Be they a product of either an anthropogenic or a glacigenic nature, ponds within forests play an extremely important role in determining hydrological features of forest micro-catchments. Water retained in these small bodies of water for example has a positive effect on the groundwater of neighbouring forest habitats, serving to recharge them during dry periods.
This article presents the results of a study conducted in the catchments of two mid-forest ponds (known as Nos. 1 and 5), which differ in terms of their recharge characteristics. The ponds are located on the land of Poland’s Siemianice Experimental Forestry Department, in the catchments of the Rivers Niesob and Pomianka as left-bank tributaries of the Prosna. The forests are located on the Southern Wielkopolska Lowland, on the Wieruszow Plateau, which is a denuded moraine plain incised by the upper Prosna. The study was carried out in the three hydrological years 2013, 2015 and 2016, which differed in terms of their precipitation totals. The 2013 hydrological year, in which precipitation totalled 711 mm (hence 139 mm above the multi-year average) was a wet year, as compared with the very dry hydrological year 2015, which featured a precipitation total of 337 mm, or just 59% of normal precipitation. The third hydrological year discussed (2016) proved to be an average year, with precipitation totalling 613 mm thus being 41 mm above the multi-year average.
The catchment of mid-forest pond No. 1, featuring 100% forest cover and covering about 7.5 ha, is located in the basin of the Niesob – a left-bank tributary of the Prosna. This study catchment is dominated by mesic habitats (occupying 98% of its area), even as the area immediately adjacent to the pond is of the mixed wet forest site-type. In contrast, the catchment of pond No. 5, again with forest cover of 100% and an area of some 20 ha, is located in the catchment of the Pomianka, again a left-bank tributary of the Prosna. This catchment nevertheless resembled that of pond 1 in featuring a prevalence of mesic habitats, albeit with wet forest in the immediate vicinity of the body of water.
The soil cover of the analysed catchments is dominated by rusty podsolic and rusty brown soils (pond No. 1), or else typical acid brown soils (pond No. 5); with the predominant species being loamy sand. Characterisation in terms of basic morphometric parameters implies that mid-forest pond No. 1 (with an area of 0.13 ha and an average depth of 1.0 m) is in the nature of an exuvial pond of near-circular shape. The length of shoreline is 118 m, and the elongation and depletion indices are of 1.1 and 2.5 respectively. In contrast, pond No. 5 (with an average depth of 1.2 m and an area of 0.096 ha) is of rectangular shape and constitutes a drainage pond fed intensively from the northwest by spring water. This body of water formed as a result of human activity. The length of the shoreline of this pond is 136 m, and the elongation and depletion ratios are of 2.5. According to information from local people, it was used as a fish pond in the 1970s.
The bottoms of the analysed ponds Nos. 1 and 5 feature organic silt of 30 cm thickness on average, overlying weak clayey sand (pond 1) or light clay (pond 5). Meanwhile, the slopes of the ponds and soils of adjacent forest habitats show a prevalence of weak clayey sand. The study confirmed that the functioning of mid-forest ponds is determined mainly in line with their nature, as well as their morphometric features. At the same time, these characteristics exert a significant influence on separate components of the water balance in such bodies of water, with this going on to affect the water cycle in a given catchment area significantly. Greater variability of water level and reserves proved to be characteristic for pond No. 1 (which lacked an outflow), while the intensively spring-fed pond No. 5 displayed only minor changes in these quantities.
The example of mid-forest pond No. 1 suggests that small non-drained bodies of water (thus assigned to the so-called non-controllable retention of water) have trends for changes in water level determined by the course of meteorological conditions in particular. In a body of water of this type it is typical to observe disappearance below ground of any water table, in hydrological years that are dry or even average in terms of precipitation. And in the practical context of the protection of water resources in forests, this will need to be seen as something unfavourable. On the other hand, the hydrology of pond No. 5 is such that the influence of meteorological conditions in shaping states and related water reserves proves non-significant.
Our calculations point to the hydraulic linkage between the water retained in forest ponds and the groundwater of adjacent habitats, with this denoting both periodic outflow of water into soils and recharge with groundwater from adjacent habitats, in the case of pond No. 1. In contrast, pond No. 5 is subject to a unidirectional flow of water from the adjacent habitat into the pond. Results further point to the nature of the interrelationship between water retained in ponds and adjacent groundwater being under the strong influence of location within a catchment, plus prevailing physiographic conditions. However, a further important matter relates to hydrogeological parameters of formations present on and below nearby slopes; as well as in the immediate vicinity of a given pond.
Analysis of the percentage contribution individual components of water balance make over whole hydrological years serves to confirm that small undrained ponds like our pond No. 1 (with the so-called evapotranspirational or absorptive non-drainage) usually have such elements of vertical water-exchange as precipitation to the surface of a pond and evaporation playing a greater role in shaping the balance. In contrast, in the outflowing and intensively spring-fed pond No. 5, it was horizontal exchange factors, such as uncontrolled spring inflow and outflow to a nearby watercourse that did most to determine the balance. In this type of pond, vertical water exchange occurs less intensively than horizontal exchange and generates no fundamental change in the overall structuring of water
Mariusz Korytowski [email@example.com], Uniwersytet Przyrodniczy w Poznaniu, Wydział Inżynierii Środowiska i Inżynierii Mechanicznej
Rafał Stasik [firstname.lastname@example.org], Uniwersytet Przyrodniczy w Poznaniu, Wydział Inżynierii Środowiska i Inżynierii Mechanicznej
Michał Fiedler [email@example.com], Uniwersytet Przyrodniczy w Poznaniu, Wydział Inżynierii Środowiska i Inżynierii Mechanicznej
APA: Korytowski, M., Stasik, R., & Fiedler, M. (2023). Zmiany składników bilansu wodnego śródleśnych małych zbiorników wodnych w zlewni Prosny (środkowa Polska). Przegląd Geograficzny, 95(2), 187-210. https://doi.org/10.7163/PrzG.2023.2.4
MLA: Korytowski, Mariusz, et al. "Zmiany składników bilansu wodnego śródleśnych małych zbiorników wodnych w zlewni Prosny (środkowa Polska)". Przegląd Geograficzny, vol. 95, no. 2, 2023, pp. 187-210. https://doi.org/10.7163/PrzG.2023.2.4
Chicago: Korytowski, Mariusz, Stasik, Rafał, and Fiedler, Michał. "Zmiany składników bilansu wodnego śródleśnych małych zbiorników wodnych w zlewni Prosny (środkowa Polska)". Przegląd Geograficzny 95, no. 2 (2023): 187-210. https://doi.org/10.7163/PrzG.2023.2.4
Harvard: Korytowski, M., Stasik, R., & Fiedler, M. 2023. "Zmiany składników bilansu wodnego śródleśnych małych zbiorników wodnych w zlewni Prosny (środkowa Polska)". Przegląd Geograficzny, vol. 95, no. 2, pp. 187-210. https://doi.org/10.7163/PrzG.2023.2.4