Spectral Decomposition of Regulatory Thresholds for Climate-Driven Fluctuations in Hydro- and Wind Power Availability

Abstract Climate-driven fluctuations in the runoff and potential energy of surface water are generally large in comparison to the capacity of hydropower regulation, particularly when hydropower is used to balance the electricity production from covarying renewable energy sources such as wind power. To define the bounds of reservoir storage capacity, we introduce a dedicated reservoir volume that aggregates the storage capacity of several reservoirs to handle runoff from specific watersheds. We show how the storage bounds can be related to a spectrum of the climate-driven modes of variability in water availability and to the covariation between water and wind availability. A regional case study of the entire hydropower system in Sweden indicates that the longest regulation period possible to consider spans from a few days of individual subwatersheds up to several years, with an average limit of a couple of months. Watershed damping of the runoff substantially increases the longest considered regulation period and capacity. The high covariance found between the potential energy of the surface water and wind energy significantly reduces the longest considered regulation period when hydropower is used to balance the fluctuating wind power

Hydraulic & Design Parameters in Full-Scale Constructed Wetland & Treatment Units: Six Case Studies

The efficiency of pond and constructed wetland (CW) treatment systems, is influenced by the internal hydrodynamics and mixing interactions between water and aquatic vegetation. In order to contribute to current knowledge of how emergent real vegetation affects solute mixing, and on what the shape and size effects are on the mixing characteristics, an understanding and quantification of those physical processes and interactions was evaluated. This paper presents results from tracer tests conducted during 2015-2016 in six full-scale systems in the UK under different flow regimes, operational depths, shapes and sizes, and in-/outlet configurations. The aim is to quantify the hydraulic performance and mixing characteristics of the treatment units, and to investigate the effect of size and shape on the mixing processes. Relative comparison of outlet configuration, inflow conditions, and internal features between the six different treatment units showed variations in residence times of up to a factor of 3. A key outcome of this study, demonstrated that the width is a more important dimension for the efficiency of the unit compared to the depth. Results underlined the importance of investigating hydrodynamics and physics of flow in full-size units to enhance treatment efficiency and predictions of water quality models

Transport of E. coli D21g with runoff water under different solution chemistry conditions and surface slopes

Tracer and indicator microbe runoff experiments were conducted to investigate the influence of solution chemistry on the transport, retention, and release of Escherichia coli D21g. Experiments were conducted in a chamber (2.25 m long, 0.15 m wide, and 0.16 m high) packed with ultrapure quartz sand (to a depth of 0.10 m) that was placed on a metal frame at slopes of 5.6%, 8.6%, or 11.8%. Runoff studies were initiated by adding a step pulse of salt tracer or D21g suspension at a steady flow rate to the top side of the chamber and then monitoring the runoff effluent concentrations. The runoff breakthrough curves (BTCs) were asymmetric and exhibited significant amounts of concentration tailing. The peak concentration levels were lower and the concentration tailing was higher with increasing chamber slope because of greater amounts of exchange with the sand and/or extents of physical nonequilibrium (e.g., water flow in rills and incomplete mixing) in the runoff layer. Lower amounts of tailing in the runoff BTC and enhanced D21g retention in the sand occurred when the solution ionic strength (IS) was 100 mM NaCl compared with 1 mM NaCl, due to compression of the double layer thickness which eliminated the energy barrier to attachment. Retained cells were slowly released to the runoff water when the IS of the runoff water was reduced to deionized water. The amount and rate of cell release was greatest at the highest chamber slope, which controlled the amount of exchange with the sand and/or the extent of physical nonequilibrium in the runoff layer, and the amount of retained cells. The observed runoff BTCs were well described using a transient storage model, but fitted parameters were not always physically realistic. A model that accounted for the full coupling between flow and transport in the runoff and sand layers provided useful information on exchange processes at the sand surface, but did not accurately describe the runoff BTCs which were influenced by physical nonequilibrium in the runoff layer

Kinematic model of solute transport in stream networks: example with phosphate retention in Morsa Watershed, Norway

A theoretical description of reactive solute transport in a network of stream channels is derived by convoluting unit solutions based on a physical representation of transport and topographical information of the distributions of solute load as well as pathways. The theory is applied to a generic analysis of the phosphate export in Morsa watershed due to the load from 620 individual households with a local wastewater treatment. Essential factors for the phosphate export is filtering of the water in stream-bed sediments through a distribution of hyporheic flow paths of various lengths. This generic study indicates that a significant portion of phosphate is retained in the hyporheic zones for a long time. The 90\% recovery time following a hypothetical remediation action in the households is expected to be in the order of one decade

Potential for high transient doses due to accumulation and chemical zonation of long-lived radionuclides across the geosphere-biosphere interface

Planning for the disposal of spent nuclear fuel is at an advanced stage in several nations around the world. Licensing of the disposal facility requires correspondingly detailed assessment of the future performance of the facility. With increased site-specific detail available to the assessment, local characteristics play an increasingly important role in determining the potential radiological risk posed by releases to the biosphere. In this paper we go beyond existing reference biosphere models and investigate the potential for specific accumulation mechanisms. The implications for the modelling carried out in long timescale performance assessment are discussed

Radiotracer applications: case studies from four continents

Case studies are a simple way to demonstrate how radiotracers can be successfully used in the environment in addressing water resources contaminant transport and coastal management issues. This paper presents ten case studies from Korea, France, Brazil, Hong Kong, Australia, Belgium and Sweden using a variety of radiotracers including 99mTc, 198Au, 3H, 82Br, 32P, 175+181Hf, 160Tb, 51Cr(III), 65Zn, 54Mn and 35S. These studies address physical transport processes such as dispersion and mixing, reactive transport and adsorption and contaminant uptake. Traced components include water, effluent, nutrients, contaminants and mud in rivers, lakes, wetlands and coastal waters.International Atomic Energy Agenc

Hyporheic flow and transport processes: Mechanisms, models, and biogeochemical implications

Fifty years of hyporheic zone research have shown the important role played by the hyporheic zone as an interface between groundwater and surface waters. However, it is only in the last two decades that what began as an empirical science has become a mechanistic science devoted to modeling studies of the complex fluid dynamical and biogeochemical mechanisms occurring in the hyporheic zone. These efforts have led to the picture of surface-subsurface water interactions as regulators of the form and function of fluvial ecosystems. Rather than being isolated systems, surface water bodies continuously interact with the subsurface. Exploration of hyporheic zone processes has led to a new appreciation of their wide reaching consequences for water quality and stream ecology. Modern research aims toward a unified approach, in which processes occurring in the hyporheic zone are key elements for the appreciation, management, and restoration of the whole river environment. In this unifying context, this review summarizes results from modeling studies and field observations about flow and transport processes in the hyporheic zone and describes the theories proposed in hydrology and fluid dynamics developed to quantitatively model and predict the hyporheic transport of water, heat, and dissolved and suspended compounds from sediment grain scale up to the watershed scale. The implications of these processes for stream biogeochemistry and ecology are also discusse

Teoria sobre sistemas de escoamento de águas subterrâneas: desafios da pesquisa para além das condições de contorno especificadas pela carga hidráulica

International audienc