Designation:D6146−97(Reapproved2018)StandardGuideforMonitoringAqueousNutrientsinWatersheds1ThisstandardisissuedunderthefixeddesignationD6146;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscriptepsilon(´)indicatesaneditorialchangesincethelastrevisionorreapproval.INTRODUCTIONVariousformsofnitrogenandphosphorusareplantnutrients,bothnaturallyoccurringandmanmade,thatcanthreatenwaterresources.Nutrientsthatrunofforinfiltratethroughthesoilprofilecanresultinunfishableandunswimmablestreams,lakes,andestuaries,andunsafesurfaceandgroundwaterusedfordrinking.Highconcentrationsofnitrateindrinkingwaterareathreattoyounginfants,andsurfacewaterscansufferfromalgalblooms,fishkills,andunpalatableandunsafewaterforswimminganddrinking.Nutrientsarealsoaddedtowatershedsbymeansofchemigation.Thisguiderecommendsaprocessfordevelopingandimplementingmonitoringprojectsfornutrientsinawatershed.ItfollowsGuideD5851withmorespecificsapplicabletowatershedsandnutrients.TheseguidelinesarepresentedforuseinthenationwidestrategyformonitoringdevelopedbytheIntergovernmentalTaskForceonMonitoring(ITFM).Thenationwidemonitoringstrategyisanefforttoimprovethetechnicalaspectsofwatermonitoringtosupportsoundwaterqualitydecision-making.Itisneededtointegratemonitoringactivitiesmoreeffectivelyandeconomicallytoachieveabetterreturnofinvestmentsinmonitoringprojects(1).2GuideD6145isofferedasaguideformonitoringactualandpotentialnonpointandpointsourcepollutionwithinawatershed.Theguideisapplicabletosurfacewaterandgroundwaterresources,recognizingtheneedforacomprehensiveunderstandingofnaturallyoccurringandmanmadeimpactstotheentirewatershedhydrologicsystem.1.Scope1.1Purpose—Thisguideisintendedtoprovidegeneralguidanceonawatershedmonitoringprogramdirectedtowardtheplantnutrientsnitrogenandphosphorus.Theguideoffersaseriesofgeneralstepswithoutsettingforthaspecificcourseofaction.Itgivesassistancefordev...
