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Calculation of lake surface characteristics using GIS tools [after Urbański, Kryla-Straszewska 2010; modified]; N/A – not applicable
| Parameter | Definition | Formula | Necessary layers | Determination method in GIS |
|---|---|---|---|---|
| Lake area characteristics | ||||
| Height above sea level | The location of the lake above sea level (m a.s.l.) | N/A | Digital Terrain Model and a polygon layer with the lake area | Zonal Statistics |
| Area (A) | Water surface area without taking the area of islands into account | N/A | Polygon layer with the lake area | Option calculate geometry area (in the attribute table) |
| Maximum length (l) | The shortest distance between the most distant points of the lake shore when measured along the line, without extending beyond the lake’s boundary | N/A | Polygon layer with the lake area | Requires a Python script |
| Maximum breadth (b) | The greatest distance between opposite shores measured along a line perpendicular to the maximum length of the lake | N/A | Polygon layer with the lake area | Requires a Python script |
| Mean breadth (b̄) | The ratio of the lake area to the maximum lake length | b̄ = A/l | Polygon layer with the lake area | Requires a Python script that counts l and the calculate option (in the attribute table) |
| Perimeter (L) | The length of the lake shoreline measured along the 0 isobath | N/A | Polygon layer with the lake area | Option calculate geometry perimeter (in the attribute table) |
| Elongation index (λ) | This parameter gives an overview of the shape of the lake surface. The greater its value, the more elongated the lake is | λ = l/b̄ | Polygon layer with the lake area | Requires a Python script that counts l and the calculate option (in the attribute table) |
| Shoreline development (DL) | This parameter shows how close the shape of the shoreline is to the shape of a circle | DL=L/(2√π⋅A) | Polygon layer with the lake area | Options of calculation several geometric and algebraic parameters (in the attribute table) |
Calculation of morphometric characteristics related to lake bathymetry using GIS tools [after Urbański, Kryla-Straszewska 2010; modified]; abbreviations – see Table 1, N/A – not applicable
| Parameter | Definition | Formula | Necessary layers | Determination method in GIS |
|---|---|---|---|---|
| Bathymetric characteristics | ||||
| Volume (V) | Lake volume | V = A · Z̄ | Polygon layer with the lake shoreline | Calculation option within the attribute table |
| Maximum depth (Zm) | Depth at the deepest point of the lake | N/A | Polygon layer with lake shoreline and raster bathymetry map | Zonal Statistics |
| Mean depth (Z̄) | The ratio of the lake’s volume to its area | Z̄ = V/A | Polygon layer with lake shoreline and raster bathymetry map | Zonal Statistics |
| Exposure or openness (Wo) | Indicator that allows assessing the intensity of the impact of external factors on the lake | Wo = A/Z̄ | Calculation option within the attribute table | Calculation option within the attribute table |
| Relative depth (Zr) | The ratio of the maximum depth to the diameter of a circle equal to the area of the lake, expressed as a percentage | Zr=50 ⋅ Zm ⋅ √π⋅(√A)−1 | Calculation option within the attribute table | Calculation option within the attribute table |
| Littoral zone | The percentage of the lake area covered by macrophytes | N/A | Raster bathymetry map | Reclassification of the bathymetric plan into two depth classes depending on the depth of the macrophyte occurrence. Then, calculation of the percentage of the class in the attribute table |