THESIS REPOSITORY : FACTORS AFFECTING UNITED STATES GEOLOGICAL SURVEY IRRIGATION FRESHWATER WITHDRAWAL ESTIMATES IN UTAH

This collection comprises the data, codes, analyses and results for my thesis. See the thesis in USU Digital Commons for more information.

PUBLIC ABSTRACT

According to the United States Geological Survey, irrigation represents about 80% of the freshwater withdrawn in Utah. On average, Utah is the second driest state in the U.S., with drier conditions projected throughout the century. Periods fluctuating between drought and flood are typical in the region. Understanding what factors affect Utah’s largest water user can inform sustainable irrigation practices, which could lead to conservation of Utah’s vital surface and groundwater. National, regional, and state analyses have identified total irrigated acreages, more efficient irrigation technologies, and freshwater availability as significant factors of irrigation withdrawals. This study sought to bring these findings up to date in Utah, and validate them at state, sub-state, and county levels. Utilizing Kendall’s Tau-b correlation test, factor relationships were assessed between the survey’s irrigation withdrawal and acreage data, as well as water year, season, and monthly freshwater availability key indicators including natural stream flows, reservoir levels, precipitation, and ambient temperatures. At the state level, no significant correlations were found between total irrigation withdrawals and total, or sprinkler, irrigated acres. This could indicate that practices such as fallowing fields, or converting to sprinkler systems, may not significantly reduce irrigation withdrawals. Relatively few significant results were found between irrigation withdrawals and water year key indicators, suggesting that historical infrastructure and practices have been adequate at overcoming annual freshwater availability fluctuations. Total and surface irrigation withdrawals were significantly negatively correlated with ground withdrawals, suggesting that conjunctive management principles have played a key role mitigating annual freshwater availability fluctuations. Groundwater stores have been overdrawn in many areas of the state, and this practice may not be sustainable under projected drier conditions. With further analyses, some significant correlations between irrigation withdrawals, and early months and seasons’ precipitation and ambient temperatures may be utilized in irrigation demand projections. Though sub-state results were similar with statewide results, county results varied, demonstrating the importance of finer scales of analyses and localized decision making. It also highlights areas that may be more affected by freshwater availability, as well as the many unique irrigation withdrawal reduction opportunities that exist within areas of Utah.

本数据集包含了本论文所涉及的数据、代码、分析和结果。欲了解更多信息，请参阅USU数字图书馆中的论文。

公开摘要
根据美国地质调查局的数据，灌溉在犹他州占到了淡水提取量的约80%。平均而言，犹他州是美国第二干旱的州，预计整个世纪都将面临更为干旱的气候。该地区典型的气候状况是介于干旱和洪水之间的波动。了解影响犹他州最大用水量的因素，有助于制定可持续的灌溉实践，进而可能实现犹他州宝贵地表水和地下水的保护。国家和区域分析已经确定了总灌溉面积、更高效的灌溉技术和淡水供应是灌溉用水量的重要因素。本研究旨在对犹他州的情况进行更新，并在州、次州和县各级进行验证。通过使用肯德尔τ-b相关测试，评估了调查中的灌溉用水量和面积数据、以及水年、季节和月度淡水供应关键指标（包括自然溪流流量、水库水位、降水量和环境温度）之间的因素关系。在州级层面，没有发现总灌溉用水量与总面积或喷灌灌溉面积之间存在显著的相关性。这可能表明，如休耕土地或转换为喷灌系统等做法，可能不会显著减少灌溉用水量。灌溉用水量与水年关键指标之间的显著结果相对较少，这表明历史基础设施和实践已足以应对年度淡水供应波动。总灌溉用水量和地表灌溉用水量与地下水抽取量呈显著负相关，这表明联合管理原则在缓解年度淡水供应波动方面发挥了关键作用。该州许多地区的地下水储存已被过度抽取，而在预期的更干旱条件下，这种做法可能不可持续。进一步的分析可能会发现灌溉用水量与早期月份和季节的降水量及环境温度之间的一些显著相关性，这些相关性可能被用于灌溉需求预测。尽管次州结果与全州结果相似，但县的结果却有所差异，这突显了精细尺度分析和本地决策的重要性。同时，这也突出了可能更多地受到淡水供应影响的地区，以及犹他州区域内存在的众多独特的灌溉用水量减少机会。