CAREER: What Governs Salt Mobilization and Transport in Upland Semi-Arid Catchments?

盐度是全球河流流域和灌区最常见的水质威胁之一。土壤和地下水中的高盐分降低了农作物的产量，威胁到世界各地社区的寿命和种植者的生计。在许多半干旱河谷，由于灌溉水含盐、根区排水不良以及土壤中天然矿物质的释放，盐分在土壤中积聚。然而，大量的盐分可以从排水干燥的高地地区的小溪进入山谷。这些高地地区往往蕴藏着大面积的盐矿，在大暴雨期间，盐矿可以溶解并流入溪流。该项目将调查如何在风暴期间调动盐分，并测量从高地地区进入河谷的盐分数量。了解这些过程有助于管理大型河流流域的整体盐分运动，从而维持作物生产力。该项目的实地工作将在科罗拉多州东南部的阿肯色河流域进行，该地区受到高土壤盐分的影响。由于该流域与世界各地其他灌溉的、受盐分影响的河谷相似，该项目的成果可以帮助其他地区。该项目还包括针对初中、高中和研究生班级的教育活动。初中和高中的教学和实地考察将向学生介绍一般和当地的水问题，向学生传授盐分和在当地水域测量盐分的知识，并努力灌输追求科学职业的愿望。教师将接受培训，以便在未来几年为在校学生提供课堂指导和实地考察体验。盐碱化是世界各地河流流域和灌溉地区最常见的水质威胁之一。半干旱和干旱地区灌区作物生产的可持续性受到过度灌溉、灌溉水质差(高盐度)、排水不足、浅层咸水地下水以及土壤和地下地下水盐碱化的威胁，所有这些都可能导致作物减产。世界各地已经进行了大量研究，以评估灌溉地区的盐分积累、装载、运输和命运，使用田间和模拟方法相结合。然而，对旱地集水区动员和向灌区河流输送盐分的关注相对较少。来自高地地区的这些盐分负荷与河流主干的盐分负荷相比可能非常大，从而导致作物产量下降，水安全状况不佳，下游地区的生态健康状况下降。该项目将通过量化风暴期间旱地集水区的盐分移动性和各种运输路径对旱地集水区总盐分输出和河流流域总盐分负荷的贡献，加强对干旱旱地集水区盐分迁移、移动和运输的了解。这些目标将通过实验室和现场降雨模拟器实验、现场数据收集、基于过程的数值模拟以及让中学生参与知识发现和现场方法的教育活动来实现。教育活动包括STEM工具包，用于指导课堂教学、实地数据收集和分析。数据收集和模型应用的研究地点在科罗拉多州东南部的下阿肯色河流域，这是一个地下水和地表水盐分水平较高的地区。为建立模型，将为SWAT流域模型开发一个盐度输送模块，该模块将包括在SWAT的主要源代码中，并在全世界传播，用于管理流域中的盐分负荷。该模块将模拟主要盐离子在土壤、地下水和地表水中的反应迁移，并将考虑土壤盐分对作物生长的影响。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Salinity is one of the most common water quality threats in river basins and irrigated regions worldwide. High salinity in soils and groundwater decreases yield from crops, threatening the longevity of communities worldwide and the livelihood of growers. In many semi-arid river valleys, salt accumulates in the soil due to salty irrigation water, poor drainage in the root zone, and the release of salt from natural mineral deposits in soils. A large quantity of salt, however, can enter the valleys from small streams that drain dry, upland areas. These upland areas often contain vast areas of salt minerals deposits, which can dissolve and flow into streams during large rainstorms. This project will investigate how salt is mobilized during storms and measure the amount of salt leaving the upland area into the river valley. Understanding these processes can assist in managing overall salt movement in large river basins and thereby sustain crop productivity. The field work for this project will take place in the Arkansas River Basin in southeastern Colorado, a region affected by high soil salinity. Due to the similarities between this basin and other irrigated, salinity-affected river valleys worldwide, results from this project can help other regions. This project also includes educational activities for middle schools, high schools, and graduate university classes. Middle school and high school instruction and field trips will introduce students to general and local water issues, teach students about salt and measuring salt in local waters, and seek to instill a desire to pursue careers in sciences. Teachers will be trained so that in-class instruction and field trip experiences can serve students attending the schools in coming years.Salinity is one of the most common water quality threats in river basins and irrigated regions worldwide. Sustainability of crop production in irrigated areas in semi-arid and arid areas is threatened by over-irrigation, poor quality of irrigation water (high salinity), inadequate drainage, shallow saline groundwater, and salinization of soil and underlying groundwater, all of which can lead to decreased crop yield. Numerous studies have been conducted worldwide to assess salinity build-up, loading, transport, and fate in irrigated regions using a combination of field and modeling methods. However, relatively little attention has been given to upland catchments that mobilize and load salt to the rivers of irrigated regions. These salt loads from upland areas can be significant compared to the salt loads in the main stem of the rivers, thus contributing to decreased crop yield, poor water security, and a decrease in ecological health in downstream regions. This project will enhance understanding of salinity mobilization, movement, and transport in arid upland catchments by quantifying salt mobilization in upland catchment areas during storm events and quantifying the contribution of various transport pathways to total salt export from upland catchments and total salt loading in the river basin. These objectives will be accomplished through laboratory and field rainfall simulator experiments, field data collection, process-based numerical modeling, and educational activities that involve middle school and high school students in knowledge discovery and field methods. Educational activities include STEM kits to guide classroom instruction, field data collection, and analysis. The study sites for data collection and model application are within the Lower Arkansas River Basin in southeastern Colorado, an area with high levels of salinity in groundwater and surface water. For modeling, a salinity transport module for the SWAT watershed model will be developed, which will be included in the main SWAT source code and disseminated for use worldwide to manage salt loadings in watersheds. The module will simulate the reactive transport of major salt ions in soils, groundwater, and surface water, and will account for the effect of soil salinity on crop growth.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.