This paper presents an improved version of a general, process-based mass-balance model (LakeMab/ LEEDS) for phosphorus in entire lakes (the ecosystem scale). The focus in this work is set on the boundary conditions, i.e., the domain of the model, and critical tests to reveal those boundary conditions using data from a wide limnological range. The basic structure of the model, and many key equations have been presented and motivated before, but this work presents several new developments. The LakeMab-model is based on ordinary differential equations regulating inflow, outflow and internal fluxes and the temporal resolution is one month to reflect seasonal variations. The model consists of four compartments: surface water, deep water, sediment on accumulation areas and sediment on areas of erosion and transportation. The separation between the surface-water layer and the deep-water layer is not done from water temperature data, but from sedimentological criteria (from the theoretical wave base, which regulates where wind/ wave-induced resuspension of fine sediments occurs). There are algorithms for processes regulating internal fluxes and internal loading, e.g., sedimentation, resuspension, diffusion, mixing and burial. Critical model tests were made using data from 41 lakes of very different character and the results show that the model could predict mean monthly TP-concentrations in water very well (generally within the uncertainty bands given by the empirical data). The model is even easier to apply than the well-known OECD and Vollenweider models due to more easily accessed driving variables.Keywords Eutrophication . Mass-balance model . Phosphorus . Lakes . Processes . Fluxes . Sedimentation . Resuspension . Mixing . Suspended particulate matter
Background and AimPhosphorus abatement has substantially improved the water quality in many anthropogenically eutrophicated lakes (Sas 1989;Jeppesen et al. 2005). Models for predicting lake response from phosphorus reductions have thus far been rather imprecise and results from abatement programs have sometimes been disappointingly modest (Sas 1989). Phosphorus is since long recognised as a crucial limiting nutrient for lake primary production (Schindler 1977(Schindler , 1978Bierman 1980;Chapra 1980;Boynton et al. 1982;Wetzel 1983;Persson and Jansson 1988;Boers et al. 1993). The literature on phosphorus in lakes is extensive. The famous Vollenweider model (Vollenweider 1968(Vollenweider , 1976 and later versions, e.g., OECD 1982), and the analysis behind this modelling, constitutes a fundamental base for water management (Wetzel 2001; Håkanson and Water Air Soil Pollut (2008) Boulion 2002). Lake modelling has gone through great changes recently with respect to predictive power.As a consequence of the Chernobyl nuclear accident, the pulse of radionuclides that subsequently passed along European ecosystem pathways has revealed, and made it possible to quantify, important transport routes (Håkanson 2000). Many algorithms that quantify these fluxes are vali...