2. Material and Methods
2.1. Research Area
2.2. Geological Setting
2.3. Channel Network
2.4. Ground Water Model
2.5. Model Calibration
2.6. Model Validation and Exploitation
3. Results and Discussion
- Channel water level clearly exerts an influence on ground water table with a typical pattern; that is, the highest drawdown takes place close to channels, and the maximum elevation of the water table is present in the middle of the area. We try to describe that influence as conductivity-dependent, because its large values for existing sandy soils may cause high exchange between canals and ground water horizons, undoubtedly contributing to the preservation of the natural values of a flooding terrace.
- Depth to water table was analysed according to the adopted criteria, which describe sandy soil wetness due to effective capillary rise. According to that criteria, maximum allowable depth to water table may not be higher than 0.45 m, the mean depth should be equal to 0.40 m, and the minimum reaching 0.5 m. The assumed threshold values of ground water table (0.3 to 0.45 m below land surface) were achieved on maximum 29% of the area if the channel water levels were increased by 0.5 m in the second analysed scenario. The first scenario (which reflected the actual status of the system) guarantees proper water levels only on 16% of the area. We wish to stress that the restoration target was achieved when ground water table position was between the adopted extremes. This was indeed an assumption. First of all, the criteria seem to be relative, and we also claim that the prescribed water level range is directly assumed as a permanent feature of well-preserved habitats (and their plant species composition), and may be used for scenario comparisons in hydrologic and water management analyses. The appropriateness of the applied threshold values results from their extensive use over the area of Poland and firm relation to crucial soil properties.
- Hydrologic conditions on sandy terrace favorable for dominating Carex species and widespread Molinia meadows were possible in the middle of the area. As shown by the modelling results, they were not achieved in close-to-channel zones, which would require other hydrologic remediation.
- Adaptive channel water management is no doubt an option for the maintenance of habitats on sandy deposits of flat river valleys. More detailed scenario studies are indispensable for the decision making on the extent of restoration area.
Conflicts of Interest
- Wheeler, B.; Shaw, S. A focus on fens-controls on the composition of fen vegetation in relation to restoration. In Restoration of Temperate Wetlands; Wheeler, B., Shaw, S., Fojt, W., Robertson, R., Eds.; Wiley: Chichester, UK, 1995. [Google Scholar]
- Grygoruk, M.; Bańkowska, A.; Jabłońska, E.; Janauer, G.; Kubrak, J.; Mirosław-Świątek, D.; Kotowski, W. Assessing habitat exposure to eutrophication in restored wetlands: Model-supported ex-ante approach to rewetting drained mires. J. Environ. Manag. 2015, 152, 230–240. [Google Scholar] [CrossRef] [PubMed]
- Brandyk, A.; Majewski, G. Modeling of hydrological conditions for the restoration of Przemkowsko-Przecławskie Wetlands. Annu. Set Environ. Prot. 2013, 15, 371–392. [Google Scholar]
- Brandyk, A. Ground water—Fed system restoration on the area of Przemkowsko-Przecławskie Wetlands. Ann. Wars. Univ. Life Sci. SGGW Land Reclam. 2011, 43, 13–23. [Google Scholar] [CrossRef]
- Grootjans, A.; Wołejko, L. Conservation of Wetlands in Polish Agricultural Landscapes; Wydawnictwo Lubuskiego Klubu Przyrodników: Szczecin, Poland, 2007. [Google Scholar]
- Okruszko, T. Hydrologic Criteria in Wetlands Protection; Treatises and Monographs; Warsaw University of Life Sciences Publishing: Warsaw, Poland, 2005. (In Polish) [Google Scholar]
- Pierzgalski, E.; Pawluśkiewicz, B.; Gnatowski, T.; Brandyk, A. Utrzymanie urządzeń melioracyjnych na obszarach Natura 2000 na przykładzie Bagna Całowanie. In Gospodarowanie w Dolinach Rzecznych na Obszarach Natura 2000; Pawluśkiewicz, B., Ed.; Warsaw University of Life Sciences Publishing: Warsaw, Poland, 2013. (In Polish) [Google Scholar]
- Oświt, J. Roślinność i Siedliska Zabagnionych Dolin Rzecznych na tle Warunków Wodnych; Rocz. Nauk Rol., Ser. D., Ed.; Warsaw University of Life Sciences Publishing: Warsaw, Poland, 1991. (In Polish) [Google Scholar]
- Querner, E.; Ślesicka, A.; Mioduszewski, W. Water management in the Central Biebrza Basin (gospodarka wodna w środkowym basenie biebrzy). In Proceedings of the International Conference Agricultural Effects on Ground and Surface Waters, Wageningen, The Netherlands, 15–17 October 2000.
- Brandyk, A.; Kiczko, A.; Majewski, G.; Kleniewska, M.; Krukowski, M. Uncertainty of Deardorff’s soil moisture model based on continuous TDR measurements for sandy loam soil. J. Hydrol. Hydromech. 2016, 64, 23–29. [Google Scholar] [CrossRef]
- Szuniewicz, J. Charakterystyka Kompleksów Wilgotnościowo-Glebowych pod Kątem Parametrów Systemu Melioracyjnego; Institute of Technology and Life Sciences Publishing: Raszyn, Poland, 1979. (In Polish) [Google Scholar]
- Stelmaszczyk, S.; Okruszko, T.; Meire, P. Nutrients availability and hydrological conditions of selected wetland ecosystems in the Biebrza river valley. Ann. Wars. Univ. Life Sci. SGGW Land Reclam. 2015, 47, 3–17. [Google Scholar] [CrossRef]
- Pierzgalski, E.; Pawluśkiewicz, B.; Gnatowski, T.; Brandyk, A. The Estimation of Ditch Network, Warszawicki and Wilga-Wisła Channels Influence on Soil Water Conditions of Całowanie Peatland Protected Area; Materials of Faculty of Civil and Environmental Engineering, Department of Environmental Improvement, Warsaw University of Life Sciences: Warsaw, Poland, 2011. [Google Scholar]
- Keizera, F.; Schot, P.; Okruszko, T.; Chormański, J.; Kardel, I.; Wassen, M. A New look at the Flood Pulse Concept: The (ir) relevance of the moving littoral in temperate zone rivers. Ecol. Eng. 2014, 64, 85–99. [Google Scholar] [CrossRef]
- Dietrich, O.; Schweigert, S.; Steidl, J. Impact of climate change on the water balance of fen wetlands in the Elbe Lowland. In Proceedings of the 13th International Peat Congress, Tullamore, Ireland, 8–13 June 2008; International Peat Society: Jyväskylä, Finland, 2008. [Google Scholar]
- McDonald, M.; Harbaugh, W. A Modular Three—Dimensional Finite Difference Groundwater Flow Model; Openfile Report No. 6; United States Geological Survey: Washington, DC, USA, 1998.
© 2016 by the authors; licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC-BY) license (http://creativecommons.org/licenses/by/4.0/).