40 60 



Plant Cover in Percent 



Intro, fig. 45. Relationship between intersection line and 

 production of eggs and larvae of Anopheles quadrimaculatus 

 (Malaria Control on Impounded Wafer, 1947). 



(acreage to be cleared, density, predominating species, 

 and tolerance to flooding); soil conditions and types; 

 and the existence, location, and extent of marginal 



31 



Usinger: Introduction 



and aquatic plants. Shore-line plant* DM) l>e classified 

 into ecological ty] was done bj lie- and H 



1945, for the southeastern United States) (intra. 

 43) and then rated m terms of intersection Line (air- 

 water-plant-intorfaco) values (Hess and Hall, 

 (p. 5, intro. fig. 5). An accompanying figure (intra. 

 fig. 44) shows the relative intersection value 

 each of the ecological types (woods, coppice, etc.) 

 and gives the production in terms of eastern Anop 

 quadrimaculatus larvae por square foot. The correla- 

 tion between intersection line and numbers of i 

 and larvae is shown (intro. fig. 45). 



From the above, it is evident that marginal vegeta- 

 tion is of primary importance to Anopheles mosqmio 

 production. It also influences other aquatic insects. 

 Therefore, shore-line filling (intro. fig. 46) and clear- 

 ing (intro. fig. 47) are essential operations both during 

 the preparation of a reservoir and after the water has 

 been impounded. On surveys it is useful to try to 

 estimate the cost of such operations by dividing the 

 reservoir into areas classified according to type of 

 shore line. 



3. Water level schedules are of great importance 

 in reservoir management. They not only affect the_ 



DEEPENING AND FILLING 



SPOIL BANK LEVELING AND FILLING 



?-^#/ ( ^^j;ut_J^,) N %^ ^ait J 



rr*T im~ i.t te? . r TT 



■|'I MM ' mM ' r TTTr^r<^TTTTTTTTrrTM'l'iwvMMMMnnTT»f*V*r^ 



CLEARING OF BIGHIS AND INDENTATIONS 



LTPPER LIMITS Of CLEARING 



" I||il .i .1.1,1. 



1 1 1 1 , 1,1 . 1 1 1 .y v ' ■ ' ■ ' ' 



/ <* 



•0 



••© 



SPOIL BANK SPREADING 



SELECTIVE CLEARING 



F Brush and Debris f ^ 



R.rnonl Lmils^lCa^JvJ^Y^ cie.r.n. 1Mb 



CLEARING IN EXTREMELY FLAT AREAS 



UNAL RECONDITIONING 



Spoil Bank Spread 

 Toward Margin 



LOW STUMPING 



MARGINAL DRAINAGE 



Intro, fig. 46. Filling operations used in preparing reservoirs 

 of the Tennessee Valley Authority (Malaria Control on Impounded 

 Water. 1947). 



Intro, fig. 47. Clearing operations as used in preparing reser- 

 voirs of the Tennessee Valley Authority (Malaria Control on 

 Impounded Water, 1947). 



