Instream Uses 



Not all uses require removing water from its source. 

 Many uses depend on the amount of water that 

 remains in the water course itself. These include 

 hydroelectric power generation, navigation, water- 

 based recreation, and flow requirement for aquatic 

 habitat. 



In 1975, hydroelectric power supplied approx- 

 imately 15 percent of the total national electric power 

 production. Conventional hydroelectric plants are 

 projected to generate only about 6 percent more 

 electricity in 2000 than in 1975. However, as alter- 

 native costs increase, hydropower generation may be 

 viewed with increasing interest. Hydroelectric power 

 plants produce power without consuming fossil fuels, 

 without polluting water or air, and without creating 

 possible radiation hazards. These plants have long 

 lives, low operating costs, and low outage rates. 

 Two disadvantages are the high construction costs 

 and potential interruption of free-flowing streams. 



The Nation's rivers and lakes have served as avenues 

 for public and commodity transportation from the 

 time of the earliest inhabitants. Since about 1770, 

 the extent and capacity of inland and intracoastal 

 waterway systems have continually increased to the 



point where they now include more than 25,000 

 miles of navigable channels, canals, and reservoirs. 



Total domestic waterborne traffic increased from 

 829 million tons in 1965 to about 1,000 milUon 

 tons in 1974. By the year 2000, about 1,500 miUion 

 tons are expected. Almost all of this will be bulk 

 goods, such as coal, grain, crude oil, and other 

 petroleum products. In 1974, waterborne commerce 

 was about one-fourth of the total intercity freight 

 measured in ton miles. 



Streamflows are also needed to support outdoor 

 recreation activities and fishery habitats for commer- 

 cial fisheries. A discussion of flows and flow require- 

 ments at the national, or even regional level, tends 

 to obscure water problems that might surface from 

 analyses in local areas. For example, it has been 

 computed that nationally flows of 1,040 billion 

 gallons a day would be ideal to support fishery 

 requirements. The average national flow is 1,242 

 billion gallons a day. Unfortunately, not all regions 

 and subregions share equally in the average annual 

 flow. 



In a subsequent section of this chapter, the ade- 

 quacy of supplies to support fisheries will be analyzed 

 in terms of a depletion analysis. The criteria for this 

 analysis will also be discussed. 



Bulky products such as oil, coal, wheat, and chemicals are efficiently transported on waterways. 



286 



