Livrables
Main springs in the Bihac area (Klokot, Privilica, Ostrovica and Toplica) satisfy current regulations for public water-supply drinking waters in Bosnia and Herzegovina. NH4, NO2 and HPO4 showed only occasionally concentration above maximal permitted concentration. Physico-chemical analyses of all tapped springs in the Bihac region made by the Public Health Institute - Bihac in 2003 and 2004, and the results satisfy the present regulations. Presence of microorganisms in each spring as indicator of faecal pollution does not point at the anthropogenic influence on water.
One could not define clear difference on bacteriological correctness of waters before and after the war, because the state of protection was very similar in both periods and not any improvement of quality of all spring waters after the war was shown.
Measurements of spring and river waters showed that the major pollutants in water were ammonia, nitrites and phosphates. Increased ammonia concentrations in Una River downstream from Bihac are indicators of pollution of faecal waste waters, soil erosion and of filtered waters from waste dumps, etc. Waste waters are being left without being processed before, and the final collector of all these waste waters is Una River. The presence of ammonia concentrations in the spring water indicates the possible water pollution from Croatian side (fields Krbavsko Polje and Korenicko Polje).
In all tested water samples, there was only a small amount of nitrate concentrations detected. Sulphates occurred in natural water in high concentrations. In springs they range from 3.9 to 6.6mg/l, and in the water of Una River basin from 20.0 to 29.4mg/L. The concentration of phosphates was detected in all researched waters samples taken in September 2004 except in Una River in Ripac. In all researched waters maximal detergent content is 0.003mg/L which cannot present the hazard to the ecosystem stability in Una River basin. In some water samples, there was no detergent content found. Wastewaters of the urban sewage of town Bihac outflow to Una River in Vrkaic, downstream of the town without any treatment.
The same situation is with all other industrial wastewaters in the Bihac area. No reliable data on locations and characteristics of illegal waste deposits exist in Bihac. Hygienic-sanitary state of resident houses is in general not satisfactory, faecal material pollute the soil, ground and surficial waters. Unknown consequences of contamination yet exist from toxic matters, which were stored in abandoned military facilities. The most important are the ex-airport and tunnels of eljava (close to Bihac) and Udbina (in field Krbavsko Polje, Croatia).
Valid protection of water-supply springs and Una River is not possible without finding the solution of waste water purification of town Bihac, settlements, and industry prevent illegal waste deposits, sanitation of terrain, regular exploitation of quarries and prevention measures in agriculture.
The understanding of groundwater behavior like residence times, their flow paths and mixing between different aquifers is essential for the protection of karst water in both countries. Also for the protection of karst water in both countries, knowledge on dynamics of groundwater flow, groundwater residence times, recharge rates and mixing between different aquifers is essential.
The concentrations of natural and anthropogenic trace substances can provide insights into these questions. In this study concentrations of stable isotopes (d18O and d2H), chlorofluorocarbons (CFC-11, CFC-12, CFC-113), sulphur hexafluoride (SF6), tritium (3H), helium (He) and neon (Ne) as well as the isotope ratio of helium (3He/4He) were measured in spring, lake and surface water.
The complexity of the karst system requires an approach using several such tracers, since one alone leaves too much ambiguity in interpretation. A multi-tracer approach was applied for the determination of mean residence times in ten springs. For groundwater dating in many cases a two-component model is used, describing the mixture between two water contributions of different age. For example this can be the combination of an exponential model for the young and a piston flow model for the old component.
As expected from hydrological point of view, the springs show very different mean residence times. The young water component in the springs shows MRTs between 0.1 and 0.8 years, whereas the old component is between 2 and 130 years (s. pages 12-15 in final report of P2). The information about the residence time of water in an aquifer is very important regarding the eventual pollution and storage capacities of the aquifers.
The Plitvice Lakes consist of a series of 16 lakes separated by tufa barriers and waterfalls. In this very complex aquatic system calcium carbonate precipitates intensively, forming tufa barriers in the presence of microphytes and macrophytes.
The area was proclaimed as a National Park almost 60 years ago and included into the UNESCO World Heritage List in 1979. In this WP we tried to identify the sources of eutrophication process in the Plitvice Lakes area to see whether it is a consequence of anthropogenic pollution or a natural process. The results of physico-chemical measurements of water at 15 sampling points along a flow distance of about 12 km, including sites with very intense CaCO3 precipitation, show that temperature, pH, alkalinity, and hence the saturation index of CaCO3, show significant change in downstream flow and also some seasonal variations.
The results show that the carbon exchange process plays an important role for tufa precipitation. Additionally, DOC values are also higher in some clean stream waters, where tufa does not precipitate in spite of otherwise favorable physico-chemical conditions for calcite precipitation, such as the high degree of supersaturation. In this case probably DIC inhibits tufa deposition. No systematic difference in concentration of these species between clear and eutrophicated waters was observed. d13C values of DIC in water of the Plitvice Lakes area steadily increase downstream from the karst springs (d13C= 12.5) to the river mouth (d13C= 10.0). Simultaneously, increase of 14C activity of DIC in downstream flow in the same area was observed as the consequence of the exchange process between the atmospheric CO2 and DIC in water at rapids and waterfalls. According to the chemical and isotopic measurement of water there is indication that the concentration of DIC is higher in the areas where the process of eutrophication is pronounced and that higher DOC concentration in water can inhibit the calcite precipitation in form of tufa.
These measurements do not indicate recent anthropogenic pollution of lake waters, and higher concentration of DOC in some sampling points can be a consequence of input of natural organic matter (humus) to the lake water. The chronology of the pollutant input was established by measuring activities of anthropogenic and natural radionuclides, which gave us the sediment accumulation rate and thus the age of specific sediment layers. For the smaller lakes higher sedimentation rates are obtained for the anthropogenic tracer 137Cs. In contrast sedimentation rates in the larger lakes give similar values for 137Cs and 210Pb. One possible explanation for the higher sedimentation rates in the smaller lakes is the higher water temperature during the warm months and accordingly quicker carbonates precipitation than in the bigger, colder lakes. By measurements of 14C in sediment cores we found the increased values of 14C at the depths between 5 and 10cm, which are the consequence of the bomb-produced 14C in the period 1949-1963 and they correspond to the peak values in 137Cs activity. The relative composition of minerals for each sediment core shows prevalent presence of calcite.
Also the content of organic matter is the highest in this core as the consequence of transport of terrestrial material. At the same location the concentration of most trace elements including phosphorus is the highest causing the high degree of the eutrophication process in this area. Trace elements and organic matter content decrease from the uppermost lake downstream to the lowest lake. This fact indicates that the most of trace elements in sediments could be of natural origin due to transport from the main springs and their steady deposition along downstream lakes. Content of trace elements along the 40 cm sediment cores from all sampling sites is much below maximum concentrations permitted for metals in soils in EU. There is no significant difference among the trace element concentration in the upper segment of all cores, corresponding to last 50 years when higher anthropogenic influence can be expected, and the lower part of the cores, corresponding to the period 100-200 years before present.
During the first and second year of the project, activities of Partner No.4, together with hydrogeologists from Sarajevo (Partner No.5) were focused to collection, preparation and organization of data, which served as a background for elaborating a hydrogeological model and further modeling of intrinsic vulnerability, hazard and risk assessment of surface and groundwater resources in the area of transboundary aquifers between the Plitvice Lakes catchment area (Croatia) and Una Rriver catchment area in the Bihac region (Bosnia and Herzegovina).
All relevant data collected during the field work (1st and 2nd report period) and the results of previous studies have been incorporated into the GIS form suitable for an intrinsic vulnerability and risk modeling and assessment. At the end of the 2nd reporting period hydrogeological map scale 1:100,000 and the structuring of data base were completed. All hydogeological data (hydrographic surface network, results of tracing tests, water objects and karst morphological elements - springs, lakes, wells, swallow holes, pits etc.) were elaborated on map 1:25,000 with the amounts and accurancy of data appropriate to satisfy the scale of final map scale 1: 100,000.
Analysis and data management was performed within the Geographic Information System (GIS) with the aid of Arc/Info software (ESRI Cal. USA) and the analysis results can be visualised and modelled through the ArcMap-ArcView software. This interpretation produced important data for establishing the hazard spatial distribution and data about vegetation characteristics important for modeling an intrinsic vulnerability of waters and groundwater. During the 3rd reporting period intrinsic vulnerability and risk assessment of surface waters and groundwater were completed.
Within the whole study area, approximatelly 2752 km2 large, following thematic maps were prepared: 1. Hydrogeological map and data base, scale 1:100,000; 2. Land use map, scale1:100,000; 3. Unclassified and classified hazard maps and database, scale 1:100,000; 4. Intrinsic vulnerability map, scale 1: 100,000; 5. Risk map, scale 1:100,000.
In spite of the fact that restriction of vulnerability, hazard and risk assessment originated from the quantity and quality of data and the applied method, used approach shows many advantages for end-users:
- Formation of general base with all existing, geological, structural, morphological and hydrogeological data about surface water and groundwater resources relevant for intrinsic vulnerability assessment, distribution of different types of hazards and its potential impact - risk assessment on surface water and groundwater quality.
- Obtained maps and data bases are very useful tool for land use planning regarding the surface and ground water protection and water authorities of both countries can use such data for urgent decision making.
- The structure of data bases and layers prepared in GIS-forms allow their further application for other purposes in the future.
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