Lake Management Plan
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Questions? |
8.0.4 Inlets and Outlets
By combining the loading and concentration of the Inlets and comparing them to the outlet, the chemical nature of the lake is revealed.
The inlets for Pelican Lakes are Bob Creek, Duck Lake, Spring Creek, and the Pelican River Inlet. The only outlet is the Pelican River Outlet.
Total inlet/outlet loading is calculated by taking the sums of the inlets/outlet. The total inlet/outlet concentration is what the concentration of the substance would be if the flow of the inlets/outlet where combined. Concentration is calculated by taking the sum of the Mass Flow Rates divided by the Total Flow. The mass flow rate is the sites concentration multiplied by the sites flow, and the total flow is the sum of the inlets/outlet flow.
Flow
The combined flow from the inlets mirrors the outlet flow (see figure below). This result is expected, and means that most of the water that is flowing into the PGOLID lakes is flowing back out. The peaks in flow correspond to spring thaw and usually occur in May-June.
Total Phosphorus
The total phosphorus loading is calculated by taking into account both the phosphorus concentration in the water and the volume of flow passing through a certain area. In streams, phosphorus loading is a better indicator for water quality than phosphorus concentration. A stream with high phosphorus concentration that is just a trickle of water could be depositing less phosphorus into a lake than a stream with low phosphorus concentration and high flow.
The combined phosphorus loading from the inlets mirrors the phosphorus loading at the outlet. As pulses of phosphorus enter the PGOLID lakes, much of that phosphorus exits back out of the system. A portion of the phosphorus stays in the lake and gets taken up by plants and algae. If all the phosphorus was staying in the lake and not flowing back out, it would be a problem and would contribute to the lake getting greener with more plants and algae.
The peaks in phosphorus loading correspond with the peaks in flow (see figure below). These peaks occur in the spring (April-June) as spring thaw and rains contribute to higher water levels.
