Stormwater harvesting in ephemeral streams: how to bypass clogging and unsaturated layers

To cope with water scarcity in drylands, stormwater is often collected in surface basins and subsequently stored in shallow aquifers via infiltration. These stormwater harvesting systems are often accompanied by high evaporation rates and hygiene problems. This is commonly a consequence of low infiltration rates, which are caused by clogging layers that form on top of the soil profile and the presence of a thick vadose zone. The present study aims to develop a conceptual solution to increase groundwater recharge rates in stormwater harvesting systems. The efficiency of vadose-zone wells and infiltration trenches is tested using analytical equations, numerical models, and sensitivity analyses. Dams built in the channel of ephemeral streams (wadis) are selected as a study case to construct the numerical simulations. The modelling demonstrated that vadose-zone wells and infiltration trenches contribute to effective bypassing of the clogging layer. By implementing these solutions, recharge begins 2250–8100% faster than via infiltration from the bed surface of the wadi reservoir. The sensitivity analysis showed that the recharge rates are especially responsive to well length and trench depth. In terms of recharge quantity, the well had the best performance; it can infiltrate up to 1642% more water than the reservoir, and between 336 and 825% more than the trench. Moreover, the well can yield the highest cumulative recharge per dollar and high recharge rates when there are limitations to the available area. The methods investigated here significantly increased recharge rates, providing practical solutions to enhance aquifer water storage in drylands.

     

Would different methodologies for assessing carbon leakage exposure lead to different risk levels? A case study of the Brazilian industry

Energy-intensive industries play an important role in low-carbon development, being particularly exposed to climate policies. Concern over possible carbon leakage in this sector poses a major challenge for designing effective carbon pricing instruments (CPI). Different methodologies for assessing carbon leakage exposure are currently used by different jurisdictions, each of them based on different approaches and indicators. This paper aims to analyse the extent to which the use of different methodologies leads to different results in terms of exposure to the risk of carbon leakage, using the Brazilian industry sector as a case study. Results indicate that carbon leakage exposure is an expected outcome of eventual CPI implementation in Brazilian industry. However, results vary according to the chosen methodology, so the definition of the criteria is paramount for assessing sectoral exposure to the risk of carbon leakage.

Key policy insights

• Despite increasing discussion about the implementation of carbon pricing on the Brazilian industrial sector, the evaluation of carbon leakage risks is still neglected.

• Assessments of the risk of carbon leakage are directly related to the indicators and criteria used by each methodology. Thus, a given subsector may present different levels of exposure to carbon leakage depending on the methodological choice.

• More than a purely technical discussion, the methodological definition of carbon leakage risk is a political discussion – it can be well-conducted, leading to the success of a CPI, or even sabotaged, by implicitly subsidizing energy-intensive industries.

     

Palaeoceanographic changes in the North Atlantic during the Mid‐Pleistocene Transition (MIS 31–19) as inferred from planktonic foraminiferal and calcium carbonate records

Marine sediments from the Integrated Ocean Drilling Project (IODP) Site U1314 (56.36°N, 27.88°W), in the subpolar North Atlantic, were studied for their planktonic foraminifera, calcium carbonate content, and Neogloboqudrina pachyderma sinistral (sin.) δ¹³C records in order to reconstruct surface and intermediate conditions in this region during the Mid‐Pleistocene Transition (MPT). Variations in the palaeoceanography and regional dynamics of the Arctic Front were estimated by comparing CaCO₃ content, planktonic foraminiferal species abundances, carbon isotopes and ice‐rafted debris (IRD) data from Site U1314 with published data from other North Atlantic sites. Site U1314 exhibited high abundances of the polar planktonic foraminifera N. pachyderma sin. and low CaCO₃ content until Marine Isotope Stage (MIS) 26, indicating a relatively southeastward position of the Arctic Front (AF) and penetration of colder and low‐salinity surface arctic water‐masses. Changing conditions after MIS 25, with oscillations in the position of the AF, caused an increase in the northward export of the warmer North Atlantic Current (NAC), indicated by greater abundances of non‐polar planktonic foraminifera and higher CaCO₃. The N. pachyderma sin. δ¹³C data indicate good ventilation of the upper part of the intermediate water layer in the eastern North Atlantic during both glacial and interglacial stages, except during Terminations 24/23, 22/21 and 20/1. In addition, for N. pachyderma (sin.) we distinguished two morphotypes: non‐encrusted and heavily encrusted test. Results indicate that increases in the encrusted morphotype and lower planktonic foraminiferal diversity are related to the intensification of glacial conditions (lower sea‐surface temperatures, sea‐ice formation) during MIS 22 and 20.     

The last deglaciation in the Picos de Europa National Park (Cantabrian Mountains,northern Spain)

A sedimentological and geochemical study of the Lago Enol sequence (Cantabrian Mountains, northern Spain), together with detailed geomorphological mapping, provides a first record of glacier evolution and climate change over the last 40 ka in the Picos de Europa National Park. The Enol glacier retreated from its maximum extent prior to 40 ka BP as demonstrated by the onset of proglacial lacustrine sedimentation in two glaciated depressions: the Comella hollow to the north (before 40 ka BP) and the Lago Enol (before 38 ka BP). These results support previous evidence that the maximum extent of southern European glaciers occurred earlier than in northern Europe. Alternation of homogeneous and laminated proglacial sediments during the glacier retreat illustrate a dynamic glacial evolution during the Marine Isotope Stage (MIS) 3 (40–26 ka BP). A slight warming is detected at 26 ka ago with the change from proglacial sediments (in a lake located in contact to the glacier) to glaciolacustrine sedimentation (in a non‐contact or distal lake). Finally, the onset of organic‐rich sediments took place at 18 ka ago. This last transition occurred in two phases, similarly to the North Atlantic Last Termination, suggesting a link between North Atlantic Deep Water formation oscillations and palaeohydrological variability in the Cantabrian Mountains. Copyright © 2009 John Wiley & Sons, Ltd.     

Analytic element modelling for strip aquifers

The Analytic Element Method (AEM) provides a convenient tool for groundwater flow analysis in unbounded continuous domains. The AEM is based on the superposition of analytic functions, known as elements, useful at both regional and local scales. In this study, analytic elements for strip aquifers are presented. Such aquifers occur in riverine or coastal deposits and in outcrop zones of confined aquifers. Local flow field is modelled indirectly, using a reference plane related to the aquifer domain through the Schwarz‐Christoffel transform. The regional flow is obtained as a solution of the one‐dimensional flow equation. The proposed methodology was tested by modelling two hypothetical situations, which were compared to exact solutions. It is shown that regional boundaries can be reproduced exactly while local fields are adequately reproduced with analytic elements. The developed elements are applied to simulate a real flow field in northeastern Brazil showing good agreement with measured water levels. Copyright © 2011 John Wiley & Sons, Ltd.     

Estimating impacts of warming temperatures on California's electricity system

Despite a clear need, little research has been carried out at the regional-level to quantify potential climate-related impacts to electricity production and delivery systems. This paper introduces a bottom-up study of climate change impacts on California's energy infrastructure, including high temperature effects on power plant capacity, transmission lines, substation capacity, and peak electricity demand. End-of-century impacts were projected using the A2 and B1 Intergovernmental Panel on Climate Change emission scenarios. The study quantifies the effect of high ambient temperatures on electricity generation, the capacity of substations and transmission lines, and the demand for peak power for a set of climate scenarios. Based on these scenarios, atmospheric warming and associated peak demand increases would necessitate up to 38% of additional peak generation capacity and up to 31% additional transmission capacity, assuming current infrastructure. These findings, although based on a limited number of scenarios, suggest that additional funding could be put to good use by supporting R&D into next generation cooling equipment technologies, diversifying the power generation mix without compromising the system's operational flexibility, and designing effective demand side management programs.     

Study of bond stress–slip relationship and radial dilation in prestressed concrete

This paper presents two test procedures for evaluating the bond stress–slip and the slip–radial dilation relationships when the prestressing force is transmitted by releasing the steel (wire or strand) in precast prestressed elements. The bond stress–slip relationship is obtained with short length specimens, to guarantee uniform bond stress, for three depths of the wire indentation (shallow, medium and deep). An analytical model for bond stress–slip relationship is proposed and compared with the experimental results. The model is also compared with the experimental results of other researchers. Since numerical models for studying bond‐splitting problems in prestressed concrete require experimental data about dilatancy angle (radial dilation), a test procedure is proposed to evaluate these parameters. The obtained values of the radial dilation are compared with the prior estimated by numerical modelling and good agreement is reached. Copyright © 2012 John Wiley & Sons, Ltd.     

Subfossil and modern diatom plankton and the paleolimnology of Rotsee (Switzerland) since 1850

The diatom biostratigraphy of the topmost sediment meter of Rotsee, Central Switzerland, is characterized by a major change fromCyclotella comensis-dominated toStephanodiscus hantzschii/S. parvus-dominated assemblages. A comparison between old phytoplankton samples, taken between 1910–1930, and subfossil diatom assemblages is used for dating the upper 35 cm of the core. There is evidence that the change in dominant diatoms occurred in 1919/20, thus before the opening of an artificial inlet in 1922, and is due to increasing eutrophication. Furthermore, the sedimentary carbonate content can be used as a good indicator for past phytoplankton productivity in Rotsee.     

Evidence of annual layering in Holocene sediments of Soppensee,Switzerland

A succession of fine dark and light laminations, covering a time span of ca 6,000 years (Allerød to Atlantic), was observed in the sediment of Soppensee, Central Switzerland. These laminations, consisting of dark, organic and diatom-rich winter/spring layers and light calcite summer layers, are shown to be varves by means of several independent pollen and diatom analyses, as well as thin-section studies of the sediment micro-structure.     

Etude de la couche limite de surface sahelienne — Experience Yantala

This paper presents data concerning the energy budget in the surface layer in the Sahel region (a semi-desert area). The results are drawn from a measurement campaign made in the Niamey region in the Niger, in April–May 1984 (the Yantala Campaign). The sensible heat flux is computed with the profile method, the ground heat flux is deduced from measurement of the temperature field, and the radiative net flux is measured directly with a balancemeter. The latent heat flux, which is deduced from the energy budget balance is very weak and within the accuracy limit of the method. The diurnal variation of the net flux is symmetrical, with a maximum at noon. On the other hand, the sensible heat flux variation is asymmetrical, with an afternoon decrease much slower than the morning increase. After 3.30 pm, it becomes higher than the net flux. This is compensated for by the sign change of the ground heat flux, whose maximum is found in the morning at 11 am. The second part of this paper shows the importance of one term in the surface-layer energy budget: the long-wave radiative divergence between the ground and the top of the surface layer in high superadiabatic conditions. We show, with a radiative model on the one hand and direct measurement of the radiative divergence on the other hand, that this term reaches several tens of W m^-2 in the superadiabatic conditions found in the Sahel region.