Brooks J R, Mushet D M, Vanderhoof M K, Leibowitz S G, Christensen J R, Neff B P, Rosenberry D O, Rugh W D, Alexander L C
U.S. Environmental Protection Agency, National Health and Environmental Effects Research Laboratory, Western Ecology Division, Corvallis, OR USA.
U.S. Geological Survey, Northern Prairie Wildlife Research Center, Jamestown, ND USA.
Water Resour Res. 2018 Mar 9;54(2):995-977. doi: 10.1002/2017WR021016.
Understanding hydrologic connectivity between wetlands and perennial streams is critical to understanding the reliance of stream flow on inputs from wetlands. We used the isotopic evaporation signal in water and remote sensing to examine wetland-stream hydrologic connectivity within the Pipestem Creek watershed, North Dakota, a watershed dominated by prairie-pothole wetlands. Pipestem Creek exhibited an evaporated-water signal that had approximately half the isotopic-enrichment signal found in most evaporatively enriched prairie-pothole wetlands. Groundwater adjacent to Pipestem Creek had isotopic values that indicated recharge from winter precipitation and had no significant evaporative enrichment, indicating that enriched surface water did not contribute significantly to groundwater discharging into Pipestem Creek. The estimated surface-water area necessary to generate the evaporation signal within Pipestem Creek was highly dynamic, varied primarily with the amount of discharge, and was typically greater than the immediate Pipestem Creek surface-water area, indicating that surficial flow from wetlands contributed to stream flow throughout the summer. We propose a dynamic range of spilling thresholds for prairie-pothole wetlands across the watershed allowing for wetland inputs even during low flow periods. Combining Landsat estimates with the isotopic approach allowed determination of potential (Landsat) and actual (isotope) contributing areas in wetland-dominated systems. This combined approach can give insights into the changes in location and magnitude of surface water and groundwater pathways over time. This approach can be used in other areas where evaporation from wetlands results in a sufficient evaporative isotopic signal.
了解湿地与常年溪流之间的水文连通性对于理解溪流流量对湿地输入的依赖至关重要。我们利用水中的同位素蒸发信号和遥感技术，研究了北达科他州派普斯特姆溪流域内湿地与溪流的水文连通性，该流域以草原坑洼湿地为主。派普斯特姆溪呈现出一种蒸发水信号，其同位素富集信号约为大多数蒸发富集的草原坑洼湿地中发现的信号的一半。派普斯特姆溪附近的地下水同位素值表明其补给来自冬季降水，且没有明显的蒸发富集，这表明富集的地表水对排入派普斯特姆溪的地下水贡献不大。在派普斯特姆溪内产生蒸发信号所需的估计地表水面积高度动态变化，主要随流量大小而变化，且通常大于派普斯特姆溪紧邻的地表水面积，这表明湿地的地表径流在整个夏季都对溪流流量有贡献。我们提出了整个流域草原坑洼湿地溢出阈值的动态范围，即使在低流量时期也允许湿地输入。将陆地卫星估算值与同位素方法相结合，可以确定湿地主导系统中的潜在（陆地卫星）和实际（同位素）贡献区域。这种综合方法可以深入了解地表水和地下水路径的位置和大小随时间的变化。这种方法可用于其他因湿地蒸发产生足够蒸发同位素信号的地区。
