Water Table Depth (WTD) NIMS grid Atqasuk, Alaska 2015

Water table depth (WTD) measurements were taken along the Networked Info-mechanical Systems (NIMS) grid in Atqasuk, Alaska during the summer of 2015. The NIMS grid is situated about 50 meters to the south of the 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 every few days 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.

2015年夏季，于阿拉斯加州阿特卡萨克（Atqasuk）的网络化信息机械系统（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网格位于国际苔原实验（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表征，则在此处布设WTD测管以监测整个生长季的地下水位变化。例如，若样地半湿半干，则跳过该样地，不布设测管。
WTD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米及48~49米区间。本次共在阿特卡萨克的NIMS网格中布设了22根WTD测管。
在6月中旬至8月中旬的夏季无雪期，每隔数日开展一次测量。WTD的计算方式为：测管上方或下方的地下水位深度（单位：厘米，负值代表水位高于测管顶端，正值代表水位低于测管顶端高度）与测管顶端距地面高度的差值。
若存在持续积雪、其他实验设施的干扰或破坏，或WTD测管至永冻层（permafrost）上表面全程干燥，则未开展测量（数据记录表中记为NA）。