WASTES IX RELATION TO AGRICULTURE AND FORESTRY 



69 



oxidation in a ditch. Promising reports on adapt- 

 ing this system for animal wastes have ap- 

 peared, even though animal wastes are much more 

 concentrated than sewage effluent. 



The Georgia and Ohio stations are investigat- 

 ing the treatment of poultry manure-litter with 

 micro-organisms. The treatment permits birds to 

 be replaced on the same litter and provides an 

 odor-free and fly-free environment. 



Dilution of Organic Wastes in Streams 



The adverse effects of animal wastes, sewage, 

 and processing wastes moving into streams are 

 conditioned by the flow of the stream. Consider 

 the Connecticut River. Average annual flow of 

 this river at Hartford is 10.4 billion gallons per 

 day. During September and October 1930, the 

 river reached a low flow of 1.9 billion gallons per 

 day; and the maximum was 207 billion gallons 

 per day in March 1936. Let us assume that organic 

 wastes from sewage, industry, and agriculture 

 dumped into this river in the Springfield-Hartford 

 area is equivalent in biochemical oxygen demand 

 (BOD) to that from the raw sewage of a popu- 

 lation of 3 million people. That is, it is assumed 

 that the daily BOD load dumped into the river is 

 500,000 pounds. 



Under average annual flow of the Connecticut, 

 the added wastes would induce a BOD in the 

 stream of 6 p.p.m. (Water with 5 p.p.m. BOD is 

 considered to be on the verge of pollution.) Under 

 ow flows such as occurred in late summer of 1930 

 and 1966, the specified waste load would induce a 

 BOD of 31 p.p.m. Under a spring flow of 65 bil- 

 lion gallons per day, this waste load would induce 

 a BOD of 1 p.pm. (Water at 1 p.p.m. BOD is 

 considered relatively pure.) 



The flow of the Connecticut is relatively stable. 

 But consider the Bad River in southwestern South 

 Dakota. This stream drains a watershed of 3,107 

 square miles and has an average daily flow of 114 

 million gallons per day. The Bad is dry 3 or 4 

 months every year. Peak flow has been recorded at 

 1.9 billion gallons of water a day. There is high 

 variability in the amount of organic wastes that 

 a stream such as the Bad could assimilate. 



Engineers concerned with assimilation of wastes 

 in streams are interested in minimizing degree and 

 duration of low flows. Research and development 

 programs on watershed management in the U.S. 

 Department of Agriculture and land-grant uni- 



versities are directly related to nature of stream- 

 flow. 



Foresters have been interested in the relation of 

 forested watersheds to streamflow for over 100 

 years. A commission appointed by the Wisconsin 

 State Legislature in 1867 pointed out the relation- 

 ship between forest cover and streamflow. The 

 American Forestry Congress in 1886 adopted a 

 resolution relating to the management of public 

 lands "with a view to maintaining and preserving 

 a full supply of water in all rivers and stream-." 

 Research in the National forests pertaining to 

 water yield began in Colorado in 1910. It became 

 immediately evident that reductions in forest 

 cover brought about increased total streamflow 

 because of reduced transpiration and increased 

 interception of precipitation at the ground sur- 

 face. More recent research separating water yield 

 into seasonal parts indicates the highest percent- 

 age increase from reduced cover occurs during the 

 normally low-flow season. A moderate level of 

 research relating forest cover to water yield is in 

 progress in most of the major climatic and vegeta- 

 tion zones. 



In the Rocky Mountains of Colorado, studies 

 have shown that removal of half the lodgepole 

 pine-spruce-fir forest by strip and block cutting 

 from a watershed in the snow zone produced about 

 a 25-percent increase in total annual streamflow. 

 Most of this increase came mainly during the 

 spring freshet, but streamflow was also found to 

 be higher during the summer and autumn follow- 

 ing treatment. 



Cutting woody vegetation in the mountains of 

 southern California produced an annual water 

 yield of 1.3 acre-feet per acre of riparian areas, and 

 0.11 acre-feet per acre of upland deep soils. In both 

 cases, the streams, which had formerly dried up in 

 the summer and fall, flowed continuously after 

 treatment. 



At the Coweeta Hydrologic Laboratory in North 

 Carolina, water yield increased 17 acre-inches 

 aero during the (irsr year after all trees and shrubs 

 had been cut. Maintenance of clear-cut conditions 

 su-tained an increase of 11 acre-inches in water 

 yield from the experimental watershed for more 

 than L5 years. 



Clear-cutting the mature hardwood cover 

 watershed at the Femora Experimental F 

 West Virginia decreased the annual number of 



