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首页> 外文学位 >Regional-scale groundwater flow and salt transport models for exploring agro-environmental remediation strategies in an irrigated river valley.
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Regional-scale groundwater flow and salt transport models for exploring agro-environmental remediation strategies in an irrigated river valley.

机译：区域规模的地下水流和盐分迁移模型，用于研究灌溉河谷中的农业环境修复策略。

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摘要

Irrigated lands in Colorado's Lower Arkansas River Valley (LARV), like many such lands worldwide, face an uncertain future as pressures on the region's limited water resources continue to increase. This work describes 1) the study locations, 2) data-collection efforts for system characterization and for support of model development, 3) development, calibration, and testing, of groundwater flow and salt transport models and 4) application of the models for describing baseline conditions and for exploring the trade-offs of potential solution strategies for two distinct regions in the LARV [referred to as the Upstream Study Region (USR) and the Downstream Study Region (DSR)].;Data indicate high soil water salinity that is exacerbated by shallow saline groundwater tables in the regions. Extensive soil water salinity surveys reveal average electrical conductivity of soil saturated extract, EC e, throughout the LARV that are near or exceeding crop salt tolerance thresholds in the 3-5 dS m-1 range. Soil water extracted from cultivated field soil samples averaged 4.1 and 6.2 dS m-1 between the USR and DSR, respectively. Of the more than 122,000 locations surveyed for soil water salinity in the LARV over a 7-year survey period, 42% exceeded the estimated crop salt tolerance threshold for the recorded crop type. These conditions correspond to estimated average crop yield reductions of 6% in the USR and 17% in the DSR.;Simulated output from model runs of several alternative management interventions (reduced irrigation applications, reduced canal seepage, lease-fallowing of cultivated land, and combinations thereof) is compared to baseline model results and relative improvements in water table depth and reduced non-beneficial consumptive use are quantified. Potential for lowering the water table by up to 1.1 and 0.7 m on average in the USR and DSR, respectively, is demonstrated. Under each of the investigated scenarios, patterns of groundwater return flows to the river varied, highlighting the need to augment river flows to avoid violations to the interstate river compact that governs river operations in the LARV. In addition to simulating conditions resulting from altered groundwater flow, the calibrated baseline groundwater flow models provide the simulated subsurface flow required for salt transport simulations, whether for the non-reactive solute transport models described herein or for multi-species reactive transport models being developed in parallel research.;Baseline salinity conditions are quantified using the modified subsurface variably saturated solute transport code UZF-MT3DMS. The modified code was developed and verified with 1-, 2-, and 3-dimensional simulations under a variety of conditions, including steady, unsteady, nonreactive and reactive conditions. The average simulated groundwater return salt loads to the Arkansas River are 5,200 and 5,800 MT (metric tons) wk-1, respectively. An evaluation of the baseline model output suggests that chemical reaction processes, such as precipitation and dissolution, should be incorporated into the salt transport models. By providing the simulations with a mechanism for adding and releasing salt to and from storage, model fits to observations of groundwater salt concentrations, soil water salt concentrations, and seasonal salt loading dynamics associated with groundwater return flows likely will be improved.;Without only a minimum level of intervention, the productivity of irrigated agriculture and the environmental quality of the stream-aquifer system in the LARV will remain at or below current sub-par levels. Due to the ever-increasing demand (and value) of water along Colorado's urbanized Front Range, the potential remains for permanent land dry-up as the water is reallocated to other uses. However, simulations of corrective actions that include mitigating inefficient application and delivery of irrigation water offer hope that the LARV's long and rich history of crop production will continue. Alternative management intervention scenarios highlight opportunity for lowering water tables for improving growing conditions, reducing non-beneficial consumptive use, and restoring river water quality. (Abstract shortened by UMI.).
机译：像全世界许多此类土地一样，科罗拉多州下阿肯色河谷（LARV）的灌溉土地面临不确定的未来，因为该地区有限水资源的压力持续增加。这项工作描述了1）研究地点，2）用于系统表征和支持模型开发的数据收集工作，3）地下水流和盐分运输模型的开发，校准和测试以及4）模型的描述基线条件和探索LARV中两个不同区域[称为上游研究区（USR）和下游研究区（DSR）]的潜在解决方案之间的取舍。数据表明土壤高盐度即该地区的浅层地下水地下水位加剧了这一情况。广泛的土壤水盐度调查显示，整个LARV中土壤饱和提取物EC e的平均电导率接近或超过3-5 dS m-1范围内的农盐耐受极限。从耕地土壤样品中提取的土壤水在USR和DSR之间分别平均为4.1 dS m-1和6.2 dS m-1。在为期7年的调查期内，LARV在超过122,000个土壤水盐度调查地点中，有42％超出了所记录作物类型的估计作物盐耐性阈值。这些条件对应于USR估计的平均农作物减产6％，DSR的平均农作物减产17％;几种替代管理干预措施的模拟运行的模拟产出（减少灌溉应用，减少运河渗漏，耕地的租用和将其组合与基准模型结果进行比较，并对地下水位深度的相对改善和减少的非有益消费量进行量化。结果表明，在USR和DSR中，地下水位平均降低了1.1到0.7 m。在每种调查方案下，流向河流的地下水回流方式各不相同，这突出表明有必要增加河流流量，以避免违反管理拉拉夫河流域的州际河流契约。除了模拟地下水流量变化产生的条件外，校准的基线地下水流量模型还提供了盐迁移模拟所需的模拟地下流量，无论是本文所述的非反应性溶质迁移模型还是正在开发的多物种反应性迁移模型。使用改良的地下可变饱和溶质运移代码UZF-MT3DMS对基线盐度条件进行定量。修改后的代码是在各种条件下（包括稳定，不稳定，非反应性和反应性条件）通过一维，二维和3维仿真开发和验证的。进入阿肯色河的模拟地下水平均回盐负荷分别为wk-1 5200和5800 MT（吨）。对基线模型输出的评估表明，应将化学反应过程（例如沉淀和溶解）纳入盐迁移模型中。通过为模拟提供一种向存储库中添加盐和从存储库中释放盐的机制，该模型适合于地下水盐浓度，土壤水盐浓度以及与地下水回流相关的季节性盐负荷动态的观测，可能会得到改善。 LARV的最低干预水平，灌溉农业的生产力以及流水含水层系统的环境质量将保持在或低于目前的低于标准水平。由于科罗拉多州城市化的锋芒山脉地区对水的需求（和价值）不断增长，当水重新分配给其他用途时，土地永久枯竭的可能性仍然存在。但是，通过模拟纠正措施（包括减轻灌溉用水的低效使用和输送），可以使LARV悠久而丰富的农作物生产历史得以延续。替代性管理干预方案突显了降低地下水位以改善生长条件，减少非有益消耗性用水以及恢复河流水质的机会。 （摘要由UMI缩短。）。

著录项

  • 作者

    Morway, Eric D.;

  • 作者单位

    Colorado State University.;

  • 授予单位 Colorado State University.;
  • 学科 Engineering Civil.
  • 学位 Ph.D.
  • 年度 2014
  • 页码 321 p.
  • 总页数 321
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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