Task: Question Answering
Input (English): Background Paragraph: The water level is seasonal, being lowered by about 10 feet (3.0 m) over the winter. The reservoir fills in the spring from snow melt and underground springs. The lake is usually at full level by late spring, but in the occasional years of low snow melt and low rainfall, it may remain up to several feet below its typical level. Water is let out of the lake in the fall so that ice will not damage docks and other structures around the lake. This also leads to excellent water quality, as a significant portion of the water is replaced every year. 
Story: Alpine lake had low water levels this spring although the lake is usually at full level by late spring. Last year was a very wet year with lots of precipitation. Rangers were planning on letting water out of the lake in the fall so that ice will not damage docks and other structures around the lake. The water levels were high enough in the fall so they proceeded in lowering the water level by 10 feet.. 
Question: When is the water quality better, during spring, or during fall?
Output (English): during spring.