Modeling the Groundwater Pollution Along the Lower Course of the Tundzha River, Bulgaria
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Modeling the Groundwater Pollution Along the Lower Course of the Tundzha River, Bulgaria Radko Petkov National Institute of Meteorology and Hydrology, Bulgarian Academy of Sciences, Sofia, Bulgaria [email protected] Abstract At present mankind has faced more seriously than ever the problem of environmental protection. Under the conditions of the contemporary stage of social-economic development, the optimal solution of this issue is possible if environmentally friendly technologies are designed and implemented and strict control on emissions from pollution sources and other measures are realized. The existence of 7 Natura 2000 protected areas along the lower reaches of the Tundzha River requires, when developing new projects and facilities, to apply an ecological approach to site selection from the viewpoint of minimum impact on groundwater quality. The problem becomes particularly relevant, if the rather diverse nature and character of groundwater contaminants are taken into account. Groundwater represents a major source for meeting water demand in many settlements (for drinking and irrigation purposes) and the control on preserving this source is of strategic importance. In ecological respect, the location of facilities has to be substantiated as early as at the design stage in such a manner that possibly minimal impact on groundwater is achieved, so that water quality in the respective region could be preserved in the process of water use. The selection of an optimal site for such facilities, aimed at maintaining water quality within the range of the specified norms, is a task, which is practically still intractable. Prior to the construction of a given object that under certain circumstances might be a potential source of groundwater pollution, it is expedient to make a preliminary assessment and prediction of contamination in the area, intended for the facility site, with the aim of defining its optimal positioning in conformity with the norms for groundwater quality and cost of this object. The case with fixed location of the pollution sources, when contaminant migration to the water bodies is considered, represents a similar problem. Without the element of optimizing the pollution sources site location, the problem is solved using simulation models. The paper shows the numerical modeling of groundwater pollution in the terraces along the lower course of the Tundzha River. The proposed hydrodynamic model of the problem will be in a 3D non-stationary case (x,y,z,t) of migration of non-conservative admixtures for non-pressure head groundwater flow. Keywords : optimizing the pollution sources, groundwater pollution, head groundwater flow, contaminant migration. Introduction Infiltration of atmospheric precipitation represents a relatively high share of the recharge of groundwater filtration flow. The understanding of these processes is essential for defining the hydro-environmental risk of groundwater pollution with ingredients released by industrial enterprises. Hydrogeological conditions are favourable for the processes of contaminant accumulation in groundwater. The relatively high groundwater levels shorten the way of vertical filtration of precipitation. When fallen on arable land, rainfall provides the possibility of migration of contaminants that have not been assimilated by the plants by means of descending infiltration to the aquifer layers. During the recent decades the trend towards increased contaminant amounts is also observed for surface water. Many of the water intake facilities are built on alluvial-proluvial deposits of river terraces, where the BALWOIS 2012 - Ohrid, Republic of Macedonia - 28 May, 2 June 2012 1 groundwater is in direct hydraulic connection with the river flow. In this way nitrates reach drinking water too, although sanitary-protection zones are available. Impacts on groundwater status resulting from anthropogenic activities Point sources of groundwater pollution - landfills, earth lagoons, former uranium mines, tailing ponds, industrial sites, settlements without sewage systems, petroleum stations. Settlements without sewage systems and landfills (not meeting the requirements of environmental legislation) are the most important point sources for the groundwater status. They are sources of ammonium and sodium emissions. This is the result of poor management of landfills or absence of an insulating screen on their bottom, as well as the presence or absence of waste water treatment plants in the settlements. All existing dumps and landfills, not conformable with the national and European legislation, had been subject to closure till July 2009. The construction of new regional landfills with reliable hydraulic insulation layers in the base is envisaged at the places, where necessary. The new future facilities are intended to serve several municipalities. The earth lagoons are typical earth formations, encountered at distilleries and rose-distilleries, in livestock- and poultry-breeding farms. Diffuse sources of groundwater pollution and land use survey Agriculture has been considered as a source of groundwater diffuse pollution. The arable lands from the Land Use Map are attributed to the underground water bodies and the vulnerability of the upper soil layer to contaminant permeation has been evaluated. The unregulated landfills, dunghills, etc., as well as leakages from overworked pipes of sewage systems, are also important diffusion sources. Programme for rural development • National Agri-environment Programme for Bulgaria • Strategy for the construction of regional landfills for waste released from settlements • Programmes for improving the environmental status aggravated by economic activities in the past • Identification of vulnerable areas with nutrient components in groundwater • Development of good agricultural practices in vulnerable areas Specific problems of groundwater management in the region of the Tundzha River - Pollution with ammonium, phosphates, nitrates, manganese and iron; - Uranium deposits, inoperative at present – a great part of them have a local monitoring network, tailored to the specific hydrological, hydrogeological, climatic, agrotechnical, mining and technical conditions of the respective site; - Soil pollution with heavy metals – typical for areas with atmospheric pollution, significant discharges of wastewater, intensive chemical impact on agriculture and loaded traffic. The largest share of arable lands with heavy metal pollution is in the Plovdiv and Haskovo districts; - Soil salinization – closely linked to irrigation, since groundwater is not properly regulated and as a result water mineralization is increased. The largest areas with soil salinization are in the Sliven and Plovdiv (Belozem village) regions; - Increased sulphate content in the region of the East Maritsa basin. Characteristics of groundwater in the East Aegean region Geological structure BALWOIS 2012 - Ohrid, Republic of Macedonia - 28 May, 2 June 2012 2 Fig. 1. The East Aegean basin Groundwater The territory of the Tundzha municipality falls within the Yambol-Elhovo hydrogeological region. It incorporates the similar Yambol and Elhovo syncline forms, which are filled with Neogene deposits and alluvial sediments of the Tundzha River and its tributaries – the Popovska, Kalnitsa, Arapliiska and Yavuz Dere Rivers. The main aquifer horizon in the region is the alluvial one. The Neogene sediments are moderately aquiferous only in the region of Elhovo-Izgrev-Boyanovo. The Quaternary here is represented only by the alluvial deposits of the Tundzha River and its bigger tributaries. The width of the Tundzha terrace is from 1 to 4 km. It becomes narrower due to the lateral and under-riverbed rock threshold at the Konevets village, ending at the rock threshold near the Knyazhevo village. In both places the larger part of the terrace groundwater flow is discharged in the river. The thickness of the terrace deposits ranges from 8 to 25 m, the gravelly-sandy layer occupying more than half of it. The rest part belongs to the clays, which are found mainly in the uppermost zone of the section. The water transmissivity reaches up to 1000-1200 m²/d, and the water level transfer – 5.5 10³m²/d. The recharge of the aquifer horizon is realized at the expense of precipitation. It is supposed that the fissure and fissure-karst water from the bedrock discharged in the valley also takes part in the recharge. Having these hydrogeological characteristics, the alluvial deposits are referred to as strongly aquiferous ones. The total mineralization of groundwater in the Yambol-Elhovo region is from 0.7 to 1.13 g/l and the general hardness is 6.2-13.3 mg.equ/l. The water macro composition is quite diverse. The predominating points are with hydrocarbonate-calcium-magnesium water. Soils and soil resources The territory of the Tundzha municipality refers to the Mediterranean soil district, the Middle Thrace – Tundzha province. The soil cover is characterized by great diversity. The prevailing soil types are smolnitzas, lessivated, planosols, solonchaks, solonetz soils and sedimentary soil types (Appendix 6, Appendix 7). 1. Chernozem – smolnitzas (Vertisols, VR, FAO, 1988), represented by common (leached – eutric, VRe), carbonate (calcic) and gleyic (meadow smolnitzas). The smolnitzas are characterized by a thick soil profile, well expressed humus horizon (50-70 cm), relatively high humus content (2.5-3.5 %) and a relatively homogeneous profile. According to their mechanical composition they are slightly clayey to heavily