Seawater encroachment

Seawater. Encroachment of seawater into coastal wells is a phenomenon that is limited to within a few kilometers from the seashore. It is noticeable as rising salinity and is connected to overpumping that causes significant lowering of the local water table. Seawater encroachment disappears with a decrease in the pumping rate and restoration of the local water table. Seawater stored in aquifer rocks since the last coverage of the terrain by the... 

Salinization is often observed in heavily pumped coastal wells. This observation is commonly based solely on chlorine concentration data, and is almost always attributed to seawater encroachment, which is made possible because of overpumping. The real cause of salinization has to be investigated in each case with the aid of complete chemical and isotopic analyses. 

Increased interest in use of subsurface strata as waste-disposal sites, in problems involving seawater encroachment, and in extension of the concept of freshwater resources to water containing as much as lOg/kg total dissolved solids (TDS) (Kohout, 1981) has increased interest in the composition and distribution of deeper saline fluids in sedimentary strata. 

The three main natural sources of soil salinity are mineral weathering, atmospheric precipitation, and fossil salts (those remaining from former marine or lacustrine environments). The human activities that add salts to soil include irrigation and saline industrial wastes. Seawater encroachment can also harm soils. 

Encroachment of seawater in coastal wells as a result of overpumping and an extreme lowering of the water table (section 17.6)... 

Fig. 6.21 Chloride measurements in a coastal well on Prince Edward Island. The well was operated daily from 8 a.m. to 5 p.m. and it was analyzed at these times 8 p.m. (circles) and 5 p.m. (+) (following Tremblay et al., 1973). Encroachment of seawater was concluded, with immediate bearing on management (see text).

Overpumping of a well may change the local pressure distribution in the water system to the extent that water from an adjacent aquifer may breach in and change the water properties. Thus overintensive pumping can introduce new complications. An obvious example is encroachment of seawater into coastal wells. 

Overpumping makes room for the encroachment of seawater (close to the coast) and deeper saline groundwaters (in certain regions). 

Twenty-seven-year-old pipeline failure incident located in municipal area. Oil leaking from the pipeline ignited resulting in an explosion and fire that also produced an oil spillage into an adjacent seaport that spread across 3000 square meters of seawater surface. The director of the State Administration of Work Safety cited an unreasonable oil-pipeline layout, negligent pipeline supervision, and unprofessional handling of oil leakage before the blasts. Afterward, China s President ordered safety checks on the country s oil and gas pipeline network. Urban encroachment onto the pipeline route also was a factor. 

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