Adjusting to Climate Change: Implications of Increased Variability and Asymmetric Adjustment Costs for Investment in Water Reserves

In this paper we study the determination of optimal water storage capacity in a region, taking into account that the supply of the resource, the flow into the reserve, is uncertain, that a measure of the uncertainty, the variance, is likely to increase with climate change, that building capacity is costly, and that the development of water resources may entail alsoenvironmental costs. We find that water storage capacity in the long run ispositivelyrelated to increases in uncertainty if the marginal benefit of water withdrawal isconvexand that, for the case of costly reversibility of investment, a range of inaction for investment appears, and the stability of water storage capacity with respect to changes in variance increases.     

Recyclable Fe3O4@Polydopamine (PDA) nanofluids for highly efficient solar evaporation

Volumetric solar evaporations by using light-absorbing nanoparticles suspended in liquids (nanofluids) as solar absorbers have been widely regarded as one of the promising solutions for clean water production because of its high efficiency and low capital cost compared to traditional solar distillation systems. Nevertheless, previous solar evaporation systems usually required highly concentrated solar irradiation and high capital cost, limiting the practical application on a large scale. Herein, for the first time in this work, polydopamine (PDA)-capped nano Fe3O4 (Fe3O4@PDA) nanofluids were used as solar absorbers in a volumetric system for solar evaporation. The introduction of organic PDA to nano Fe3O4 highly contributed to the high light-absorbing capacity of over 85％in wide ranges of 200–2400 nm because of the existence of numerous carbon bonds and pi (π) bonds in PDA. As a result, high evaporation efficiency of 69.93％under low irradiation of 1.0 kW m-2 was achieved. Compared to other nanofluids, Fe3O4@PDA nanofluids also provided an advantage in high unit evaporation rates. Moreover, Fe3O4@PDA nanofluids showed excellent reusability and recyclability owing to the preassembled nano Fe3O4, which significantly reduced the material consumptions. These results demonstrated that the Fe3O4@PDA nanofluids held great promising application in highly efficient solar evapo-ration.     

Genetic differentiation in a pelagic crustacean (Meganyctiphanes norvegica: Euphausiacea) from the North East Atlantic and the Mediterranean Sea

Meganyctiphanes norvegica (M. Sars)is a pelagic crustacean that plays a key role in marine food webs of North Atlantic Ocean and marginal seas. We studied eight population samples collected in the European Atlantic and Mediterranean Sea. By means of single strand conformation polymorphism analysis (SSCP) and direct sequencing, we investigated a segment of 158 base pairs of the mitochondrial gene coding for the subunit 1 of NADH dehydrogenase. We found 12 sequence variants among the 385 individuals studied. Analysis of molecular variance (AMOVA) showed that 14.75% of the total genetic variability was explained by differences between populations, thus indicating absence of panmixia for these populations. Pairwise comparisons revealed three distinct genetic pools: the first one represented by Cadiz Bay, the second one by the Ligurian Sea, and the third one included all the NE Atlantic samples. We also investigated one population from the Alboran Sea (within the Mediterranean basin, east of the Strait of Gibraltar). This population was found to be genetically intermediate between the NE Atlantic samples and the Ligurian sample, suggesting that the restriction to the gene flow is not associated with the Strait of Gibraltar, but possibly with the Oran–Almeria oceanographic front. The present work indicates that M. norvegica, although endowed with a high dispersal capacity because of its pelagic habit, can develop separate breeding units inside the same oceanic basin (the Atlantic). Furthermore, the Ligurian sample should be considered as a distinct evolutionary entity, separated from the Atlantic population. Received: 2 May 1999 / Accepted: 26 November 1999     

Soil drying in a tropical forest: Three distinct environments controlled by gap size

Soil water and temperature regimes in the tropical moist forest on Barro Colorado Island, Panama, were simulated directly from meteorological data using the model SWEAT. Separate field observations from root-exclusion, litter-removal and control treatments in one small and one large forest gap were used for calibration and validation. After irrigating all treatments to field capacity, soil matric potential and temperature were measured over 17 days at four depths ≤50 mm using the filter-paper technique and bead thermistors. Understorey environments were also simulated under the same initial conditions. The results suggest that three distinct scenarios, controlled by gap size, describe how the above- and below-ground processes controlling soil drying are coupled: (1) in the large gap, root water extraction by surrounding trees is negligible so soil drying is dominated by evaporation from the soil surface. Soil temperature is dominated by direct solar heating and cooling due to evaporation. (2) In the small gap, root water extraction dominates soil drying with soil evaporation playing a minor role. Soil temperature is still dominated by direct sunlight with some cooling due to evaporation. (3) In the understorey, root water extraction dominates soil drying. Soil temperature is dominated by heat conduction from deep soil layers with some evaporation and sensible heat transfer. The contrasting soil drying regimes imposed by variation in canopy structure enhance micro-environmental heterogeneity and the scope for differential germination and seedling establishment in coexisting tropical tree species.     

Determinants of the marginal willingness to pay for improved domestic water and irrigation in partially electrified Rwandan villages

Access to water for domestic and irrigation uses remains limited across Sub-Saharan Africa, particularly in rural areas. While the technical feasibility of implementing innovative technologies to improve water supply has been often evaluated, less is known about the drivers that motivate users to pay for obtaining the inherent benefits of improved water supply. In this article, the determinants of the marginal willingness to pay (mWTP) for improved domestic and irrigation water are investigated. For this purpose, a contingent valuation study is performed in rural Rwanda. This study uses survey data from 316 households situated in 8 villages, in which ~20% of the households receive electricity thanks to microgrids powered by solar energy. It is found that the mWTP for improved domestic water supply is influenced by the proportion of children in the household, business ownership, and satisfaction with water quantity and quality. The mWTP for irrigation is determined by respondent education, business ownership and crop area planted. This paper contributes to the literature by allowing a comparison of the determinants of the mWTP for improved domestic water supply to the determinants of the mWTP for irrigation. Another contribution is to examine the mWTP for improved water infrastructure in partially electrified villages. Identifying areas with high marginal benefits from water can guide infrastructure investment and electrification efforts while improving well-being and increasing revenues in rural areas.     

Integrated river basin management in rapidly urbanizing areas: a case of Shenzhen, China

The rapid urbanization of China is causing a burden on their water resources and hindering their sustainable development. This paper analyzes effective methods to integrated river basin management (IRBM) using Longgang River basin of Shenzhen as an example, which is the city with the fastest rate of urbanization in China and even the whole world. Over the past 20 years, China has undergone a population boom due to the increase of immigrant workers and rapid development of laborintensive industries, which led to the sharp increase of water consumption and sewage discharge. However, the construction of the water infrastructure is still lagging far behind the environmental and social development, with only 32.7% of sewage in the district being treated. Currently, every water quality indicator of the Longgang River basin was unable to meet the required corresponding environmental standards, which further aggravated the water shortages of the region. Thus, an analytical framework is proposed to address the IRBM of the study area. The problems with the current management system include the lack of decentralization in decision-making, lack of enforcement with redundant plans, weak management capacity, financial inadequacy, and a poor system of stakeholder participation. In light of the principles of IRBM and the situation of the region, corresponding measures are put forward, including an increase of power given to sub-district offices, fewer but more feasible plans, capacity building among stakeholders, a combination of planning and marketing for overcoming financial inadequacy, and profound reform in the public participation system. The framework and institutional suggestions could inform similar processes in other representative river basins.     

Photoreactivity of humic substances: relationship between fluorescence and singlet oxygen production

Humic substances are natural compounds abundantly present in the environment. They play a significant role in the natural attenuation of pollution in surface water due to their capacity to generate reactive species upon solar light excitation. Finding physico chemical parameters related to this property would be of a great help in the prediction studies of the organic pollutants fate. In this work, we investigated relationships between the ability of the humic substances to produce singlet oxygen and their fluorescence properties. For this, a series of sixteen humic acids, fulvic acids, and water-extractable organic matter from soils were studied. The steady-state singlet oxygen concentrations in the irradiated humic substances solutions were measured by monitoring the loss of furfuryl alcohol added as a singlet oxygen scavenger. The emission spectra of the sixteen samples were also recorded. Values of the steady-state singlet oxygen concentrations and the emission intensities showed significant variations among the humic samples and a parallel increase. Thus, here we demonstrate that the rate of singlet oxygen production and the emission intensity of the humic samples are correlated, the best correlation being obtained for emission wavelengths between 500 and 580 nm. This correlation which was never reported until now can be used to estimate the singlet oxygen-production capacity of the humic substances based on their fluorescent properties.     

Effect of pollutant decay on steady-state concentration distributions in variable depth flow

Pollutants discharged together in a variable-depth flow can separate laterally if the decay mechanisms differ e.g. evaporation is more effective in shallow water, but floc breakup is more effective in deeper faster flow. Ray tracing of concentration information away from a point source (similar to mathematical optics) is used to quantify the effects of decay. The concentration reduction rate along a ray increases with decay rate divided by flow speed and with angle between the flow and information directions. Pollutant concentrations tend to fractionate towards regions of smaller decay rate divided by flow speed.     

Effects of Contaminant Decay on the Diffusion Centre of a River

Many contaminants exhibit decay (radioactive decay, consumed by bacteria, heat loss or evaporation through the surface, dissolution by turbulence). For a non-symmetric river with non-reversing flow, the effects of decay are allowed for in specifying the diffusion centre, i.e. the optimal position for a steady discharge. Three families of exact solutions are presented that illustrate the effect on the diffusion centre of cross-channel variation in the decay (uniform, decreasing or increasing with depth). The diffusion centre is shifted to deeper or to shallower water accordingly as the temporal decay divided by flow speed decreases or increases with water depth.     

气温变化对西南山区流域森林水文效应影响的模拟

为了揭示气温变化对西南山区流域森林水文效应的影响,用生物物理/动态植被模型SSiB4/TRIFFID与流域地形指数水文模型TOPMODEL的耦合模型SSiB4T/TRIFFID模拟了西南山区长江上游梭磨河流域森林水文效应对气温变化的响应,分析了气温变化对植被不同演替阶段的流域总径流和总蒸发以及冠层截流蒸发、植被蒸腾和土壤蒸发的影响。结果表明,（1）梭磨河流域森林（常绿针叶林）蒸腾与草和灌木差异小,森林蒸腾潜热比草和灌木仅高1~4 W.m-2,森林冠层截留蒸发高于草和灌木,但土壤蒸发明显低于草和灌木覆盖,森林覆盖流域总蒸发低于草和灌木覆盖甚至低于裸土蒸发,因此增加了流域总径流量,但森林增加径流的作用随土壤蒸发的减小而减小。（2）气温减小1℃将通过减小森林冠层截留蒸发和蒸腾而使森林增加流域总径流量的作用增加;相反,气温增加将增加森林冠层截留蒸发和蒸腾而使森林增加总径流量的作用减小。（3）当温度增加4℃,由于森林总蒸发较草和灌木明显增加,对于较高的土壤蒸发,森林增加总径流量的作用已不明显;对于较低的土壤蒸发,森林减小了流域总径流量。     

Social,environmental, and economic consequences of integrating renewable energies in the electricity sector: a review

The global shift from a fossil fuel-based to an electrical-based society is commonly viewed as an ecological improvement. However, the electrical power industry is a major source of carbon dioxide emissions, and incorporating renewable energy can still negatively impact the environment. Despite rising research in renewable energy, the impact of renewable energy consumption on the environment is poorly known. Here, we review the integration of renewable energies into the electricity sector from social, environmental, and economic perspectives. We found that implementing solar photovoltaic, battery storage, wind, hydropower, and bioenergy can provide 504,000 jobs in 2030 and 4.18 million jobs in 2050. For desalinization, photovoltaic/wind/battery storage systems supported by a diesel generator can reduce the cost of water production by 69% and adverse environmental effects by 90%, compared to full fossil fuel systems. The potential of carbon emission reduction increases with the percentage of renewable energy sources utilized. The photovoltaic/wind/hydroelectric system is the most effective in addressing climate change, producing a 2.11–5.46% increase in power generation and a 3.74–71.61% guarantee in share ratios. Compared to single energy systems, hybrid energy systems are more reliable and better equipped to withstand the impacts of climate change on the power supply.

     

Effect of environmental flows on deep,anoxic pools

A series of field surveys were carried out on two permanent pools of the upper Glenelg River in SW Victoria, Australia. One was representative of the wider and deeper pools while the other was representative of the more-narrow and shallower pools. Both pools showed a typical seasonal cycle of warm, brackish, oxygen-poor, summer conditions and cool, oxygen-rich, low-salinity, winter conditions. The summer salinity increases were larger than expected, suggesting possible saline groundwater inflow from unidentified springs. Both pools contained anoxic water in their deeper sections but this was permanent only in the deeper pool. A simple model of the flushing rate of such anoxic pools subject to flows, such as environmental flow releases, was developed, based on an energy balance between the potential energy required to lift the anoxic layer and the kinetic energy derived from the river flow. The results were tested against and in agreement with the field measurements. The model also suggests that the anoxic layers are resilient to all but the largest environmental flows.     

基于水文学方法的珠江流域生态流量研究

珠江流域水资源丰富,但由于水体污染等原因,水质性缺水问题较为突出,区域水环境、水生态以及水安全等成为急需解决的重要科学问题。开展生态流量研究对于评价地表水文过程演变对区域水环境与水生态的影响具有重要理论意义,并为区域水资源优化配置和可持续开发利用提供科学依据。基于此,运用各种＂水文学＂方法（包括最小月平均流量法、改进的7Q10法、NGPRP法、逐月最小生态径流计算法和逐月频率计算法）对珠江流域11个主要水文控制站点的实测月径流量做了全面而系统的研究,分析珠江流域生态径流过程,并通过与Tennant法对比分析,选择逐月最小生态径流计算法和逐月频率计算法分别计算了各水文控制站的最小生态径流量和适宜生态径流量,除个别站点外,其评价结果分别处于Tennant法＂中＂和＂最佳＂的等级。对于逐月频率计算法中保证率的选取方法,研究表明各月径流系列均取50%最适合珠江流域。研究同时为仅利用水文资料中的多年逐月径流数据来确定生态需水提供了一种新的研究思路。     

云南高原典型林分林下枯落物持水特征研究

森林枯落物具有重要生态水文功能,通过实地调查与实验分析,对云南高原湖泊纳帕海流域3种典型林分枯落物储量、持水量和持水过程进行了研究。结果表明：高山松（pinus densata）林下枯落物储量最大,白桦林（Betula platyphylla Suk.）次之,川滇高山栎（Quercus aquifolioides）灌丛最小,林下枯落物储量最大持水量和有效拦蓄量大小排序表现出和枯落物储量相同的顺序;不论是储量、最大持水量还是有效拦蓄量,各林分枯落物都表现出半分层大于未分解层。3种林下枯落物在0～2 h内吸水较快,在10 h后吸水速明显减缓,用对数方程对3种林下枯落物未分解层和半分解层持水量与浸水时间进行拟合,用幂函数方程对吸水速率与浸水时间进行拟合,结果显示相关系数都较高。     

On-line determination of respiration rates of aquatic organisms in a mono-phase oxystat at steady-state dissolved oxygen tensions

On-line determination of respiration rates at steady-state dissolved oxygen tensions was performed in a thermostatted measuring chamber equipped with a galvanic oxygen electrode. The measuring chamber is designed to completely exclude gas bubbles from the liquid phase and is named a mono-phase oxystat. Additions of oxygenated water to maintain steady-state dissolved oxygen tensions are controlled by a computer, and the respiration rate is determined from the rate of these additions. An external loop with a flow cell in a spectrophotometer makes it possible to determine and control the concentration of algal cells in the mono-phase oxystat and allowed simultaneous determination of respiration and filtration rates of filter-feeding invertebrates. Because the system maintains steady-state conditions the experiments do not suffer from time limitations. The response time of the system is negligible compared to the response time of other open systems. Received: 7 November 1996 / Accepted: 6 December 1996     

Are policy incentives for solar power effective? Evidence from residential installations in the Northeast

State incentives for solar power have grown significantly in the past several years. This paper examines the effectiveness of policy incentives to increase residential solar photovoltaic (PV) capacity. We use county-level panel data and control for demographic characteristics, solar resources, and pro-environmental preferences. Results show that among financial incentives, rebates have the most impact with an additional $1 per watt rebate increasing annual PV capacity additions by close to 50%. Factors that affect financial returns to solar PV such as electricity price and solar insolation are also found to be significant. Results also point to a significant positive relationship between hybrid vehicle sales and residential PV capacity growth, indicating the importance of pro-environmental preferences as a predictor of solar PV demand. Back of the envelope calculations suggest that the cost of carbon mitigation through rebates is around $184 per ton of CO₂.     

Can we measure carrying capacity with foraging behavior?

Carrying capacity is one of the most important, yet least understood and rarely estimated, parameters in population management and modeling. A simple behavioral metric of carrying capacity would advance theory, conservation, and management of biological populations. Such a metric should be possible because behavior is finely attuned to variation in environment including population density. We connect optimal foraging theory with population dynamics and life history to develop a simple model that predicts this sort of adaptive density-dependent change in food consumption. We then confirm the model's unexpected and manifold predictions with field experiments. The theory predicts reproductive thresholds that alter the marginal value of energy as well as the value of time. Both effects cause a pronounced discontinuity in quitting-harvest rate that we revealed with foraging experiments. Red-backed voles maintained across a range of high densities foraged at a lower density-dependent rate than the same animals exposed to low-density treatments. The change in harvest rate is diagnostic of populations that exceed their carrying capacity. Ecologists, conservation biologists, and wildlife managers may thus be able to use simple and efficient foraging experiments to estimate carrying capacity and habitat quality.     

A model for the analysis of seasonal aspects of water quality control

A multiseasonal mathematical programming model for the analysis of water quality control within a river basin is presented. Phenomena of interseasonal variation in flow intensity and the river's pollutant assimilative capacity are introduced into the model by defining several seasons and their characterizations by seasonal parameters. An application of the model to a typical case situation is reported. The results suggest that seasonal adjustments in the treatment levels of wastewater treatment plants involve a considerable saving potential in comparison with a situation in which treatment levels are rigidly determined for the entire year.     

The Optimal Joint Provision of Water for Irrigation and Hydropower

This study develops a dynamic optimization model to analyze the intertemporal allocation of surface water for irrigation and for hydropower production in the western United States. The issue arises because peak irrigation demands may not coincide with periods of peak demand for power. Water released for irrigation in the spring reduces the reservoir head and diminishes the capacity to generate power during summer peak demands. The optimization model is applied to irrigation districts in central California. Results show considerable deviation between the actual and the optimal allocations. Suboptimal behavior is linked to the districts' failure to articulate clear property rights to the scarce water resources.