# Temporal and Spatial Diversity of Renewable Groundwater Resources in the River Valley
## 2 Background to the Study Site  
### Topography and Geomorphology  
The research area is located in the Middle Vistula valley, in the Kampinos National Park region, where the main geomorphological units determining the current shape of the valley are the result of processes occurring from the end of the Pleistocene. The morphogenesis of the Vistula valley is typical of the Central European Lowlands and it represents a complete set of accumulative sequences that are not as well developed on other sections of the valley. It is associated most closely with the period of the last (Vistulian) glaciation, which was started by the accumulation of the youngest ice-dammed lake sediments in the Warsaw Plain, followed by the development of denudation, deep fluvial erosion, aeolian processes and sequence accumulation in the Vistula valley. As a result, three over-flood terraces of the Vistula River have developed: Otwock (I), Falenica (II) and Praga (III), built up in places by extensive dune complexes and accumulations of aeolian sands [41] (Figures 1 and 2). In the Otwock Terrace (I), the dominant terrain forms are dune hills, giving the area a varied relief. Sediments of the Otwock Terrace reach a maximum thickness of 16 m. The terrain elevations within the terrace range from 66.19 to 100.58 m a.s.l. (above sea level), with an average of 77.28 m a.s.l. Dune-forming  
Figure 1: Location of the study area: (**A**)—on the background of Major Groundwater Reservoir no. 222; (**B**)—groundwater monitoring points (adapted from [35,36]).  
processes, related to the lowering of the groundwater table, started in the Oldest Dryas. The decline of dune-forming processes fell at the beginning of the Allerod [42]. In the Oldest Dryas and Bolling periods, fluvial erosion led to the dissection of the Otwock sediments, followed by accumulation of the Falenica Terrace (II), also called the Kampinos Terrace. The Falenica Terrace (II), is a flat surface located at an elevation of 67.04-97.73 m a.s.l., with an average of 75.29 m a.s.l., approx. 7-10 m above the mean level of the Vistula River [41]. In the Older Dryas and the Allerod, after dissection of the Falenica Terrace and locally the Otwock Terrace and because of subsequent accumulation, the Praga Terrace (III) was formed [41]. It occurs at an elevation of 63.24-95.74 m a.s.l., with an average of 72.77 m a.s.l., i.e., about 4-7 m above the mean level of the Vistula River [42]. In the Holocene, the Vistula valley was an area of fluvial accumulation of sands, mineral and organic sediments, and muds forming a two-part floodplain within a 7-8 m deep incision in the Praga Terrace [43; 44]. The floodplain was divided on the lower (IVa) and upper (IVb) plain. The average elevation of the IVa area is 71.21 m a.s.l. For level IVb, the average elevation is 71.66 m a.s.l., higher than for IVa due to significant anthropogenic transformations of the terrain, represented by embankments and levees.  
Figure 2: Study area characteristics: (**A**)–river network and morphology based on DEM \(10\times 10\) m; (**B**)–geomorphological units (adapted from [6; 41]).