Laserfiche WebLink
<br /> <br />Urban and Industrial Development <br /> <br />Point sources of contamination to surface- <br />water bodies are an expected side effect of urban <br />development. Examples of point sources include <br />direct discharges from sewage-treatment plants, <br />industrial facilities, and stormwater drains. These <br />facilities and structures commonly add sufficient <br />loads of a variety of contaminants to streams to <br />strongly affect the quality of the stream for long <br />distances downstream. Depending on relative <br />flow magnitudes of the point source and of the <br />stream, discharge from a point source such as a <br />sewage-treatment plant may represent a large <br />percentage of the water in the stream directly <br />downstream from the source. Contaminants in <br />streams can easily affect ground-water quality, <br />especially where streams normally seep to ground <br />water, where ground-water withdrawals induce <br />seepage from the stream, and where floods cause <br />stream water to become bank storage. <br />Point sources of contamination to ground <br />water can include septic tanks, fluid storage tanks, <br />landfills, and industrial lagoons. If a contaminant <br />is soluble in water and reaches the water table, <br />the contaminant will be transported by the slowly <br />moving ground water. If the source continues to <br />supply the contaminant over a period of time, <br />the distribution of the dissolved contaminant <br />will take a characteristic "plumelike" shape (see <br />Box M). These contaminant plumes commonly <br />discharge into a nearby surface-water body. If <br /> <br />the concentration of contaminant is low and the <br />rate of discharge of plume water also is small rela- <br />tive to the volume of the receiving surface-water <br />body, the discharging contaminant plume will <br />have only a small, or perhaps unmeasurable, <br />effect on the quality of the receiving surface-water <br />body. Furthermore, biogeochemical processes <br />may decrease the concentration of the contaminant <br />as it is transported through the shallow ground- <br />water system and the hyporheic zone. On the <br />other hand, if the discharge of the contaminant <br />plume is large or has high concentrations of <br />contaminant, it could significantly affect the <br />quality of the receiving surface-water body. <br /> <br /> <br /> <br />Point source of urban runoff to surface water in <br />Indiana. (Photograph by Charles Crawford.) <br /> <br />"Contaminants in streams can easily <br />affect ground-water quality, especially <br />where streams normally seep to <br />ground water, where ground-water <br />withdrawals induce seepage from the <br />stream, and where floods cause stream <br />water to become bank storage" <br /> <br />66 <br />