Lake Budgets

The overall lake mass balance focuses on the total inflow, outflow, and net release/retention within the lake. It is useful for understanding the how much water and nutrients enters the lake, how much leaves, and how much is released or retained in the sediments.

Equations

ΔStorage = Net Inflow - Outflow + Net Release/Retention

Net Inflow = Total Inflows + Precipitation - Evaporation

Total Inflows = Gauged Tributaries + Ungauged + Total Agricultural Pumping

The timeseries plots show the annual and monthly timeseries of the primary lake mass balance terms. The Outflow term is plotted as negative values to represent the loss of mass from the water column. When the Net Release/Retention term is positive (above the x-axis), then this indicates a net gain (release) of mass in the water column from the sediment (or air for TN); negative values below the x-axis indicate a net loss (retention) from the water column to the sediment (or air for TN).

The annual volumes, for example, show that total net inflows are roughly balanced by outflows with relatively little change in storage as the lake generally maintains a constant volume over the long term. The annual TP loads, however, show alternating patterns of net release (positive values) and net retention (negative values) as the lake sediments release and retain TP in varying amounts each year (see Nutrient Cycling section for more details).

💡 Chart Tips

• Hide a term on any chart by clicking on it in the legend.
• On monthly timeseries, click-and-drag or use the scroll wheel to zoom in and out.

Annual Timeseries

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Monthly Timeseries

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To better understand the seasonal cycles of each mass balance term, the seasonality plots show the monthly value for each water year (Oct to Sep), as well as the long-term mean monthly values. The lake Storage, for example, generally has the highest volumes in April and May, while the highest TP loads and concentrations for lake Storage occur in July and August. The seasonality of the storage TP is driven by a large release of TP during June and July as shown by large positive values of the Net Release/Retention term, which switches direction to become negative in August and September as the algal biomass settles out of the water column.

Seasonality Plots

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Term: