Pena Blanca Lake water quality issues return
Water quality issues at Pena Blanca have returned once again and the Department is forced to suspend winter trout stockings until conditions improve. Rainbow Trout originally scheduled to be stocked at Pena Blanca Lake will now be redirected to Parker Canyon Lake. The lack of dissolved oxygen that has afflicted the lake the last several years during the fall and early winter months is thought to be caused by a natural process known as lake turnover. Lake turnover is the process of a lake’s water turning over from top (epilimnion) to bottom (hypolimnion). During the summer, the epilimnion, or surface layer, is the warmest due to heating by the sun. The deepest layer, the hypolimnion, where sunlight doesn’t penetrate is the coldest. During the fall, the warm surface water begins to cool. As water cools, it becomes more dense, causing it to sink. This dense water forces the water of the hypolimnion to rise, “turning over” the layers. Shallow lakes experience very little turnover while deeper lakes experience major differences as water of different temperatures mix.
Historically, lake turnover at Pena Blanca Lake has occurred in October; however now that the lake is much deeper than it was prior to the completion of the renovation that time frame has shifted and lake turnover is now occurring much later in the year and water quality conditions during the process have been much more severe. For more information on the winter trout stocking program and the stocking schedule: https://www.azgfd.com/fishing/stockschedule/