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Scientific Basis for Water Resources Management (Proceedings of the Jerusalem Symposium, September 1985). IAHS Publ. no. 153.

The management of Lake Kinnereî and its drainage basin

MOSHE GOPHEN The Yigal Allon Kinneret Limnological Laboratory, PO Box 345, Tiberias 14102, Israel

ABSTRACT Since 1964, when the National Water Carrier system began to operate, Lake Kinneret has been primarily utilized as the national water reservoir. The lake is also intensively exploited for fisheries, recreational activities and tourism. Recent manmade interventions thoroughly affected the drainage basin-lake ecosystem: the lake is heavily loaded by nutrients from sewage, fish-pond wastes and organic soils (peat) degradation; the fishery and stocking managements of the lake are primarily aimed at food production but not at water quality improvement. A management programme for the drainage basin and the lake was outlined and its implementation already started. This management programme is based on the lake food-web structure: reduction of nutrients contributed by sewage, fish-pond wastes and peat dégradants and modifications of the present fisheries and stocking operations. Full implementation of the presented management programme can probably prevent lake eutrophication and water quality deterioration.

L'aménagement du lac Kinneret et de son bassin de drainage RESUME Le lac Kinneret est utilisé principalement comme un reservoir national d'eau a partir de 1964 quand le système national d'adduction d'eau (National Water Carrier) est entré en fonction. Le lac est intensivement exploité pour la pêche, pour les loisirs et pour le tourisme. L'intervention humaine, récente, a affectée l'écosystème du lac et du bassin de drainage. Le lac est chargé de nutrients provenant des eaux d'égout, des eaux des étangs piscicoles et des produits résultant de la dégradation de la tourbe. La pêche et le peuplement du lac avec des poissons avait pour but la production des denrées et non l'amélioration de la qualité de l'eau. Un programme pour l'aménagement du bassin du drainage et du lac a été esquissé et sa mise en oeuvre a commencé. Ce programme est basé sur la structure de la chaîne alimentaire du lac: réduction des nutrients provenant des eaux d'égout, des eaux d'étangs piscicoles et résultant de la dégradation de la tourbe; la modification du système actuel de la pêche et du peuplement piscicole du lac. L'exécution complete de ce programme d'aménagement préviendra probablement 1'eutrophisation du

127

128 Moshe Gophen

lac et la deterioration de la qualité de l'eau.

INTRODUCTION

Lake Kinneret, a warm monomictic lake situated in the north of Israel in the Syrian-African Rift Valley, is the only natural fresh-water lake in Israel and the whole of the Middle East. The surface area of the lake is 170 km , with a drainage basin of 2730 km2 located mostly to the north of the lake. The volume of the lake is 4 x 109 m3 and the ratio between the drainage basin area and lake volume (m2m 3) is 0.68, a relatively high value for nonpolluted lakes. The maximum depth of the lake is 43 m and average depth is 24 m. The lake mixes December-April and begins stratification in April-June and is completely stratified from June to November. A short intermediate period occurs during April-June when thermal stratification forms and oxygen is gradually depleted from the hypolimnion.

Since 10 June 1964, when operation of the National Water Carrier system began, the lake has been primarily utilized as the national water reservoir. Lake Kinneret currently supplies 30-35% of water consumption in Israel, about half which is currently used for drinking. However, in the near future the percentage of drinking water will be increased to 80%. Consequently, the quality of the lake water is of national concern.

In order to formulate the principles to optimize a lake management programme, one should integrate the following information:

(a) The impact of manmade modifications on the system, particularly on water quality.

(b) The present environmental conditions of the Kinneret ecosystem.

(c) External constraints on the system, proposed benefits and consequently priorities of lake utilization.

Management considerations of health aspects, salt balance and water level lowering proposals will be discussed separately.

MANMADE MODIFICATION IN THE NATURAL DRAINAGE BASIN-LAKE ECOSYSTEM

An historical view of human intervention in the Kinneret ecosystem includes the following main changes:

(a) The current population in the basin area has increased from about 20 000 in the early twenties to approximately 255 000, resulting in an increase in sewage production.

(b) The southern dam at the Jordan outflow was constructed in 1930 as part of an electricity production system followed by a deepening of the Jordan outlet. It then became possible to control the lake water level.

(c) In 1957 the Hula Lake and surrounding swamps were drained exposing the peat soils to the air with enhanced degradation of organic compounds followed by a gradual (averaging 7-8 cm per year) lowering of the peat-soil surface due to consolidation and removal of dust by wind.

(d) The construction and operation of the National Water Carrier

The management of Lake Kinneret 129

(NWC) system (10 June 1964) which removes from the lake an average quantity of 10s m3 of water per day.

(e) In 1967, the construction of the saline spring canal on the west-side of the lake was completed. The "saline spring canal" diverts approximately 20 10 m water containing 40-60 x 10 t of salt out of the lake annually. As a result 30% less salt entered the lake and salinity of the water has dropped from 395 ppm CI in the early sixties to 212 ppm in 1983.

(f) The lake is intensively stocked with both exotic fish (silver carp from 1969; grey mullet from 1958; Oreochromis aureus from 1958) and native fish (Sarotherodon galilaeus from 1951).

NUTRIENT SUPPLY FROM THE DRAINAGE BASIN TO THE LAKE

Population increases, drainage of the lake and swamps in the Hula Valley, and intensification of agricultural cultivation including fish ponds are the main contribution to nutrient input in the drainage basin area. The sources of about 25-35% of the total nutrient input are located north of the Israeli monitored area and not clearly identifiable. The monitored nutrient sources (Table 1) are:

Nitrogen Of the total nitrogen annually supplied to the lake, 65,31 and 4% is in the form of N-NO3, organic nitrogen and N-NH3, respectively. One of the main sources of nitrogen compounds in the drainage basin of Lake Kinneret is the organic peat soils in the Hula Valley. A major part of the nitrogen is drained from the peat as N-NO3 and the remainder as N-NH3 and organic N. Another two important nitrogen sources are sewage and waste waters from fish ponds which supply mostly organic and N-NH3 and contribute more than 50% of the external load of organic nitrogen.

Phosphorus The major source of P is suspended particles eroded from the bottom or walls of the water flow routes. Other important sources of dissolved (orthophosphate and other components), and particulate organic-P are waste water from fish ponds and sewage. Of the total phosphorus measured in the Jordan inflow to the lake, approximately 55% and 12% is due to organic P and dissolved P forms, respectively. The input of organic P originated in fish pond wastes and sewage is stable compared with particulate inorganic P which is relatively increasing during the flood season when erosion activity is higher.

The N:P ratios of external laods (Table 1) are similar to other non-polluted lakes in the world (LBRI & NIRA, 1984).

Contribution of nutrients to the external load Total quantities of most of the organic nutrients (P and N compounds), dissolved P and ammonia are relatively constant. They mostly originated in sewage and fish pond wastes. Nevertheless, organic N and ammonia from the peat are positively associated with water flux through the organic soils during winter floods or in summer-fall season in order to put out peat fires.

Fluctuating contributions to the external loads are nitrates from

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the peat which were approximately 25% of the total input of N-NO3 to the lake (Geifman, 1982). The external load of carbon was approximately 10% of the total C input and the other 90% are contributed by algal photosynthetic fixation (Serruya et al., 1980). The natural vegetation period in the drainage basin area is short (2-3 months) and the summer-fall season is dry without transport of organic substance. Therefore, organic substances produced by plants are degraded on land and the contribution of organic matter by terrestrial vegetation to the lake is low.

Sewage production The total quantity of sewage produced in the Israeli territory of the drainage basin area of Lake Kinneret is approximately 10-11 105m3 year"1; of which 5-6 106m3 flowed directly into the lake prior to 1982 (Shacham, 1983). Currently sewage input is 1.5-2 106m3 year *. Most of the sewage is primarily treated and in a few settlements there are secondary or tertiary treatment plants.

FISHERY MANAGEMENT AND STOCKING POLICY

The lake is intensively utilized as a fishery resource (Table 2). The present exploitation of the lake is based on laws for fishery management regulations established about 40 years ago, and slightly

TABLE 2 Averaged annual fishing in Lake Kinneret*: cichlids and bleaks - 1960/1982; grey mullet - 1966/1982; silver carp - 1978/1982

Fish species Average annual % of average total catch for respective (t) period

Cichlids 331 (92) 20 Bleaks 985 (156) 60 Grey mullet 200 (38) 11 Silver carp 131 (50) 7

*From Sarid & Golani, 1950-1982; S.D. in parentheses.

modified later. Moreover, these laws were formulated and officially implemented when the lake was not utilized as a national water reservoir. After 1964 (operation of NWC), laws and policy for fishing management remained in force although limnological conclusions aimed at water quality improvement suggested modifications were necessary. Moreover, a stocking programme and fishery policy primarily aimed at food production did not consider water quality improvement. As a result present exploitation of zooplanktivorous bleaks (800-1000 t annually) is insufficient while that of S. galilaeus is declining. In order to increase the income

132 Moshe Gophen

of fishermen exotic fish are stocked.

LAKE-FOOD WEB STRUCTURE

Two superimposed food chains have been indicated in the ecosystem of Lake Kinneret (Serruya et al., 1980). The major components of these two pathways are: (i) the heavy bloom forming alga Peridinium (March-June) and the most efficiently known Peridinium consumer, the Galilee St Peter's fish (Sarotherodon galilaeus). Peridinium is very poorly consumed by zooplankton and most of it is degraded via a detrital pathway; (ii) nannoplanktonic algae (mainly chlorophytes, chrysophytes and cyanophytes, herbivorous zooplankters and zooplanktivorous fish, mainly bleaks (Mirogrex sp. and Acanthobrama sp.). The dominant, but slower, pathway is the Peridinium detritus-S. galilaeus, however the second channel is more active.

Increasing the input of available nutrients (organic P and N compounds, ammonia, dissolved P) from external (sewage, fish-pond wastes) and/or internal, enhanced resuspension processes, may initiate a shift towards Peridinium suppression and enhancement of nannoplanktonic blooms in summer-fall (Pollingher & Herman, 1977). An increase in nannoplankton biomass would also result from a reduction of zooplankton grazing capacity (Fig.1) due to intensified prédation by fish. These successive events adversely affect water quality because it is difficult to remove nannoplankton from supplied water.

44

36

28

20

'i i l . . . . I . . . . i , , . , 1970 1073 1990

Y E A R S

FIG.l Average total zooplankton standing stock wet biomass (g ,m 2) in Lake Kinneret during 1969-1984.

' (w.w.) ax = -1.5 g ,m~2year_ 1 / r 2 = 0.79; P <0.01.

(w.w.) ^

MULTIANNUAL CHANGES IN THE ECOSYSTEM

Drainage basin (Table 1, Geifman & Dexter, 1984) During the period of 1969/1970-1983/1984 a clear trend of increasing external load of dissolved P (orthophosphate) and N-NH3 from the drainage basin to the lake was observed whilst reduction of total phosphorus was indicated only during summers of the same period. Nevertheless,


the organic nitrogen load clearly declined during 1982/1983-1983/ 1984.

Lake The total load of nitrogen, organic-nitrogen and total phosphorus in the lake, calculated separately for four separate layers (0-12 m, 12-22 m, 22-32 m, 32-bottom) are presented in Fig.2. Nitrogen load indicate three periods: 1969-1973, 1974-1981 and 1982-1984; an increase in the nitrogen load in 1974-1981 with consequent reduction in 1982-1984 are clearly shown. The P-load data suggest a two-step increase, 1973-1978 and 1978-1981 followed by a moderate decline in 1982-1984. It should be noted that the decline in total N and P in the lake during 1982-1984 coincides with a similar reduction in the external nutrient source (Geifman & Dexter, 1984).

The increase in nutrient concentrations in the lake may have caused changes in the food web structure (Pollingher & Berman, 1977). Nannoplanktonic algae partly replaced Peridinium and became more abundant, leading to a lower phytoplankton biomass throughout a full year cycle and particularly in summer-fall seasons. The summer-fall blooms of nannoplankton deteriorated water quality. It indicates that, contrary to other lakes, eutrophication in Lake Kinneret is reflected by a reduction of total phytoplankton biomass, an increase in specific productivity and unstable species composition.

In addition to nutrient enrichment, zooplankton biomass (mostly herbivorous cladocerans) dropped (Fig.l) also resulting in nannoplankton enhancement (Gophen & Pollingher, 1985). This is an example how phytoplankton community structure and biomass can be modified with or without external nutrients load increase.

Ton P

Ton N

5300

•4500

3500

2500

I I I I I I I I I I I I I I I I I 1970 «75 1980

YEARS

FIG.2 Total standing stocks (tons) of total phosphorus ( . . . . ) , total nitrogen ( ) and organic nitrogen ( )

in Lake Kinneret during 1969-1984. Sum of total load calculations are based on annual averages of concentrations and the volumes of four separate layers (0-12 m, 12-22 m, 22-32 m, 32-bottom). (Data compiled by S. Serruya, K11-I0LR database.) Average water level -210 m.

134 Moshe Gophen

Management options are aimed at reduction of nannoplankton by lowering nutrient levels, resulting in dominance of Peridinium pathway when Peridinium is sufficiently pressed by fish (S. galilaeus) grazing. Removal of Peridinium cells from NWC system is easily performed by slight chlorination which damage the Peridinium flagellae resulting in rapid sedimentation of the heavy cells. Reduction of prédation on zooplankton by fish may result in a higher reduction of nannoplankton.

LAKE UTILIZATION: OPTIONS AND PRIORITIES

Water supply The majority of utilized lake water is pumped through the National Water Carrier (NWC) operated by the National Water Supply Company "Mekorot". The NWC system annually transports 400-430 106m3 from the lake to the southern part of the country where a large part of the agricultural areas are located.

The intake of the NWC system is situated about 500 m from the shoreline in the northwest part of the lake at a depth of 12 m, therefore the pumped water is mostly epilimnetic. Pumping of hypolimnic waters occurs when the thermocline is tilted upwards in the northwest part of the lake in summer. About 100-150 10 m3 of water is pumped from the lake epilimnion by local consumers.

About 150-200 106m3 of the natural lake water sources are utilized for irrigation and drinking in the drainage basin area before reaching the Kinneret. These waters are collected or pumped from water lines for direct use or stored in reservoirs. The annual quantity of evaporated water from the lake is 300 10 m . The average annual water yield to the lake is 840 106m (Mero, 1978).

Fisheries (Tables 2 and 3) (Sarid & Golani, 1950-1982) Lake Kinneret is intensively exploited for fisheries. Annual total catches varied during 1960-1982 between 1110 t in 1962 and 2159 t in 1971. The annual average total catch for the period of 1960-1982 was 1635 t (+ S.D. 313), i.e. 96.2 kg ha 1. Intensive stocking activity is also carried out. The annual income of fisheries is approximately 3 x 106 US$ from about 300 licensed fishermen.

TABLE 3 Stocking activity in Lake Kinneret during 1960-1982; total numbers (millions) of all species introduced as fingerlings (Sarid S Golani, 1950-1982)

Species Number of fingerlings (106)

Sarotherodon galilaeus 31 Oreochromis aureus 32 Silver carp 12 Grey mullet 28

TOTAL 103


Information presented in Table 2 indicates that more than half of the annual catch is of bleaks and the rest is shared between cichlids, silver carp, mugilids and small quantities of other species. The commercial value of cichlids and mugilids is relatively high and that of bleaks is very low.

Recreation and tourism Since Lake Kinneret is the only freshwater lake in Israel it is very attractive for recreational activities including camping, swimming, water-skiing, windsurfing, sailing, tourist cruises etc. It was estimated that maximum numbers of 50-80 000 people per day used the lake beaches during summer (May-October) holidays.

Priorities On a national basis it was recognized by the Water Commission and Ministry of Agriculture that present priorities of lake utilization are those of water supply (domestic and drip irrigation). Therefore, considerations for lake management should give the highest classification to options which will lead to prevention of water quality deterioration. These aspects also have economic significance because water treatment at a level of source management are probably less expensive than other options.

MANAGEMENT! RECOMMENDATIONS AND THEIR PRESENT IMPLEMENTATION

Drainage basin

Recommendations : To reduce external loads of nutrients according to the following priorities:

(a) Organic nutrients originating in sewage and fish pond wastes. The reasons for the high level of priority given to the elimination of sewage and fish pond organic nutrients are multifold. The nutrients are readily available to lake algae; these wastes include pathogenic elements to man and fish; nutrient (mostly organic) concentrations are relatively high and they flow in controlled systems (pipes and canals) making their management highly feasible.

The proposed management is to restrict fish ponds by partial conversion to other crops; deepening of ponds for sewage storage with mixed clean water for irrigation, and fish culturing; construction of reservoirs for sewage storing and reuse for irrigation. There is no danger of the nutrients leaking through the soils irrigated with these waters. It was found that the drainage water from cultivated organic soils in the area contain very low concentrations of P and N compounds due to the high absorption capacity of the peat (Geifman, 1982).

(b) Peat dégradants: Since most of the degraded compounds are nitrogenous, which is less effective in enhancing Kinneret algal productivity relative to phosphorus (Serruya et al., 1980), peat management has a lower priority compared to sewage and fish ponds. Management recommendations are aimed at prevention of floods on the peat area by elevation of the Jordan Canal walls, agrotechnical operations to reduce the rate of peat soil surface erosion and maintaining efficient drainage systems.

136 Moshe Gophen

Present implementation During the last three years, more than 20 sewage reservoirs and deep storage (sewage with clean water) fish ponds were constructed (Kinneret Authority, personal communication). In these reservoirs, approximately 4 10 m of raw sewage which previously entered the lake, is stored and reused for irrigation.

In 1975, the total area of fish ponds in the Hula Valley was 16 km2. At the end of 1984 fish ponds area was restricted to about 6 km2, of which 3.4 km2 was in the west and 2.7 km2 in the eastern part of the valley (Weil, personal communication). Of the western ponds, 1.3 km2 are utilized as deep "pond-reservoirs" and the rest are either drained to the Hula Nature Reserve and to the western canal, or partly stored in the Einan Reservoir. The Jordan Canal walls were recently elevated and peat floods were partly reduced. The suggested impact of these activities (sewage storage and fishpond restrictions) on external nutrient supply to the lake has been previously discussed (Geifman & Dexter, 1984) and concentrations of sewage bacteria (faecal coli) in the Jordan inlet waters were also lowered (Table 4).

TABLE 4 Representative values of faecal coli counts (no./100 ml) in Jordan inlet waters during 1980-1984 (Yigal Allon, Kinneret Limnological Laboratory, Annual Reports, 1980-1984, T.Bergstein-Ben-Dan)

Date

9.11.80 20.11.80 1.12.80

18.12.80 18.12.80 18.12.80

2. 2.80 22.11.81 19. 1.82 21. 4.82 29. 4.82

6. 5.82 8.12.82

17.11.83 27. 2.84

Faecal coli/ 100 ml

11 10

6 48 28

8 4 1

4 2 2

3 1

970 550 770 900 100 700 650 280 874 250 800 050

17 600 loo

Sampling si te

Jordan inlet Jordan inlet Jordan inlet Arik Bridge Jordan inlet 800 m from Jordan Jordan inlet Jordan inlet Jordan inlet Jordan inlet Jordan inlet Jordan inlet Jordan inlet Jordan inlet Jordan inlet

inlet

Lake

Recommendations-Fisheries (a) To increase stock biomass of Sarotherodon galilaeus in the

lake by improvement of stocking procedures of this fish i.e. shifting the introduction season from November at present to early summer and the weight of the fingerlings to more than 6 g; increase


gradually (4-5 x 10 fingerlings per year, and more after a test period of three years) the number of stocked fingerlings; to prevent fishing activity in the spawning area of cichlids in the Beteicha Lagoons in the northeast part of the lake to improve natural reproduction of S. galilaeus.

(b) To reduce fish prédation pressure on zooplankton by increasing exploitation of bleaks and eliminate stocking of silver carp and 0. aureus.

PRESENT IMPLEMENTATION - FISHERIES

A three-year test programme started in 1984. Silver carp stocking was eliminated, introduction of 0. aureus was reduced to 0.5 x 10 year ; 4.5 x 10 fingerlings of S. galilaeus per year are now stocked during early - and mid-summer and their weight varied between 1 and 10 g. Fishing prevention in the Beteicha Lagoons was not implemented. These activities were the outcome of a compromise decision of proposed recommendations and official fisheries authority requirements. Intensification of bleak fishery was not yet done, due to market demand limitations of this fish.

CONCLUSIONS

By implementing recommendations presented in this paper, water quality deterioration in Lake Kinneret can be prevented. I believe that the fully implemented programme for the lake and drainage basin management can be a basis for the prevention of eutrophication as well as efficient utilization of the lake by its consumers for water supply, fisheries and recreation.

ACKNOWLEDGEMENT I wish to express my thanks to Dr D.Wynne and Mr K.D.Hambright for reviewing the manuscript.

REFERENCES

Geifman, Y. (1982) Pollutants balance from the watershed to Lake Kinneret (in Hebrew). Memorandum.

Geifman, Y. & Dexter, H. (1984) Kinneret watershed-monitoring system: investigations of multiannual changes of pollutant quantities and Jordan discharge (in Hebrew). Mekorot Watershed Unit.

Gophen, M. & Pollingher, U. (1985) Relationships between food availability, fish prédation and the abundance of the herbivorous zooplankton community in Lake Kinneret. Arch. Hydrobiol. Suppl. (in press).

Hydrological Service (1968-1982) Hydrological Year Book of Israel. Ministry of Agricultural, Water Commission. (Data for 1983-1984 by personal communication.

LBRI (Lake Biwa Research Institute) & NIRA (National Institute for Research Advancement) (Eds)(1984) Data Book of World Lakes.

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The management of Lake Kinnereî and its ... - hydrologie…hydrologie.org/redbooks/a153/iahs_153_0127.pdf · QCM'—iM'coi-HinvrjOcri'-H e n MMMMMMCMMM M M M M M M M M I I I I I

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