St. Johns:The amazing on again, off again river

I live about 10 minutes walk from the Saint Johns river here in Visalia, California. There is a well maintained walking/biking trail that follows the river for quite a ways. I walk it at least every other day if possible. Its one of my favorite areas because its semi-wild in the sense there are no structures and the plant life is pretty much left alone. Also, there is a dirt trail close to the river and you can avoid any people or bike traffic on the paved trail. The river runs west out of the Sierra Nevada mountains and then swings north towards the Pacific ocean. The amazing thing is, the powers that be, Central Valley Project Water Association., can turn the river on and off at will. The river is now controlled by the Terminus damn at lake Kaweah which is in the foothills just west of Three Rivers and Sequoia National Park. By shutting a gate, the river can be left to dry up. Amazing. The river only runs a few feet deep at the most and feeds a lot of agricultural land with irrigation pumps here and there along its length. Earlier this year it was running full bore and this was due to last winters record snow fall in the mountains. About a month ago the river was "turned off" and within less than a week a person could walk the whole length without getting the soles of your shoes wet. They've since turned it back on and its running at about a 10th of its capacity. I think the recent snow and rain in the mountains has made the lake level high enough that they can do this. When I first walked the dry river bottom I was appalled at the loss of life. Thousands of dead minnows, catfish fingerlings, frogs and millions upon millions of clams. Most of the clams are in the 1/8" to 1/4" range. The smell was pretty intense. There was the occasional crawdad remains but very few of them. I found out that they burrow way down into the sand when the river is shut down. Yesterday I saw a few huge ones in the shallow water munching on some plant life. I think the clams and fish are released from the lake in the spring. The clam obviously as eggs or larva. I did see a large flock of great egrets and some other water birds taking advantage of the receding waters when they turned off the river. At least some of the aquatic life wasn't wasted.