Lake Kinneret water – a damaged treasure
Ruth Landau, 351/14 Yefeh Nof St., Safed, Israel
Beginning in 1990, exploitation of L. Kinneret brought down water levels, causing the release of nutrients from sediments to affect water quality. The Kinneret sardine population expanded, impacting water quality through its degeneration.
With increased production of desalinated and recycled water in recent years, pumping of Kinneret water was reduced. However, the long delay in implementation of these measures allowed pollutants to accumulate. Water quality continues to fall and the two main fisheries have collapsed.
The media and researchers are reluctant to reveal the effect of management policy on water quality.
Take a trip around L. Kinneret with a well-informed guide and you will be treated to fascinating stories that enhance the unique beauty of the lake. You will also learn that the lake had contributed, in earlier years, as much as one third of Israel’s water supply through the National Water Carrier.
You may be told that Kinneret water quality has deteriorated, but if you ask questions about the nature of this deterioration and its cause, the answers will probably be evasive, vague or erroneous. The guide may quote a webpage or newspaper report stating that organic pollution of Kinneret water is due to cows grazing nearby. Or the remarks on radio of a respected water engineer may be used to give credence to the idea that tourism and water quality are seriously in conflict.
The media, including a cute little duck on the internet (5), use the Kinneret water level as a constant reminder of the need to conserve water. Good, but these reports do not inform the public of the link between water level and water quality.
Lack of public awareness of the fragility of L. Kinneret has allowed over-exploitation of Kinneret water and neglect of measures such as increased desalination, recycling and public conservation of potable water. The long delay in applying these measures resulted in a water crisis and also the degradation of Kinneret water quality.
By dispelling false notions and presenting information not available to the public, further pollution of the Kinneret may be prevented.
Standards of water quality
The Kinneret Limnological Laboratory (KLL) traces yearly trends in water quality by means of an index that combines various parameters (2). This index dropped by 13.2 % between the period 1991 – 2002 and the period 2003 – 2006, to a level that is considered to be barely acceptable by the standards of Israeli water experts (2, 35). Further changes in various parameters, especially toxic algae and salinity, brought the water quality index for 2011 down to a level considered to be unacceptable by these standards (2).
The KLL report for 2012 shows a further decline in water quality. Oxygen concentration in summer 2012 was lower than any recorded value for L. Kinneret. There were increases in chlorophyll, primary production, phosphorous, fecal coliforms, suspended solids and turbidity – all characteristic of eutrophication (over-nourishment).
According to the KLL report, the over-average rains of 2011/12, coming after a series of drought years, brought polluted effluents into the lake. While these effluents must have had some effect in winter and spring, they cannot account for the great decline in Kinneret water quality in 2012. In previous years, before low water levels de-stabilized the lake’s ecology, effluents did not appreciably harm water quality. It seems more likely that the continued decline in water quality is due to internal production and accumulation of pollutants (discussed in the next sections).
With increased use of desalinated and recycled water the water crisis has abated; hopefully, the treated and diluted Kinneret water is potable when it reaches the kitchen faucet. Still, there are questions that should be asked in order to prevent recurrence. Was the water crisis in Israel due entirely to six drought years or has administration some responsibility in the matter? What role did the scientific establishment play in the water crisis?
How Kinneret water quality dropped to unacceptable standards
Before pumping of Kinneret water into the National Water Carrier began in 1965, there was some knowledge of the physical, chemical and biological parameters of the lake (15, 27, 33). The impact of water level on water quality could be surmised from the inner contours of the lake. L. Kinneret is more like a cup than like a saucer: the sides descend steeply to about 40 meters leaving a narrow littoral (shallow inshore area). Lowering of water level does not affect the surface area as severely as it affects the volume; therefore it increases heat energy per unit volume. Warmed-up organic sediments release nutrients which, at higher water levels, are limited to sources outside of the lake (29).
Low rainfall in the winter of 1972/73 resulted in the lowering of lake level to -211.8 m (maximum level is -209 m). Despite low nutrient yields from external sources, there were increased nutrients in the water column in 1973/74 (29).
The alga Peridinium, the most abundant organism in the lake at that time, decreased while other algae including toxic blue-green algae increased. This alteration is due to the pivotal role of phosphate nutrients: Peridinium thrives in a low phosphate environment which limits other algal species.
Thus scientific observations of the 1970′s answered the question “how much water can be taken without severe damage to water quality”. A ‘red line’ should have been drawn at a water level of -212m. However in the 1980′s, in order to enlarge supply, management decided to operate at lower lake levels than in previous years (7). Thus the bounty of good rainfall would not be wasted by flowing down the southern Jordan River.
When lake level fell below -212 m at the end of the dry season in 1989, 1990 and again in 1991 (Fig.1) water quality began to deteriorate. Until the 1990′s the lake was characterized by an annual pattern that stabilized organic content; otherwise the lake would have dried up over the thousands of years in its history. Every year there was an intense spring bloom of Peridinium (you would come out from a swim with a reddish-brown coating). Other algal species dominated in summer and fall but in smaller quantities (7, 8, 29, 34).
In the 1990′s Peridinium spring blooms began to appear erratically (Fig. 1) and there were 4 no-bloom years from 2008 to 2011. As these algal blooms are the main food supply of amnun hagalil (musht or Tilapia) it is not surprising that this valuable fish stock has declined (22, 37). But most important in respect to water quality, the disappearance Peridinium blooms is concurrent with the rise of toxic blue-green algae (2, 12, 14, 34)
Role of the lavnun, Acanthobrama terraesanctae
A ‘red line’ of -212 m was confirmed by super-abundant broods of the lavnun (Kinneret sardine) hatched in1990, 1991 and 1992 (18, 20, 21). The lavnun population is limited by mortality soon after hatching because at this stage the small, slow-moving fish (larva) depends on patches of food items small enough for its tiny mouth (23). Apparently, in the early 1990′s such food was well supplied. The super-abundance of small lavnun indicates eutrophy (abundant nutrients), a condition that reduces water quality.
Whereas Kinneret water quality studies had previously ignored fish, the conspicuous growth of the lavnun population in the 1990′s brought attention to the role of fish in the lake. The lavnun came to be regarded as an enemy of water quality due to its consumption of crustacean zooplankton, the organisms that were believed to be the main water cleaners. (9, 25, 28, 35) In an effort to counter this ‘enemy’, the ‘dilul’ (thinning) project began in 1994, paying fishermen to remove lavnun under commercial size. Yearly ‘dilul’ catch, up to 700 T, had no discernable impact because the amount removed was insignificant in relation to the total lavnun population (21).
The ‘dilul’ project provided data (3) from which lavnun population size in the late 1990′s was estimated at ~30,000 tonnes, implying a density of ~180 gm /square meter of lake surface. From pond culture it is known that at such high densities, epidemics of parasites and other diseases can be expected. Thus the occurrence of such epidemics in the late 1990′s and again more recently is confirmation of high population estimates (21).
Studies in the 1950′s (15) and the 1970′s (10) both showed crustacean zooplankton to be the main items in the guts of adult lavnun, and there was some evidence of sardine predation reducing zooplankton (10, 17). No gut-content observations have been reported since 1977.
When the lavnun population expanded in the 1990′s, it could not be sustained by crustacean zooplankton since there was no compensating increase in this food source (2). Instead there was increased abundance of food organisms much smaller than crustacean zooplankton. These organisms form aggregates called ‘lake snow’, a suitable food source for the lavnun (11).
By consuming tiny organisms, the lavnun became a more important cleaner of lake water than crustacean zooplankton; its eating habits do not harm water quality as claimed. However, the huge lavnun population is in itself a pollution problem, not recognized by Kinneret managers due to their reliance on erroneous stock estimates.
In the 1990′s conventional methods based on abundance, mortality and growth data, were replaced by acoustic monitoring (8, 32). The estimates, given in numbers of ’large’ and ‘small’ fish presumed to be lavnun, amounted to about a tenth of the number required to account for the lavnun population, estimated by conventional methods. With fish size and species only vaguely defined, acoustic data are useless for any analysis of lavnun impact on water quality.
While acoustic monitoring requires the use of a research vessel and other expensive equipment, sampling catches with only a ruler and scales (1 gm accuracy) has produced information which is far more relevant to water quality than acoustic results.
Among 575 lavnun specimens observed in the 2010/2011 fishing season, only 19 had reached 15 cm or more (Fig. 2). Except for the smallest specimens the fish were underweight, especially the 19 largest fish (Fig.3). The poor condition of the fish can be partly explained by parasitic infestation (Fig.4); however other disease organisms were probably involved as the degree of parasitic infestation was not high, but weight loss was extremely high (Fig. 3 & 4).
The Dept of Fisheries tried, without success, to revive the lavnun stock by restricting fishing in 2010/11 and previous seasons. The high mortality, ~70% per year, indicated by 2010/11 size distribution data (Fig. 2) was not due to fishing but to density dependent disease epidemics. The fishery collapsed because older commercial-sized fish (13 cm and over) are more vulnerable than small fish.
Disease-ridden, rotting lavnun are polluting Kinneret water. The continued descent in water quality since 2001, when water level approached -215 MSL, is probably due to accumulation of dead lavnun.
Comments on the Report of the Government Investigative Committee on Water Management in Israel (published 2010)
As threats of water rationing are no longer heard, only the high price of water reminds Israelis of the recent water crisis. However questions remain: What caused the crisis? Can it happen again? Has water quality been affected?
The public is under the impression that 6 years of drought were reason enough for a water crisis. The Water Committee, however, found that the crisis was basically due to mismanagement that began long before the drought years. Natural resources had been over-exploited, while long-term planning for desalination of sea water was neglected along with other measures that might have alleviated the situation. Neither the public nor the government was informed of this unsustainable policy (4).
The Report, over 400 pages long, contains only a few lines in the supplement on LakeKinneret. The authors note that in 1967 a water level ‘red’ line was set at -212 m due to fear of the reaction of salt springs at lower levels. But later the ‘red’ line receded 5 times, reaching -215.5 m, the lowest level at which the pumps of Mekorot can operate.
Apparently, management considers salinity but not biological toxins as water quality factors. Citing a letter from Dr. Zahari, Director of Kinneret Limnological Laboratory, the Report notes that fluctuations in water level are biologically harmful. This is a true but misleading statement; rotting vegetation at the shoreline is messy but not the main biological injury to water quality. The Report fails to mention data on increases in toxic algae (2, 12) which prosper at low water levels. If the Report contained this information, it would have been harder to convince its readers of the high quality of Israeli tap water in 2010.
The Report also failed to mention KLL testimony to the Water Committee, submitted in 2009. This document (35 tamar_zahari.pdf) contains data showing deterioration of water quality with water level between 1991 and 2006. Return to higher water levels in 2003 – 2006 did not bring back the better water quality of former years, indicating accumulation of pollutants.
An obvious source of accumulated pollutants is the massive disease-ridden, rotting lavnun. But as mentioned in the section on lavnun, since the 1990′s, acoustic surveys supplied ‘official’ under-estimates of the fish population. In keeping with this policy, the KLL testimony regards the lavnun as detrimental to water quality due to consumption of zooplankton (35)
Loss of objectivity in scientific research on L. Kinneret
Kinneret research is largely sponsored by the same government bodies that manage the lake; nevertheless, until the mid-1980′s, work was objective and on a high standard, as recognized internationally. Difficulties arose when management decided to enlarge storage capacity and usage of L. Kinneret by lowering the ‘red line’ below -212 m, as outlined above. Research projects expanded, introducing new technology and complex analyses (24, 32, 36) some of which give a false impression of advancing knowledge. Technology can be a smoke-screen for misinformation and suppression of data.
For more than 20 years, both research and media reports carefully avoided linkage of low water levels to poor water quality (2, 5, 7, 8, 12, 14, 34). But recently some scientists have come out of the closet and disclosed the connection (see previous section). However, research on Kinneret fish populations with few exceptions continues to disregard scientific ethics in its unabashed support of management policy. Suppression of authentic fisheries research serves the same purpose as suppression of linkage between water level and water quality: both divert attention away from the role of management in damaging water quality.
Fisheries biology has a low status in limnology (study of lakes). Fish are presumed to play a minor role, so distortion of data is not given importance and it seems improbable for the lowly sardine to play a central role in the Kinneret ecosystem.
The scientific name of the lavnun, Acanthobrama terraesanctae, denotes a species peculiar to the holy land, for it is endemic to L. Kinneret, i.e. not found in any other country. The fish evolved in harmony with its environment so that it helps to maintain its stability. The lavnun’s high fecundity, with its peculiar 4 days off and on spawning cycle, ensures survival in spite of predation on eggs, and also enables expansion in eutrophic conditions. The lavnun becomes a cleaner of lake water when zooplankton cannot cope with the huge influx of tiny organisms.
Another stabilizing feature of the lavnun is its extremely low growth rate. The lavnun’s spawning on stones at the water’s edge made it possible to demonstrate this low growth rate in laboratory-hatched larvae, confirming evidence of low growth rate in adult fish (22). These and other observations were ignored when the lavnun was accused of harming water quality by its predation on zooplankton.
Observing attributes of nature, scientists develop respect for its laws and they see danger in ignoring these laws. But such a mentality is dismissed as unrealistic for environmental research because management, dealing with economics and politics, has little regard for biological processes.
Faced with growing demand for water during years of drought, management policy understandably caused serious deterioration in Kinneret water quality. What is difficult to understand and justify is the deterioration of scientific work for which management is largely responsible. Support is given to costly projects that do not further knowledge (32, 36) while simpler reliable methods are discontinued, leaving a gap in current data. Pressure to produce results in conformity with management policy impinges on all areas of study, but most especially those concerned with fish. As a result, science does not serve either management or the public to the best of its ability.
The recent water crisis might have been averted, if, instead of compromising their integrity, scientists had stubbornly proclaimed the dangers of over-exploiting Kinneret water. Then, with alternative strategies implemented in the 1980′s, Israel would have water in both quantity and quality even in drought years
Deterioration of Kinneret water quality began in the early 1990′s when water level dropped close to -213 MSL. Since the year 2001, when water level approached -215 MSL, an unacceptable standard of water quality prevails. During periods of higher water levels after the 1990′s, the previous level of water quality did not return, indicating accumulation of pollutants.
The most obvious pollutants are rotting lavnun (Kinneret sardine). This fish population expands during periods of low water levels, and on reaching ~30,000 tonnes, density-dependent disease epidemics cause high mortality of commercial-sized lavnun, ruining the fishery and polluting water.
The recent water crisis was caused by over-exploitation of water resources, including Kinneret water, aggravated by drought. Together with management the scientific establishment bears responsibility for this crisis and also for misinforming the public in regard to the impact of water level on water quality.