Environmental effects of land reclamation and regulation of rivers in the Bzura river near Łowicz

The article shows the influence of land reclamation and regulation of rivers on the transformation of the environment in the Bzura pradolina near Lowicz. At the beginning of the 19th century the Bzura river was of an anastomosing type. The interchannel area was occupied by wetlands and peatbogs mainly of a fluviogenic origin due to high level of alluvial water. In the Bzura valley habitats of swamps and wet deciduous forest alternated. Five watermilIs were located in the channels. The land reclamation and regulation of rivers started at the beginning of the 19th century. First of all, watermills were removed. A new channel to concentrate runoff of the Bzura river was dug. Afterwards the same works were carried out in the minor streams and drainage ditches were constructed. These activities had the various influence on the environment. The direct result is a change in river pattern of the area. A multi-channel system of the Bzura river has been changed into a single-channel one; the channel became straightened, shortened and dredged. The increase of the river gradient caused a drop in the water level and the emergence of downcutting tendency. Transport and sedimentary processes changed as well. Principally, regulation of rivers and land reclamation have resulted in an accelerated removal of precipitation waters from the catchment and, in consequence, a temporary or permanent decline in the groundwater level and the desiccation of the valleys. The secondary effect of land drainage comprises changes of vegetation communities, land use and the pradolina landscape. Meadows have been converted to arable area of low productivity, peatbogs have degraded. The performed works have turned out to be unfavourable for moisture conditions in the valley and for agriculture.Artykuł przedstawia wpływy melioracji i regulacji rzek na przekształcenie środowiska w dolinie Bzury w okolicach Łowicza. Na początku XIX w. dno doliny było zabagnione, a Bzura miała charakter rzeki anastomozującej i płynęła 3-4 korytami. Prace regulacyjne przeprowadzono w XIX w., a melioracyjne w XX w. Bezpośrednim następstwem tych prac jest całkowicie zmieniona sieć wodna obszaru. Wie1okorytowy układ Bzury przekształcono w jednokorytowy, przy tym koryto wyprostowano, skrócono i pogłębiono, co spowodowało ożywienie procesów erozyjnych. Obniżeniu uległ także poziom wód gruntowych, który spowodował osuszenie dna doliny. Następstwem osuszenia są zmiany zespołów florystycznych, sposobu zagospodarowania terenu i całkowicie zmieniony krajobraz pradoliny