Water Balance of Lakes

Description

The most basic in river basin hydrology is the water balance – and so it is for lakes. Most lakes have outflows, but some of the most famous lakes of the world are terminal lakes with no outflow, for example, the Caspian Sea, Lake Chad, and the Dead Sea. The water level in the overflowing lakes is rather stable, while the water level in the terminal lakes varies with the climate. In some lakes with small upstream catchment, the inflow to the lake is dominated by the precipitation on the lake, but usually inflow rivers are the dominating source of inflow to a lake. Some lakes only have subsurface inflow, but in most lakes, the most important inflow is from rivers. There also exist kettle lakes, which are part of the groundwater system with only subsurface inflow and outflow.

The water balance of a lake is

$$\begin{array}{lll} \frac{{dVOl}}{{dt}} & = A(h)\frac{{dh}}{{dt}}\\ & = {Q_{\rm{in}}} - {Q_{\rm{out}}}(h) + {Q_{\rm{gwin}}} -{Q_{\rm{gwout}}} + (P - E)\,A(h) \end{array}$$

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