Modelling water quality response to climate and large-scale land-use change using the world's longest water quality time series (1868 to date)

估计表明，与工业化前的水平相比，人类活动已经使生物可利用氮进入环境的速度翻了一番。这导致地表水和地下水的营养丰富，导致溶解氧水平低，栖息地、淡水和河岸生物多样性丧失，饮用水质量下降，在一些地方，藻类水华的发生增加。在全球范围内，西欧被认为是河流氮素流动的“热点”，一些硝酸盐浓度最高的地区出现在英国的河流中，特别是泰晤士河。这是由于英国的人口密度、高投入农业的范围，以及英国河流相对畅通的小性质。人类通过大规模土地利用和管理变化对河流营养和碳通量的潜在影响已经得到证明，并被认为可能比预计的气候变化影响对水质产生更大的影响。英国最近的研究表明，以地下水为主的河流集水区在20世纪50年代、60年代和70年代表现出与农业集约化有关的长期(即30年)硝酸盐反应。这一点尤其重要，因为地下水流动缓慢，因此通过地下水从陆地转移到河流可能需要长达数十年甚至数百年的时间。在过去，对目前地下水中所含物质的不确定性导致了人们对可能存在的营养“定时炸弹”的讨论，因为它将在未来的某个时候影响河流。已经表明，以地下水为主的河流对集水区变化的反应需要多年的监测数据(可能追溯到1940年代)，以便充分了解土地向河流转移的速度和规模。这为长期集水功能的重要性提供了一个重要的新视角，但令人担忧的是，在英格兰，在1974年水务当局成立之前，几乎没有数据来支持对这种过程的解释。对此，研究人员使用存档的纸质记录构建了世界上最长的水质时间序列，包括从1868年到现在泰晤士河上游的每月平均硝酸盐浓度。这使得人们能够独特地洞察在这段时期内受人类直接影响影响的水质变化、集水区对土地利用和土地管理政策变化的反应的时间和特征，以及将这些影响的程度与气候变化在足够长的时期内的潜在影响进行比较。拟议的研究将利用泰晤士河的这一记录来开发新的方法和模型，与传统的统计方法相结合，来描述和预测河流营养物质浓度在短期和长期的变化。这将允许地下水营养物质运输的速率使土地向河流转移，并将有助于确定预计的气候变化影响是否会像土地利用的大规模变化一样对水质构成严重威胁。这将使淡水和集水科学家能够更好地了解长期过程，并将帮助政策制定者优先采取行动并做出决定。它还将说明需要如何管理监测方案以提供适当的数据，以及如果我们要有效和可持续地长期管理我们的自然资源，就需要如何解释这些数据。

Estimates suggest human activity has doubled the rate at which biologically available nitrogen enters the environment when compared to pre-industrial levels. This has led to nutrient enrichment of surface and groundwaters causing low dissolved oxygen levels, loss of habitat and freshwater and riparian biodiversity, lowered drinking water quality and, in some places, increased occurrence of algal blooms. Globally, Western Europe is regarded as a 'hot spot' of riverine nitrogen flux and some of the highest nitrate concentrations are found in UK rivers, particularly the River Thames. This is due to the population density, the extent of high-input agriculture within the country, and the small, relatively unimpeded nature of UK rivers. The potential for human impact on riverine nutrient and carbon fluxes by large-scale land-use and management change has been demonstrated, and suggested to be of potentially greater water quality significance than projected climate change impacts. Recent UK work has shown that groundwater-dominated river catchments exhibit a long-term (i.e. >30 year) nitrate response linked to agricultural intensification in the 1950s, 60s and 70s. This is particularly significant because groundwater flows are slow so transfers from the land to rivers via groundwater may take up to tens or even hundreds of years. In the past uncertainty about what is presently contained in the groundwater led to talk of a possible nutrient 'time bomb', due to affect rivers at some point in the future. It has been shown that groundwater-dominated river responses to changes in the catchment require many years of monitoring data (possibly going back further than the 1940s) in order to fully understand the rate and magnitude of land to river transfers. This has provided a crucial new perspective on the importance of long-term catchment function, but alarmingly, in England, there are few data from before the establishment of the water authorities in 1974 to support interpretation of such processes. In response to this researchers have used archived paper records to construct the world's longest water quality time series comprising monthly average nitrate concentrations for the River Thames upstream of London for the period 1868 to the present. This allows a unique insight into water quality changes affected by direct human influences over the period, the timing and character of catchment responses to changing land use and land management policy, and comparison of the magnitude of these influences with potential impacts of climate change over a sufficiently long period. The proposed research will use this Thames record to develop new methods and models, coupled with traditional statistical methods, to characterise and predict changes in river nutrient concentrations in both the short- and long-term. This will allow the rates at which groundwater nutrient transport can make land to river transfers and will help to identify whether projected climate change impacts will be as big a threat to water quality as large-scale changes in land use. This will enable freshwater and catchment scientists to gain a better understanding of long-term processes and will help policymakers to prioritise actions and make decisions. It will also show the ways in which monitoring programmes need to be managed to provide appropriate data, and the ways in which those data need to be interpreted if we are to manage our natural resources effectively and sustainably in the long-term.