Charakteristics of the Lakes in Radunia River Catchment According to the EU Water Framework Directive

Transcription

1 Paper N 0 : I.03 Charakteristics of the Lakes in Radunia River Catchment According to the EU Water Framework Directive Teresa Jarzębińska Abstract: Radunia River is the tributary of Motława which flows into Vistula River. The length of Radunia is km and the catchment area 861 km 2. Catchment area of Radunia River is characterized by many lakes and rivers. Essential parts of the catchment consist of agricultural land (52%) and forests (38%). The main functions of the catchment area are agriculture, tourism, and recreation. There are 68 lakes in Radunia River catchment. Their total area is 34.4 km 2, corresponding to 4% of the whole basin. Many lakes have been physically modified over the years. In hydraulic power plants were constructed and put into operation on Radunia River. To increase the energy potential of Radunia River 3 control weirs were installed. Their aim was to control the outflow from the lakes. Apart from the production of electric energy, the water of Radunia River and its tributaries were widely used for propelling of turbines in the mills. Recently appeared a very important and new user of water from Radunia River i.e. water intake for the City of Gdańsk. According to the EU WFD Radunia River catchment was divided in to 12 water bodies. In the paper the main problems of the water resources management in the catchment are presented. The typology, reference conditions and establishment of objectives for the lakes are also described. Keywords: EU WFD, water bodies, typology of the lakes, water resources management 1. Introduction The Water Framework Directive of the European Union (EU WFD) was passed on 23 October 2000 and entered into force on 22 December Three years later, i.e. on 22 December 2003, Member States should implement this Directive in their national legislation. Poland entered into the EU on 1 May From this moment we are also obliged to adapt our laws to the

2 28 Jarzębińska recommendations of the EU WFD. In the same time started the Grant No KBN Nr PBZ KBN 061/T07/2001 of the Committee of the Scientific Research Methodical basis of the national project of the integrated development of the water resources management in Poland. In the frame of the study it was decided to carry out pilot projects in a number of selected Polish river basins. One of them was the Radunia River catchment. This project was carried out by the Institute of Hydro-engineering of the Polish Academy of the Sciences and Gdańsk University of Technology. The paper present the results of the studies concerning the characteristics and typology of the lakes existing in this catchment. 2. Radunia River The source of Radunia River is at the elevation 165 m above sea level few kilometers south from Lake Stężyckie. Then it flows through the chain of 7 lakes of glacial origin. These are: L. Stężyckie, L. Raduńskie Górne, L. Raduńskie Dolne, L. Kłodno, L. Brodno Małe, L. Brodno Duże and L. Ostrzyckie. Water surface elevation of first three lakes is controlled by the weir Chmielonek. Next 3 lakes are controlled by the weir Brodnica Dolna and finally the outflow of Radunia from L. Ostrzyckie is controlled by weir Ostrzyce. Water level variation in these lakes ranges from m to m. Total water surface area of these lakes is 33 km 2 and their volume about m 3 which gives important retention capacity and thus secures the uniform discharge of the river over the whole year. Downstream from the control weir Ostrzyce, Radunia flows through a small lake Trzebno. Along the next 13 km the river has mountain character (slope 2.2 ) and then flows into reservoir Rutki created by the dam. The volume of the reservoir is m 3 and operational head 12.0 m. Average discharge in this cross-section is 3.2 m 3 /s and maximum discharge 18.8 m 3 /s. Further downstream (3.5 km) is the mill Żukowo operating on the head 2.75 m. In the km 41.0 there is another regulating weir Lniska with the head 2.50 m. In km 31.0 there is reservoir Łapino of the volume m 3 and hydraulic power plant using the head of 13.8 m. Power scheme Bielkowo consists of a small control weir, diversion channel, 2 reservoirs, concrete power shaft, steel penstock and power plant operating on the head of m. This high head was obtained by the utilization of river section of high slope forming a large loop and water diversion. Immediately downstream there is the largest reservoir Straszyn ( m 3 ) with hydraulic power plant and at present water supply for the city of Gdańsk. Next there is a chain of three run-off-river power plants with reservoirs: Prędzieszyn, Kuźnice and Juszkowo. Control weir (km 12.0) Pruszcz Gdański begins the Radunia Channel which initially flows parallel to the Old Radunia River. The last hydraulic power-plant Pruszcz Gdański is already situated on Radunia Channel. The Old Radunia River flows through Żuławy Gdańskie and discharges into Motława River. Radunia Channel which runs at the foot of high plateau joins Motława River in the center of Gdańsk. It was constructed in XIV century to supply water for mills and defensive moats in Gdańsk. Channel discharge amounts to 7 m 3 /s. The Old Radunia River flows within flood dykes, has no tributaries and has practically transition character for flood discharges. Total length of Radunia River from its source to the discharge of the Old Radunia into Motława River is km.

3 Charakteristics of the Lakes in Radunia River Catchment according to the EU Water Framework Directive 29 Fig.1 Radunia River and its catchment

4 30 Jarzębińska 3. Catchment of Radunia River Total catchment area of Radunia River is 861 km 2 which includes also the catchment of Old Radunia River from Pruszcz Gdański to the inflow into Motława. This area amounts to 24.8 km 2. The catchment of Radunia Channel is 52 km 2. If we take into account that the river channel of Old Radunia serves only for conveying flood discharges and the main river bed is Radunia Channel then total catchment area will decrease to 836 km 2. The elevations in the catchment vary from -0.3 m below sea level at the area of depression near the outflow of Radunia to Motława up to 328 m (Wieżyca Mountain) which is situated at the watershed of Radunia and Wierzyca Rivers. The density of river network over the whole catchment is uniform and may be regarded as average. In its upper course Radunia flows through several lakes of tunnel valley type of glacial origin. In the catchment of Radunia River there are 68 lakes of the total water surface of 33 km2 which amounts to nearly 4% of the catchment. These lakes vary considerably in size ranging from 1 to 735 ha. In the lower course of Radunia River there are 5 artificial reservoirs used mainly for hydro energy. Their total water surface is 196 ha. The main tributaries of Radunia are: Mała Supina (km 48), Strzelenka (Strzelniczka) (km 44), and Reknica (km 29). In the longitudinal cross-section of Radunia the following three sections can be distinguished. In the initial upper course Radunia flows through a chain of glacial origin lakes. Along this course of 30 km it is difficult to distinguish the river channel and therefore it is assumed that the real beginning of the river is in the km 73 (cross-section Ostrzyce) at the elevation 158 m. It may be assumed that Radunia River in its upper course has typically lowland character. From Ostrzyce Radunia flows through high plateau of Pojezierze Pomorskie. Downstream of Goręczyno (water gauge) there is the section of consecutive narrowings and widenings of the valley. Within wide valley sections the channel slope is mild (0.2 ) and the river has lowland character. In the regions of gorges Radunia becomes mountain river. In some places it has a character of a torrent where the slopes reach even the values of 4 to 7. Downstream from Kolbudy the slope of Radunia River becomes milder. In natural conditions it amounted to 1.6. Along this section several weirs and hydraulic power plants were constructed which cause the decrease of natural slope within the backwater. The average elevation of the catchment is 164 m above sea level. The geological structure of Radunia catchment bears typical character of several glacial periods. The catchment area of Radunia River is utilized in the following way: agricultural lands - 52%, forests - 32%, and waters - 4%. Inhabitated areas do not exceed 1% of the catchment area. The main functions of the area are: agriculture, tourism, and recreation. The terrains close to Gdańsk are used for housing schemes, services and small industry. The eastern part is the base of the development of Gdańsk, the middle part serves mainly for agriculture and the western part is dominated by tourism and recreation. Especially there are very good conditions for sailing and all kinds of water recreation.

5 Charakteristics of the Lakes in Radunia River Catchment according to the EU Water Framework Directive Lakes in the Radunia River catchment Lakes are the basic hydrographic elements in Radunia catchment and are the main form of surface waters. There are 68 natural water reservoirs, whose surface exceeds 1 ha. Total surface area of the lakes amounts to 3274 ha, which constitutes 4% of the Radunia catchment. The highest lake concentration is in the western, part of the catchment. Lakes occupy there 10.5% of the catchment, which is the highest lake indicator in Poland. Small amount of lakes is in the eastern part of the catchment. Lakes in Radunia catchment are characterized with great variation of types, size and relation to the hydrographic system. Position and morphometry of the lakes in Radunia catchment depend on their variable genesis. Most of them have glacial origin. Few lakes (Raduńskie, Ostrzyckie) have been physically modified over the years as the result of changes of the water levels for the water resources management purposes. Lakes situated in the Radunia catchment show considerable variation in the trophy, chemical and sanitary state. More than half of the lakes are eutrophic reservoirs. They are shallow, have unfavorable oxygen conditions and well developed microflora. They belong to the II class of water quality. 5. Typology of the lakes According to the WFD Radunia River catchment is situated in ecoregion 14; Central plains. Differentiation of the lake types is done using the typology System A (altitude, mean depth, surface area and geology). This typology gives potentially 13 different types of lakes in Poland. In practice in the catchment of Radunia River only 4 types of the lakes exist. The typology is presented in tables 1-3. Table 1 Altitude typology of the lakes Type Aititude [m asl.] Number of the lakes % high > mid-altitude lowland < Total: The geological typology was done taking into account the contents of calcium compounds (25 mg Ca/l). There are 16 lakes examined with the surface area higher than 50 ha. 14 from them have the calcareous character. Additionally it has been decided to use System B to determine the optional factors for assessment of the residence time and mixing characteristics of the water. 11 lakes have the Schindler coefficient higher than 2, and 10 of them are stratificated.

6 32 Jarzębińska Table 2 Size typology of the lakes Surface area [km 2 ] Number of the lakes % < 0.5 x) > Total: x) proposed typology in Annex II of WFD gives the value 0.5 km 2 as the lower limit of the lake surface. In this paper, because of significant differentiation of lake surface, the group of lakes with smaller surface area was distinguished. Table 3 Depth typology of the lakes Mean depth [m] Number of the lakes % < > Lack of data Total: The typology has the abiotical character. Due to the lack of knowledge it is not possible to establish reference conditions for the lakes. We can estimate the physical and chemical characteristics of the lakes only. Water of the lakes in Radunia River catchment is characterized by a good physico-chemical quality and can be accounted to II class of water quality. This was caused by the presence of chemical and organic compounds. The remaining indicators account lakes water to the I class. The biological quality of water secures the requirements of the II class. Water flowing out from Lake Ostrzyckie is accounted to the III class because of high concentration of chlorophyl a. Its increase is observed in March, July and August during intensive development of plant organisms. In relation to the previous years most water quality indicators remained on the same level or even improved. Current status of the lakes is the following: from 16 lakes, 10 have the good and 6 the moderate conditions. The main reasons for failure to meet objective in the future are phosphorus and nitrogen loadings from agriculture. Summary The study of the typology and reference conditions for the surface water bodies in Poland, according to the WFD, is still in progress, therefore the conclusions can have only very general character. 1. Differentiation of the lake types in Radunia River catchment is carried out using the typology System A. Additionally two optional factors from System B are in use.

7 Charakteristics of the Lakes in Radunia River Catchment according to the EU Water Framework Directive The typology has the abiotical character. Due to the lack of knowledge it is not possible to establish at present current ecological status, reference conditions and future objectives for the lakes. 3. In general water quality of the lakes (physical, chemical and biological) can be regarded as good. 4. From the preliminary assessment carried out it can be concluded that the majority of the lakes will fail to meet the high ecological status in But the identification of the need for further characterisation, including environmental monitoring, will be the basis for planning the programme of actions in the future. References Jarzębińska T., Majewski W (1993): Hydraulic power plants on the Radunia River. In: Proceedings International Seminar European Workshop Preservation of the industrial heritage Gdańsk Outlook. TUG Gdańsk, May 11-14,1993 DIRECTIVE 2000/60/EC of the European Parliament and of the Council Majewski W. et al (2004), Characteristics of Radunia Catchment in view of WFD, Internal Report, Institute of Hydro-Engineering in Gdańsk, in Polish. Majewski W. et al. (2005), Multivariate Analysis of the Modernization of the Development of Water Management in Poland, Institute of Hydro-Engineering Gdańsk, in Polish. Author Dr ing. Teresa Jarzębińska: Gdańsk University of Technology, Faculty of Civil and Environmental Engineering, tjarz@pg.gda.pl

8

9