Subsurface Structure and Flow Regime for Rocky Mountain Hillslopes with Different Geologies

美国西部山区的融雪是干旱的山间盆地农业、工业、城市和自然生态系统的重要水源。山区融雪成流过程受气候、植被、地质等因素的共同作用。地下水在将水从入渗点输送到河流中的作用目前知之甚少。本研究使用最先进的仪器对六个不同地质的落基山脉山坡的地下进行成像。此外，还利用计算机模拟模型计算地下水流量和储水动态，并对径流进行预测。一个重要的目标是找到地质和流动状态之间可预测的关系。由此产生的见解对于理解当前和未来气候和土地利用情景对河流流量的大小和时间的影响至关重要。这些见解将有助于机构、公司和个人更好地管理土地和水资源。作为项目的一部分，两名研究生和三名本科生将获得广泛的地质和水文测量以及计算机模拟技术的经验。此外，将与怀俄明大学地质博物馆合作建造一个巡回博物馆展览，以吸引落基山脉地区的居民和游客参与地质和水文研究。该研究结合了最先进的地球物理和水文测量和建模技术，研究了三种不同地质条件下山坡的地下水流和储存。将回答以下研究问题：为这项研究选择的六个落基山脉山坡的风化带，代表了前寒武纪岩石上古老的花岗岩表面、年轻的火山表面和最近的冰川沉积物，它们的不同或相似程度如何？Q2。在多大程度上可以确定六个落基山脉山坡的地下水力特性和流动状况？Q3。在流域尺度上，斜坡地下模型复杂性对径流和水平衡预测的影响是什么？其中三个山坡位于怀俄明州，目前正在由两名调查人员进行测量。另外三个山坡是在爱达荷州(2)和新墨西哥州(1)的临界区天文台提出的。六个山坡是成对的，所以三个地质都由两个山坡代表。测量将包括浅层地震折射，以确定地下孔隙结构，时延电阻率层析成像，以确定渗透带水动力学，以及水文监测，以评估水输入和山坡水文响应。数值模型将与参数估计算法相结合来估计地下水力参数。综合流域模型将用于研究斜坡模型复杂性对径流和水平衡预测的影响。该研究侧重于地下水文过程和径流生成，但也有助于更好地理解山坡风化过程和山坡生态功能。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Snowmelt from mountainous regions in the western US is a vital source of water for agriculture, industry, cities, and natural ecosystems in the dry inter-mountain basins. The transformation of snowmelt into streamflow in mountainous regions is influenced by the interplay between climate, vegetation, and geology. The role of the subsurface in transporting water from the point of infiltration to the stream is currently poorly understood. This study uses state-of-the-art instruments to image the subsurface of six Rocky Mountain hillslopes with different geologies. In addition, computer simulation models are used to calculate subsurface water flow and storage dynamics and to predict streamflow. An important goal is to find predictable relationships between geology and flow regime. The resulting insights are critical for understanding the impact of current and future climate and land use scenarios on the magnitude and timing of streamflow. Such insights will facilitate better land and water management by agencies, companies, and individuals. Two graduate students and three undergraduate students will gain experience with a broad range of geological and hydrological measurement and computer simulation techniques as part of the project. In addition, a traveling museum exhibit will be constructed in collaboration with the University of Wyoming Geological museum to engage residents and visitors of the Rocky Mountain region in geological and hydrological research. The study combines state-of-the-art geophysical and hydrological measurement and modeling techniques to examine subsurface water flow and storage in hillslopes with three different geologies. The following research questions will be answered: Q1. How different or similar are the weathering zones of the six Rocky Mountain hillslopes selected for this study that represent old granitic surfaces, young volcanic surfaces, and recent glacial deposits over Precambrian rock?, Q2. To what level of detail can subsurface hydraulic properties and flow regimes be determined for the six Rocky Mountain hillslopes?, and Q3. What is the impact of hillslope subsurface model complexity on streamflow and water balance predictions at the watershed scale? Three of the hillslopes are in Wyoming and are currently being measured by the two investigators. The other three hillslopes are proposed in Critical Zone Observatories in Idaho (2) and New Mexico (1). The six hillslopes are paired so that each of the three geologies are represented by two hillslopes. Measurements will consist of shallow seismic refraction to determine subsurface porosity structure, time-lapse electrical resistivity tomography to determine vadose zone water dynamics, and hydrological monitoring to assess water inputs and hillslope hydrologic response. Numerical models will be combined with parameter estimation algorithms to estimate subsurface hydraulic parameters. Integrated watershed modeling will be used to investigate the effect of hillslope model complexity on streamflow and water balance predictions. The study focusses on subsurface hydrological processes and streamflow generation but also contributes to a better understanding of hillslope weathering processes and hillslope ecological functioning.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.