Digitized Maps of the Potentiometric Surface of the Sparta Aquifer in North-Central Louisiana, 1886 to 2012 (ver. 1.1, April 2021)

The Sparta aquifer is a primary source of groundwater in north-central Louisiana with more than 60 million gallons of water per day being withdrawn in 2015, and public supply and Industry account for over 90 percent of the water-use demand from the Sparta aquifer (Collier, 2018). Concentrated withdrawals from the Sparta aquifer have caused regional water-level declines within the Sparta aquifer (McGee and Brantly, 2015). Widespread concern about the potential effects of declining water levels has brought forth many questions regarding the sustainability of the aquifer as well as continued saltwater intrusion. In cooperation with the Louisiana Department of Transportation and Development, the U.S. Geological Survey (USGS) Lower Mississippi-Gulf (LMG) Water Science Center created a digital dataset of the potentiometric surfaces of the Sparta Aquifer in Arkansas, Kentucky, Louisiana, Mississippi, Missouri, and Tennessee, which was developed from eight (USGS) reports. The potentiometric surfaces range in years from 1886 (predevelopment) to 2012 and cover north-central Louisiana with a selection of surfaces extending into the nearby states of Arkansas, Louisiana, Mississippi, Missouri, and Tennessee. Each surface was georeferenced to North American Datum 1983 and projected to USA Contiguous Albers Equal Conic projection. Once georeferenced, individual contour lines were digitized, and attributes were included for each potentiometric surface. Included for each report is a zipped folder containing the georeferenced surface and a shapefile that includes the digitized contour lines. The digital dataset of potentiometric surfaces provides the framework necessary to further investigate total volume of water and how it has changed through time within the Sparta aquifer. First release: April 2019; revised April 2021 (version 1.1). The previous version can be obtained by contacting the USGS Lower Mississippi-Gulf Water Science Center using the "Point of Contact" link on the landing page on ScienceBase. Reference: Collier, A.L., 2018, Withdrawals, in million gallons per day, by source type and water use category in the Parishes of Louisiana, 2014-2015: U.S. Geological Survey data release, https://doi.org/10.5066/F78051VM McGee, B.D., and Brantly, J.A., 2015, Potentiometric surface, 2012, and water-level differences, 2005-12, of the Sparta Aquifer in north-central Louisiana: U.S. Geological Survey Scientific Investigations Map 3313, 2 sheets, https://dx.doi.org/10.3133/sim3313 Potentiometric maps included in this dataset: Brantly, J.A., Seanor, R.C., McCoy, K.L., 2002, Hydrogeology and potentiometric surface of the Sparta aquifer in northern Louisiana, October 1996: U.S. Geological Survey Water-Resources Investigations Report 02-4053, 3 sheets, https://doi.org/10.3133/wri024053 McGee, B.D., and Brantly, J.A., 2015, Potentiometric surface, 2012, and water-level differences, 2005-12, of the Sparta Aquifer in north-central Louisiana: U.S. Geological Survey Scientific Investigations Map 3313, 2 sheets, https://dx.doi.org/10.3133/sim3313 Reed, J. E., 1972, Analog simulation of water-level declines in the Sparta sand, Mississippi embayment: U.S. Geological Survey Hydrologic Atlas 434, 1 sheet, https://doi.org/10.3133/ha434 Ryals, G. N., 1980, Potentiometric maps of the Sparta Sand, northern Louisiana and southern Arkansas, 1900, 1965, 1975, and 1980: U.S. Geological Survey Open-File Report 80-1180, 1 sheet, https://doi.org/10.3133/ofr801180 Schrader, T. P., 2004, Status of water levels and selected water-quality conditions in the Sparta-Memphis aquifer in Arkansas and the Sparta aquifer in Louisiana, spring-summer 2001: U.S. Geological Survey Scientific Investigations Report, 3 sheets, https://doi.org/10.3133/sir20045055 Schrader, T.P., 2007, Potentiometric surface in the Sparta-Memphis aquifer of the Mississippi Embayment, spring 2007: U.S. Geological Survey Scientific Investigations Map 3014, 1 sheet, https://doi.org/10.3133/sim3014 Schrader, T. P., and Jones, J. S. (2007). Status of Water Levels and Selected Water-Quality Conditions in the Sparta-Memphis Aquifer in Arkansas and the Status of Water Levels in the Sparta Aquifer in Louisiana, Spring 2005: U.S. Geological Survey Scientific Investigations Report 2007-5029, 2 sheets, https://doi.org/10.3133/sir20075029 Smoot, C. W., and Seanor, R. C. (1991). Louisiana ground-water map no. 3: Potentiometric surface, 1989, and water-level changes, 1980-89, of the Sparta aquifer in north-central Louisiana: U.S. Geological Survey Water-Resources Investigations Report 90-4183, 2 sheets, https://doi.org/10.3133/wri904183

斯帕塔含水层（Sparta aquifer）是路易斯安那州中北部的主要地下水源，2015年日取水量超过6000万加仑，其中公共供水与工业用水占该含水层用水需求的90%以上（Collier, 2018）。对斯帕塔含水层的集中开采已引发区域水位下降（McGee and Brantly, 2015）。社会各界对水位下降潜在影响的广泛担忧，催生了诸多关于含水层可持续性及持续咸水入侵的研究议题。

美国地质调查局（U.S. Geological Survey, 简称USGS）下密西西比-墨西哥湾（Lower Mississippi-Gulf, 简称LMG）水科学中心与路易斯安那州交通与发展部合作，基于8份USGS研究报告，构建了覆盖阿肯色州、肯塔基州、路易斯安那州、密西西比州、密苏里州和田纳西州的斯帕塔含水层测压水面（potentiometric surfaces）数字化数据集。

本次数据集包含的测压水面年份跨度为1886年（开发前基准）至2012年，其空间范围以路易斯安那州中北部为核心，部分测压水面延伸至邻近的阿肯色州、密西西比州、密苏里州和田纳西州。所有测压水面均采用北美大地基准1983（North American Datum 1983）进行地理参考，并投影至美国本土连续阿尔伯斯等面积圆锥投影（USA Contiguous Albers Equal Conic projection）。完成地理参考后，研究团队对各条等高线进行数字化处理，并为每个测压水面添加配套属性信息。

每份配套研究报告均包含一个压缩文件夹，内含已完成地理参考的测压水面数据，以及包含数字化等高线的形状文件（shapefile）。该数字化测压水面数据集为进一步分析斯帕塔含水层总水量及其随时间的变化规律提供了核心框架。

本数据集首次发布于2019年4月，2021年4月完成修订（版本1.1）。旧版数据集可通过联系USGS下密西西比-墨西哥湾水科学中心获取，具体操作可通过ScienceBase主页上的"联系人"链接完成。

### 参考文献
1. Collier, A.L., 2018, 2014-2015年路易斯安那州各堂区按水源类型和用水类别划分的取水量（单位：百万加仑/日）：美国地质调查局数据发布，https://doi.org/10.5066/F78051VM
2. McGee, B.D., and Brantly, J.A., 2015, 路易斯安那州中北部斯帕塔含水层2012年测压水面及2005-2012年水位差：美国地质调查局科学调查图3313，共2张，https://dx.doi.org/10.3133/sim3313

### 本数据集包含的测压图
1. Brantly, J.A., Seanor, R.C., McCoy, K.L., 2002, 路易斯安那州北部斯帕塔含水层的水文地质与1996年10月测压水面：美国地质调查局水资源调查报告02-4053，共3张，https://doi.org/10.3133/wri024053
2. McGee, B.D., and Brantly, J.A., 2015, 路易斯安那州中北部斯帕塔含水层2012年测压水面及2005-2012年水位差：美国地质调查局科学调查图3313，共2张，https://dx.doi.org/10.3133/sim3313
3. Reed, J. E., 1972, 密西西比河冲积扇斯帕塔砂层水位下降的模拟分析：美国地质调查局水文图集434，共1张，https://doi.org/10.3133/ha434
4. Ryals, G. N., 1980, 1900、1965、1975及1980年路易斯安那州北部与阿肯色州南部斯帕塔砂层测压图：美国地质调查局公开文件报告80-1180，共1张，https://doi.org/10.3133/ofr801180
5. Schrader, T. P., 2004, 2001年春夏季节阿肯色州斯帕塔-孟菲斯含水层及路易斯安那州斯帕塔含水层的水位与部分水质状况：美国地质调查局科学调查报告，共3张，https://doi.org/10.3133/sir20045055
6. Schrader, T.P., 2007, 2007年春季密西西比河冲积扇斯帕塔-孟菲斯含水层测压水面：美国地质调查局科学调查图3014，共1张，https://doi.org/10.3133/sim3014
7. Schrader, T. P., and Jones, J. S. (2007). 2005年春季阿肯色州斯帕塔-孟菲斯含水层水位与部分水质状况及路易斯安那州斯帕塔含水层水位状况：美国地质调查局科学调查报告2007-5029，共2张，https://doi.org/10.3133/sir20075029
8. Smoot, C. W., and Seanor, R. C. (1991). 路易斯安那州地下水图集第3号：路易斯安那州中北部斯帕塔含水层1989年测压水面及1980-1989年水位变化：美国地质调查局水资源调查报告90-4183，共2张，https://doi.org/10.3133/wri904183