Changes to the structure of the hydrographic network within the Silesia-Cracow area of zinc and lead exploitation

The traditions related to mining activities in the Silesia-Cracow area go back to the 11^th century when lead, silver, and iron ores were exploited from open pit mines. For centuries, the growth in ore exploitation was an incentive for the development of other industries (hard coal mining, steelmaking). This, in consequence, resulted in progressive urbanization. The areas analyzed are of highly transformed character, mainly because of mining activities. These changes are especially seen in relation to the aquatic environment since this component is exposed to heavy modifications due to the mining processes. Hence the study was carried out in order to determine the quantitative changes in the surface hydrographic network. It was found, that of the 62 main watercourses (existing during the whole analyzed period) 25 changed only slightly in terms of their length, 20 shortened by a few hundred meters and 17 lengthened. In the case of the aggregated length of the tributaries, the value increased for the 41 main watercourses, for 10 of them it was constant and was reduced slightly for a further 11. The areas where the length of the watercourses increased and the drainage density grew were found to be as well those where the total area of wetlands decreased. The element of the hydrographic network which was affected by the most changes was the water bodies. During the analyzed period of over 200 years, their number increased from 154 to 1413.