Groundwater and nutrient dynamics in heterogeneous agricultural catchments

异质农业流域的地下水和养分动态

• 批准号: 2323404
• 金额: --
• 依托单位: University of Aberdeen
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2019
• 资助国家: 英国
• 起止时间: 2019 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2323404
• 关键词: Groundwater; nutrient; dynamics; heterogeneous; agricultural

In Irish and Scottish agricultural regions, groundwater is increasingly recognised as a major pathway for water and nutrient inputs to streams [1]. Groundwater also serves as a buffer, maintaining river flow during dry periods and diluting high nutrient concentrations delivered via surface pathways. It is acknowledged that nutrients inputs from groundwater are inversely correlated with groundwater residence times. Understanding groundwater pathways and residence time in catchments is key to improving agricultural management and to predicting catchment resilience to climatic change. Traditional conceptual models oversimplify the relationship between the shallow groundwater system with short flow paths, young age and high nutrient load on the one hand, and deeper groundwater with longer flow paths, older age and lower nutrient load on the other hand. Irish and Scottish catchments however are characterised by a complex subsurface composed of glacial deposits overlying fractured bedrock, both highly heterogeneous, which complicates this model by creating deep and rapid preferential flow paths through highly-permeable glacial deposits and fractured zones. In addition, variable aquifer confining conditions, dictated by variability in glacial deposit thickness also influences groundwater recharge and nutrient attenuation processes. Both in turn result in complex spatial distribution, timing and magnitude of water and nutrient inputs to streams. This project aims at providing a better understanding of the importance of hydrogeological controls on groundwater and nutrient inputs to streams in agricultural catchments. It will built on recent advances in using geophysical data to model groundwater pathways and residence times developed by the project team [2], complemented by high-resolution monitoring of groundwater and surface water including nutrients and isotopes (stable and radioactive) to further constrain pathways and residence times. The research will use the Glen Burn catchment in Northern Ireland extensively monitored by the team [3]. The catchment is characterised by a bedrock juxtaposing weathered/fractured greywacke and poorly-consolidated sandstone, both overlain by poorly-draining, spatially heterogeneous, glacial-till. It is equipped with 16, multi-depth boreholes, and a river discharge gauge. It also benefits from availability of extensive, multi-scale geophysical datasets. The research will involve; 1/mapping catchment-scale nutrients distribution in streams and boreholes (soil, shallow and deep aquifer) as well as stable and radioactive isotope sampling; 2/modelling catchment-scale distribution of groundwater flow paths and residence times using a distributed groundwater numerical model parameterised with aquifer properties derived from multi-scale geophysical data (borehole, ground and TELLUS airborne surveys); 3/assessing the relationship between streamflow/nutrient distribution, and groundwater discharge/residence time; 4/testing land-use management scenarios for nutrient reduction and optimisation of mitigation measures. The studentship will be implemented as part of a long-established collaboration with Dr Rachel Cassidy, AFBI (Agri-Food and Biosciences Institute), which will provide additional supervision and placements. The student will benefit from cutting-edge training in hydrogeology and groundwater flow modelling (UoA, QUB); hydrogeophysics (UoA, AFBI); hydrogeochemistry (QUB); and advanced nutrient monitoring and analysis as well as training in translating research outcomes into policy guidance (AFBI). They will also benefit from wider, QUADRAT-wide training courses, including the field geophysics course currently run on the study site.

在爱尔兰和苏格兰农业地区，地下水越来越被认为是向溪流输入水和养分的主要途径[1]。地下水还可以起到缓冲作用，在干旱时期维持河流流量，并稀释通过地表路径输送的高营养浓度。人们承认，来自地下水的养分输入与地下水停留时间成反比。了解地下水路径和流域内的停留时间是改善农业管理和预测流域对气候变化的适应能力的关键。传统的概念模型过度简化了流动路径短、年龄小和养分负荷高的浅层地下水系统与流动路径长、年龄大和养分负荷低的深层地下水之间的关系。然而，爱尔兰和苏格兰流域的特点是复杂的地下结构，由覆盖断裂基岩的冰川沉积物组成，两者都高度异质，通过高渗透性冰川沉积物和断裂带形成深层和快速的优先流动路径，使该模型变得复杂。此外，由冰川沉积厚度变化决定的可变含水层限制条件也会影响地下水补给和养分衰减过程。两者反过来又导致河流的水和养分输入复杂的空间分布、时间和数量。该项目旨在更好地了解水文地质控制对农业流域溪流地下水和养分输入的重要性。它将建立在项目团队开发的利用地球物理数据模拟地下水路径和停留时间方面的最新进展的基础上[2]，并辅以对地下水和地表水的高分辨率监测，包括营养物和同位素（稳定和放射性），以进一步限制路径和停留时间。 该研究将使用该团队广泛监测的北爱尔兰格伦伯恩流域[3]。该流域的特点是基岩并置有风化/破裂的杂砂岩和松散的砂岩，两者都覆盖着排水不良、空间不均匀的冰川沉积物。它配备有 16 个多深度钻孔和河流流量计。它还受益于广泛、多尺度的地球物理数据集的可用性。该研究将涉及； 1/绘制流域规模的养分在溪流和钻孔（土壤、浅层和深层含水层）中的分布以及稳定和放射性同位素采样； 2/使用分布式地下水数值模型对地下水流动路径和停留时间的流域规模分布进行建模，该模型参数化了来自多尺度地球物理数据（钻孔、地面和TELLUS机载调查）的含水层特性； 3/评估水流/养分分布与地下水排放/停留时间之间的关系； 4/测试减少养分和优化缓解措施的土地利用管理方案。 该学生奖学金将作为与 AFBI（农业食品和生物科学研究所）的 Rachel Cassidy 博士长期合作的一部分实施，该研究所将提供额外的监督和安置。学生将受益于水文地质学和地下水流建模（UoA、QUB）的前沿培训；水文地球物理学（UoA、AFBI）；水文地球化学（QUB）；先进的营养监测和分析以及将研究成果转化为政策指导的培训（AFBI）。他们还将受益于更广泛的 QUADRAT 范围的培训课程，包括目前在研究地点运行的现场地球物理学课程。