Laserfiche WebLink
<br />APPENDIX C <br /> <br />Reservoir Preparation, Maintenance, and Water Level Management <br />in Relation to Mosquito Prevention and Control <br /> <br />Man-made impoundments range in size from large multipurpose <br />reservoirs with thousands of acres to small farm ponds of less than <br />an acre. Mosquito-producing conditions associated with both large <br />and small impoundments are basically similar but vary greatly in <br />magnitude. They include emergent vegetation and/or floating debris <br />in shallow water areas which are protected from wave action; undrained <br />depressions, borrow pits, sloughs, and marshes within the summer <br />fluctuation zone; and rising or constant pool levels which cause the <br />water to rewain in relatively flat areas with vegetation for more <br />than four or five consecutive days during the mosquito production <br />season. Several species of Anopheles and Culex mosquitoes, inc1udi1l8 <br />Culex tarsalis, are frequently produced in impoundments that have <br />protected shallow water areas with emergent vegetation and/or flotage. <br />The flat vegetated areas of reservoirs and ponds, which are alternately <br />inundated and exposed by fluctuating water levels, may also be highly <br />favorable for the production of several species of Aedes and Psorophora <br />mosquitoes. Aedes vexans is one of the most common and widespread of <br />these species. It is almost axiomatic that reservoirs and ponds which <br />are free of vegetation and flotage do not produce mosquitoes. <br /> <br />It is often difficult to control mosquito production on a reser- <br />voir that has not been properly prepared prior to impoundage. Clear- <br />ing and drainage are the principal reservoir preparation measures for <br />mosquito prevention and control. The overall objective of these <br />measures is to prevent or minimize the development of favorable <br />mosquito-producing habitats in any portion of the reservoir which is <br />within flight range of human population. <br /> <br />Clearing includes removal of trees, underbrush, vines, fences, <br />and debris from the reservoir basin. For mosquito control purposes, <br />the normal summer fluctuation zone should be completely cleared <br />except for isolated trees and sparse vegetation located along abrupt <br />shorelines that will be exposed to wave action. It is not necessary <br />to clear timber from the deeper portions of the reservoir basin where <br />it will be completely submerged at normal summer minimum pool elevation. <br />Timber rooted below the normal summer minimum pool level but extending <br />above that elevation way be felled and securely tied down in lieu of <br />disposal. This practice sometimes has advantages in fisheries manage- <br />ment. Where clearing operations extend over several seasons, it is <br />sometimes necessary to remove regrowth from the normal summer fluctua- <br />tion zone immediately prior to impoundage. <br /> <br />C-l <br />