26 Artificial Aquatic Habitats 



demonstrated by transferring water from one pond into another by a 

 large pump. The pond from which water is being pumped may drop 

 several feet and the other pond rise in proportion, but if the pump is 

 stopped, water will seep out of the high pond and into the low one, so 

 that within a very short time both will again be at ground water level. 



Since levels in gravel pits fluctuate from one to three feet during most 

 years, this annual fluctuation should be taken into consideration when 

 bottom contours are being planned. The exposure of large areas of the 

 bottom, as a result of normal annual fluctuation, is unsightly and may be 

 avoided if the more shallow areas are deepened. 



Where gravel beds are extensive, gravel digging operations can be 

 planned to create areas of open water up to four or five acres, or to create 

 relatively narrow meandering channels. Once the spoil banks have become 

 vegetated with trees, shrubs and herbaceous plants, the channel arrange- 

 ment is more attractive to anglers than is a large area of open water. 



Gravel-pit ponds are thermally stratified in summer because they are 

 surrounded by high lands that reduce the wind action on the water. 



Stripmine Lakes 



Stripmine lakes result from the flooding of surface excavations after the 

 removal of coal deposits. Layers of coal may vary in depth below the 

 surface, and stripmining equipment can operate at a profit on deposits as 

 deep as 50 to 90 feet. Before the coal can be stripped, the top soil and 

 clay overburden must be removed. This operation is done with giant 

 cranes supplied with digging buckets which pile the waste material in 

 long ridges running parallel to the cuts they are making. As the coal in 

 each cut is exliausted, the crane moves over to dig a new cut parallel to 

 the other one, and the material from the new strip is piled into or along 

 the previously exhausted excavation. Thus, strip mining actually turns 

 land upside down (because the topsoil is buried under the clay over- 

 burden ) and leaves an area of land as a series of long parallel ridges many 

 feet high. In some stripped areas, water collects in the valleys between 

 these ridges and forms long narrow lakes usually connected to similar 

 lakes between other ridges by channels. The last "cut" or strip that the 

 crane makes before abandoning an area is not filled in and may form 

 a lake several hundred feet wide, as deep as 60 feet, and a mile or more 

 long, depending upon the size of the stripped area, the depth of the coal, 

 and the lengths of the booms of the stripping cranes. 



Coal deposits are associated with deposits of sulfur, iron, and other 

 minerals. When the abandoned mines are flooded, these dissolved minerals 

 often make the mine ponds too acid to provide a habitat for aquatic 

 organisms.-- However, ponds become less acid with age; the sulfuric 

 acid buffered with calcium from limestone deposits and other carbonates, 



