Seasonal water table depth (WTD) measurements from a Mobile Instrumented System Platform (MISP) grid, Atqasuk, Alaska, 2017

Water table depth (WTD) measurements were taken along the Mobile Instrumented System Platform (MISP) grid in Atqasuk, Alaska during the summer of 2017. The MISP 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 and 48-49. A total of 22 WTD tubes were installed into the MISP 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 (centimeter) 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.

2017年夏季，在阿拉斯加州阿特卡萨克的移动监测系统平台（Mobile Instrumented System Platform, MISP）网格沿线开展了地下水位深度（Water table depth, WTD）测量工作。该MISP网格位于国际苔原试验（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WTD监测管以监测整个生长季内的地下水位变化。例如，若样地存在半饱和与半干燥区域，则跳过该样地，不布设监测管。WTD监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米区间处。本次共在阿特卡萨克的MISP网格内布设了22根WTD监测管。在夏季无雪期（6月中旬至8月中旬），每周开展一次测量工作。WTD的计算方式为：以测量管顶端距地面的高度为基准，地下水位相较于测量管的埋深（单位：厘米；负值表示水位高于测量管，正值表示水位低于测量管顶端高度）与该基准值的差值即为地下水位深度。若存在持续积雪、其他试验设施的干扰或破坏，或WTD监测管干燥至永久冻土层上表面，则未开展测量（数据记录表中记为NA）。