70 



MISCELLANEOUS PUBLICATION NO. 10 65, U.S. DEPARTMENT OF AGRICULTURE 



low-flow days (less than 50 gallons per acre per 

 day) from 79 to 24 during the 4 years following 

 cutting. More recent clear-cuttings increased water 

 yield 6 inches in the 1965 growing season — by far 

 the driest growing season of record. Attaining this 

 increase during a drought is remarkable. 



One-third of the United States is forested. These 

 forests, with associated range and alpine areas, 

 yield about three-fourths of the Nation's stream- 

 flow. More than any other lands, the management 

 of our forests is important to the quality and 

 quantity of water. Research results indicate that 

 if studies are continued and improved watershed 

 practices are applied to suitable areas, the amount 

 of high-quality usable water available to the Na- 

 tion can be increased by 14 million acre-feet annu- 

 ally. Such a bounty would exceed the average an- 

 nual flow of the Connecticut River, 11.5 million 

 acre-feet, and approach that of the Colorado 

 River, 15 million acre- feet. Cost of producing this 

 extra water from forest lands is expected to be 

 about $10 per acre-foot — 3 cents per 1,000 gallons. 



Replacing forest with grass may not increase 

 water yield. Research at the Coweeta Ilydrologic 

 Laboratory showed that establishing well-fertil- 

 ized grass in place of forest produced no increase 

 in streamflow. "With loss in fertility and resulting 

 poorer grass production, streamflow increased 

 slightly. 



At the Coshocton Hydrologic Field Station in 

 Ohio, establishing a farm woodlot on a 44-acre 

 watershed reduced water yield. By the 19th year 

 after the trees were planted, runoff was 5.32 inches 

 below what it would have been had it not been 

 forested. This finding is the inverse of the results 

 for clear-cutting forests. 



Estimates (40) indicate that phreatophytes 

 (deep-rooted, water-loving plants growing in 

 flood plains) nonbeneficially use some 25 million 

 acre-feet of water annually from the subsurface 

 flow of the streams in the Western United States. 



Cooperative research involving the U.S. Depart- 

 ment of Agriculture, the Bureau of Reclamation, 

 and the Arizona, New Mexico, and Wyoming agri- 

 cultural experiment stations is underway to de- 

 velop economical methods of eliminating phreato- 

 phytes. Salt cedar is one of the worst pests among 

 phreatophytes. Studies indicate that applications 

 of 2,4-D and 2,4,5-T will kill a high percentage 

 of the top growth, but regrowth from the roots 



takes place [111). Research indicates that a more 

 effective chemical method of controlling these 

 plants is urgently needed. 



Forestry research pertaining to the abatement 

 of wild forest fires is important in the modulation 

 and continuity of flow of streams arising in forests. 

 When the surface mulch of the forest floor is 

 burned, rate of infiltration of rainfall and absorp- 

 tive capacity of the soil is greatly impaired. Run- 

 off during the storm becomes excessive, and re- 

 serve moisture in the burned-over soil is propor- 

 tionally lessened. 



A forest fire started near Yucaipa, Calif., on 

 July 4, 1950, and burned some 650 acres of chap- 

 paral-covered foothills. On July 6, while mopup 

 crews were still on the fire, an intensive thunder- 

 shower dumped three-fourths of an inch of rain 

 over the burned and surrounding area. The high 

 runoff from the burned area caused a flood that 

 blocked roads, yet little or no water flowed from 

 adjacent unburned areas. 



On a burn, snow cover melts faster during spring 

 than it does under forest trees. This impairs modu- 

 lation of streamflow. Also, frost will penetrate 

 into the soil of a burn and thereby accentuate run- 

 off. For example, at the Hubbard Brook Experi- 

 mental Forest in New Hampshire, the soil seldom 

 freezes in the deep forest, whereas the soil on a 

 burn would freeze. 



The importance of improved technology on 

 watershed protection for modulation of stream- 

 flow is indicated by the fact that preliminary jflans 

 for a program for cleaning up the Potomac River 

 include costly structures to be installed primarily 

 to avert low flows. 



Plant Residues on Farms and Ranches 



Farm wastes coming under the category of plant 

 residues do have uses: bedding for poultry and 

 livestock; mulch; soil organic matter; a small 

 amount in ensilage; and some use in manufacture 

 of corrugated cartons, insulating boards, etc. By 

 far the greatest use is as a mulch. 



Spreading plant residues over the ground has 

 been referred to in English as "mulching" since 

 1802. Horticulturists have long been interested in 

 this use of plant residues. In the early years of this 

 century, the preferred culture of apple orchards in 

 New England was that of using a deep mulch un- 

 der each tree. Use of stubble mulching for erosion 

 control and economy of operation was attempted 



