Fig. 1.
Groundwater flow directions in a river valley for a straight section of the stream: gaining stream – A, equilibrium conditions – B and losing stream – C (based on Bajkiewicz-Grabowska 2020).
Fig. 2.
Concept of the hyporheic zone and hyporheic flow in the corridor of a meandering river valley (modified scheme based on Williams (1986), Winter et al. (1998), and Alley et al. (2002).
Fig. 3.
Location of the study area (based on an orthophotomap from www.geoportal.gov.pl).
Fig. 4.
Hydrogeological cross-section through the sediments of the Warta River meander. Dashed lines indicate profiles (borehole number in parentheses) that are located near the cross-sectional line and were used to interpret the geological structure.
Table 1.
Granulometric and hydraulic characteristics of meander sediments.
| No. | Depth | Grain uniformity index U | Hydraulic conductivity k | Clay + Silt (<0.063 mm) | Sand (0.063–2 mm) | Gravel (2–63 mm) | Type* | |||
|---|---|---|---|---|---|---|---|---|---|---|
| Fine sand | Medium sand | Coarse sand | PN-EN ISO 14688 | PN-B-02480 | ||||||
| [m] | [–] | [m · h−1] | [%] | [–] | ||||||
| P1 | ||||||||||
| P1/4 | 2.2 | 1.78 | 0.81 | 1.5 | 81.1 | 17.0 | 0.4 | 0.0 | FSa | SiSa |
| P1/5 | 3.0 | 2.11 | 0.99 | 1.7 | 58.7 | 27.5 | 12.1 | 0.0 | FSa | FSa |
| P1/7 | 4.3 | 1.53 | 0.65 | 2.4 | 93.8 | 3.6 | 0.2 | 0.0 | FSa | SiSa |
| P2 | ||||||||||
| P2/2 | 1.6 | 1.64 | 1.91 | 0.4 | 39.9 | 59.3 | 0.4 | 0.0 | MSa | FSa |
| P2/3 | 3.0 | 1.54 | 1.65 | 0.6 | 59.1 | 39.6 | 0.7 | 0.0 | FSa | FSa |
| P2/4 | 3.7 | 2.00 | 5.85 | 0.2 | 8.9 | 83.2 | 7.3 | 0.4 | MSa | MSa |
| P3 | ||||||||||
| P3/3 | 2.0 | 2.18 | 1.19 | 1.4 | 47.0 | 43.8 | 7.8 | 0.0 | FSa/MSa | FSa |
| P3/5 | 2.7 | 2.00 | 1.41 | 1.0 | 45.7 | 45.1 | 8.2 | 0.0 | FSa/MSa | FSa |
| P3/8 | 3.4 | 2.00 | 0.99 | 1.6 | 59.1 | 25.6 | 12.8 | 0.9 | FSa | FSa |
| P3/10 | 4.1 | 2.79 | 1.91 | 0.4 | 32.4 | 55.4 | 10.9 | 0.9 | MSa | MSa |
| P3/12 | 4.5 | 2.00 | 3.98 | 0.6 | 14.8 | 76.7 | 7.4 | 0.5 | MSa | MSa |
Fig. 5.
Water flow in the hyporheic corridor within the meander bend.
Fig. 6.
River and groundwater levels (H) in the hydrological years 2022–2024 against the background of precipitation (P).
Fig. 7.
Direction of groundwater flow in the hyporheic corridor of the Warta River during losing stream conditions – A, the transition from losing stream to gaining stream conditions – B and gaining stream conditions – C.
Fig. 8.
Direction of groundwater flow in the hyporheic corridor of the Warta River during a rise in river water levels due to precipitation.