156 Theories and Techniques of Management 



Figure 6.9. Aerial view of fall drawdown shows lake area reduced by more 

 than 50 per cent. 



from nature where water levels are rarely stable, but are usually in a 

 state of fluctuation, often mild, but sometimes very severe during floods. 

 Flood-plain lakes in the valleys of rivers are subject to the rivers' fluctua- 

 tions and, because these lakes are relatively shallow, these fluctuations 

 may cause extreme changes in the surface areas of these lakes. 



Prior to 1920, changes in water levels similar to those described above 



