining the level of water purification operations that is required.  In , polluting enterprises, whether mines or paper mills, are obligated to participate in pollution removal operations.

Mr. Dwight Williamson, one of the organizers of the symposium, provided research data on the organic elements in municipal sewage water in comparison with the drainage water from agricultural areas.  These elements, which are defined as plant nutrients, constitute 10% of the volume of municipal sewage.  However, in water drained from farming areas these elements are much fewer.  Nevertheless, in the State of alone, about 47,000 tons of phosphorous compound are collected from agriculture every year, providing one of the main components of agricultural fertilizers.  So while, on the one hand, these elements accumulate in natural pools, on the other hand they have to be returned to agriculture for use in the various crops.

Dr. Michael Paterson, who takes part in the Canadian government’s research into experimental lakes, fish ponds and oceans, described a unique study of the State of , in which areas larger than the entire State of Israel were flooded by building dams and creating artificial reservoirs.  In the course of the study of the effects of the construction of these reservoirs, it was shown that the presence of mercury in the bodies of fish was eight times higher, because of bacteria in the reservoir water that can turn inorganic mercury into a methyl-mercury compound that is absorbed in the bodies of fish.

At the same time, during the first five years after the dam was built and the area was flooded, the level of carbon emissions in the flooded area decreased, but, on the other hand, there was a rise in the quantity of methane gas produced by the organic substance in the water. Other effects of the construction of the dams are in the biological sphere, due to a 40% drop in the water level of the rivers on the dam’s slope because the river’s natural flow is stored. This has led to a reduction in the river’s animal population, from molluscs to fish, as their breeding areas are much smaller. However, there have been no changes in the plankton mass nor in single-celled algae, or in the level of phosphorous compounds in the water.

From the Israeli side, Dr. Alon Rimmer of the research laboratory addressed the symposium.  His work addresses a variety of hydrological aspects of water sources, their physical, chemical and biological characteristics, and details their varied long-term effects on the quality of the water in .  In the course of the last 40 years there has been a continuous drop in the quantity of water available for use in , decreasing from 600 million cubic meters a year to only 400 million cubic meters annually. This decrease stems mainly from a reduction in the amount of rainfall in the , but also from the increased use of the water of the River Jordan and its tributaries in the upper catchment basin, before the water even reaches .  According to several models, the drop in rainfall is not a worldwide phenomenon but a local occurrence.  

Dr. Rimmer also spoke of Lake Kinneret’s salinity level in the water which is relatively high in comparison with the salinity of the water of its sources in its northern catchment basin: “In 1965 we started operating the salt water carrier, which diverts some of the water from the saline springs in Lake Kinneret to the southern part of the River Jordan.  The operation of this carrier caused a decrease in water salinity; nevertheless, the salinity level has been gradually increasing over the last 25 years.  During this time, less sweet water has been entering , causing the salinity level to increase. This entire process is solely the result of human activity, because the climatic changes that affect the rate of water evaporation in the lake are minor, and cannot cause such fluctuations in salinity.  (Every year about 250 million cubic meters of water out of the overall amount that reaches it evaporate from .)

In his lecture, Professor Avital Gasith from the Faculty of Life Sciences at Tel Aviv University, who was also responsible for the symposium’s entire academic program and provided constant scientific advice to the organizers, reviewed the effect of the fluctuations of Lake Kinneret’s level at the lake’s edges, and the consequent effect on the marine animals that live in it. 

It transpires that the drop in the level of ’s water has exposed the stones and rocks of the shoreline, and these are no longer accessible to several types of living creatures whose whole existence and reproduction depend on the rocks and stones close to the beach.  These include a type of sardine that is very prevalent in the lake: it lays its eggs among the pebbles, and the eggs can only develop when they are attached to the stones.  Without stones, there is no reproduction. But even when the water level rises, providing them with stones, these fish have a very short “window of opportunity” – only one or two weeks, before the stone gets covered by algae that do not allow the fish eggs to adhere to the stone surface.

In drought years the availability of stones along the beaches drops sharply.  In addition, there are sandy areas which are ordinarily the laying grounds for St. Peter’s fish (tilapia).  These fish dig niches in the sand, and protect the eggs that are laid in them until they are hatched, and also afterwards.  Due to the recent years of drought, the whole population of St. Peter’s fish in the Kinneret has been almost totally lost. And while the quantity of fish in the lake decreases, the quantity of plankton and algae, which serve as food for the fish, constantly increases.

In his lecture, Dr. Assaf Sukenik, head of the Yigal Allon Kinneret research laboratory, rounded out the details on the same subject: “There have been periodic changes in the Kinneret’s ecological system since 1932, starting with the building of the fish dam that year, then the drying-up of the Hula Lake at the start of the ‘50s, the inauguration of the National Water Carrier in 1964, the intensive fishing of the lake that has been going on since the ‘60s, and the diversion of the River Jordan’s sewage water, which meant less entry of pollutants and organic substances from agricultural sources into the lake as a result of the renewed flooding of the peat areas in the Hula Lake wetland.  Since 1994, the Kinneret’s water level has been dropping while, at the same time, the population has grown, as have the pollutants that drain into the Kinneret from farmed areas, from fish ponds and from crop spraying. The fish population has been constantly depleting since 1993.  All these changes have been caused by human intervention.”

A population of toxic algae has been developing in the Kinneret’s water with enormous seasonal growth surges.  This “growth” is nourished by the seasonal increase of nitrogenous compounds in the lake during the months of March and April.  During the summer months, the concentration of nitrogen in the water drops sharply.  These algae are fought by means of chlorine, which kills them.

This picture was completed by Dr. Ora Hadas and Dr. Gideon Gal of the Kinneret laboratory.  In her presentation, Dr. Hadas focused on research into the development of toxic algae in the Kinneret’s water: before 1960 there was no scientific proof of the actual existence of toxic-causing organisms in water.  Now it is known that there are two kinds of single-cell species that have adapted to the lake’s conditions, and are found at different depths.  They create colonies in the upper area of the water and are clearly seen, because the microbes produce coloured substances that are either green or brown.

Dr. Gideon Gal gave a scientific report on his research, which has a quantitative approach to sustainable management of the Kinneret and takes into account the continually mounting pressure on the Kinneret’s eco-system in recent years.

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