Water Table Depth (WTD) NIMS grid Atqasuk, Alaska 2013

Water table depth (WTD) measurements were taken along the Networked Info-mechanical Systems (NIMS) grid in Atqasuk, Alaska during the summer of 2013. The NIMS grid is situated about 50 meters to the south of the International Tundra Experiment (ITEX) dry site. If a uniform representation of the water table within each plot was visible, then a WTD tube was placed there to measure the change in water table throughout the season. For instance if the plot was half saturated and half dry, then that plot was skipped and no tube was placed there. The exact location of WTD tubes are as follows: Between meters 0-1, 3-4, 5-6, 7-8, 9-10, 11-12, 13-14, 15-16, 17-18, 19-20, 21-22, 23-24, 25-26, 32-33, 34-35, 36-37, 38-39, 40-41, 42-43, 44-45, 46-47 & 48-49. A total of 22 WTD tubes were installed into the NIMS grid in Atqasuk. Measurements were made once a week during the summer snow free period between mid June and mid August. WTD was calculated as the difference between the depth (cm) of the water table above or below the measuring tube (- Values = water above tube, + Values= water level below the height of the tube) and the height of the top of the measuring tube above the ground level. Measurements were not made (NA in data sheet) if there was persistent snow cover, interference or disturbance from other experimental infrastructure, or if water table depth tubes were dry to the upper surface of the permafrost.

2013年夏季，在阿拉斯加州阿特夸斯克（Atqasuk）的联网信息机械系统（Networked Info-mechanical Systems, NIMS）网格沿线开展了地下水位深度（Water table depth, WTD）测量工作。NIMS网格位于国际冻原实验（International Tundra Experiment, ITEX）干旱样地以南约50米处。若某样地内地下水位分布均匀且可被观测，则在此处布设地下水位测管，以监测整个生长季的地下水位变化。例如，若样地一半区域处于饱和状态、另一半区域干燥，则跳过该样地，不布设测管。
地下水位测管的精确布设位置如下：0~1米、3~4米、5~6米、7~8米、9~10米、11~12米、13~14米、15~16米、17~18米、19~20米、21~22米、23~24米、25~26米、32~33米、34~35米、36~37米、38~39米、40~41米、42~43米、44~45米、46~47米以及48~49米区间。本次共在阿特夸斯克的NIMS网格中布设了22根地下水位测管。
测量工作于夏季无雪时段开展，频次为每周一次，时段覆盖6月中旬至8月中旬。地下水位深度的计算方式为：以测管管口距地面高度为基准，地下水位与测管的相对深度（单位：厘米），其中负值代表地下水位高于测管管口，正值代表地下水位低于测管管口高度。
若出现持续积雪、其他实验设施带来的干扰或破坏，或地下水位测管直至永冻层上表面仍干燥，则不进行测量，此类情况在数据表中记为NA。