Statistics for Spatial Data.

Summary
1. The thermal regime of rivers plays an important role in the overall health of aquatic ecosystems, including water quality issues and the distribution of aquatic species within the river environment. Consequently, for conducting environmental impact assessments as well as for effective fisheries management, it is important to understand the thermal behaviour of rivers and related heat exchange processes.

2. This study reviews the different river thermal processes responsible for water temperature variability on both the temporal (e.g. diel, daily, seasonal) and spatial scales, as well as providing information related to different water temperature models currently found in the literature.

3. Water temperature models are generally classified into three groups: regression, stochastic and deterministic models. Deterministic models employ an energy budget approach to predict river water temperature, whereas regression and stochastic models generally rely on air to water temperature relationships.

4. Water temperature variability can occur naturally or as a result of anthropogenic perturbations, such as thermal pollution, deforestation, flow modification and climate change. Literature information is provided on the thermal regime of rivers in relation to anthropogenic impacts and such information will contribute to the better protection of fish habitat and more efficient fisheries management.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1365-2427.2006.01597.x

The thermal regime of rivers : a review

The carbon cycle of the coastal ocean is a dynamic component of the global carbon budget. But the diverse sources and sinks of carbon and their complex interactions in these waters remain poorly understood. Here we discuss the sources, exchanges and fates of carbon in the coastal ocean and how anthropogenic activities have altered the carbon cycle. Recent evidence suggests that the coastal ocean may have become a net sink for atmospheric carbon dioxide during post-industrial times. Continued human pressures in coastal zones will probably have an important impact on the future evolution of the coastal ocean's carbon budget.

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The changing carbon cycle of the coastal ocean

Foreword 1. Introduction 2. Runoff, erosion and delivery to the coastal ocean 3. Temporal variations 4. Human impacts Appendices. Global River Database: Appendix A: North and Central America Appendix B: South America Appendix C: Europe Appendix D: Africa Appendix E: Eurasia Appendix F: Asia Appendix G: Oceania References Index.

/pdf/river-discharge-to-the-coastal-ocean-a-global-synthesis-571z1g19ts.pdf

River Discharge to the Coastal Ocean: A Global Synthesis

Running waters are perhaps the most impacted ecosystem on the planet as they have been the focus for human settlement and are heavily exploited for water supplies, irrigation, electricity generation, and waste disposal. Lotic systems also have an intimate contact with their catchments and so land-use alterations affect them directly. Here long-term trends in the factors that currently impact running waters are reviewed with the aim of predicting what the main threats to rivers will be in the year 2025. The main ultimate factors forcing change in running waters (ecosystem destruction, physical habitat and water chemistry alteration, and the direct addition or removal of species) stem from proximate influences from urbanization, industry, land-use change and water-course alterations. Any one river is likely to be subjected to several types of impact, and the management of impacts on lotic systems is complicated by numerous links between different forms of anthropogenic effect. Long-term trends for different impacts vary. Concentrations of chemical pollutants such as toxins and nutrients have increased in rivers in developed countries over the past century, with recent reductions for some pollutants (e.g. metals, organic toxicants, acidification), and continued increases in others (e.g. nutrients); there are no long-term chemical data for developing countries. Dam construction increased rapidly during the twentieth century, peaking in the 1970s, and the number of reservoirs has stabilized since this time, whereas the transfer of exotic species between lotic systems continues to increase. Hence, there have been some success stories in the attempts to reduce the impacts from anthropogenic impacts in developed nations. Improvements in the pH status of running waters should continue with lower sulphurous emissions, although emissions of nitrous oxides are set to continue under current legislation and will continue to contribute to acidification and nutrient loadings. Climate change also will impact running waters through alterations in hydrology and thermal regimes, although precise predictions are problematic; effects are likely to vary between regions and to operate alongside rather than override those from other impacts. Effects from climate change may be more extreme over longer time scales (>50 years). The overriding pressure on running water ecosystems up to 2025 will stem from the predicted increase in the human population, with concomitant increases in urban development, industry, agricultural activities and water abstraction, diversion and damming. Future degradation could be substantial and rapid (c. 10 years) and will be concentrated in those areas of the world where resources for conservation are most limited and knowledge of lotic ecosystems most incomplete; damage will centre on lowland rivers, which are also relatively poorly studied. Changes in management practices and public awareness do appear to be benefiting running water ecosystems in developed countries, and could underpin conservation strategies in developing countries if they were implemented in a relevant way.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0376892902000097

Threats to the running water ecosystems of the world

Diffuse agricultural pollution is one of the greatest challenges to achieving good chemical and ecological status of Scotland’s water bodies. The River Ythan in Aberdeenshire was designated a Nitrate Vulnerable Zone (NVZ) in the year 2000, due to the eutrophication of the Ythan Estuary and rising nitrate trends in Private Water Supply (PWS) groundwater abstractions. The third River Basin Management Plan (RBMP) for Scotland reported the Ellon groundwater body of the River Ythan catchment to be of poor chemical status as of 2021 with respect to nitrate, and forecasted groundwater recovery beyond 2027. Following two decades of NVZ designation, we investigated the drivers of groundwater nitrate across the River Ythan catchment through an analysis of long-term (2009–2018) groundwater quality monitoring data collected by the Scottish Environmental Protection Agency (SEPA) and a recent synoptic groundwater nitrate sampling survey of PWSs. Groundwater nitrate was found to remain elevated across the catchment area, and appeared to be highly sensitive to agricultural practices and meteorological forcing, indicating a high sensitivity of groundwater quality to environmental change. Further hydrogeological characterisation is recommended to better understand the effects of agricultural practices on groundwater quality, and to facilitate achievement of future RBMP goals under a changing climate.

/pdf/evaluating-groundwater-nitrate-status-across-the-river-ythan-14a8cul7.pdf

Evaluating Groundwater Nitrate Status across the River Ythan Catchment (Scotland) following Two Decades of Nitrate Vulnerable Zone Designation

Quantifying catchment-scale water cycling over longer periods is important as wet and dry precipitation cycles can adversely affect blue (groundwater and discharge) and green (evapotranspiration) water fluxes and storage dynamics (Orth & Destouni, 2018; Yang et al., 2021). Spatially distributed modelling approaches are, in many circumstances, essential for spatio-temporal evaluation of the nonstationarity of flow paths and storage dynamics within catchments (Fatichi et al., 2016). When linked with tracers and water age tracking, such models can also aid in understanding the ecohydrological separation of water sources (McGuire & McDonnell, 2015). Here, we present a visualization of results from a tracer-aided ecohydrological model to explore spatiotemporal dynamics of water flux-storagetracer-age interactions through wet and extreme dry cycles (including the European 2018 drought). This visualization extends beyond the traditional “snapshot” of spatial catchment conditions or temporal depiction of a single “point”, aiding more rapid identification of key ecohydrological regions for changes in flux-storage interactions, as well as tracer dynamics and water ages during periods of specific interest (visualization time-stamps). Intrinsically, the visualization provides a further novel understanding of spatial differences in catchment response and interactions under wet and dry conditions. Importantly, the application of such visualization approaches are limited only by model outputs, and the visualization results presented here are shown for a catchment with broadly similar soil and land use characteristics of extensive parts of the North European Plain and at a scale where process aggregation is lessened (Smith et al., 2021). EcH2O-iso is a tracer-aided ecohydrological model coupling vegetation-soil-atmosphere energy, water and tracer mass-balance with a simultaneous solution of vegetation dynamics and water age (Kuppel et al., 2018; Maneta & Silverman, 2013). Energy and water balance are estimated with a top-down approach from the canopy to the sub-surface. The energy balance is solved iteratively for temperature (canopy and surface) to estimate latent, sensible, and ground heat, soil temperatures and net radiation. Water balance is solved in five model storages: canopy, surface and soil (three storage layers) with vertical movement through all storages, and lateral movement (kinematic wave) in surface and deep soil water. Evapotranspiration components are derived from the energy balance. Water ages and isotopic tracers are estimated in each storage with complete mixing. The Demnitzer Millcreek catchment (DMC, 66km) is a mixed-land use mesoscale catchment in north-east Germany. The DMC has annual mean precipitation and discharge of 560 and 60 mm, respectively with stream flow being groundwater-dominated (Smith et al., 2020; Smith et al., 2021). Four major land use units are distinguishable: agricultural, coniferous forest, wetlands and broadleaf forest. The soils are primarily sandy brown earths, with peaty podzolic soils in wetlands and peaty gleys fringing the channels. Discharge and stream chemistry time-series (1990–present) and soil moisture, sap flow, soil and Received: 8 September 2021 Revised: 17 December 2021 Accepted: 20 December 2021

https://onlinelibrary.wiley.com/doi/pdfdirect/10.1002/hyp.14460

Chris Soulsby

Papers

Evaluating Groundwater Nitrate Status across the River Ythan Catchment (Scotland) following Two Decades of Nitrate Vulnerable Zone Designation

Visualizing catchment‐scale spatio‐temporal dynamics of storage‐flux‐age interactions using a tracer‐aided ecohydrological model