No abstract

An analytical model is developed for the transverse diffusion of solutes from steady sources placed in a natural stream with steady discharge. In theoretical derivations, the steady-state convective diffusion equation for a natural stream is convertEd into an approximate equation suitable for analytical treatment by the introduction of cumulative partial discharge as an independent variable. Analytical solutions for the latter equation are obtained for point and line source injections of solutes. The validity of the model is tested using data from four natural streams, three of which are alined straight, while one has mild curves. The verification was satisfactory for the three straight channels, and the constant in Elder's formula for the transverse diffusion coefficient ranged from 0.2 to 0.3. In the curved channel, the model appears workable, but an increase of the diffusion coefficient in the downstream direction is observed. The applications to stream problems are discussed in the final section. The model may be employed for the description and prediction of thermal and other waste disposal problems, simulation studies by tracers, and the determination of transverse diffusion coefficient. Another use of the model, the estimation of mixing distances, is explained and demonstrated using the data of the Water Research Association, England.

No abstract

The United States is undergoing a dramatic growth of population and demands on its natural resources. The effects are widespread and often produce significant alterations of the environment. The hydrologic benchmark network was established to provide data on stream basins which are little affected by these changes. The network is made up of selected stream basins which are not expected to be significantly altered by man. Data obtained from these basins can be used to document natural changes in hydrologic characteristics with time, to provide a better understanding of the hydrologic structure of natural basins, and to provide a comparative base for studying the effects of man on the hydrologic environment. There are 57 benchmark basins in 37 States. These basins are in areas having a wide variety of climate and topography. The benchmark basins and the types of data collected in the basins are described. 1. BLACKWATER RIVER NEAR BRADLEY, ALA. (02369800) Location. About 50 miles inland from the Gulf of Mexico, south-central Alabama. Drainage area. 86.8 sq mi. Physiographic area. East Gulf Coastal Plain section of the Coastal Plain province of the Atlantic Plain. Climate. Average annual precipitation: about 61 in. Monthly mean temperature extremes: 52°and81°F. Topography. The uplands are gently rolling ridges which are somewhat broken in the central part of the basin. A few sinks and depressions are scattered in the eastern basin area. Basin elevations range from 125 to 300 ft. Rock type. Clay, sandy clay, sand, gravel, and sandstone. Vegetation. About 90 percent of the basin is covered by pine and hardwood forest. The remainder is in pasture and row crops. The upland forest is predominantly longleaf pine, and there is a dense wiregrass ground cover. The lowland forest is about 90 percent pine and 10 percent bay hardwood; the undergrowth is dense. Manmade influences. About 60 percent of the basin is publicly owned. Sections of this land are subject to being logged every 10 years. Extensive erosion control is practiced. The remaining 40 percent is 70 percent forest and 30 percent pasture and cultivation. Not more than 10 percent of the privately owned forests are normally cut in any one year. The land in row crops may produce unproportionately high sediment yields. Three small communities are within the basin. Gage location. Lat 31°01'45", long 86°42' 35", in SWi/4 sec. 24, T. 1 N., R. 25 W., 1.2 miles southeast of Bradley. Flow characteristics. Stream is perennial. Average annual runoff: about 23 in. Water quality. No information. Ground water. Water-table conditions prevail. Small to moderate quantities of water are yielded to domestic wells. Springs and seeps occur in the lower basin. Data collected. Type Period of record Low-flow streamflow measurements at 36 sites in the basin _ Various times. Continuous streamflow _____December 1967-present. Groundwater levels (intermittent observations in three wells) __________December 1968-present. Continuous precipitation ___December 1967-present. Type Period of record Cont...

No abstract