The lake is relatively shallow, with an average depth of and only at its deepest point near the dam at the west end of the lake. The eastern end is the shallowest where the River Yeo enters. It is a hard water area with high mineral content that is vulnerable to eutrophication in the summer, that can cause algal blooms, with transient water layers. As a result, a research programme has been established to observe and measure the limnology of the lake. When full it contains and supplies of water each year. Water can also be taken from its larger neighbour Chew Valley Lake to balance the supply.
