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

Hydrology in Scotland

The seasonal variation of oxygen-18 has been observed in precipitation, groundwater and streamwater in the Allt a' Mharcaidh catchment, Cairngorm mountains, Scotland. Precipitation showed strong seasonal variation in its isotopic signature over the 1995-1998 study period. As anticipated, such variation was substantially damped in groundwater and surface water. Nevertheless, 18 O proved a useful tracer, indicating the influence of spring snowmelt events and summer rainfall on stream waters. Detailed examination of the seasonal variation in δ 18 O levels in various catchment waters provided an insight into mixing processes and a first approximation of mean residence times. Preliminary estimates for the latter are 5 years for shallow and deeper groundwater respectively. These longer-term data sets demonstrate the ability of the catchment to effectively mix new precipitation with resident soil and groundwater over the hydrological year. This implies that the influence of groundwater on the hydrology and hydrochemistry upland catchments has been underestimated.

Seasonal hydrology of oxygen-18 in the Allt a' Mharcaidh, Scotland : implications for water movement and residence times

Foreword to the special volume: environmental change, land management and water quality in Scotland.

Diffuse Nitrogen pollution from agriculture maintains high pressures on groundwater and aquatic ecosystems. Further mitigation requires targeted measures that reconcile agricultural interests in environmental protection. However, the agriculture‐related processes of catchment N modeling remain poorly defined due to discipline‐specific data and knowledge gaps. Using field‐experimental data, crop N uptake responses to fertilizer management were parsimoniously conceptualized and integrated into a catchment diffuse‐N model. The improved catchment modeling further facilitated integration with agricultural budget‐based assessments. The integrated analysis in a mesoscale catchment disentangled contrasting agri‐environment functional mechanisms in typically flashy chemodynamic and transport‐limited chemostatic export regimes. Moreover, the former was actively responsive to interannual climatic variability and agricultural practices; the latter exhibited drought‐induced enhancement of N enrichment, which could likely be mitigated through reduced fertilization. This interdisciplinary integration of data and methods provided an insightful evidence base for multi‐sector targeted measures, especially under cumulative impacts of changing climate and fertilizer‐use intensities.

https://onlinelibrary.wiley.com/doi/pdfdirect/10.1029/2021GL096833

Chris Soulsby

Papers

Hydrology in Scotland

Seasonal hydrology of oxygen-18 in the Allt a' Mharcaidh, Scotland : implications for water movement and residence times

Foreword to the special volume: environmental change, land management and water quality in Scotland.

Functional Multi‐Scale Integration of Agricultural Nitrogen‐Budgets Into Catchment Water Quality Modeling

Hydrological processes in the hyporheic zone determine salmonid embryo survival and performance