DYNAMICS OF BRÂGLEZ RIVERBED (SOMEŞAN PLATEAU)

Dynamics of Brâglez Riverbed (Someşan Plateau). The main left tributaries of Someş along Surduc – Jibou sector (Brâglez, Almaş and Agrij), are characterized by the presence of obvious processes of lateral and vertical erosion at the level of the riverbeds. The field observations, as well as the position of these rivers and their catchment areas in the neighborhood of the lower Someş subsidence area, would easily be grounds for explaining the riverbed processes as caused by an unstable fluvial base level. More precisely, this base level would be moving downwards under the influence of subsidence movements of Tisa Plain or even because of the subsidence affecting Guruslău Basin. Starting from these more or less speculative deductions, this paper aims at checking and confirming the above-mentioned explanations or finding other causes for the dynamics of riverbed processes. In this sense, we analysed a correlation between the drainage in the catchment area and at the level of the riverbeds, on one hand, and the riverbed geomorphological processes, on the other hand. Brâglez River (in western Someşan Plateau) will be considered as a study case, as it provides an accelerated dynamics of riverbed processes. This situation will be compared with the one in the eastern part of the same plateau, where rivers like Borşa, Luna or Lujerdiu do not present obvious riverbed processes despite the similar climatic and geological conditions

THE CONFLUENCE RATIO OF THE TRANSYLVANIAN BASIN RIVERS

There are many possibilities to assess the hydrological and geomorphological evolution of a territory. Among them, one remarks the confluence ratio of the rivers belonging to different catchment areas. The values of this indicator may provide information regarding the stage of evolution of the fluvial landforms in the Transylvanian Basin. Also, the values may serve for the calculation of other parameters of catchment areas like: the degree of finishing of the drainage basin for its corresponding order, the density of river segments within a catchment area etc. To calculate the confluence ratio, 35 catchment areas of different orders have been selected. The confluence ratio varies between 3.04 and 6.07. The large range of values demonstrates the existence of a heterogeneous lithology and of morphological and hydrographical contrasts from one catchment area to the other. The existence of values above 5, correlated also with observations in the field, reveals an accelerated dynamics of the geomorphological processes in those catchment areas. This dynamic is mainly supported by the high landform fragmentation due to the first order rivers. In contrast, the catchment areas that have a confluence ratio below 5 are in a more advanced stage of evolution with stable slopes, unable to initiate new first order river segments

MINING LAKES OF THE AGHIREŞ AREA: GENESIS, EVOLUTION AND MORPHOMETRIC ASPECTS

Mining lakes of the Aghireş area: Genesis, evolution and morphometric aspects. Mining activities are heavily influencing and destroying the landscape worldwide. In Aghireş mining perimeter, exploitation workings have led to extreme and irreversible environmental damages, especially regarding the geomorphologic and hydrological situation. After cessation of underground mining and initiation of quarry exploitation, certain mining galleries collapsed and were afterwards flooded by precipitation and re-ascending groundwater, leading to the formation of lacustrine units. Later, the abandoned quarries have undergone the same flooding process. In this paper, we report on the genesis, evolution and the current characteristics of these bodies of water, referred to as mining lakes. In addition, using the GIS technology, the morphometry of the mining lakes is presented in this paper. Due to their predominant current use, as for recreational purposes, the sustainable management of the mining lakes is an important ecological and socio-economical factor for the Aghireş area. For the majority of mining lakes, restoration measures may be necessary due to the demands of the European legislation as well as to the demands of a specific socio-economic use in the future (e.g. bathing lakes or fishing lakes). These aspects of investigation will constitute a prerequisite for effective environmental management and rehabilitation strategies

CORRELATIONS BETWEEN SURFACE-WATER CHARACTERISTICS AND GEOLOGICAL SUBSTRATUM IN AGHIRES MINING AREA, ROMANIA

The exploitation activities from Aghireş generated a series of lakes, drainage ditches and creeks, specific for mining. In this paper, the physical and chemical parameters of the mining lakes are presented, the results being then correlated with the characteristics of the geological substratum. For the physico-chemical testing, three different water samples have been collected for each of the ten mining lakes. The samples where then analyzed in the field, by using a portable multi-parameter measuring instrument. The final results confirm the initial premise that the water quality is influenced by the geological substratum. The parameters that stand out the most are the pH, electric conductivity, and salinity, which vary quite significantly between the collected samples. The pH parameter is the most illustrative in this respect, given that three of the mining lakes have an extremely acidic water environment (with pH levels lower than 4.0), while the rest of the lakes have neutral pH levels. This difference can be explained by the presence of pyrite, associated with coal deposits in the underlying formations of acidic lakes