## 2 Study Area  
In the administrative division of Poland, Lake Piaseczno (51\({}^{\circ}\)23\({}^{\prime}\)03\({}^{\prime\prime}\) N; 23\({}^{\circ}\)01\({}^{\prime}\)46\({}^{\prime\prime}\) E) is located in the centre of the Lublin Voivodeship, in the northern part of the Leczna Poviat, in the Ludwin Commune, within the physiographic unit of the Leczna-Wlodawa Lake District included in the macroregion of Polesie Podlaskie (East Poland) (Figure 1). In the hydrographic division, Lake Piaseczno is included in the catchment of the Wieprz River, in the upper part of the catchment of the Piwonia Poludniowa River. The river originates in the vicinity of the lake, and has no surface connection with it. Therefore, its catchment is described as a surface-closed-drainage catchment [33]. Lake Piaseczno is classified as a very deep lake, with a maximum depth of 38.8 m and a high water volume (10.67 million m\({}^{3}\)). It is a dimtictic lake in the bradymictic type, and, in terms of trophic status, it is mesotrophic (Table 1). Catchment morphology is one of the elements that determines a lake's hydrological conditions and land use structure. The catchment of Lake Piaseczno is not physiologically differentiated from the remaining area of the Lake District. \begin{table}
\begin{tabular}{c c} \hline
**Absolute Height** & **Surface Area** \\
170.6 (m a.s.l.) & 84.7 (ha) \\
**Length** & **Max. Width** \\
1464 (m) & 819 (m) \\
**Shape Index** & **Length of Shoreline** \\
0.4 & 3788 (m) \\
**Shoreline Development** & **Mean Bottom Inclination** \\
1.16 & 4\({}^{\circ}\)50\({}^{\prime}\) \\
**Max. Depth** & **Mean Depth** \\
38.8 (m) & 12.6 (m) \\
**Depth Index** & **Volume** \\
0.32 & 10,674 (thousand m\({}^{3}\)) \\
**Type of Mixing** & **Trophic Status** \\ bradymixion & mesotrophy \\ \hline \end{tabular}
\end{table} 
Table 1: The morphometric parameters of Lake Piaseczno on the background of its bathymetric plan (a.s.l., above sea level) [33]. Figure 1: The location of Lake Piaseczno (white arrow) in the Léczna-Wlodawa Lake District. Adapted from [32]. The area is dominated by very gentle undulating plains of a higher accumulation horizon, with an indistinctly marked watershed, evidently contrasting with the lake basin landform with steep slopes. This determines rarely occurring surface runoff, which is related to the presence of very permeable formations and the ecological structure of the catchment [33]. The lake has no inflows or outflows. It is primarily fed by precipitation waters supplying allochthonic substances from the catchment with surface runoff. In the summer period, it is subject to complete thermal stratification. Part of the area around the lake constitutes a sandy beach that alternates with shore vegetation and shrubs dominated by _Salix cinerea_ and _Betula pubescens_. To the north and south, the lake is adjacent to a mixed forest, and in its northwestern fragment it neighbours on formerly active swamps and peatlands separated by a relatively narrow transitional zone [34; 35; 36]. Morphological, landscape and habitat properties, as well as anthropogenic activity, determine the diversity of land use in the catchment of Lake Piaseczno (Figure 2, Table 2). This largely affects the state of its surroundings, resulting in the current recreation-agricultural-forest character of the lake catchment (natural forms, extensively cultivated arable land and recreational building development (numerous cottages and two holiday resorts)). Based on the above, the lake catchment was divided into sectors with a growing share of investment land related to stationary recreation (Table 2). Pursuant to general guidelines for the use, protection and reclamation of lakes, and based on the categories of susceptibility to degradation and classes of water cleanliness [37], Lake Piaseczno is included as a lake with good natural conditions, where the use and preservation of the current state of the lake should be in accordance with the rules for the protection of particularly valuable water resources [13].