Urban Water Conservation and Efficiency Potential in California

Improving urban water-use efficiency is a key solution to California's short-term and longterm water challenges: from drought to unsustainable groundwater use to growing tensions over limited supplies. Reducing unnecessary water withdrawals leaves more water in reservoirs and aquifers for future use and has tangible benefits to fish and other wildlife in our rivers and estuaries. In addition, improving water-use efficiency and reducing waste can save energy, lower water and wastewater treatment costs, and eliminate the need for costly new infrastructure

Assessing the costs of adapting to sea-level rise: a case study of San Francisco Bay

Atmospheric concentrations of carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), tropospheric ozone (O3), chlorofluorocarbons (CFCs), and other trace gases are growing due to human activities. These trace gases are transparent to incoming solar radiation and trap outgoing infrared (heat) radiation, acting like a blanket to warm the Earth. Without any of these gases in the atmosphere, the surface of the Earth would be about 35 C (70 F) colder than at present, and life, if any could exist, would be quite different. This natural greenhouse effect is being intensified by human activities that accelerate the emission of these trace gases, such as the combustion of fossil fuels and deforestation. One of the direct consequences of climatic changes will be a rise in sea level due to the melting of land ice and the expansion of the upper layers of the ocean as they warm. This study presents a method for assessing the costs to society of protecting against an increase in sea level, and applies this method to the San Francisco Bay area -- a region of great ecological diversity, economic importance, and vulnerability. Hydrodynamic effects around the margin of San Francisco Bay are evaluated, structural options for protecting property are identified and chosen for threatened areas, and estimates of costs of protection are determined. For the purposes of this study, a one-meter sea-level rise was assumed, and all development below the future 100-year high tide elevation in San Francisco Bay was considered to be at risk. The types of shoreline protection proposed include constructing new levees and seawalls, raising existing levees and bulkheads, raising buildings, freeways and railroads where necessary, and replenishing beaches. The costs described here are not the total costs of protection -- for example, no estimates are available for evaluating costs of protecting natural ecosystems. Other 3 costs left out are described in detail in the text

Quantum chaos: an introduction via chains of interacting spins-1/2

We introduce aspects of quantum chaos by analyzing the eigenvalues and the eigenstates of quantum many-body systems. The properties of quantum systems whose classical counterparts are chaotic differ from those whose classical counterparts are not chaotic. The spectrum of the first exhibits repulsion of the energy levels. This is one of the main signatures of quantum chaos. We show how level repulsion develops in one-dimensional systems of interacting spins 1/2 which are devoid of random elements and involve only two-body interactions. In addition to the statistics of the eigenvalues, we analyze how the structure of the eigenstates may indicate chaos. The programs used to obtain the data are available online.Comment: 7 pages, 3 figure

Waste Not, Want Not: The Potential for Urban Water Conservation in California

The largest, least expensive, and most environmentally sound source of water to meet California's future needs is the water currently being wasted in every sector of our economy. This report, "Waste Not, Want Not," strongly indicates that California's urban water needs can be met into the foreseeable future by reducing water waste through cost-effective water-saving technologies, revised economic policies, appropriate state and local regulations, and public education

China’s rising hydropower demand challenges water sector

Demand for hydropower is increasing, yet the water footprints (WFs) of reservoirs and hydropower, and their contributions to water scarcity, are poorly understood. Here, we calculate reservoir WFs (freshwater that evaporates from reservoirs) and hydropower WFs (the WF of hydroelectricity) in China based on data from 875 representative reservoirs (209 with power plants). In 2010, the reservoir WF totaled 27.9 × 109 m3 (Gm3), or 22% of China’s total water consumption. Ignoring the reservoir WF seriously underestimates human water appropriation. The reservoir WF associated with industrial, domestic and agricultural WFs caused water scarcity in 6 of the 10 major Chinese river basins from 2 to 12 months annually. The hydropower WF was 6.6 Gm3 yr−1 or 3.6 m3 of water to produce a GJ (109 J) of electricity. Hydropower is a water intensive energy carrier. As a response to global climate change, the Chinese government has promoted a further increase in hydropower energy by 70% by 2020 compared to 2012. This energy policy imposes pressure on available freshwater resources and increases water scarcity. The water-energy nexus requires strategic and coordinated implementations of hydropower development among geographical regions, as well as trade-off analysis between rising energy demand and water use sustainability

Climate Change and the Integrity of Science

We are deeply disturbed by the recent escalation of political assaults on scientists in general and on climate scientists in particular. All citizens should understand some basic scientific facts. There is always some uncertainty associated with scientific conclusions; science never absolutely proves anything. When someone says that society should wait until scientists are absolutely certain before taking any action, it is the same as saying society should never take action. For a problem as potentially catastrophic as climate change, taking no action poses a dangerous risk for our planet

Water and sanitation provision in a low carbon society: The need for a systems approach

In the face of climate change threatening to cause major alterations to hydrological cycles and taking into account the relationship between water, energy use, and food production, water management challenges today prove more complex than ever to address. This paper, recognising the progress made through science and engineering in the last century, reflects on the need to manage water resources more sustainably. It proposes that a change in mindsets is required in order to reconsider our approach in applying established solutions and utilising current technologies and tools to deliver them, with a renewed focus on re-assessing what the real problems are from a systems perspective. Focusing on the water-energy-food nexus, water reuse using desalination processes as a management option is revisited. Findings demonstrate that interdisciplinary, integrated and holistic solutions have the potential to deliver benefits across different sectors, disciplines, and systems, with a real potential for taking us a bit closer to sustainability

The prediction of future from the past: an old problem from a modern perspective

The idea of predicting the future from the knowledge of the past is quite natural when dealing with systems whose equations of motion are not known. Such a long-standing issue is revisited in the light of modern ergodic theory of dynamical systems and becomes particularly interesting from a pedagogical perspective due to its close link with Poincar\'e's recurrence. Using such a connection, a very general result of ergodic theory - Kac's lemma - can be used to establish the intrinsic limitations to the possibility of predicting the future from the past. In spite of a naive expectation, predictability results to be hindered rather by the effective number of degrees of freedom of a system than by the presence of chaos. If the effective number of degrees of freedom becomes large enough, regardless the regular or chaotic nature of the system, predictions turn out to be practically impossible. The discussion of these issues is illustrated with the help of the numerical study of simple models.Comment: 9 pages, 4 figure

Predicting language learners' grades in the L1, L2, L3 and L4: the effect of some psychological and sociocognitive variables

This study of 89 Flemish high-school students' grades for L1 (Dutch), L2 (French), L3 (English) and L4 (German) investigates the effects of three higher-level personality dimensions (psychoticism, extraversion, neuroticism), one lower-level personality dimension (foreign language anxiety) and sociobiographical variables (gender, social class) on the participants' language grades. Analyses of variance revealed no significant effects of the higher-level personality dimensions on grades. Participants with high levels of foreign language anxiety obtained significantly lower grades in the L2 and L3. Gender and social class had no effect. Strong positive correlations between grades in the different languages could point to an underlying sociocognitive dimension. The implications of these findings are discussed