https://doi.io-warnemuende.de/10.12754/msr-2000-0041
doi:10.12754/msr-2000-0041
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Oder Basin - Baltic Sea Interactions (OBBSI) : Endbericht - Final Report
Abstract. Coastal zones adjacent to large river systems play an outstanding role for trade, transport, agriculture, fisheries and energy production, as well as tourism. They are under intensive human use and a preferred location for harbors, industries and settlements. At the same time coastal zones are of extraordinary ecological value and a transformer and sink for terrestric nutrients and pollutants. Water quality of the coastal waters itself as well as of rivers draining into these systems is a key factor for sustainable development and management of these regions. River loads of nitrogen (N) and phosphorus (P) have very much increased world-wide compared to pre-industrial times. These changes are due to man made emissions from diffuse and point sources in river catchments and result in an increased supply of organic matter (i.e., eutrophication) in coastal seas. Consequently widespread oxygen deficiency in bottom waters and sediments of the coastal seas, accompanied by a change in the structure and stock of the benthic communities and large scale fish kills, have been observed. A long-term effect of eutrophication is the enrichment of organic matter in the sediments reflecting an imperfect reworking of phytoplankton biomass. Modern research, focused on ecological impacts of altered biogeochemical fluxes in the coastal zone on freshwater and marine systems has advanced to the point where ecological science can estimate and predict, to a large extent, fluxes of biogeochemically important elements for environmental management applications. Integrated coastal zone and river basin management needs interdisciplinary and spatial integrative research. The project OBBSI (Oder Basin - Baltic Sea Interaction) funded by the German Volkswagen Foundation (Volkswagenstiftung) tries to meet this challenge. The Oder basin and estuary The basin of the river Oder (Polish Odra) covers an area of about 120.000 km² with a population above 13 million people and drains into the central part of the Baltic Sea, the Baltic Proper. With high nutrient load, the Oder is one of the most important sources of eutrophication in the central Baltic Sea, and its respective coastal zone suffers from severe water quality problems. The coastal zone, which is directly affected by the River Oder, can be divided into the inner coast, with the Oder Lagoon (Oder or Stettiner Haff or in Polish the Zalew Szczecinski) and the outer coast covering the Oder Bight (Polneranian Bight), a part of the Baltic Sea. The islands of Usedom and Wolin separate both parts from each other. The Oder Lagoon: The lagoon covers an area of about 680 km². In the regional development plan the islands of Usedom (Gennany) and Wolin (Poland) with their attractive landscape, sandy beaches and reed zones are devoted for sustainable environmental protection and tourist development. The lagoon is dominated by the water inflow of the Oder and has a water exchange time of only several months. It is characterized by heavy eutrophication with intensive algal blooms in summer. The poor surface water quality on the inner shorelines oriented towards the lagoon is one main obstacle for future development in this direction. Due to the ongoing pollution the lagoon has lost its function as a sink for nutrients. Neither fixation of nutrients in sediments nor distinct denitrification takes place to a high degree. The Oder (Pomeranian) Bight: Open boundaries towards the Baltic Sea cause intensive water exchange in the bay. Despite this, it has an important function as a purification unit for the Baltic Sea. The sandy sediments show high denitrification rates and reduce the nitrogen input with the River Oder. Nitrogen is the main limiting element for the primary production of the Baltic Sea and therefore of superior importance. Purification processes in the Pomeranian Bight increase water quality and diminish long distance effects by the River Oder plume. This is important for the already intensively used swimming beaches at the outer shoreline of the islands and an essential economic factor for the islands. The water quality of the Pomeranian Bight and to a much higher degree the water quality of the Oder Lagoon cannot be restored by internal measures inside these systems or local management. The systems are too much linked to the River Oder and its large basin. The large population in the Oder catchment and the poor state of sewage treatment as well as the large and in some regions intensively used agricultural area in the hinterland are the main reason for the quality problems in ground, surface and coastal wafers. The water quality in the lagoon is an indicator and mirror of this pollution in the river basin. Due to its size, economical and ecological importance on one side and its heavy pollution on the other, the Oder System becomes an outstanding case, which support the urgent need for integrated management. Tbe project OBBSI (Oder Basin - Baltic Sea Interactions) Efficient coastal zone and river basin management requires a sound scientific basis. Concerning water quality and eutrophication problems, the project contributed important basic information and model tools for the Oder catchment and its coastal zone: • Compilation of nutrient data (nitrogen and phosphorus) of diffuse and point sources for the Oder Catchment, River and Lagoon, as well as basic collection about socio-economic aspects (development of population, industry, ecomomy). • Quantitative description of nutrient retention and transformation in the Oder catchment as well as nutrient budgets for the Szczecin Lagoon. • GIS-data base (catchment and coastal zone, scale 1:200000) containing hydrography, morphometry, land use, groundwater and administrative units. • Complete information on sewage treatment and nutrient load at HELCOM 'hot spots' (Katowice, Glogow, Lodz, Ostrawa, Szczecin, Wroclaw, Poznan and Zielona Gora) and basic cost-benefit-analysis of current and improved waste water treatment. • Complete compilation and evaluation of law in Poland and Germany concerning sustainable water quality management. • Conceptual model of nutrient transformation and retention in the catchment as well as the development and application of an eutrophication box-model for the lagoon. River basin: environmental economy Efficient water management requires detailed information about the current situation. This includes natural scientific data basis as well as information about the socio-economic situation and its development. Therefore one goal was the collection of micro- and macroeconomic data (e.g. rate of unemployment, water consumption, personal income). Special interest was put on the existing sewage treatment plants and the discharge pattern at the "hot spots" defined by HELCOM (Katowice, Glogow, Lodz, Ostrawa, Szczecin, Wroclaw, Poznan and Zielona Gora). Beside this computer calculation tools for cost and benefit analysis were developed. This includes e.g. a cost calculation program for future wastewater investments or a tool for the calculation of income and employment effects resulting from the investments. Altogether, wastewater treatment in Poland is far below the standard of Westeuropean countries. 35% of the wastewater receives only insufficient treatment and 30% is discharged without any purification. Concerning the "hot spots" the situation is similar. 59% of the whole wastewater receives no purification, 24% is mechanically treated and only 17% receive an advanced purification. There is an urgent need for an extension of the capacities and an upgrading of the cleaning stages. This also includes a modernization of the wastewater canal system, which is often dramatically overloaded. On the basis of these results, detailed cost/benefit analysis for optimal water management are possible in future. Some general recommendations are given. With respect to cost efficiency it makes more sense to create individual solutions for every situation and location and to allow a stepwise fulfillment of new standards. To demand that new standards have to be met in the whole area at a certain time is problematic. This means e.g. that in some cases it makes more sense to adjust the canal system to the hydraulic load before the implementation of a new purification stage at the wastewater treatment plants. River basin: nutrient input and transformation Nutrient inputs from diffuse sources within the river basin vary in space and time in the scale of kilometers and decades. Riverine nutrient transformation varies in the scale of kilometers and days. A modeling approach is required which is capable of handling the different scale levels. As a first step, modeling concepts have been developed for water quality analyses of the Oder river and its main tributaries taking the hydrologic and morphologic conditions into consideration. These box concepts were to be parameterized and calibrated based on classified morphologic information of the main river sections and measured data sets from three discharge years. For the German/Polish Oder river system a unified medium scale (M 1:200,000) GIS basis has been created, supplemented by the larger Haff tributaries at the German side. The river polygons have been provided by the Institute of Freshwater Ecology Berlin-Friedrichshagen. The river network information has been enhanced by a routing model to reflect the flow directions and conjunctions between rivers. Further, as an integral part of the GIS basis and resulting from a parallel Polish-German Joint Project (PAN/DVWK Joint Project "Investigation on the quantity of diffuse entries in the rivers of the catchment area of the Odra and the Pomeranian Bay to develop decision facilities for an integrated approach on waters protection" - Diffuse Entries in Rivers of the Odra Basin -, UBA 1996 - 2000), the sub-catchments of the Oder basin have been included at a scale between 1:500,000 and 1:200,000 with the themes hydrography, hydro-meteorology, land use (including nutrient surplus 1989/90), soils, groundwater conditions, relief, and municipalities. The Czech part of the Oder basin could not be included into detailed analyses due to the lack of Czech project partners. For the time being, the implemented modeling procedures allow scenario analyses on nutrient loads in river sections as effected by land use changes. Methodical considerations on a modeling approach suitable for sectoral quantification of the nutrient transport and elimination are concluded. For the large rivers of the Oder system in Poland (Oder, Warta, Notec), an eco-morphologic description has been worked out by the Poznan group (Prof. Ilnicki, Agricultural University Poznan) within the frame of a work contract, which is suitable for parameterization of the approach. Water quality and discharge data to calibrate the model were provided for the period 1993/95 for 32 selected gauging stations and river sections at the main rivers by the Institute for Meteorology and Water Management(IMGW), Wroclaw within the same work contract. The Brandenburg State Environmental Agency, Frankfurt (Oder) Branch, supported the project work by delivery of water quality and discharge data 1996 to 1998 for gauging stations in the Polish-German border region. A certain problem was posed by the given temporal resolution of only two resp. four weeks of the routinely measured quality data. For process-oriented analyses, especially following the 1997 Oder summer flood, 'snapshots' of the Oder system as a whole are required but could not be provided. Coastal Zone: eutrophication modeling Assessment of the effects of changed nutrient discharges in coastal areas requires analysis on the scale of decades. Severe effects of eutrophication have been observed for several decades. Therefore, the first step for the modeling of nutrient fluxes for management applications is the elaboration of box models, which ignore the short-term details of circulation patterns, but are suitable for a long-term hind- and forecast assessment (scenarios). A layered "box model" was developed to evaluate the major effects of estuarine eutrophication of the Szczecin lagoon which can be compared with integrating measures (Chl a, sediment burial, sediment oxygen consumption, in- and output of total nutrient loads) and use it to hindcast the period 1950-96 (the years when major increase in nutrient discharges by the Oder River took place). The following state variables are used to describe the cycling of the limiting nutrients (nitrogen and phosphorus): phytoplankton (Phy), labile and refractory detritus (DN, DNref, Dp , DPref), dissolved inorganic nitrogen (DIN), dissolved inorganic phosphorus (DIP) and oxygen (O2). The three layers of the model include two water layers and one sediment layer. Decrease of the carrying capacity with respect to the increased supply of organic matter of the system with advancing eutrophication over the period studied is parameterized by an exponential decrease of the sediment nitrogen fluxes with increasing burial, simulating changing properties from moderate to high accumulating sediments. The seasonal variation as well as the order of magnitude of nutrient concentrations and phytoplankton stocks in the water column remains in agreement with recent observations. Calculated annual mean values of nutrient burial of 193 mmol N m-2 a-1 and 23 mmol P m-2 a-1 are supported by observed values from geological sediment records. Estimated DIN remineralization in the sediments between 100 - 550 mmol N m-2 a-1 corresponds to sediment oxygen consumption measurements. Simulated DIP release up to 60 mmol P m-2 a-1 corresponds to recent measurements. The conceptual framework presented here can be used for a sequential box model approach connecting small estuaries like the Szczecin lagoon and the open sea, and might also be connected with river box models. Environmental legislative aspects A detailed analysis of relevant laws in Germany and Poland was carried out and documented. Generally the regulations concerning point sources of pollution have a high structural similarity in both countries. The treatment of diffuse sources of pollution are treated different and a need for advanced regulations in Poland can be stated.
Citation
Christoph Humborg, Gerald Schernewski, Bodo von Bodungen, Ralf Dannowski, Jörg Steidl, Joachim Quast, Volker Wallbaum, Karl-Ulrich Rudolph, Chris Müller, Stefan Mahlburg, Wilfried Erbguth: Oder Basin - Baltic Sea Interactions (OBBSI) : Endbericht - Final Report. Meereswiss. Ber., Warnemünde, 41 (2000), doi:10.12754/msr-2000-0041