Turbidity data from the Carmel River, central California, 2014 to 2017

This data provides river turbidity measurements collected on the Carmel River, CA. Turbidity was measured to study any changes in the Carmel River’s sediment loads following the removal of the San Clemente Dam. The USGS-run DTS-12 turbidity sensor was deployed above the Sleepy Hollow Weir on the Carmel River, CA (instrument was located at 36.445250 degrees North, 121.710494 degrees West). Deployment began on December 9, 2014. After June 16, 2016, the instrument was removed for calibration. A new instrument was re-deployed on October 14, 2016, and continued to record until recovery on July 13, 2017. Due to the instrument removal and calibration, there exists an approximately 4-month long gap in data collection from June 16 to October 14, 2016. The sensor recorded turbidity, water temperature, and battery voltage at 15-minute intervals. The data are in Formazin Nephelometric Units (FNU), which are similar to Nephelometric Turbidity Units (NTU) in that both measure scattered light at 90 degrees from the incident light beam. FNU are measured with an infrared light source (by the ISO 7027 method), whereas NTU requires a white light source (EPA method 180.1). For more information on FNU and water turbidity data, please visit http://or.water.usgs.gov/grapher/fnu.html. Apparently spurious data points were removed during processing. Those included: data points in which the temperature reading dropped abruptly to zero [both temperature and turbidity values were set to "NaN" (Not A Number)], data points in which the turbidity value abruptly dropped from a non-zero value to zero and recovered immediately to near the original non-zero reading (in which case turbidity, but not temperature, values were set to "NaN"), and several points were deleted in the record in which turbidity spiked rapidly by two or three orders of magnitude and then immediately returned to much lower values. This may occur, for example, if a leaf blocked the sensor momentarily, but we considered it was likely not a real increase in turbidity. Several rapid apparent increases in turbidity remain in the record. These may be real or spurious; they did not appear abrupt enough to be clearly spurious, and so are left in the record. Turbidity spikes were also removed that coincided with equipment deployment at the site.本数据集收录了美国加利福尼亚州卡梅尔河的河水浊度实测数据。本次浊度监测旨在探究圣克莱门特大坝拆除后，卡梅尔河泥沙负荷的变化情况。美国地质调查局（USGS）运维的DTS-12型浊度传感器部署于卡梅尔河斯利普霍洛堰（Sleepy Hollow Weir）上方，地理坐标为北纬36.445250°、西经121.710494°。本次部署始于2014年12月9日。2016年6月16日，该传感器被拆卸送检校准。2016年10月14日，新传感器完成重新部署，并持续采集数据直至2017年7月13日被回收。由于传感器的拆卸校准工作，2016年6月16日至2016年10月14日期间存在约4个月的数据采集空白期。 该传感器以15分钟为采样间隔，同步记录浊度、水温与电池电压数据。浊度采用福尔马肼浊度单位（Formazin Nephelometric Units, FNU）进行计量，该单位与散射浊度单位（Nephelometric Turbidity Units, NTU）原理相似，二者均通过检测入射光束90°方向的散射光实现浊度量化。其中FNU采用红外光源，符合ISO 7027国际标准；NTU则使用白光源，遵循美国环保署（EPA）180.1检测方法。如需了解更多关于FNU及水体浊度数据的详细信息，请访问http://or.water.usgs.gov/grapher/fnu.html。 数据预处理阶段已剔除部分疑似异常数据点，具体包括：水温读数骤降至零的记录，此时水温与浊度值均被设为"NaN（非数值，Not A Number）"；浊度值从非零水平骤降至零后随即恢复至接近原非零读数的记录，此类记录仅将浊度值设为"NaN"，保留水温数据；浊度值在短时间内突增2至3个数量级后迅速回落至低水平的记录——此类情况可能由树叶短暂遮挡传感器引发，被判定为非真实的浊度变化，故予以剔除。本数据集仍保留了若干快速的浊度异常升高记录，此类信号可能为真实变化或疑似异常：因突变程度不足以明确判定为异常，故未做剔除。此外，与现场设备部署时段重合的浊度峰值也已被移除。