During the spring snowmelt, these high-elevation hydro projects operate at full load around the clock; any river flow in excess of the powerhouse capacity must be spilled (bypassed) and becomes wasted energy. The irrigation districts and PG&E must coordinate operations at the reservoirs and powerhouses to maximize both water storage and power production. In late summer and autumn, river flows are lower and the power plants are typically only operated several hours a day, on a peaking basis. The 300 megawatt New Melones Dam power station, which replaced the old Melones powerhouse in 1978, is also operated on a peaking schedule. The result is often wildly fluctuating water levels along the dam-controlled segments of these rivers. Tulloch Dam, located directly below New Melones, serves to re-regulate the river flow and ensure a consistent water level in the lower portion of the Stanislaus River.