French Lake Reservoir is a reservoir in Nevada County, California. The earthen, rock-fill French Lake Dam was first constructed in 1859, and is a candidate for the first use of rock-fill in an engineered dam. Reconstructed in 1948, it impounds Canyon Creek for flood control, irrigation water storage, municipal drinking water, and hydropower. The dam is 100 f…French Lake Reservoir is a reservoir in Nevada County, California. The earthen, rock-fill French Lake Dam was first constructed in 1859, and is a candidate for the first use of rock-fill in an engineered dam. Reconstructed in 1948, it impounds Canyon Creek for flood control, irrigation water storage, municipal drinking water, and hydropower. The dam is 100 feet high, with a length of 300 feet at its crest. It is one of ten facilities operated by Nevada Irrigation District.