Accelerated eutrophication of Beaver Lake in northwest Arkansas is a major environmental concern. When developing watershed-management plans to protect lake water quality, it is important that linkages among land-use activities and water quality of tributary streams be quantified. This study assessed longitudinal base-flow and storm-flow water quality at War Eagle Creek and quantified linkages between stream water quality and land-use conditions within the War Eagle Creek sub-watershed of the Beaver Lake watershed. We collected six water samples: three from base-flow conditions and three from storm-flow conditions during Spring 2002. In general, concentrations of nitrate nitrogen (NO3-N), total N (TN), total organic carbon (TOC), conductivity, and total dissolved solids (TDS) increased as the sampling moved downstream. All stream water-quality parameters, except phosphate phosphorus (PO4-P), were significantly correlated to the ratio of agricultural-to-forest land-use (r2 = 0.90 to 0.97). These results indicate that the ratio of agricultural-to-forest land-use within the watershed can be used to evaluate stream water quality, and that increases in this ratio may result in increased TDS, NO3-N, TN, and TOC concentrations

Chaubey, Indrajeet

Dennis, Scott

Haggard, Brian

English

UARK (University of Arkansas )

Discovery, The Student Journal of Dale Bumpers College of Agricultural, Food and Life Sciences Volume 3 Article 9 Fall 2002 Quantification of land-use impact on stream water quality Scott Dennis University of Arkansas, Fayetteville Indrajeet Chaubey University of Arkansas, Fayetteville Brian Haggard University of Arkansas, Fayetteville Follow this and additional works at: https://scholarworks.uark.edu/discoverymag  Part of the Fresh Water Studies Commons, and the Water Resource Management Commons Recommended Citation Dennis, S., Chaubey, I., & Haggard, B. (2002). Quantification of land-use impact on stream water quality. Discovery, The Student Journal of Dale Bumpers College of Agricultural, Food and Life Sciences, 3(1), 35-39. Retrieved from https://scholarworks.uark.edu/discoverymag/vol3/iss1/9 This Article is brought to you for free and open access by ScholarWorks@UARK. It has been accepted for inclusion in Discovery, The Student Journal of Dale Bumpers College of Agricultural, Food and Life Sciences by an authorized editor of ScholarWorks@UARK. For more information, please contact scholar@uark.edu. THE STUDENT JOURNAL OF THE DALE BUMPERS COLLEGEOF AGRICULTURAL, FOODAND LIFE SCIENCES 35Quantification of land-useimpact on stream water qualityScott Dennis*, Indrajeet Chaubey§, Brian E. Haggard†* Scott Dennis graduated in May 2002 with a B.S. degree in biological engineering.§ Indrajeet Chaubey, faculty sponsor, is an assistant professor in the Department of Biological and Agricultural Engineering.†Brian Haggard, faculty sponsor, is an adjunct assistant professor in the Department of Biological and Agricultural Engineering,and a research hydrologist in the USDA-ARS.ABSTRACTAccelerated eutrophication of Beaver Lake in northwest Arkansas is a major environmentalconcern. When developing watershed-management plans to protect lake water quality, it isimportant that linkages among land-use activities and water quality of tributary streams bequantified. This study assessed longitudinal base-flow and storm-flowwater quality atWar EagleCreek and quantified linkages between stream water quality and land-use conditions within theWar Eagle Creek sub-watershed of the Beaver Lake watershed. We collected six water samples:three from base-flow conditions and three from storm-flow conditions during Spring 2002. Ingeneral, concentrations of nitrate nitrogen (NO3-N), total N (TN), total organic carbon (TOC),conductivity, and total dissolved solids (TDS) increased as the sampling moved downstream. Allstream water-quality parameters, except phosphate phosphorus (PO4-P), were significantly cor-related to the ratio of agricultural-to-forest land-use (r2 = 0.90 to 0.97). These results indicatethat the ratio of agricultural-to-forest land-use within the watershed can be used to evaluatestream water quality, and that increases in this ratio may result in increased TDS, NO3-N, TN,and TOC concentrations.DISCOVERY VOL. 3, FALL 200236MEET THE STUDENT-AUTHORI graduated in May 2002 with a major in biological engi-neering.  I also attended high school in northwest Arkansaswhere baseball was a major part of my life.  I planned toplay baseball in college.  I visited many colleges that want-ed me to play for their team, however, none had a major inwhich I was interested.  An acquaintance of mine told meabout biological and agricultural engineering and immedi-ately I knew that discipline is what I would rather focus on.In my career as a student at the University of Arkansas,I have worked with teams in many design projects.  I par-ticipated in an experiment where we built a growth cham-ber to test the affects of global warming.  I was on a teamthat designed a sensor that would detect water clarity andparticipated in the design of an infrared switch for a feedbin in a chicken house that shuts an auger off when a bin isfull in order to eradicate feed spills.  I also helped developand build a chicken controlled retractable chicken cage thatallowed a chicken to determine the optimal area needed inorder to reduce psychological stress.I specialized my degree in environmental aspects, thusallowing me to research a river that not only is important tothe welfare of northwest Arkansas but also is important tome.  My family owns a farm through which the river flows.I enjoy nature, and I feel it is important to protect natural areas throughout the nation.I am a member of the American Society of Agricultural Engineers (ASAE).  ASAE allows me to continuemy education in the newest developments and latest technologies in the agricultural industry. Scott DennisINTRODUCTIONNonpoint source (NPS) transport of nutrients, sedi-ment, and pathogens from agriculturally dominatedwatersheds is amajor concern in Arkansas (Edwards andDaniel, 1992; Edwards et al., 1997). There is ample evi-dence to suggest that row crop agriculture and excessland application of animal manure have led to surfaceand ground-water pollution (Edwards et al., 1996).Increasingly, watersheds are unable to utilize anddegrade the high levels of inorganic fertilizers and ani-mal manures applied to the landscape. The result isincreases in noxious oxygen-consuming and sometimetoxic algal blooms, deteriorations of fisheries, and gener-al degradation of water quality (Park et al., 1994;Sharpley et al., 1994). The Arkansas 303(d) list (list ofwaterbodies not supporting their designated use) for2002 includes 59 stream segments totaling 1,269 milesand five lakes totaling 17,062 acres of impairment. Nineof the stream segments, totaling 70 miles, are located onsmall streams dominated and impacted by point-sourcedischarges (ADEQ, 2002).In northwest Arkansas, concern over non-point-source (NPS) pollutants entering War Eagle Creek fromthe application of animal waste and inorganic fertilizershas been increasing. War Eagle Creek is a major tribu-tary to Beaver Lake, which provides drinking water toNorthwest Arkansas. The water quality of War EagleCreek directly affects Beaver Lake, and acceleratedeutrophication from nitrogen (N) and phosphorus (P)in Beaver Lake is a major concern. Thus, it is imperativethat the water quality of tributary streams be assessed sothat watershed management plans can be developed.The agricultural land-use in the War Eagle Creek water-shed is dominated by poultry growers and beef opera-tions; therefore, animal manure is the main source offertilizer for these farmers. Even though animal manureis a good source of nutrients, excess land applicationmay result in runoff losses of nutrients and lead to accel-erated eutrophication of downstream waterbodies.To develop a watershed management plan for theBeaver Lake watershed and to protect the lake waterquality, the linkages among land-use activities andstream water quality must be understood. Similarly,there is a need to survey current land-use practices in thewatershed so that areas contributing the majority ofnutrients can be identified. Currently, data are not avail-able to quantify the changes in base-flow and storm-flowwater quality in the War Eagle Creek sub-watershed inrelation to land-use conditions; however Haggard et al.(2002) observed increasing nutrient concentrations andexport with increasing pasture land-use throughout theBeaver Lake watershed.Quantification of linkages between land-use andwater quality is needed to determine the sources of pol-lution in streams. Accurate identification of the NPSpollutants involved is also required for designing bestmanagement practices (BMPs) for stream and lakewater-quality protection.The objectives of this study were to:a. Assess longitudinal base-flow and storm-flow waterquality of War Eagle Creek at five water-quality samplingstations.b. Quantify linkages between stream water quality andland-use in the War Eagle Creek sub-watershed.MATERIALS AND METHODSThis study was conducted in the War Eagle Creeksub-watershed, located within the Beaver Lake water-shed (Fig. 1). The total area of theWar Eagle Creek sub-watershed is approximately 264 mi2. The principal land-uses in the War Eagle Creek sub-watershed are forestryand agriculture, which cover 61% and 38% of the totalwatershed area, respectively. Urban land-use within theWar Eagle Creek sub-watershed covers less than 1% ofthe area.To quantify the effect of land-use on water quality,five water-quality sampling stations were established atWar Eagle Creek. The locations of the sampling stationswere based on site accessibility while keeping them asequidistant as possible. Station 1 was themost upstreamstation at War Eagle Creek, and Station 5 was the mostdownstream (Fig. 1).Three water samples were collected during base-flowconditions at two-week intervals betweenFebruary 2002andApril 2002 at each of the five sampling sites. In addi-tion, water samples were also collected during threestorm events. At each site, three filtered samples werecollected by filtering 20 mL of stream water using 0.45µmnylonmembrane filter in the field. Three unfilteredwater samples, each 500mL in volume, were also collect-THE STUDENT JOURNAL OF THE DALE BUMPERS COLLEGEOF AGRICULTURAL, FOODAND LIFE SCIENCES 37Fig. 1. Location of the War Eagle Creek sub-watershed and water-quality sampling stationswithin the Beaver Lake basin.DISCOVERY VOL. 3, FALL 2002ed at each sampling station. Bottles and filteringsyringes were field-washed prior to sample collection.Immediately after collection, water samples were storedon ice in the dark until returned to the laboratory.Samples were transported to the laboratory for analysesof dissolved P (PO4-P), nitrateN (NO3-N), total N (TN),and total organic carbon (TOC). We also measured pHat each site using a pH meter (Oktron Corporation,model pH Testr 2), and conductivity, salinity, and tem-perature using an YSI conductivity, salinity, and temper-ature meter (YSI Corporation, model YSI85).We measured dissolved P with an autoanalyzer usingascorbic-acid reduction and NO3-N using cadmium-copper reductionmethods. TotalN andTOCweremeas-ured by converting all N and organic C into nitrogenoxide (NO) and carbon dioxide (CO2) at 950°C, respec-tively. These gases were analyzed by infrared detection ofCO2 and conversion of NO to nitrogen dioxide (NO2)and followed by NO2 decay measurement by a photomultiplier probe.The topographic or digital elevation model (DEM)and land-use data for the War Eagle Creek sub-water-shed were obtained from the Center for AdvancedSpatial Technology (CAST), University of Arkansas, andanalyzed using ArcViewGIS. The sub-watersheds drain-ing toward the each sampling station were delineatedusing DEM data and the ArcView GIS. Sub-watershedboundary for each sampling station was then intersectedwith the War Eagle Creek sub-watershed land-use datato calculate fraction of each land-use type within eachsampling station sub-watershed (Table 1).The land-use data were used to estimate the agricul-tural to forest ratio within each sub-watershed. Thelinkages among stream water quality and land-use weredetermined by regressing the measured water-qualitydata for each sub-watershed against the ratio of agricul-ture to forest area within the sub-watershed.RESULTS AND DISCUSSIONTable 2 shows the average water quality data, for threedates at each sampling station for the base and storm-flow conditions. In general, concentrations of NO3-N,TN, TOC, conductivity, and TDS increased as samplingmoved downstream in the sub-watershed, during bothbase-flow and storm-flow conditions. The only excep-tion to this trend was PO4-P concentration, whichdecreased at sampling Stations 3 and 4 during base-flowand was highly variable during storm-flow conditions.The variability in PO4-P during storm-flow conditionsmay be attributed to transport of particulate matter,which may adsorb PO4-P during the transport process.Stream pH did not change significantly among sam-pling stations. Temperature data are difficult to comparefor this study because they are a function of the time ofthe day and degree of shading by riparian vegetation.Since temperature at all the sampling stations was notcollected during the same time of the day, it is difficult toinfer trends from upstream to downstream locations.When we compared the water-quality data duringbase-flow and storm-flow conditions at each samplingstation, the data indicated that concentrations of NO3-N,TN, and TOCwere higher during storm-flow conditions(Table 2). The PO4-P concentrationswere higher duringstorm-flow conditions at sampling Stations 1, 2, and 3,and lower at Stations 4 and 5. Concentrationof TDSwashigher during base-flow conditions at Stations 1 and 2.Conductivity values were lower during storm-flow con-ditions at all the sampling stations except Station 4. Thismay have been due to dilution of streamconductivity/TDS concentrations during storm-flowconditions.Total flow of nutrients is a function of concentrationand flow volume. Flow volume is always larger duringstorm-flow events. A higher concentration duringstorm-flow conditions indicates that a significantly larg-er amount of nutrients may be transported downstreaminWar Eagle Creek, eventually enteringBeaver Lake dur-ing rainfall events.38Table 2. Average data collected from War Eagle Creek. There were 3 storm-flow and 3 base-flow sampling events.Parameter Station 1 Station 2 Station 3 Station 4 Station 5Storm-flow conditionpH 8.2 8.2 8.2 8.4 8.2Temp (°C) 12.1 11.4 9.1 8.1 8.6Conductivity(mS/cm) 30.3 43.0 70.6 100.2 130.5TDS (mg/L) 13.7 19.7 32.0 47.3 64.3NO3-N (mg/L) 0.23 0.35 0.64 1.02 1.52TN (mg/L) 0.31 0.41 0.66 1.08 1.33PO4-P (mg/L) 0.020 0.036 0.009 0.009 0.033TOC (mg/L) 1.04 1.13 0.95 1.35 1.76Base-flow conditionpH 8.5 8.2 8.2 8.3 8.2Temp (°C) 12.8 12.4 11.4 11.0 11.8Conductivity(mS/cm) 45.9 53.1 63.9 94.7 159TDS (mg/L) 19.0 23.3 28.3 35.0 59.0NO3-N (mg/L) 0.21 0.25 0.34 0.44 1.06TN (mg/L) 0.26 0.25 0.36 0.39 0.89PO4-P (mg/L) 0.007 0.029 0.007 0.024 0.048TOC (mg/L) 0.58 0.58 0.88 1.10 1.39Table 1.  Land-use and area of each sampling station sub-watershed within the War Eagle Creek sub-watershed.Land-use Watershed areas under different land use (mi2)Station 5 Station 4 Station 3 Station 2 Station 1Residential 1.60 0.28 0.02 0.00 0.00Agriculture 100.64 39.65 20.40 4.97 0.91Forest 161.16 115.89 86.68 31.06 4.44Other 0.22 0.16 0.14 0.05 0.00Total area 263.62 155.98 107.24 36.09 5.35Toquantify the linkages between land-use and streamwater quality, a linear regressionwas performed betweenagriculture-to-forest-area ratio and streamwater-qualityconcentration for each sampling station. Agriculture-to-forest-area ratio gives an indication of the dominance ofagricultural land-use in the watershed with regard to thedegree of watershed development. The ratio rangedfrom 0.16 (Station 2) to 0.62 (Station 5). In general, asthe sub-watershed area increased, the dominance ofagricultural land-use also increased. Concentration ofstream water-quality parameters as a function of agri-culture-to-forest-area ratio for each sampling station isshown in Fig. 2. An increase in the agriculture-to-forest-area ratio resulted in increased concentrations of NO3-N, TN, TDS, and TOC.The linear regression showed that all stream waterquality parameters, except PO4-P, were significantlyrelated to agriculture-to-forest-area ratiowithin the sub-watershed (Table 3). The coefficient of determination(r2) values ranged from 0.90 – 0.97 and were highly sig-nificant (p < 0.01). Only 33% of the variability in thestream PO4-P concentration could be accounted for bythe ratio of agriculture-to-forest-area, which was notsignificant (p = 0.31). This was contrary to the expectedrole of agricultural land-use in controlling streamPO4-Pconcentrations; however, annualmean PO4-P concentra-tions have shown an increasing relationshipwith pastureland-use across the entire Beaver Lake watershed(Haggard et al., 2002). More data need to be collected inthis watershed to further verify this relationship.LITERATURE CITEDArkansas Department of Environmental Quality(ADEQ). 2002 Proposed 303(d) list. ADEQ WaterDivision, Little Rock. Arkansas.Edwards, D.R., T.C. Daniel, H.D. Scott, P.A. Moore, Jr.,J.F.Murdoch, andP.F.Vendrell. 1997. Effect of BMPimplementation on storm flow quality of twoNorthwestern Arkansas streams. Trans. ASAE40:1311-1319.Edwards, D.R., T.C. Daniel, H.D. Scott, J.F. Murdoch,M.J. Habiger, and H.M. Burks. 1996. Stream quali-ty impact of best management practices in aNorthwest Arkansas Basin. J. Amer. Water Resour.Assoc. 32:499-509.Edwards, D.R. and T.C. Daniel. 1992. Potential runoffquality effects of poultry manure slurry applied tofescue plots. Trans. ASAE 35:1827-1832.Haggard, B.E., I. Chaubey, P.A. Moore, Jr., and E.H.Stanely. 2002. Nitrogen and phosphorus concentra-tions and export from an Ozark Plateau catchmentin the United States. Biosystems Engineering(In Review).Park, S.W., S. Mostaghimi, R.A. Cooke, andP.W. McClellan. 1994. BMP impacts onwatershed runoff, sediment, andnutrient yields.J.Amer.Water Resour.Assoc. 30:1011-1023.Sharpley, A.N., S.C. Chapra, R.Wedepohl, J.T.Sims, T.C. Daniel and K.R. Reddy. 1994Managing agricultural phosphorus for pro-tection of surface waters: issues and options.J. Environ. Qual. 23:437-451.THE STUDENT JOURNAL OF THE DALE BUMPERS COLLEGEOF AGRICULTURAL, FOODAND LIFE SCIENCES 39Fig. 2. Concentration of stream water-quality parameters as a function of agriculture-to-forest-area ratio in the sub-watershed.Table 3. Linear regression results to predict War Eagle Creek water qualityas a function of agriculture-to-forest-area ratio. Water quality parameter Regression equation1 R2 PNO3-N (mg/L) Y = 2.292 X - 0.109 0.97 < 0.01TN (mg/L) Y = 1.801 X + 0.032 0.95 < 0.01TDS (mg/L) Y = 94.36 X + 4.72 0.90 < 0.01TOC (mg/L) Y = 1.696 X + 0.546 0.95 < 0.01PO4-P (mg/L) Y = 0.044 X + 0.009 0.33 0.311 Y = stream water quality (e.g. NO3-N concentration); X = agriculture-to-forest-area ratio

Quantification of land-use impact on stream water quality

ScholarWorks@UARK

Discovery, The Student Journal of Dale Bumpers College ofAgricultural, Food and Life SciencesVolume 3 Article 9Fall 2002Quantification of land-use impact on stream waterqualityScott DennisUniversity of Arkansas, FayettevilleIndrajeet ChaubeyUniversity of Arkansas, FayettevilleBrian HaggardUniversity of Arkansas, FayettevilleFollow this and additional works at: https://scholarworks.uark.edu/discoverymagPart of the Fresh Water Studies Commons, and the Water Resource Management CommonsThis Article is brought to you for free and open access by ScholarWorks@UARK. It has been accepted for inclusion in Discovery, The Student Journalof Dale Bumpers College of Agricultural, Food and Life Sciences by an authorized editor of ScholarWorks@UARK. For more information, pleasecontact scholar@uark.edu, ccmiddle@uark.edu.Recommended CitationDennis, Scott; Chaubey, Indrajeet; and Haggard, Brian (2002) "Quantification of land-use impact on stream water quality," Discovery,The Student Journal of Dale Bumpers College of Agricultural, Food and Life Sciences. University of Arkansas System Division ofAgriculture. 3:35-39.Available at: https://scholarworks.uark.edu/discoverymag/vol3/iss1/9THE STUDENT JOURNAL OF THE DALE BUMPERS COLLEGEOF AGRICULTURAL, FOODAND LIFE SCIENCES 35Quantification of land-useimpact on stream water qualityScott Dennis*, Indrajeet Chaubey§, Brian E. Haggard†* Scott Dennis graduated in May 2002 with a B.S. degree in biological engineering.§ Indrajeet Chaubey, faculty sponsor, is an assistant professor in the Department of Biological and Agricultural Engineering.†Brian Haggard, faculty sponsor, is an adjunct assistant professor in the Department of Biological and Agricultural Engineering,and a research hydrologist in the USDA-ARS.ABSTRACTAccelerated eutrophication of Beaver Lake in northwest Arkansas is a major environmentalconcern. When developing watershed-management plans to protect lake water quality, it isimportant that linkages among land-use activities and water quality of tributary streams bequantified. This study assessed longitudinal base-flow and storm-flowwater quality atWar EagleCreek and quantified linkages between stream water quality and land-use conditions within theWar Eagle Creek sub-watershed of the Beaver Lake watershed. We collected six water samples:three from base-flow conditions and three from storm-flow conditions during Spring 2002. Ingeneral, concentrations of nitrate nitrogen (NO3-N), total N (TN), total organic carbon (TOC),conductivity, and total dissolved solids (TDS) increased as the sampling moved downstream. Allstream water-quality parameters, except phosphate phosphorus (PO4-P), were significantly cor-related to the ratio of agricultural-to-forest land-use (r2 = 0.90 to 0.97). These results indicatethat the ratio of agricultural-to-forest land-use within the watershed can be used to evaluatestream water quality, and that increases in this ratio may result in increased TDS, NO3-N, TN,and TOC concentrations.DISCOVERY VOL. 3, FALL 200236MEET THE STUDENT-AUTHORI graduated in May 2002 with a major in biological engi-neering.  I also attended high school in northwest Arkansaswhere baseball was a major part of my life.  I planned toplay baseball in college.  I visited many colleges that want-ed me to play for their team, however, none had a major inwhich I was interested.  An acquaintance of mine told meabout biological and agricultural engineering and immedi-ately I knew that discipline is what I would rather focus on.In my career as a student at the University of Arkansas,I have worked with teams in many design projects.  I par-ticipated in an experiment where we built a growth cham-ber to test the affects of global warming.  I was on a teamthat designed a sensor that would detect water clarity andparticipated in the design of an infrared switch for a feedbin in a chicken house that shuts an auger off when a bin isfull in order to eradicate feed spills.  I also helped developand build a chicken controlled retractable chicken cage thatallowed a chicken to determine the optimal area needed inorder to reduce psychological stress.I specialized my degree in environmental aspects, thusallowing me to research a river that not only is important tothe welfare of northwest Arkansas but also is important tome.  My family owns a farm through which the river flows.I enjoy nature, and I feel it is important to protect natural areas throughout the nation.I am a member of the American Society of Agricultural Engineers (ASAE).  ASAE allows me to continuemy education in the newest developments and latest technologies in the agricultural industry. Scott DennisINTRODUCTIONNonpoint source (NPS) transport of nutrients, sedi-ment, and pathogens from agriculturally dominatedwatersheds is amajor concern in Arkansas (Edwards andDaniel, 1992; Edwards et al., 1997). There is ample evi-dence to suggest that row crop agriculture and excessland application of animal manure have led to surfaceand ground-water pollution (Edwards et al., 1996).Increasingly, watersheds are unable to utilize anddegrade the high levels of inorganic fertilizers and ani-mal manures applied to the landscape. The result isincreases in noxious oxygen-consuming and sometimetoxic algal blooms, deteriorations of fisheries, and gener-al degradation of water quality (Park et al., 1994;Sharpley et al., 1994). The Arkansas 303(d) list (list ofwaterbodies not supporting their designated use) for2002 includes 59 stream segments totaling 1,269 milesand five lakes totaling 17,062 acres of impairment. Nineof the stream segments, totaling 70 miles, are located onsmall streams dominated and impacted by point-sourcedischarges (ADEQ, 2002).In northwest Arkansas, concern over non-point-source (NPS) pollutants entering War Eagle Creek fromthe application of animal waste and inorganic fertilizershas been increasing. War Eagle Creek is a major tribu-tary to Beaver Lake, which provides drinking water toNorthwest Arkansas. The water quality of War EagleCreek directly affects Beaver Lake, and acceleratedeutrophication from nitrogen (N) and phosphorus (P)in Beaver Lake is a major concern. Thus, it is imperativethat the water quality of tributary streams be assessed sothat watershed management plans can be developed.The agricultural land-use in the War Eagle Creek water-shed is dominated by poultry growers and beef opera-tions; therefore, animal manure is the main source offertilizer for these farmers. Even though animal manureis a good source of nutrients, excess land applicationmay result in runoff losses of nutrients and lead to accel-erated eutrophication of downstream waterbodies.To develop a watershed management plan for theBeaver Lake watershed and to protect the lake waterquality, the linkages among land-use activities andstream water quality must be understood. Similarly,there is a need to survey current land-use practices in thewatershed so that areas contributing the majority ofnutrients can be identified. Currently, data are not avail-able to quantify the changes in base-flow and storm-flowwater quality in the War Eagle Creek sub-watershed inrelation to land-use conditions; however Haggard et al.(2002) observed increasing nutrient concentrations andexport with increasing pasture land-use throughout theBeaver Lake watershed.Quantification of linkages between land-use andwater quality is needed to determine the sources of pol-lution in streams. Accurate identification of the NPSpollutants involved is also required for designing bestmanagement practices (BMPs) for stream and lakewater-quality protection.The objectives of this study were to:a. Assess longitudinal base-flow and storm-flow waterquality of War Eagle Creek at five water-quality samplingstations.b. Quantify linkages between stream water quality andland-use in the War Eagle Creek sub-watershed.MATERIALS AND METHODSThis study was conducted in the War Eagle Creeksub-watershed, located within the Beaver Lake water-shed (Fig. 1). The total area of theWar Eagle Creek sub-watershed is approximately 264 mi2. The principal land-uses in the War Eagle Creek sub-watershed are forestryand agriculture, which cover 61% and 38% of the totalwatershed area, respectively. Urban land-use within theWar Eagle Creek sub-watershed covers less than 1% ofthe area.To quantify the effect of land-use on water quality,five water-quality sampling stations were established atWar Eagle Creek. The locations of the sampling stationswere based on site accessibility while keeping them asequidistant as possible. Station 1 was themost upstreamstation at War Eagle Creek, and Station 5 was the mostdownstream (Fig. 1).Three water samples were collected during base-flowconditions at two-week intervals betweenFebruary 2002andApril 2002 at each of the five sampling sites. In addi-tion, water samples were also collected during threestorm events. At each site, three filtered samples werecollected by filtering 20 mL of stream water using 0.45µmnylonmembrane filter in the field. Three unfilteredwater samples, each 500mL in volume, were also collect-THE STUDENT JOURNAL OF THE DALE BUMPERS COLLEGEOF AGRICULTURAL, FOODAND LIFE SCIENCES 37Fig. 1. Location of the War Eagle Creek sub-watershed and water-quality sampling stationswithin the Beaver Lake basin.DISCOVERY VOL. 3, FALL 2002ed at each sampling station. Bottles and filteringsyringes were field-washed prior to sample collection.Immediately after collection, water samples were storedon ice in the dark until returned to the laboratory.Samples were transported to the laboratory for analysesof dissolved P (PO4-P), nitrateN (NO3-N), total N (TN),and total organic carbon (TOC). We also measured pHat each site using a pH meter (Oktron Corporation,model pH Testr 2), and conductivity, salinity, and tem-perature using an YSI conductivity, salinity, and temper-ature meter (YSI Corporation, model YSI85).We measured dissolved P with an autoanalyzer usingascorbic-acid reduction and NO3-N using cadmium-copper reductionmethods. TotalN andTOCweremeas-ured by converting all N and organic C into nitrogenoxide (NO) and carbon dioxide (CO2) at 950°C, respec-tively. These gases were analyzed by infrared detection ofCO2 and conversion of NO to nitrogen dioxide (NO2)and followed by NO2 decay measurement by a photomultiplier probe.The topographic or digital elevation model (DEM)and land-use data for the War Eagle Creek sub-water-shed were obtained from the Center for AdvancedSpatial Technology (CAST), University of Arkansas, andanalyzed using ArcViewGIS. The sub-watersheds drain-ing toward the each sampling station were delineatedusing DEM data and the ArcView GIS. Sub-watershedboundary for each sampling station was then intersectedwith the War Eagle Creek sub-watershed land-use datato calculate fraction of each land-use type within eachsampling station sub-watershed (Table 1).The land-use data were used to estimate the agricul-tural to forest ratio within each sub-watershed. Thelinkages among stream water quality and land-use weredetermined by regressing the measured water-qualitydata for each sub-watershed against the ratio of agricul-ture to forest area within the sub-watershed.RESULTS AND DISCUSSIONTable 2 shows the average water quality data, for threedates at each sampling station for the base and storm-flow conditions. In general, concentrations of NO3-N,TN, TOC, conductivity, and TDS increased as samplingmoved downstream in the sub-watershed, during bothbase-flow and storm-flow conditions. The only excep-tion to this trend was PO4-P concentration, whichdecreased at sampling Stations 3 and 4 during base-flowand was highly variable during storm-flow conditions.The variability in PO4-P during storm-flow conditionsmay be attributed to transport of particulate matter,which may adsorb PO4-P during the transport process.Stream pH did not change significantly among sam-pling stations. Temperature data are difficult to comparefor this study because they are a function of the time ofthe day and degree of shading by riparian vegetation.Since temperature at all the sampling stations was notcollected during the same time of the day, it is difficult toinfer trends from upstream to downstream locations.When we compared the water-quality data duringbase-flow and storm-flow conditions at each samplingstation, the data indicated that concentrations of NO3-N,TN, and TOCwere higher during storm-flow conditions(Table 2). The PO4-P concentrationswere higher duringstorm-flow conditions at sampling Stations 1, 2, and 3,and lower at Stations 4 and 5. Concentrationof TDSwashigher during base-flow conditions at Stations 1 and 2.Conductivity values were lower during storm-flow con-ditions at all the sampling stations except Station 4. Thismay have been due to dilution of streamconductivity/TDS concentrations during storm-flowconditions.Total flow of nutrients is a function of concentrationand flow volume. Flow volume is always larger duringstorm-flow events. A higher concentration duringstorm-flow conditions indicates that a significantly larg-er amount of nutrients may be transported downstreaminWar Eagle Creek, eventually enteringBeaver Lake dur-ing rainfall events.38Table 2. Average data collected from War Eagle Creek. There were 3 storm-flow and 3 base-flow sampling events.Parameter Station 1 Station 2 Station 3 Station 4 Station 5Storm-flow conditionpH 8.2 8.2 8.2 8.4 8.2Temp (°C) 12.1 11.4 9.1 8.1 8.6Conductivity(mS/cm) 30.3 43.0 70.6 100.2 130.5TDS (mg/L) 13.7 19.7 32.0 47.3 64.3NO3-N (mg/L) 0.23 0.35 0.64 1.02 1.52TN (mg/L) 0.31 0.41 0.66 1.08 1.33PO4-P (mg/L) 0.020 0.036 0.009 0.009 0.033TOC (mg/L) 1.04 1.13 0.95 1.35 1.76Base-flow conditionpH 8.5 8.2 8.2 8.3 8.2Temp (°C) 12.8 12.4 11.4 11.0 11.8Conductivity(mS/cm) 45.9 53.1 63.9 94.7 159TDS (mg/L) 19.0 23.3 28.3 35.0 59.0NO3-N (mg/L) 0.21 0.25 0.34 0.44 1.06TN (mg/L) 0.26 0.25 0.36 0.39 0.89PO4-P (mg/L) 0.007 0.029 0.007 0.024 0.048TOC (mg/L) 0.58 0.58 0.88 1.10 1.39Table 1.  Land-use and area of each sampling station sub-watershed within the War Eagle Creek sub-watershed.Land-use Watershed areas under different land use (mi2)Station 5 Station 4 Station 3 Station 2 Station 1Residential 1.60 0.28 0.02 0.00 0.00Agriculture 100.64 39.65 20.40 4.97 0.91Forest 161.16 115.89 86.68 31.06 4.44Other 0.22 0.16 0.14 0.05 0.00Total area 263.62 155.98 107.24 36.09 5.35Toquantify the linkages between land-use and streamwater quality, a linear regressionwas performed betweenagriculture-to-forest-area ratio and streamwater-qualityconcentration for each sampling station. Agriculture-to-forest-area ratio gives an indication of the dominance ofagricultural land-use in the watershed with regard to thedegree of watershed development. The ratio rangedfrom 0.16 (Station 2) to 0.62 (Station 5). In general, asthe sub-watershed area increased, the dominance ofagricultural land-use also increased. Concentration ofstream water-quality parameters as a function of agri-culture-to-forest-area ratio for each sampling station isshown in Fig. 2. An increase in the agriculture-to-forest-area ratio resulted in increased concentrations of NO3-N, TN, TDS, and TOC.The linear regression showed that all stream waterquality parameters, except PO4-P, were significantlyrelated to agriculture-to-forest-area ratiowithin the sub-watershed (Table 3). The coefficient of determination(r2) values ranged from 0.90 – 0.97 and were highly sig-nificant (p < 0.01). Only 33% of the variability in thestream PO4-P concentration could be accounted for bythe ratio of agriculture-to-forest-area, which was notsignificant (p = 0.31). This was contrary to the expectedrole of agricultural land-use in controlling streamPO4-Pconcentrations; however, annualmean PO4-P concentra-tions have shown an increasing relationshipwith pastureland-use across the entire Beaver Lake watershed(Haggard et al., 2002). More data need to be collected inthis watershed to further verify this relationship.LITERATURE CITEDArkansas Department of Environmental Quality(ADEQ). 2002 Proposed 303(d) list. ADEQ WaterDivision, Little Rock. Arkansas.Edwards, D.R., T.C. Daniel, H.D. Scott, P.A. Moore, Jr.,J.F.Murdoch, andP.F.Vendrell. 1997. Effect of BMPimplementation on storm flow quality of twoNorthwestern Arkansas streams. Trans. ASAE40:1311-1319.Edwards, D.R., T.C. Daniel, H.D. Scott, J.F. Murdoch,M.J. Habiger, and H.M. Burks. 1996. Stream quali-ty impact of best management practices in aNorthwest Arkansas Basin. J. Amer. Water Resour.Assoc. 32:499-509.Edwards, D.R. and T.C. Daniel. 1992. Potential runoffquality effects of poultry manure slurry applied tofescue plots. Trans. ASAE 35:1827-1832.Haggard, B.E., I. Chaubey, P.A. Moore, Jr., and E.H.Stanely. 2002. Nitrogen and phosphorus concentra-tions and export from an Ozark Plateau catchmentin the United States. Biosystems Engineering(In Review).Park, S.W., S. Mostaghimi, R.A. Cooke, andP.W. McClellan. 1994. BMP impacts onwatershed runoff, sediment, andnutrient yields.J.Amer.Water Resour.Assoc. 30:1011-1023.Sharpley, A.N., S.C. Chapra, R.Wedepohl, J.T.Sims, T.C. Daniel and K.R. Reddy. 1994Managing agricultural phosphorus for pro-tection of surface waters: issues and options.J. Environ. Qual. 23:437-451.THE STUDENT JOURNAL OF THE DALE BUMPERS COLLEGEOF AGRICULTURAL, FOODAND LIFE SCIENCES 39Fig. 2. Concentration of stream water-quality parameters as a function of agriculture-to-forest-area ratio in the sub-watershed.Table 3. Linear regression results to predict War Eagle Creek water qualityas a function of agriculture-to-forest-area ratio. Water quality parameter Regression equation1 R2 PNO3-N (mg/L) Y = 2.292 X - 0.109 0.97 < 0.01TN (mg/L) Y = 1.801 X + 0.032 0.95 < 0.01TDS (mg/L) Y = 94.36 X + 4.72 0.90 < 0.01TOC (mg/L) Y = 1.696 X + 0.546 0.95 < 0.01PO4-P (mg/L) Y = 0.044 X + 0.009 0.33 0.311 Y = stream water quality (e.g. NO3-N concentration); X = agriculture-to-forest-area ratio

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Quantification of land-use impact on stream water quality

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