Medeldjupet

Medeldjupet, literally the mean depth, is a term used in hydrography and physical geography to describe the average depth of a body of water. In Norwegian usage it is defined as the depth obtained when the water body’s total volume is divided by its surface area. It provides a single representative value for planning and analysis, but it does not reflect local depth variation across the area.

Calculation and units: medeldjupet = V / A, where V is the volume (cubic meters) and A is the surface area (square meters). The result is expressed in meters. Globally, the mean depth of the world’s oceans is about 3,700 meters. In lakes, medeldjupet varies widely and is typically smaller than the maximum depth.

Applications: The mean depth supports navigation planning, ecological and hydrological modeling, sediment transport studies, and water-resource management. It is commonly used together with maximum depth and depth distribution maps to describe a water body concisely.

Measurement and data sources: Depth information comes from bathymetric surveys using sonar or multibeam systems, as well as ship-based measurements. For large seas, satellite altimetry and gravity data help estimate depth where direct surveys are sparse. Modern digital bathymetry datasets enable calculation of V and A for many lakes and coastal areas.

Limitations: A single mean depth cannot capture vertical structure, habitat heterogeneity, or depth-related processes such as stratification. Water-level changes due to seasonal or climatic factors can also affect the medeldjupet of a water body.