Laserfiche WebLink
<br />48 <br /> <br /> <br />001839 <br /> <br />influencing the rate is. evaporation is air turbulence. Aligning the long <br /> <br />dimensions of the pond north-south will reduce solar radiation on the <br /> <br />water surface and should reduce evaporation losses. <br /> <br />A striking example of apparent savings resulting from wind insul- <br /> <br />ation is represented by the so-called-"charco" pits constructed in <br /> <br />recent years by the Bureau of Indian AHairs and other agencies. These <br /> <br />are oH-stream ponds constructed in the form of an inverted cone with <br /> <br />. a depth ranging from 15 to 2.5 feet. Excavated material is piled around <br /> <br />the periphery making a dike some 4 to 7 feet high, which keeps the <br /> <br />wind currents well above the water surface. Water enters the pond <br />. <br /> <br />through a pipe placed under the dike. Observations on these charcos <br /> <br />show that invariably they hold water much longer than ponds of similar <br /> <br />depth constructed in conventional manner; in fact,' once the charcos <br /> <br />are filled, they seldom go dry. A part of the savings may be attribut- <br /> <br />. <br /> <br />able to reduced seepage los s although in areas underlain by dense <br /> <br />shale where seepage losses are known to be minimal, the recession <br /> <br />in the charcos is decidedly less than in other types of stock ponds, <br /> <br />indicating that evaporation losses are lower. <br /> <br />Another example of reduced evaporation attributable to favor- <br /> <br />able construction methods was observed in the Squaw Butte experi- <br /> <br />mental area in eastern Oregon. This area contains a number of <br /> <br />trench type charcos located in small playas containing dense volcanic <br />