{"title":"Development and Application of Watershed Regressions for Pesticides (WARP) for Estimating Atrazine Concentration Distributions in Streams","authors":"S. Larson, C. G. Crawford, R. Gilliom","doi":"10.3133/WRI034047","DOIUrl":"https://doi.org/10.3133/WRI034047","url":null,"abstract":"...............................................................................................................................................................","PeriodicalId":23603,"journal":{"name":"Water-Resources Investigations Report","volume":"19 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2004-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78398293","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In 2001-02, the U.S. Geological Survey installed and sampled 28 shallow wells in urban residential and light commercial areas in Lafayette Parish, Louisiana, for a land-use study in the Acadian-Pontchartrain Study Unit of the National Water-Quality Assessment (NAWQA) Program. The wells were installed in the Chicot aquifer system, the primary source of water for irrigation and public-water supplies in southwestern Louisiana. The purpose of this report is to describe the quality of water from the 28 shallow wells and to relate that water quality to natural factors and to human activities. Ground-water samples were analyzed for general ground-water properties and about 240 water-quality constituents, including dissolved solids, major inorganic ions, trace elements, nutrients, dissolved organic carbon (DOC), radon, chlorofluorocarbons, selected stable isotopes, pesticides, pesticide degradation products, and volatile organic compounds (VOC’s). Dissolved-solids concentrations for two wells exceeded the U.S. Environmental Protection Agency Secondary Maximum Contaminant Level of 500 mg/L (milligrams per liter). Concentrations for major inorganic ions, trace elements, pesticides, degradation products, and VOC’s were less than the Maximum Contaminant Levels for drinking water. Manganese concentrations for 18 wells exceeded the Secondary Maximum Contaminant Level of 50 micrograms per liter. Arsenic concentrations increased with depth and with increased pH, bicarbonate, calcium, and magnesium concentrations. Six pesticides and three degradation products were detected in the ground-water samples. Ten VOC’s also were detected in the ground-water samples. One nutrient concentration (that for nitrite plus nitrate) was greater than 2 mg/L, a level that might indicate contamination from human activities, and was greater than the Maximum Contaminant Level of 10 mg/L. The median DOC concentration was an estimated 0.3 mg/L, which indicated naturallyoccurring DOC conditions in the shallow ground water in Lafayette Parish. Quality-control samples indicated no bias in ground-water data from collection or analysis. Radon concentrations for 19 of 20 wells sampled were greater than the U.S. Environmental Protection Agency Maximum Contaminant Level of 300 picocuries per liter (piC/L). Radon concentrations ranged from 280 to 2,220 piC/L and had a median of 389 piC/L. Radon concentrations were correlated moderately and inversely to the depth to the top of the screened interval. Chlorofluorocarbons indicated the apparent age of the ground water varied with water level and ranged from about 12 to 50 years. The Mann-Whitney rank-sum test was used to compare water-quality data in the Chicot aquifer system between four groups of wells from three NAWQA studies. The means for most constituents were less for the urban wells than for wells in the rice-growing areas. The larger dissolved-solids concentrations, particularly sodium and chloride, for samples from wells in the rice-growin
{"title":"Quality of Water from Shallow Wells in Urban Residential and Light Commercial Areas in Lafayette Parish, Louisiana, 2001 through 2002","authors":"R. B. Fendick, R. W. Tollett","doi":"10.3133/wri20034118","DOIUrl":"https://doi.org/10.3133/wri20034118","url":null,"abstract":"In 2001-02, the U.S. Geological Survey installed and sampled 28 shallow wells in urban residential and light commercial areas in Lafayette Parish, Louisiana, for a land-use study in the Acadian-Pontchartrain Study Unit of the National Water-Quality Assessment (NAWQA) Program. The wells were installed in the Chicot aquifer system, the primary source of water for irrigation and public-water supplies in southwestern Louisiana. The purpose of this report is to describe the quality of water from the 28 shallow wells and to relate that water quality to natural factors and to human activities. Ground-water samples were analyzed for general ground-water properties and about 240 water-quality constituents, including dissolved solids, major inorganic ions, trace elements, nutrients, dissolved organic carbon (DOC), radon, chlorofluorocarbons, selected stable isotopes, pesticides, pesticide degradation products, and volatile organic compounds (VOC’s). Dissolved-solids concentrations for two wells exceeded the U.S. Environmental Protection Agency Secondary Maximum Contaminant Level of 500 mg/L (milligrams per liter). Concentrations for major inorganic ions, trace elements, pesticides, degradation products, and VOC’s were less than the Maximum Contaminant Levels for drinking water. Manganese concentrations for 18 wells exceeded the Secondary Maximum Contaminant Level of 50 micrograms per liter. Arsenic concentrations increased with depth and with increased pH, bicarbonate, calcium, and magnesium concentrations. Six pesticides and three degradation products were detected in the ground-water samples. Ten VOC’s also were detected in the ground-water samples. One nutrient concentration (that for nitrite plus nitrate) was greater than 2 mg/L, a level that might indicate contamination from human activities, and was greater than the Maximum Contaminant Level of 10 mg/L. The median DOC concentration was an estimated 0.3 mg/L, which indicated naturallyoccurring DOC conditions in the shallow ground water in Lafayette Parish. Quality-control samples indicated no bias in ground-water data from collection or analysis. Radon concentrations for 19 of 20 wells sampled were greater than the U.S. Environmental Protection Agency Maximum Contaminant Level of 300 picocuries per liter (piC/L). Radon concentrations ranged from 280 to 2,220 piC/L and had a median of 389 piC/L. Radon concentrations were correlated moderately and inversely to the depth to the top of the screened interval. Chlorofluorocarbons indicated the apparent age of the ground water varied with water level and ranged from about 12 to 50 years. The Mann-Whitney rank-sum test was used to compare water-quality data in the Chicot aquifer system between four groups of wells from three NAWQA studies. The means for most constituents were less for the urban wells than for wells in the rice-growing areas. The larger dissolved-solids concentrations, particularly sodium and chloride, for samples from wells in the rice-growin","PeriodicalId":23603,"journal":{"name":"Water-Resources Investigations Report","volume":"141 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2004-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86743576","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Two-Dimensional Hydrodynamic Simulation of Surface-Water Flow and Transport to Florida Bay through the Southern Inland and Coastal Systems (SICS)","authors":"E. Swain, Melinda A. Wolfert, J. Bales, C. R. Goodwin","doi":"10.3133/WRI034287","DOIUrl":"https://doi.org/10.3133/WRI034287","url":null,"abstract":".....................................................................................................................................................................................","PeriodicalId":23603,"journal":{"name":"Water-Resources Investigations Report","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2004-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88125964","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Hydrologic drought can be defined as reduced streamflow, declining ground-water levels, and (or) reductions in lake or reservoir levels. Monthly precipitation totals, annual 7-day low-flow surface-water recurrence intervals, and month-end ground-water levels from drought years 1999-2002 show that 19992002 was the driest period of hydrologic drought in more than 50 years of record in Maine. Record lows were set in all three data sets at select locations in central Maine in April 1999, and in September 2001 and 2002. Although streamflows recovered to normal levels during 2000, ground-water levels in central Maine indicate that the drought carried over through 2000 into 2001 and 2002 in some locations. In 2001, annual 7-day low flows with greater than 100-year recurrence intervals were recorded in central Maine and low flows with up to 75-year recurrence intervals were recorded in coastal areas. In 2002, annual 7-day low flows with greater than 100-year recurrence intervals were recorded at 4 of 14 stations analyzed statewide, placing it as the driest single year of hydrologic drought on record. Month-end groundwater levels at one location in central Maine indicate that the recent hydrologic drought years were the most severe in more than 50 years in that region. The period from 1947 to 1950 may have been the only comparable period of drought to the 1999-2002 period, in Maine. The 1960s drought, although extreme in the far northern and far southern regions of the State, was most exceptional for its duration from 1963 to 1969. INTRODUCTION Drought is among the most complex and least understood of all natural hazards, affecting more people than any other natural hazard (American Meteorological Society, 1997). Although drought typically is not considered a problem in the humid northeastern United States, it is a normal, recurring feature in all climatic regimes. Drought is a temporary aberration, relative to some long-term (tens of years) average condition, as opposed to aridity, which is a permanent feature of some regional climates (American Meteorological Society, 1997). Many questions still remain concerning the physical mechanisms responsible for the onset, persistence, and spatial extent of regional hydrologic drought in the northeast because of hydrologic variability and the inherent complexity of hydrologic systems (Bradbury and others, 2002). Dry conditions were present in Maine from 1999 to 2002, with a severe drought in 2001-2002. Most U.S.Geological Survey (USGS) monitoring wells, and many streamflow-gaging stations, set record lows during this period. An estimated 7 percent, or approximately 17,000 private wells in Maine went dry in the 9 months prior to April 2002 (Maine Emergency Management Agency, 2002). Wells in central Maine were the most likely to have low water levels. Thirtyfive public water supplies, including eight large community systems, were affected severely (Andrews Tolman, Maine Drinking Water Program, written communication
水文干旱可以定义为河流流量减少、地下水位下降和(或)湖泊或水库水位下降。1999-2002年干旱年的月降水总量、年7天低流量地表水重现间隔和月末地下水位表明，1999-2002年是缅因州50多年来水文干旱最干旱的时期。1999年4月、2001年9月和2002年9月，缅因州中部选定地点的所有三个数据集都创下了历史新低。虽然河流流量在2000年恢复到正常水平，但缅因州中部的地下水位表明，在一些地方，干旱持续了2000年至2001年和2002年。2001年，缅因州中部记录到的年7天低流量大于100年的重现间隔，沿海地区记录到的年低流量高达75年的重现间隔。2002年，在全州分析的14个站点中，有4个站点记录了超过100年重复周期的7天低流量，使其成为有记录以来最干旱的水文干旱年。缅因州中部一个地方月末的地下水位表明，最近的水文干旱年份是该地区50多年来最严重的。1947年至1950年可能是缅因州唯一可与1999年至2002年相比的干旱时期。1960年代的干旱虽然在该国最北部和最南部地区极为严重，但在1963年至1969年期间却是最为罕见的。干旱是所有自然灾害中最复杂和最不为人所知的灾害之一，影响的人数比任何其他自然灾害都多(美国气象学会，1997年)。尽管干旱在潮湿的美国东北部通常不被认为是一个问题，但它在所有气候制度中都是一个正常的、反复出现的特征。相对于一些长期(几十年)的平均状况，干旱是一种暂时的失常，而干旱是一些区域气候的永久特征(美国气象学会，1997年)。由于水文变异性和水文系统固有的复杂性，东北地区区域性水文干旱的发生、持续和空间范围的物理机制仍然存在许多问题(Bradbury等，2002)。1999年至2002年，缅因州一直处于干旱状态，2001年至2002年发生了严重干旱。大多数美国地质调查局(USGS)的监测井和许多流量测量站在此期间创下了历史新低。在2002年4月之前的9个月里，缅因州约有7%的私人水井干涸(缅因州紧急事务管理局，2002年)。缅因州中部的水井最有可能出现低水位。35个公共供水系统，包括8个大型社区供水系统，受到严重影响(Andrews Tolman, Maine Drinking water Program, written communication, 2003)。大多数主要地表水水库的放水量低于其调节最小流量，水生生物的溪流流量减少，关键的夏季灌溉受到限制。缅因州农业部的一项用水调查显示，2001年和2002年，缅因州农民的农作物损失超过3200万美元，其中一些野生蓝莓种植者的作物损失高达80%至100%，28%的缅因州农民对此作出了回应(缅因州农业用水管理咨询委员会，2003年)。由于缺乏防备计划，过去全国范围内干旱的影响已经加剧(美国气象学会，1997年)。任何准备计划的一个组成部分将包括基于该地区历史干旱的气象和水文阈值。在1999-2002年期间，水资源专业人士、农民、企业主和其他关注河流流量、储水量或地下水位的人缺乏必要的定量历史信息，无法将1999-2002年干旱的严重程度与历史干旱进行比较，也无法评估干旱对水资源造成压力的潜力。由于未来缅因州将发生干旱，水资源专家将受益于1999年至2002年缅因州水文条件的记录和分析。特别是，缅因州的应急管理人员和公共供水供应商将从这些信息中受益，因为他们可以更好地了解干旱如何在水文系统中移动的复杂性，从而更好地预测干旱的影响。本报告的目的是记录1999年至2002年干旱水文条件的相对区域和历史严重程度，并提供有关缅因州干旱发生和持续的信息。 本报告将1999-2002年的日平均流量、月末地下水位和月总降水量与选定站点的历史统计数据进行了比较。本文还研究了降水、地表水和地下水之间的相互作用，这次干旱期和历史干旱的每年7天地表水低流量重复周期，以及历史干旱的月末地下水水位与地下水统计数据的比较。干旱可以根据多种参数进行测量或定义，包括降水不足、河流流量、地下水位、土壤湿度和经济影响。这些参数的强度、持续时间和时空范围之间的关系定义了许多不同类型的事件，所有这些事件都可以被认为是干旱。例如，该州北部地区没有降雨的生长季节与全州范围内降雨量低于平均水平的多年期的特征不同，但两者都可以被认为是干旱。尽管干旱可以严格地定义为正常降水的百分比，但它更经常被定义为一段时间的水分不足，足以对一个地区的社会或经济活动产生一些不利影响(Changnon, 1980;保尔森等人，1991)。在过去，对自然资源管理人员来说，将多种定义整合到干旱的综合测量中是有问题的。干旱的许多定义使得很难宣布干旱的开始或结束，或在干旱期间评估其严重程度。美国气象学会将干旱分为四种类型，包括气候干旱、农业干旱、水文干旱和社会经济干旱(American Meteorological Society, 1997)。气候干旱通常由降水亏缺阈值或实际降水与正常降水之比来定义。农业干旱将气候干旱与农业效应联系在一起，主要是土壤水分缺乏的结果。水文干旱的定义是河流流量减少、地下水位下降和(或)湖泊或水库水位减少。社会经济干旱将一些经济产品的供给和需求与气候、农业和(或)水文干旱的要素联系在一起(美国气象学会，1997)。这些类型的干旱通常同时发生;然而，水文干旱通常与气候干旱和农业干旱不同步或滞后。气象因素，如温度、风和相对湿度，可以加剧干旱的严重程度和影响(美国气象学会，1997)。尽管这里定义的四种干旱类型的各个方面都发生在1999年至2002年的缅因州，但本报告主要记录了水文干旱的特征以及气候干旱是如何促成它的。以前的研究很少有关于缅因州历史干旱的记录。1991年，美国地质勘探局在美国各州定义了多年的历史干旱，并在一份关于洪水和干旱的国家水资源摘要中计算了它们的复发间隔(Paulson等人，1991)。《缅因州水资源概况》确定的干旱期列于表1 (Maloney和Bartlett, 1991): 2 1999-2002年缅因州的干旱状况:历史视角。由Maloney和Bartlett在1991年的《国家水资源概要》中确定的1938 - 1988年缅因州历史干旱的低流量复发间隔[低流量复发间隔，流量小于特定值的平均时间间隔;表1中干旱的复发间隔是根据与月平均流量的累积偏差计算的。这种方法在《国家水资源概要》(Jordan and Jennings, 1991)中对各州洪水和干旱摘要的介绍部分进行了描述。干旱的强度被考虑在内，但持续时间没有考虑在内;持续时间从1年到6年不等的干旱在相同的尺度上排名。这种方法可能适用于确定多年的干旱期，或在美国西部等依赖水库的系统中为总缺水分配复发间隔，但除了最近似的条件外，它不适用于东部各州。这是因为美国东部的干旱既取决于降水总量，也取决于降水时间。美国东北部的资源管理人员经常使用国家指数来评估区域条件，尽管这些指数可能更适合全国范围的水状况监测(Skaggs, 1975)。 通常，国家指数不能给那些受干旱影响的人或那些制定政策的人提供地方评价和行动的基础(Russell等人，1970年)。甚至一个地区内的不同用户组也可能经历
{"title":"Drought Conditions in Maine, 1999-2002: A Historical Perspective","authors":"P. Lombard","doi":"10.3133/WRI034310","DOIUrl":"https://doi.org/10.3133/WRI034310","url":null,"abstract":"Hydrologic drought can be defined as reduced streamflow, declining ground-water levels, and (or) reductions in lake or reservoir levels. Monthly precipitation totals, annual 7-day low-flow surface-water recurrence intervals, and month-end ground-water levels from drought years 1999-2002 show that 19992002 was the driest period of hydrologic drought in more than 50 years of record in Maine. Record lows were set in all three data sets at select locations in central Maine in April 1999, and in September 2001 and 2002. Although streamflows recovered to normal levels during 2000, ground-water levels in central Maine indicate that the drought carried over through 2000 into 2001 and 2002 in some locations. In 2001, annual 7-day low flows with greater than 100-year recurrence intervals were recorded in central Maine and low flows with up to 75-year recurrence intervals were recorded in coastal areas. In 2002, annual 7-day low flows with greater than 100-year recurrence intervals were recorded at 4 of 14 stations analyzed statewide, placing it as the driest single year of hydrologic drought on record. Month-end groundwater levels at one location in central Maine indicate that the recent hydrologic drought years were the most severe in more than 50 years in that region. The period from 1947 to 1950 may have been the only comparable period of drought to the 1999-2002 period, in Maine. The 1960s drought, although extreme in the far northern and far southern regions of the State, was most exceptional for its duration from 1963 to 1969. INTRODUCTION Drought is among the most complex and least understood of all natural hazards, affecting more people than any other natural hazard (American Meteorological Society, 1997). Although drought typically is not considered a problem in the humid northeastern United States, it is a normal, recurring feature in all climatic regimes. Drought is a temporary aberration, relative to some long-term (tens of years) average condition, as opposed to aridity, which is a permanent feature of some regional climates (American Meteorological Society, 1997). Many questions still remain concerning the physical mechanisms responsible for the onset, persistence, and spatial extent of regional hydrologic drought in the northeast because of hydrologic variability and the inherent complexity of hydrologic systems (Bradbury and others, 2002). Dry conditions were present in Maine from 1999 to 2002, with a severe drought in 2001-2002. Most U.S.Geological Survey (USGS) monitoring wells, and many streamflow-gaging stations, set record lows during this period. An estimated 7 percent, or approximately 17,000 private wells in Maine went dry in the 9 months prior to April 2002 (Maine Emergency Management Agency, 2002). Wells in central Maine were the most likely to have low water levels. Thirtyfive public water supplies, including eight large community systems, were affected severely (Andrews Tolman, Maine Drinking Water Program, written communication","PeriodicalId":23603,"journal":{"name":"Water-Resources Investigations Report","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2004-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83381345","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Cross Lake is a shallow, monomictic lake that was formed in 1926 by the impoundment of Cross Bayou. The lake is the primary drinking-water supply for the City of Shreveport, Louisiana. In recent years, the lakeshore has become increasingly urbanized. In addition, the land use of the watershed contributing runoff to Cross Lake has changed. Changes in land use and urbanization could affect the water chemistry and biology of the Lake. Water-quality data were collected at 10 sites on Cross Lake from February 1997 to February 1999. Water-column and bottom-material samples were collected. The water-column samples were collected at least four times per year. These samples analyzed included physical and chemical-related properties such as water temperature, dissolved oxygen, pH, and specific conductance; selected major inorganic ions; nutrients; minor elements; organic chemical constituents; and bacteria. Suspended-sediment samples were collected seven times during the sampling period. The bottom-material samples, which were collected once during the sampling period, were analyzed for selected minor elements and inorganic carbon. Aside from the nutrient-enriched condition of Cross Lake, the overall water-quality of Cross Lake is good. No primary Federal or State water-quality criteria were exceeded by any of the water-quality constituents analyzed for this report. Concentrations of major inorganic constituents, except iron and manganese, were low. Water from the lake is a sodium-bicarbonate type and is soft. Minor elements and organic compounds were present in low concentrations, many below detection limits. Nitrogen and phosphorus were the nutrients occurring in the highest concentrations. Nutrients were evenly distributed across the lake with no particular water-quality site indicating consistently higher or lower nutrient concentrations. No water samples analyzed for nitrate exceeded the U.S. Environmental Protection Agency’s Maximum Contaminant Level of 10 milligrams per liter. Based on nitrogen to phosphorus ratios calculated for Cross Lake, median values for all water-quality sites were within the nitrogen-limited range (less than or equal to 5). Historical Trophic State Indexes for Cross Lake classified the lake as eutrophic. Recent (1998-99) Trophic State Indexes classify Cross Lake as mesotrophic-eutrophic, which might indicate a reduction in eutrophication. Sedimentation traps indicate that Cross Lake is filling at an average rate of 0.41 inch per year. Concentrations of fecal-coliform and streptococci bacteria generally were low. Fecal coliform was detected in higher concentrations than fecal streptococci. High bacteria concentrations were measured shortly after rainfall-runoff events, possibly washing bacteria from surrounding areas into the lake.
{"title":"Water-quality and bottom-material characteristics of Cross Lake, Caddo Parish, Louisiana, 1997-99","authors":"B. McGee","doi":"10.3133/WRI034135","DOIUrl":"https://doi.org/10.3133/WRI034135","url":null,"abstract":"Cross Lake is a shallow, monomictic lake that was formed in 1926 by the impoundment of Cross Bayou. The lake is the primary drinking-water supply for the City of Shreveport, Louisiana. In recent years, the lakeshore has become increasingly urbanized. In addition, the land use of the watershed contributing runoff to Cross Lake has changed. Changes in land use and urbanization could affect the water chemistry and biology of the Lake. Water-quality data were collected at 10 sites on Cross Lake from February 1997 to February 1999. Water-column and bottom-material samples were collected. The water-column samples were collected at least four times per year. These samples analyzed included physical and chemical-related properties such as water temperature, dissolved oxygen, pH, and specific conductance; selected major inorganic ions; nutrients; minor elements; organic chemical constituents; and bacteria. Suspended-sediment samples were collected seven times during the sampling period. The bottom-material samples, which were collected once during the sampling period, were analyzed for selected minor elements and inorganic carbon. Aside from the nutrient-enriched condition of Cross Lake, the overall water-quality of Cross Lake is good. No primary Federal or State water-quality criteria were exceeded by any of the water-quality constituents analyzed for this report. Concentrations of major inorganic constituents, except iron and manganese, were low. Water from the lake is a sodium-bicarbonate type and is soft. Minor elements and organic compounds were present in low concentrations, many below detection limits. Nitrogen and phosphorus were the nutrients occurring in the highest concentrations. Nutrients were evenly distributed across the lake with no particular water-quality site indicating consistently higher or lower nutrient concentrations. No water samples analyzed for nitrate exceeded the U.S. Environmental Protection Agency’s Maximum Contaminant Level of 10 milligrams per liter. Based on nitrogen to phosphorus ratios calculated for Cross Lake, median values for all water-quality sites were within the nitrogen-limited range (less than or equal to 5). Historical Trophic State Indexes for Cross Lake classified the lake as eutrophic. Recent (1998-99) Trophic State Indexes classify Cross Lake as mesotrophic-eutrophic, which might indicate a reduction in eutrophication. Sedimentation traps indicate that Cross Lake is filling at an average rate of 0.41 inch per year. Concentrations of fecal-coliform and streptococci bacteria generally were low. Fecal coliform was detected in higher concentrations than fecal streptococci. High bacteria concentrations were measured shortly after rainfall-runoff events, possibly washing bacteria from surrounding areas into the lake.","PeriodicalId":23603,"journal":{"name":"Water-Resources Investigations Report","volume":"14 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2004-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84088332","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The U.S. Geological Survey collected data from 29 wells and 24 surface-water sites in the Mermentau River Basin, 1998-2001, to better understand ground-water and surface-water quality; aquatic invertebrate communities; and habitat conditions, in relation to land use. This study was a part of the National Water-Quality Assessment Program, which was designed to assess water quality as it relates to various land uses. Water-quality data were evaluated with criteria established for the protection of drinking water and aquatic life, and bed-sediment data were compared to aquatic-life criteria. Water-quality and ecological data were analyzed statistically in relation to drainage area and agricultural land-use intensity. Concentrations of nutrients and major inorganic ions in ground water and surface water generally were highest in the southeastern part of the study area where soils contain thick loess deposits. Peak concentrations of nutrients in surface water occurred March-May at two sites with high agricultural intensity; the lowest concentrations occurred August-January. The greatest potential for eutrophic conditions in surface water, based on nutrient concentrations, existed March-May, at about the same time or shortly after ricefields were drained. Secondary Maximum Contaminant Levels established by the U.S. Environmental Protection Agency (USEPA) were exceeded for sulfate, chloride, iron, or manganese in samples from 20 wells, and for iron or manganese in samples from all surface-water sites. Fewer pesticides were detected in ground water than in surface water. In 11 of the 29 wells sampled, at least one pesticide or pesticide degradation product was detected. The most frequently detected pesticides or pesticide degradation products in ground water were the herbicides bentazon and atrazine. Concentrations of 4 7 pesticides and degradation products were detected in surface water. At least 3 pesticides were detected in all surface-water samples. In 72 percent of the samples at least 5 hydrophylic pesticides were detected, and in more than 70 percent of the samples at least 3 hydrophobic pesticides were detected. Although atrazine concentrations in three samples collected in the spring exceeded 3 ~giL (micrograms per liter), the USEPA Maximum Contaminant Level of 3 ~giL was not exceeded because it is based on an annual average of quarterly samples. Concentrations larger than 3.0 ~giL were not detected in samples collected during other times of the year. Tebuthiuron was detected at all surface-water sites; the largest concentration (6.33 ~giL) was detected at a site on Bayou des Cannes, and was the only detection that exceeded the criterion (1.6 ~giL) for the protection of aquatic life. Malathion was detected at 16 surface-water sites; the largest concentration (0.113 ~giL) was detected at a site on Bayou Lacassine, and was the only detection that exceeded the criterion (0.1 ~giL) for the protection of aquatic life. Concentrations of fipronil excee
{"title":"Environmental setting, water quality, and ecological indicators of surface-water quality in the Mermentau River Basin, southwestern Louisiana, 1998-2001","authors":"S. C. Skrobialowski, S. Mize, D. K. Demcheck","doi":"10.3133/WRI034185","DOIUrl":"https://doi.org/10.3133/WRI034185","url":null,"abstract":"The U.S. Geological Survey collected data from 29 wells and 24 surface-water sites in the Mermentau River Basin, 1998-2001, to better understand ground-water and surface-water quality; aquatic invertebrate communities; and habitat conditions, in relation to land use. This study was a part of the National Water-Quality Assessment Program, which was designed to assess water quality as it relates to various land uses. Water-quality data were evaluated with criteria established for the protection of drinking water and aquatic life, and bed-sediment data were compared to aquatic-life criteria. Water-quality and ecological data were analyzed statistically in relation to drainage area and agricultural land-use intensity. Concentrations of nutrients and major inorganic ions in ground water and surface water generally were highest in the southeastern part of the study area where soils contain thick loess deposits. Peak concentrations of nutrients in surface water occurred March-May at two sites with high agricultural intensity; the lowest concentrations occurred August-January. The greatest potential for eutrophic conditions in surface water, based on nutrient concentrations, existed March-May, at about the same time or shortly after ricefields were drained. Secondary Maximum Contaminant Levels established by the U.S. Environmental Protection Agency (USEPA) were exceeded for sulfate, chloride, iron, or manganese in samples from 20 wells, and for iron or manganese in samples from all surface-water sites. Fewer pesticides were detected in ground water than in surface water. In 11 of the 29 wells sampled, at least one pesticide or pesticide degradation product was detected. The most frequently detected pesticides or pesticide degradation products in ground water were the herbicides bentazon and atrazine. Concentrations of 4 7 pesticides and degradation products were detected in surface water. At least 3 pesticides were detected in all surface-water samples. In 72 percent of the samples at least 5 hydrophylic pesticides were detected, and in more than 70 percent of the samples at least 3 hydrophobic pesticides were detected. Although atrazine concentrations in three samples collected in the spring exceeded 3 ~giL (micrograms per liter), the USEPA Maximum Contaminant Level of 3 ~giL was not exceeded because it is based on an annual average of quarterly samples. Concentrations larger than 3.0 ~giL were not detected in samples collected during other times of the year. Tebuthiuron was detected at all surface-water sites; the largest concentration (6.33 ~giL) was detected at a site on Bayou des Cannes, and was the only detection that exceeded the criterion (1.6 ~giL) for the protection of aquatic life. Malathion was detected at 16 surface-water sites; the largest concentration (0.113 ~giL) was detected at a site on Bayou Lacassine, and was the only detection that exceeded the criterion (0.1 ~giL) for the protection of aquatic life. Concentrations of fipronil excee","PeriodicalId":23603,"journal":{"name":"Water-Resources Investigations Report","volume":"110 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2004-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89329459","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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