1 Technical report No 71 The rivers of the Black Sea by Shalva Jaoshvili This document presents the result of a study of the discharge of river water and river load into the Black Sea. The volume of river water and load is investigated by individual river, by region and in total over the whole sea. The data used here came from hydrometric observations, field studies and calculations. This book is intended for Black Sea researchers - geographers, geologists, hydrologists and oceanologists. Editors: Professor I. Khomerki, Doctor of Technical Sciences Professor G. Gigineishvili, Doctor of Geographical Sciences Professor A. Kordzadze, Doctor of Physics and Mathematical Sciences 2 The rivers of the Black Sea Contents Introduction .....................................................................................................................3 1. River-estuary-sea: a unified natural system ............................................................ 5 2. Natural features of the black sea coastline ............................................................ 9 3. coastline and estuaries ......................................................................................... 16 4. Volume of river discharge into the Black Sea....................................................... 28 5. Freshwater balance of the Black Sea ................................................................... 36 6. River loads discharged into the Black Sea ........................................................... 38 Conclusions ................................................................................................................... 49 References ................................................................................................................... 51 3 Introduction The Black Sea, or the Euxine Sea or Pontus Axeinus as it was known in antiquity, is one of the cradles of civilisation. The history of mankind is deeply rooted in its shores. It has always been a lodestone for travellers and researchers because of its strategic position and the richness of its natural resources. The Euxine Sea was well known to the peoples of the eastern Mediterranean littoral. The first records we have of the Pontus Axeinus date back to the 5th century BC. The voyage of Jason to Colchis is described with a fair degree of verisi- militude in the myth about the Argonauts, which began in the 13th–14th centuries BC, and there is a description of the Euxine Sea in Homer’s Odyssey. Herodotus, Strabo and Ptolemy have left us a host of meticulously collected information, and a detailed description of the shores and estuaries can be found in Polybius’ Histories (201–120 BC) (6, 109, 115). Proper hydrographic study of the Black Sea was begun at the end of the 18th century. The first accurate charts of the entire sea were drawn up in 1825–36 by Captain Mangarani, and Black Sea navigational directions were published in 1851. Comprehensive studies of the Black Sea, its shores and waters, were begun in the second half of the 19th century (43,115). The Black Sea is now one of the most studied of all the marine basins on our planet. This has engendered a requirement for more precise data from additional research such as the balance between water and river load, sediment formation and a wide range of other sub- jects. The situation has been made more complex in recent years by the ever-increasing level of pollution, with its links to the outflow of water and river load from the surrounding landmass. Interest in the Black Sea stems not just from its strategic position and the biological richness of its waters. It is also of great economic significance internationally. The economic role of the Black Sea has increased over recent years since, after the disintegration of the Soviet Union, six Black Sea littoral countries (Bulgaria, Georgia, Russia, Rumania, Turkey, Ukraine) reasserted their interest in these waters. Of prime importance to the Black Sea economy is the transportation of cargo, locally and as part of the ancient Silk Route, and the production and transportation of oil. The need to transport oil has driven the recent expan- sion of the existing ports and there are plans for new ports to be built. There are many industrial and military sites located around the Black Sea. Moreover, the Black Sea was, in the recent past, an important resort and holiday destination - a fact which must not be lost sight of. While this role diminished throughout the 1990s, the Black Sea resorts and recreational areas have once again begun to attract tourists. The international Black Sea Economic Cooperation Area (BSEC), comprising the six littoral States and Azerbaijan, Albania, Armenia, Greece and Moldova, was set up in 1992 to exert some control over these complex economic issues. All these circumstances give support to the conclusion that a new approach to Black Sea issues is necessary, one which will entail meticulous study of the sea’s biology, all the more urgent now as human life has more and more negative impact on the already poor ecologi- cal condition of the sea. This new raft of work will attempt to quantify the amount of river discharge — water and load — disgorging into the Black Sea. Much is expected from a study at this level. The aggregate amount of fresh water entering the sea is still known only approximately; precise informa- tion is long overdue. New data from hydrometric observations and research over recent years has enabled more precise figures to be calculated for the amount of river water enter- ing the Black Sea; these calculations have included the effect of artificial control of the flow. River load is the factor least studied, in the Black Sea as in other regions. There are other associated issues here, too, such as erosion of riverbanks, artificial beach formation, pollu- 4 The rivers of the Black Sea tion of the sea etc. These issues are particularly topical now, when shoreline retreat, caused by a decreasing amount of bank-forming deposits, has become irreversible, and are played out against a background of observable increase in the ocean levels worldwide, with pollution in the Black Sea already reaching threatening level. Accurate quantitative assessments of river load reaching the sea are also necessary for any proper research into current sediment forma- tion processes on the sea bottom. It must also be remembered that the virtually locked water basin of the Black Sea is many ways similar to an ocean, especially in the relation between river load distribution and deposition. Given its more favourable conditions and the less extensive scope of work in- volved, the Black Sea can be regarded as a natural laboratory (110). In recent years, with ‘new times’ entering the political situation, the spirit of new times has entered the Black Sea research arena, too, and investigations have become international in character. A Black Sea Regional Committee (BSRC) was set up in 1996 under Unesco’s Intergovernmental Oceanographic Commission, tasked with coordinating and intensifying scientific research on the Black Sea. One of its key projects (pilot project 2: Black Sea sediment fluxes) conducts research into flows of river load into the sea, and our document is part of this project. 5 1. River-estuary-sea: a unified natural system All the rivers run into the sea yet the sea is not full unto the place from whence the rivers come thither they return again. Ecclesiastes All rivers flow into oceans, seas and lakes. The inflow of fresh water back into a water basin completes the regular hydrologic cycle. This process has continued ceaselessly for billions of years and will continue while our planet still exists. The hydrologic cycle begins with evaporation from the surface of the ocean, replenishing atmospheric humidity. Water vapour condensation is followed by precipitation, initiating surface runoff. Precipitation also feeds soil- and groundwaters which then contribute to river formation. The total volume of the hydrosphere is currently 1.5 billion km3. Ninety-four percent of this volume is concentrated in the oceans of the world, 4 % is derived from subsur- face water, 1.6 % is locked in polar ice and 0.15 % is vapour in the atmosphere. Surface fresh water only accounts for 0.25 % of the hydrosphere, or 360 000 km3. Lakes occupy 278 000 km3, surface humidity accounts for 81 000 km3 and 1 200 km3 is concentrated in river channels. While river channels hold an apparently small volume of water at any one time, the process of water exchange within their bounds is in effect uniquely and extremely active. These channel flows are replaced on average every 11 days — six times more active than the oceans or subsur- face waters (56). The rapidity of this hydrologic cycle means that channel flows process almost 33 times as much water and rivers deliver around 38 830 km3 fresh water a year to the oceans of the world. (56). A further 3 000 km3 comes from polar ice (52) and subsurface water contributes 2 400 km3 (42) to the oceans. In total, the flow of fresh water from the landmass to the Ocean is 44 230 km3, with the flow in internal (closed) areas boosting this to 45 060 km3 a year (56). The hydrologic cycle is a global phenomenon and the process is to a large extent dependent on our planet’s physical and geographical features. Even though moisture and water are distributed unequally around the globe, due to the heterogeneity of natural conditions, the hydrologic cycle is ubiquitous and uninterrupted, albeit moving at varying pace, and every droplet of water in