?url_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Adc&rft.relation=https%3A%2F%2Fpure.iiasa.ac.at%2Fid%2Feprint%2F4590%2F&rft.title=Modeling+the+Impacts+of+Diffuse+Pollution+on+Receiving+Water+Quality&rft.creator=Shanahan%2C+P.&rft.creator=Somlyody%2C+L.&rft.description=Nonpoint+or+diffuse+pollutants+represent+a+major+cause+of+water-quality+degradation+of+rivers%2C+estuaries%2C+lakes%2C+and+reservoirs+and+have+become+increasingly+significant+in+countries+where+point+sources+of+pollution+are+largely+controlled.+Nonpoint+sources+cause+eutrophication%2C+oxygen+depletion%2C+sedimentation%2C+acidification%2C+and+salinization+in+receiving+water+bodies%2C+introduce+pathogenic+organisms+and+other+pollutants%2C+and+through+shock+loads+of+pollutants%2C+cause+mortality+and+morbidity+of+aquatic+organisms.+The+major+sources+of+nonpoint+pollution+include+agriculture%2C+silviculture%2C+construction%2C+and+urban+runoff.+%0D%0A%0D%0AThe+potential+effects+of+nonpoint+source+pollutants+on+receiving+water+may+be+evaluated+using+water-quality+models.+A+recommended+procedure+is+to%3A+1)+establish+study+objective+and+constraints%3B+2)+determine+pollutant+interactions%3B+3)+perform+a+screening+analysis%3B+and+4)+select+a+water-quality+model+and+complete+the+analysis.+In+the+screening+analysis%2C+simple+analytical+tools+are+used+to+evaluate+the+potential+severity+of+impacts+and+the+time+scales+at+which+impacts+occur.+We+describe+a+screening-level+model+that+evaluates+the+response+to+a+conceptual+spike+load+of+unit+strength.+Water-quality+models+may+be+either+relatively+simple+analytical+models+or+more+complex+numerical+models.+For+many+situations%2C+an+analytical+model+will+provide+sufficient+analysis+of+a+problem+and+no+further+evaluation+is+required.+For+more+complex+problems%2C+numerical+water-quality+models+can+provide+a+detailed+and+rigorous+analysis.+%0D%0A%0D%0AAnalytical+models+are+available+to+describe+a+variety+of+pollutant+and+receiving+water+situations.+We+describe+models+for+the+following%3A+streams+and+rivers+--+simple+conservative+and+nonconservative+pollutant+inflows%2C+probabilistically+described+conservative+pollutant+inflows%2C+biochemical+oxygen+demand+and+dissolved+oxygen%2C+suspended+sediment%2C+and+adsorptive+micropollutants%3B+lakes+and+reservoirs+--+nutrient+loading+(eutrophication)%2C+and+micropollutant+loading%3B+and+estuaries+--+nonconservative+pollutant+inflows.+A+table+of+available+numerical+models+and+their+applicability+and+capabilities+is+also+provided.+%0D%0A%0D%0AA+case+study+of+Lake+Balaton%2C+Hungary+--+which+formed+the+subject+of+a+major+policy+oriented+research+of+IIASA+and+the+Hungarian+Academy+of+Sciences+at+the+late+seventies%2C+early+eighties+--+illustrates+the+procedure+for+assessing+nonpoint+source+pollutant+impacts.+Lake+Balaton+is+a+large+but+shallow+lake+which+is+experiencing+water-quality+degradation+due+to+nutrient+inflows+and+consequent+eutrophication.+Approximately+70%25+of+the+nutrient+load+comes+from+nonpoint+sources.+The+largest+single+load+is+the+inflow+from+the+Zala+River+which+varies+over+time+with+precipitation.+Analysis+of+historical+data+shows+that+a+monthly+time+scale+should+be+used+to+capture+the+effects+of+this+variability+on+the+response+in+the+most+western%2C+hypertrophic+basin+of+Lake+Balaton.+Analysis+with+the+unit-load+screening+model+illustrates+that+short+time+scales+must+be+considered+to+evaluate+the+response+to+nonpoint+source+loads+of+the+Zala+River+itself+while+much+longer+time+scales%2C+on+the+order+of+a+year%2C+suffice+for+evaluating+the+response+of+the+entire+lake.&rft.publisher=WP-95-002&rft.date=1995-01&rft.type=Monograph&rft.type=NonPeerReviewed&rft.format=text&rft.language=en&rft.identifier=https%3A%2F%2Fpure.iiasa.ac.at%2Fid%2Feprint%2F4590%2F1%2FWP-95-002.pdf&rft.identifier=++Shanahan%2C+P.+%3Chttps%3A%2F%2Fpure.iiasa.ac.at%2Fview%2Fiiasa%2F2377.html%3E+%26+Somlyody%2C+L.+%3Chttps%3A%2F%2Fpure.iiasa.ac.at%2Fview%2Fiiasa%2F1584.html%3E++(1995).++Modeling+the+Impacts+of+Diffuse+Pollution+on+Receiving+Water+Quality.+++IIASA+Working+Paper.+IIASA%2C+Laxenburg%2C+Austria%3A+WP-95-002+++++