Call Holman Services beavers- we just helped build a steel building next to this dam built by Holman Services in Cow Creek. It was interesting so we figured we would share. This is located near Marble Falls, Texas and Lago Vista. Why would you ever build a dam? Well dams and their reservoirs provide recreation areas for fishing and boating. They help people by reducing or preventing floods. During times of excess water flow, dams store water in the reservoir; then they release water during times of low flow, when natural flows are inadequate to meet water demand.