Aug 11, 1980 - ... Y.: 1972, Nutrients supply to Lake Kinneret (Hebrew), Mekorot Water Co. ... Syers, J. K., Harris, R. F., and Armstrong, D. E.: 1973, J. Environ.
S T U D I E S ON LAKE KINNERET (SEA OF GALILEE) W A T E R S H E D
I: Characterization of water and suspended load in Lake Kinneret Tributaries* YORAM AVNIMELECH Technion, Israel Inst. of Technology, Haifa, Israel**
(Received 18 June, 1980; Revised 11 August, 1980) Abstract. A description of the water quality in Lake Kinneret watershed is given. Water of high quality is supplied by the Jordan tributaries. Suspended matter and soluble components are introduced into the water along the intensively cultivated Hula valley. The suspended matter introduced is very high in organic matter and nutrients. A partial purification of the water occurs downstream, in the Jordan canyon. The nutrient contents in the river are highly correlated with the suspended load.
1. Introduction Lake Kinneret drains a catchment area of 2738 km 2, from an altitude of 2800 m (Mount Hermon) down to the Lake itself, located 209 m below sea level (Figure 1). The Jordan River is the most important inlet to the Lake. It is nourished during base flow by springs originating at an elevation of about 200 m above MSL. The Jordan tributaries flow through steep rocky river beds into the H u h valley, located at an elevation of about 100 m. The Hula valley is an alluvial valley, occupying an area of about 150 km 2, surrounded by mountains from three sides. It drains southward, through a narrow opening partially blocked by a basaltic flow. The valley got its name from the former Lake Hula, which was drained in 1952-1957 to add about 20 km 2 of arable land, to conserve water and to eliminate malaria. The soils exposed by the drainage of the Lake and surrounding marshes are rich in organic matter, ranging from about 10 % up to 60 %. An intensive process of organic matter mineralization and release of nutrients, mainly nitrates, is taking place in this region (Avnimelech et al., 1978). The Hula valley is populated and intensively cultivated, the main land uses being cotton, apple plantations and fish ponds. Decomposition products of the organic soils, drainage of nutrient rich water from fish ponds, and fertilized fields, as well as municipal sewage effluents, all originating in the Hula valley, are the main potential sources of pollutants in the watershed (Geifman, 1972). The Jordan is regulated within the Hula valley as a part of the drainage operations and distributed into two main canals- the western and eastern ones. Water flow is * This work is a contribution of the Faculty of Agricultural Engineering, Technion, Israel Inst. of Technology, Haifa, Israel The work was supported by the Lake Kinneret Authority. ** The author is presently at the USDA, SEA, Water Quality Management Lab, P.O. Box 1430, Durant, OK 74701, U.S.A. Water, Air, and Soil Pollution 14 (1980) 451-460. 0049-6979/80/0144-0451501.50. Convrif,ht © 1980 by D. Reidel Publishing Co., Dordrecht, Holland, and Boston, U.S.A.
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usually slow and laminar throughout the valley. South of the Hula valley, the canals merge and the Jordan flows through a canyon, leading the water to the lake. The gradient in this portion of the Jordan is steep. The elevation at the southern edge of the Hula valley is 60 m above MSL, while the lake, 15 km to the south, is at an elevation of 209 m below MSL. The flow is turbulent and the river bed consists of rocks and stones covered by dense algal mats.
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Fig. 1. Lake Kinneret Watershed. (Circled numbers mark the location of sampling stations.)
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Rains occur only during the winter (November-March) and are unevenly distributed. Thus, the flow of water in the Jordan as well as in the other tributaries during this time is highly variable and includes the occurrence of flash floods (Figure 2). W(zter dlsc horqj~e
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Intensive efforts are made to minimize and control the input of nutrients from the watershed into the Sea of Galilee in order to avoid eutrophication of the Lake. The seriousness of this hazard can be appreciated by recognizing that the Lake is one of the primary sources of water in Israel in addition to its recreational, historical and religious importance. One of the steps taken is the establishment of a monitoring system, conducted by the watershed unit of the Mekorot Water Co. The present report brings forth concise results, based on this monitoring system, on the composition of the water and suspended matter in the Jordan and Meshosim rivers and their change during the year and location. The following papers in this series will describe some processes controlling the water composition in the Jordan.
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2. Materials
and Methods
The monitoring system is based on manual weekly sampling and analysis of the water in key locations. During floods, sampling is done at least once a day. Sampling locations, (Figure 1) reported here are at the three Jordan tributaries: Dan (station no. 1) about 1 km down stream from the springs, Hermon (station 2k and Snir (station 3) at their entrance to the Hula valley. Further downstream, water is sampled from the Joseph bridge (station 4) - a point at which the three tributaries merge. The next point (station 5), Hurl bridge, is at the southern part of the Hula valley. The last sampling point of the Jordan is Aric bridge (station 6), near the inlet of the Jordan into the Lake. The Mesoshim river is sampled near its inlet into the Lake (station 7).
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Samples are carried to the laboratory in an ice box. Most chemical parameters are analysed according to conventional methods (Rand et al., 1976). Total P and organic N are determined colorimetrically after a persulphate digestion (Raveh and Avnimelech, 1979), and organic C potentiometrically (Raveh and Avnimelech, 1972). Organic P is obtained as the difference between total P and P soluble in HC1 0.04 N. 3. Results and Discussion
The irregular pattern of flow in the Jordan is demonstrated in Figure 2, the hydrograph for the hydrological years 1972/73 and 1973/74, as recorded by the Israeli hydrological service, at the Huri bridge (station no. 5). The annual and seasonal irregulatory of the flow is demonstrated here for two consecutive years, the first, 1972/73, a dry year and the second, 1974/75 an 'average' year. The water discharge, fluctuates from low values of less than 1.5 m 3 s-1 during the summer, up to above 100 m a s -1 during the floods, in the winter. The water composition varies throughout the year. During floods, the water carries a high load of suspended matter, associated with a high load of suspended nutrients. In addition, an increase of soluble nitrates, sulphate and ammonium is also detected. The winter base flow, in between the floods, carries clearer water, containing an average suspended matter load of about 50 mg 1- t. The level of soluble compounds is also lowest during this period. The summer flow is typified by a relatively high load of suspended matter, a large portion of which is algal cells. Water composition and properties, for the different sampling stations, averaged for the hydrological years 1974/751977/78, are given in Table I. Throe groups of sampling points are given in Table I: (a) the Jordan tributaries, as they enter the H u h valley, (2) the stations along the Jordan River, and (3) the sampling station at the outlet of the Meshoshim river. The throe main tributaries, Dan, Hermon and Snir have different water composition, both due to the geohydrological properties of their aquifers and due to the distance of the sampling point from the springs. The Dan spring and the Hermon river represent two different aquifers (Wakshal and Nielsen, 1980). The different properties of these aquifers are demonstrated through the large difference in the sulphate content of the water. The sampling point in Dan is situated very close to the spring The water at that point is hardly affected by drainage water, storms or erosion. The sampling points of Hermon and Snir rivers are at the outlets of sizeable watersheds (141 and 623 km z, respectively) and the water carries a load of suspended materials especially during storms. Thus, all suspended components are higher in these points as compared to the Dan spring. The throe tributaries join to form the Jordan river near the Joseph bridge. Very slight cultural enrichment of the water occurs up to this point. The effects of intensive agriculture and human activity are mainly reflected in the water composition changes between Joseph and Hurl bridges. Most of the drainage from irrigated and fertilized fields, as well as from fish ponds, urban and rural settlements is introduced into the
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