Collaborative Research: Evaluating how the sampling integration scale affects field estimates of groundwater transit time and nitrogen fluxes

地下水从地下水位的补给到河流的排泄所需的时间是含水层的一个基本特性，关系到地下水中污染物的迁移速度和水资源管理的其他方面。 该项目的目标是一个严格的定量比较的三种新的方法来估计每一个三个变量的过境时间和非点源硝酸盐污染：（a）平均过境时间（MTT）的地下水在含水层，（B）的水和硝酸盐流量的大小从含水层流，和（c）硝酸盐降解量发生在地下水渗透到溪流之前。 这三种方法都是基于地下水和河流水文和示踪测量，然而，数据收集方法和分析策略有很大的不同。对阐明优势和局限性的方法的并行评估尚不存在，本项目将在北卡罗来纳州农业区的两条溪流中完成。该项目将在纽斯河流域进行，北卡罗来纳州正在对该流域进行雄心勃勃的管理。以减少氮（N）污染和相关的有害藻华和鱼类死亡的纽斯河河口。 几年的努力并没有减少河口N输入。地下水过境时间的N，这可能会延长几十年，是一个潜在的重要因素。 通过比较三种新的方法来测量MTT，硝酸盐通量和硝酸盐降解，该项目将更好地定义这些方法的优缺点。 研究结果将为改进适用于水资源和土地管理的评估战略提供实际指导。 该项目将为两所大学（北卡罗来纳州）的学生提供高级水文培训。州和犹他州大学），以及处理非点源污染物的州监管机构的实际结果和见解。

The transit time of groundwater, from recharge at the water table to discharge at streams, is a fundamental aquifer characteristic relevant to rates of contaminant transport in groundwater and other aspects of water resource management. The project goal is a rigorous quantitative comparison of three novel approaches for estimating each of three variables related to transit time and non-point-source nitrate contamination: (a) the mean transit time (MTT) of groundwater in aquifers, (b) the magnitude of water and nitrate flux from aquifers to streams, and (c) the amount of nitrate degradation occurring in groundwater prior to seepage into streams. Each of the three approaches is based on groundwater and stream hydrologic and tracer measurements, however, the data collection methods and analysis strategies differ greatly. A side-by-side evaluation of the approaches elucidating strengths and limitations does not exist and will be completed by this project in two streams in an agricultural region of the N.C. Coastal Plain.The project will take place in the Neuse River watershed, site of an ambitious basin-wide regulatory effort by the state of N.C. to reduce nitrogen (N) contamination and associated harmful algal blooms and fish kills in the Neuse River estuary. Several years of effort have not reduced estuarine N input. Groundwater transit times for N, which can extend for decades, are potentially an important contributing factor. By comparing three novel approaches to measuring MTT, nitrate flux, and nitrate degradation, this project will better define the pros and cons of the approaches. The results will provide practical guidance to improve assessment strategies applicable to water resource and land management. The project will provide advanced hydrologic training for students at two universities (N.C. State and the Univ. of Utah), and practical results and insight for state regulators dealing with non-point-source pollutants.