RUI: Using Stable Isotopes to Characterize the Soil Water Budget Across a Climate Gradient

5011031气候与土壤水分收支有着复杂的联系，因为它控制着土壤的水和热通量，并影响土壤的形成和土壤性质。该项目将使用稳定同位素地球化学结合气候和土壤物理监测来调查土壤水收支和土壤水分运动方式如何在气候梯度上变化。将在华盛顿州中部的三个地点监测降水、积雪融化和土壤水分，这些地点的年降雨量在136厘米到23厘米之间，主要在冬季以雪的形式出现。这项研究的假设是，水在土壤中渗透的方式(例如活塞流与优先流)、蒸发与蒸腾的速率以及土壤深层水/地下水补给的时间在这种气候梯度的不同水文季节中是可以预测的。为了验证这一假设，将通过两种方法收集土壤水分并进行分析：1)直接平衡土壤岩心与二氧化碳；2)吸力蒸渗仪。稳定同位素测量将与气候测量和土壤物理监测相结合，以确定流动和静止土壤水的数量和停留时间，并量化蒸发速率、蒸腾速率和向下渗透通量。这些参数将反过来与场地特征有关，如降雨量、土壤特性和植被类型/密度。此外，还将评估土壤特性和土壤水分同位素的站点内变异性。这项研究将探索积雪融化主导系统中土壤水分收支如何受到气候的影响，并填补我们对关键上层土壤区域水分运动详细动力学的了解的空白。所获得的信息将对污染物运输、生物地球化学循环、农业和林业实践、水管理等领域产生重大而广泛的影响。此外，该项目还将涉及一项外联计划，在当地学校安装降水收集器和气象站，并将其纳入K-12课程。这一外展计划将加强中央华盛顿大学(CWU)的科学家和当地学校的科学教师之间现有的伙伴关系。这些研究活动将有助于在华威大学建立一个活跃的本科生研究环境，并将利用最近建立的地球化学实验室和相关仪器。

5011031GazisClimate is complexly linked to the soil water budget in that it controls water and heat fluxes to the soil as well as influencing soil formation and soil properties. This project will use stable isotope geochemistry combined with climatic and soil physics monitoring to investigate how the soil water budget and styles of soil water movement vary across a climate gradient. Precipitation, snow melt and soil water will be monitored at three sites in central Washington State that have annual precipitation ranging from 136 cm to 23 cm, occurring mostly as snow in the winter months. The hypothesis underlying this research is that the style in which water percolates through the soil (e.g. piston flow vs. preferential flow), the rates of evaporation versus transpiration, and the timing of deep soil water/groundwater recharge varies predictably during different hydrologic seasons across this climate gradient. To test this hypothesis, soil water will be collected and analyzed by two methods: 1) direct equilibration of soil cores with CO2; 2) suction lysimeter. Stable isotope measurements will be combined with climatic measurements and soil physics monitoring to determine amounts and residence times of mobile versus stationary soil water and to quantify evaporation rates, transpiration rates, and downward percolation fluxes. These parameters will in turn be related to site characteristics such as precipitation, soil properties, and vegetation type/density. In addition, within-site variability in soil characteristics and soil water isotopes will be assessed.This research will explore how the soil water budget in a snowmelt-dominated system is influenced by climate and fill a gap in our understanding of the detailed dynamics of water movement in the critical upper soil region. The information gained will have significant broader implications in areas such as contaminant transport, biogeochemical cycling, agricultural and forestry practices, water management, etc. In addition, the project will involve an outreach program, in which precipitation collectors and weather stations are installed at local schools and incorporated into the K-12 curriculum. This outreach program will strengthen existing partnerships between scientists at Central Washington University (CWU) and science teachers at local schools. The research activities will contribute to an already active undergraduate research environment at CWU and will take advantage of recently built Geochemistry laboratories and associated instrumentation.