Modeling the effect of development on internal phosphorus load in nutrient‐poor lakes

Abstract

[1] A steady state lake phosphorus (P) mass balance model was used to predict the equilibrium P concentration (annual, volume-weighted average) of the lake water from natural and anthropogenic, external and internal P inputs. Internal P load was modeled as the product of sediment release rates and anoxic factors. Both these components were predicted from lake P concentration computed from external load to create a link between external and internal load components. Such estimates allow the modeling and setting of objectives of several hundred lakes on the Canadian Shield. In particular, estimates of predevelopment lake P concentration made by removing all anthropogenic inputs were compared with postdevelopment conditions in which additional loading was added to the model. This was accomplished by determining how much development would increase external as well as internal phosphorus load and ultimately annual average lake P concentrations. By comparing proposed lake development scenarios with existing or predevelopment scenarios, it can be determined whether water quality objectives will be exceeded.

Estimating internal P loading in a deep water reservoir of northern China using three different methods

“…Parts of the retained P would be buried as a permanently immobilized P fraction, whereas other parts would be mobile P, susceptible to releasing PO 4 3− to the overlying water. For Nürnberg and LaZerte (2004) revealed several stages about internal load changed with external load. External load triggers internal load and in turn internal load delays the recovery procedure from eutrophication stage.…”

“…Therefore, internal P loading contributes to reservoirs (or lakes) loading significantly. In shallow lakes, internal P loading was widely regarded as a great source of nutrient (Welch and Cooke 1995;Nürnberg and LaZerte 2004;Steinman et al 2009). However, internal nutrient released from sediment is often related to anoxia (Hupfer and Lewandowski 2008).…”

“…Orihel et al (2013) showed that the release nutrient from sediment stimulated the blooms of toxigenic cyanobacteria. As a result, it can be found that internal P loading delays the lake recovery even after reducing the external input and very important in water eutrophication (Zhou et al 2001;Nürnberg and LaZerte 2004;Søndergaard et al 2012;Bertrand et al 2015).…”

Historical changes (1905–2005) in external phosphorus loads to Loch Leven, Scotland, UK

“…This was because the rate of hydraulic discharge rate was unchanged and in-lake P concentrations remained high (Carvalho et al, this volume) as a result of increased P release from the sediments. This seemed to be 'compensating' for the reduction in TP load from the catchment (Spears et al, this volume) as has been observed in other lakes (Søndergaard et al, 2003;Nürnberg & LaZerte, 2004). This suggests that, while internal recycling appears to delay recovery in terms of in-lake water quality parameters, it also promotes recovery in terms of increasing the rate at which TP from internal sources is exported from the system.…”

“…However, on an annual timescale, P retention has remained positive, suggesting that TP continues to accumulate in the lake sediments. Such accumulations are important in terms of lake recovery because, when external TP loads are reduced, these internal sources tend to release P into the water column causing a considerable delay in recovery (Sas, 1989;Gulati & van Donk, 2002;Søndergaard et al, 2003;Nürnberg & LaZerte, 2004;Jeppesen et al, 2005;Søndergaard et al, 2007;Spears et al, this volume). That said, in most lakes, P release from the sediments also promotes recovery because it increases the rate at which TP from internal sources can be exported from the system, especially during the summer months (Sondergaard et al, 2001).…”