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.

/pdf/the-changing-carbon-cycle-of-the-coastal-ocean-53srxu7f9q.pdf

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

Modelling the Hydrological Controls on Aluminium Leaching in a Forest Soil Impacted by Acid Deposition in Upland Wales

Near-surface flowpath dominance in a pristine humid tropical rainforest

Disentangling the Effects of 66 Years of Water Management and Hydroclimatic Change on the Urban Hydrology and Water Quality of the Panke Catchment, Berlin, Germany

Quantitative estimations of ecohydrological water partitioning into evaporation and transpiration remains mostly based on plot‐scale investigations that use well‐instrumented, small‐scale experimental catchments in temperate regions. Here, we attempted to upscale and adapt the conceptual tracer‐aided ecohydrology model STARRtropics to simulate water partitioning, tracer, and storage dynamics over daily time steps and a 1‐km grid larger‐scale (2565 km2) in a sparsely instrumented tropical catchment in Costa Rica. The model was driven by bias‐corrected regional climate model outputs and was simultaneously calibrated against daily discharge observations from 2 to 30 years at four discharge gauging stations and a 1‐year, monthly streamwater isotope record of 46 streams. The overall model performance for the best discharge simulations ranged in KGE values from 0.4 to 0.6 and correlation coefficients for streamflow isotopes from 0.3 to 0.45. More importantly, independent model‐derived transpiration estimates, point‐scale residence time estimates, and measured groundwater isotopes showed reasonable model performance and simulated spatial and temporal patterns pointing towards an overall model realism at the catchment scale over reduced performance in the headwaters. The simulated catchment system was dominated by low‐seasonality and high precipitation inputs and a marked topographical gradient. Climatic drivers overrode smaller, landcover‐dependent transpiration fluxes giving a seemingly homogeneous rainfall‐runoff dominance likely related to model input bias of rainfall isotopes, oversimplistic Potential Evapotranspiration (PET) estimates and averaged Leaf Area Index (LAI). Topographic influences resulted in more dynamic water and tracer fluxes in the headwaters that averaged further downstream at aggregated catchment scales. Modelled headwaters showed greater storage capacity by nearly an order of magnitude compared to the lowlands, which also favoured slightly longer residence times (>250 days) compared to superficially well‐connected groundwater contributing to shorter streamflow residence times (<150 days) in the lowlands. Our findings confirm that tracer‐aided ecohydrological modelling, even in the data‐scarce Tropics, can help gain a first, but crucial approximation of spatio‐temporal dynamics of how water is partitioned, stored and transported beyond the experimental catchment scale of only a few km2.

Tracer‐aided ecohydrological modelling across climate, land cover, and topographical gradients in the tropics

Stream nitrate nitrogen (NO3) concentrations and concentration-discharge (C-Q) relationships are key indicators of water quality. However, their long-term variability and response to climate change in large-scale catchments are still poorly understood. Here, we report a synoptic survey and long-term observations (2000-2021) in the Spree catchment (10,105 km2), Germany, to identify the spatial-temporal patterns in stream NO3 concentrations and C-Q relationships, as well as the underlying environmental drivers. We found that in the context of gradual reduction of nitrate inputs, the stream NO3 concentrations had a decreasing trend, but showed different magnitudes at different spatial scales (-0.01-0.48 mg L-1 yr-1). In the upstream parts of the catchment - with a high proportion of farmland - high levels of stream NO3 concentration remained with a risk of eutrophication due to the large nitrogen legacy. Especially in winter, stream NO3 concentrations were much higher due to the groundwater export with high NO3 concentrations, a decreased dilution effect of rainfall and vegetation uptake became clear. Consequently, the large nitrogen legacy in the upper catchment resulted in NO3 concentrations not significantly changing with streamflow and showing chemostatic behavior. This was different from NO3 dynamics in the mid- and lower-catchment areas, which were positively related to streamflow, showing a chemodynamic behavior. Further, we found the export patterns (i.e. enrichment vs. dilution) of stream NO3 concentrations strongly correlated with the export regimes (i.e. chemostatic vs. chemodynamic), which were also affected by drought conditions. This is probably due to the decrease in stream depth which would enhance benthic removal leading to a decrease in stream NO3 concentrations. Reduced hydrological connectivity leads to higher spatial heterogeneity of residual NO3 in soil and drainage water, which will result in chemodynamic behavior of stream NO3 concentrations. After rewetting, the export of these high NO3 concentration in soils led to elevated stream NO3 concentrations, resulting in a positive correlation with streamflow. Our work revealed significant heterogeneity in stream NO3 concentrations and C-Q relationships at different spatial-temporal scales in large catchments. Critically, current stream NO3 concentrations and C-Q relationships are likely to respond strongly to future drought, leading to challenges for future land and water management. 

Quantifying changes and trends of NO3 concentrations and concentration-discharge relationships in a complex, heavily managed, drought-sensitive river system

Chris Soulsby

Papers

Modelling the Hydrological Controls on Aluminium Leaching in a Forest Soil Impacted by Acid Deposition in Upland Wales

Near-surface flowpath dominance in a pristine humid tropical rainforest

Disentangling the Effects of 66 Years of Water Management and Hydroclimatic Change on the Urban Hydrology and Water Quality of the Panke Catchment, Berlin, Germany

Tracer‐aided ecohydrological modelling across climate, land cover, and topographical gradients in the tropics

Quantifying changes and trends of NO3 concentrations and concentration-discharge relationships in a complex, heavily managed, drought-sensitive river system