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

Exploring nature based strategies in upland landscapes for managing low flows and stream temperatures

Key drivers controlling daily stable isotope variations in precipitation of Costa Rica: Caribbean Sea versus Eastern Tropical Pacific Ocean moisture sources

Abstract. Conceptualizing passive storage in coupled flow–isotope models can improve
the simulation of mixing and attenuation effects on tracer transport in many
natural systems, such as catchments or rivers. However, the effectiveness of
incorporating different conceptualizations of passive storage in models of
complex karst flow systems remains poorly understood. In this study, we
developed a coupled flow–isotope model that conceptualizes both “fast-flow” and
“slow-flow” processes in heterogeneous aquifers as well as
hydrological connections between steep hillslopes and low-lying depression
units in cockpit karst landscapes. The model tested contrasting
configurations of passive storage in the fast- and slow-flow systems and was
optimized using a multi-objective optimization algorithm based on detailed
observational data of discharge and isotope dynamics in the Chenqi Catchment
in southwestern China. Results show that one to three passive-storage zones distributed
in hillslope fast-/slow-flow reservoirs and/or depression slow-flow reservoirs
provided optimal model structures in the study catchment. This optimization
can effectively improve the simulation accuracy for outlet discharge and
isotope signatures. Additionally, the optimal tracer-aided model reflects
dominant flow paths and connections of the hillslope and depression units,
yielding reasonable source area apportionment for dominant hydrological
components (e.g., more than ∼ 80 % of fast flow in the total
discharge) and solute transport in the steep hillslope unit of karst flow
systems. Our coupled flow–isotope model for karst systems provides a novel,
flexible tool for more realistic catchment conceptualizations that can
easily be transferred to other cockpit karst catchments.


Effects of passive-storage conceptualization on modeling hydrological function and isotope dynamics in the flow system of a cockpit karst landscape

Water transit time and young water fraction are important metrics for characterizing catchment hydrologic function and understanding solute transport. Hydrological and biogeochemical processes in karst environments are strongly controlled by heterogenous fracture-conduit networks. Quantifying the spatio-temporal variability of water transit time and young water fractions in such heterogeneous hydrogeological systems is fundamental linking discharge and water quality dynamics in the karst critical zone. We used a tracer-aided hydrological model to track the fluxes of water parcels that entered a karst catchment as rainfall, time-stamping each hour of rain input individually. Using this approach, the variability of transit times and water age distributions were estimated in the main landscape units in the karst catchment of Chenqi in Guizhou Province, Southwest China. The estimated mean young water (i.e <~2 months old) fractions were 0.39, 0.31 and 0.10 for output fluxes from the hillslope unit, catchment outlet and slow flow reservoirs (matrix and small fractures), respectively. Marked seasonal variability in sources of runoff generation and associated hydrological connectivity between different conceptual stores were the main drivers of young water fraction dynamics in each landscape unit. The water age and travel time distributions were strongly influenced by the water storage dynamics reflecting catchment wetness conditions. Even though the contribution of young water to runoff was greater, the older water turnover was generally accelerated at moderately high flows during wet season.

Chris Soulsby

Papers

Exploring nature based strategies in upland landscapes for managing low flows and stream temperatures

Key drivers controlling daily stable isotope variations in precipitation of Costa Rica: Caribbean Sea versus Eastern Tropical Pacific Ocean moisture sources

Effects of passive-storage conceptualization on modeling hydrological function and isotope dynamics in the flow system of a cockpit karst landscape

Characterising the variability of transit time distributions and young water fractions in a karst catchment using flux tracking

Influence of vegetation canopies on precipitation partitioning and isotope fractionation in northern upland catchments