76 LIMNOLOGY, WATER SUPPLY AND WASTE DISPOSAL 



continues until the advent of the autumn rains. 



During the summer of 1937, Mr. Charles P. Hoover, Chief Chemist 

 for the Columbus City Division of Water, asked me to carry out some sort 

 of an algal survey for the Department. This type of work was new to 

 me at the time, but I felt that a weekly survey for one year would 

 be valuable as a base plan. The samples were taken at Griggs Reservoir 

 and proved their worth because we found the winter months to be 

 especially unproductive. Little beyond sporadic sampling was done 

 during the summers of 1938, '39, '40, and '41. These fortunately did not 

 show any serious algal problems. I say fortunately because such occasional 

 sampling would have been of little value if a "bloom" of some particularly 

 bad alga had started. It was not until the spring of 1942 that we went on 

 a basis of regular samples beginning with the clearing of spring turbidity 

 and extending to the period of fall turbidity, or of periods of low temper- 

 ature and overcast sky. We are very fortunate (algologically speaking) 

 in having spring and fall turbidity as it reduces our danger period to 

 about four months, July to November. Two stations were established at 

 Griggs Reservoir, one near the Dam crest, and one about 300 yards above. 

 Two stations were established at O'Shaughnessy and two more about two 

 miles farther north. The four stations above O'Shaughnessy Dam fulfilled 

 a dual purpose. They were located so as to check the possible influence of 

 sewage effluent on plankton production and as a warning of what we might 

 expect down river at Griggs Reservoir. 



Next in importance was the method of collecting. Consideration of 

 this factor was definitely colored by the needs and desires of those in 

 charge of the Water Plant. Should the collections be extremely accurate, 

 should they show absolute total plankton, should counts be in standard 

 units, or would fairly accurate quantitative counts be satisfactory. The 

 judgment that the Algologist exercises here will determine to a great extent 

 what the Chemist will later consider success or failure. Furthermore, to 

 be perfectly frank, here is where the problem of relative cost enters, if this 

 is a problem. For a trial period we took each sample by putting 25 gallons 

 of river water through a Number 20 Bolting Silk Plankton Net. This 

 sample was made up to 50 cc during preservation and then standard pro- 

 cedures used to effect a count, although the "Standard Unit" was not 

 adopted. The advantages are that it requires a minimum of equipment, 

 that most any of the Water Plant personnel can be readily trained to make 

 the collections, and also that all organisms of any considerable size are 

 retained. A few of the very small organisms do go through but these 

 as far as we know have little effect on the water. 



Counts of the organisms in these samples are made and the results 

 translated directly into organisms per gallon of raw river water. Where 

 random samples through the summer would have little value, these weekly 

 samples present an integrated picture of the plankton concentrations of 

 any one station. All that is now necessary is for the algologist to analyze 

 them on the basis of particular genera present or upon the basis of total 



