mentioned above would be easier to 

 assess. For example, rather than pro- 

 hibiting canals that connect fresh and 

 saline areas, the actual ecological cost 

 of such canals needs to be evaluated and 

 the information incorporated into either 

 a regulation or a tax. 



EUTROPHICATION 



Eutrophication is the result of the 

 overloading of a water body with nutri- 

 ents. Eutrophication can be reduced by 

 limiting nutrient sources and by treat- 

 ing runoff. Wastewater-caused eutrophi- 

 cation includes both point sources 

 (e.g., domestic and industrial efflu- 

 ents) and non-point sources (e.g., 

 agricultural and urban runoff). Point 

 sources are much easier to manage 

 because the water is more easily col- 

 lected and there are standard methods 

 available for dealing with the wastes 

 (secondary and tertiary treatment) . 

 Mechanical treatment of waste water is 

 expensive, however. Management of non- 

 point sources is typically limited to 

 reducing the levels of pollutants in 

 runoff . 



Management practices that can sig- 

 nificantly reduce agricultural runoff 

 and associated problems include 

 mulching, grassed waterways, minimum 

 tillage, minimizing pesticide applica- 

 tions by using pesticides only when 

 warranted by significant outbreaks 

 (integrated pest management), careful 

 planning of critical areas close to 

 water bodies, use of manure as a sub- 

 stitute for inorganic fertilizers, and 

 limited use of fertilizers. These 

 practices take advantage of the tendency 

 of living organisms to hold water and 

 its dissolved and suspended constituents 

 in the soil rather than letting it run 

 off. 



Likewise, one approach to control- 

 ling urban runoff involves reducing the 

 availability of pollutants to storm 

 flows. This can include reducing air 

 pollution, reducing the application of 

 fertilizers and pesticides, improved 

 street sweeping, periodic flushing of 



collection systems, separation of storm 

 drains and sewers, minimizing exposed 

 land surface during construction, and 

 maintaining good vegetative cover in 

 erodible areas (EPA 1977). Other means 

 of controlling urban runoff directly 

 alter the storm water path, flow rates, 

 or loadings. Temporary storage of storm 

 water in storage basins or ponds, and 

 use of porous pavement can help decrease 

 the amount of runoff entering a water 

 body per storm. Treatment of urban run- 

 off by standard sanitary and industrial 

 wastewater treatment can also be uti- 

 lized to lessen the impact of storm 

 water (EPA 1977). All of these steps 

 are costly, and a method to compare 

 their costs with the environmental 

 benefits they produce is essential to 

 rational decision making. 



In some new developments, the natu- 

 ral drainage system can be utilized in 

 its existing undeveloped, vegetated 

 state to slow and reduce runoff by 

 infiltration. In these cases, leaving 

 enough land in its natural state can be 

 seen as an alternative to more techno- 

 logical solutions. Construction costs 

 of a natural drainage system are approx- 

 imately half of those of a conventional 

 channelized and sewered system (Lynard 

 et al. 1980). Leaving large tracts of 

 natural land in developed areas is it- 

 self expensive, however, because it 

 increases transportation costs. Weigh- 

 ing the costs and benefits of this 

 approach to waste water treatment is not 

 something that can be easily general- 

 ized. A site-specific analysis that 

 adequately incorporates environmental 

 costs is needed. 



Many believe that a partial return 

 to an overland flow regime is feasible 

 in many locations in the MDPR, and would 

 alleviate many environmental problems, 

 especially in mid-and-upper basin areas. 

 The plan would involve converting upland 

 runoff from channels and toward overland 

 flow by redirecting existing drainage 

 canals into wetland areas. This would 

 not be costly, it would not affect up- 

 land drainage systems, and it could be 

 accomplished in steps. It would, how- 

 ever, require the dedication of large 



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