Water Resources Research
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Have <scp>C</scp>hinese water pricing reforms reduced urban residential water demand? Abstract China continues to deal with severe levels of water scarcity and water pollution. To help address this situation, the Chinese central government initiated urban water pricing reforms in 2002 that emphasized the adoption of increasing block rate (IBR) price structures in place of existing uniform rate structures. By combining urban water use records with microlevel data from the Chinese Urban Household Survey, this research investigates the effectiveness of this national policy reform. Specifically, we compare household water consumption in 28 cities that adopted IBR pricing structures during 2002–2009, with that of 110 cities that had not yet done so. Based on difference‐in‐differences models, our results show that the policy reform reduced annual residential water demand by 3–4% in the short run and 5% in the longer run. These relatively modest reductions are consistent with the generous nature of the IBR pricing structures that Chinese cities have typically chosen to implement. Our results imply that more efforts are needed to address China's persistent urban water scarcity challenges.
Water Resources Research - Tập 53 Số 6 - Trang 5057-5069 - 2017
Assessment of Risks to Public Water Supply From Low Flows and Harmful Water Quality in a Changing Climate Abstract Water resources planning and management by water utilities have traditionally been based on consideration of water availability. However, the reliability of public water supplies can also be influenced by the quality of water bodies. In this study, we proposed a framework that integrates the analysis of risks of inadequate water quality and risks of insufficient water availability. We have developed a coupled modeling system that combines hydrological modeling of river water quantity and quality, rules for water withdrawals from rivers into storage reservoirs, and dynamical simulation of harmful algal blooms in storage reservoirs. We use this framework to assess the impact of climate change, demand growth, and land‐use change on the reliability of public water supplies. The proposed method is tested on the River Thames catchment in the south of England. The results show that alongside the well‐known risks of rising water demand in the south of England and uncertain impacts of climate change, diffuse pollution from agriculture and effluent from upstream waste water treatment works potentially represent a threat to the reliability of public water supplies in London. We quantify the steps that could be taken to ameliorate these threats, though even a vigorous pollution‐prevention strategy would not be sufficient to offset the projected effects of climate change on water quality and the reliability of public water supplies. The proposed method can help water utilities to recognize their system vulnerability and evaluate the potential solutions to achieve more reliable water supplies.
Water Resources Research - Tập 55 Số 12 - Trang 10386-10404 - 2019
Cost‐effective alternatives for mitigating <i>Cryptosporidium</i> risk in drinking water and enhancing ecosystem services Under the multibarrier paradigm, water quality management barriers that mitigate risk to consumers are required at multiple points from the catchment to the tap . We present a cost‐effectiveness analysis of 13 catchment‐ and treatment‐based management alternatives for mitigating Cryptosporidium risk in the Myponga water supply catchment, South Australia. A broad range of costs and benefits are identified and valued, including setup, operation and maintenance, and opportunity costs, and benefits for ecosystem services including water quality, biodiversity, carbon sequestration, and farm production services. The results suggest that the cost‐effectiveness of investment in water quality management can be substantially enhanced by considering the costs of management and the benefits for ecosystem services, in addition to Cryptosporidium removal effectiveness. Cost‐effectiveness of investment in management alternatives is dependent upon the desired level of Cryptosporidium removal effectiveness by both the catchment and treatment barriers. The combination of a spatially targeted 25% restriction in water course access of nondairy cattle and treatment by enhanced coagulation provides the most (net) cost‐effective Cryptosporidium risk mitigation strategy. This combination may achieve 0.614 log removal at a net cost of A$0.7 million and (net) cost‐effectiveness of A$1.14 million per log removal. Additional risk mitigation can be achieved through the addition of ultraviolet irradiation treatment, higher levels of water course access restriction for cattle, and the adoption of dung beetles in the catchment. Economic valuation of a range of costs and benefits of management priorities can support cost‐effective water quality management investment decisions and inform elements of policy design such as cost‐sharing arrangements and spatial targeting.
Water Resources Research - Tập 45 Số 8 - 2009
Experimental testing of transient unsaturated flow theory at low water content in a centrifugal field Experimental measurements and theoretical predictions of transient moisture conditions have been compared for a sandy soil approaching hydrostatic equilibrium in a centrifugal field. Starting near saturation, samples were centrifuged at constant speed with a constant suction at the outflow boundary. Water flowed freely out of the sample through a porous plate. Step increases in centrifuge speed produced transient moisture conditions suitable for comparison between experiment and theory. Measurements of electrical conductivity by a direct contact four‐electrode technique indicated the water content according to a calibration based on known moisture conditions at various equilibrium states. A specially modified centrifuge permitted electrical measurements during centrifugation. For comparison, the transient water contents were computed by a finite‐difference solution of Richards' equation (modified by replacing gravitational with centrifugal potential), using soil characteristics measured previously by steady state techniques. The time dependence of water content changes, used as the basis for comparison between experiment and theory, shows agreement which is reasonable given the degree of uncertainty of the measurements. The experiment confirms, within a factor of 4, the validity of Richards' equation for moisture conditions as dry as 25% of saturation, over a hydraulic conductivity range of 5 × 10−11 to 1 × 10−8 m/s, and in a centrifugal field up to about 200 g .
Water Resources Research - Tập 26 Số 9 - Trang 1951-1960 - 1990
Macrophytes as indicators of land‐derived wastewater: Application of a δ<sup>15</sup>N method in aquatic systems We measured δ15 N signatures of macrophytes and particulate organic matter (POM) in six estuaries and three freshwater ponds of Massachusetts to assess whether the signatures could be used as indicators of the magnitude of land‐derived nitrogen loads, concentration of dissolved inorganic nitrogen in the water column, and percentage of N loads contributed by wastewater disposal. The study focused specifically on sites on Cape Cod and Nantucket Island, in the northeastern United States. There was no evidence of seasonal changes in δ15 N values of macrophytes or POM. The δ15 N values of macrophytes and POM increased as water column dissolved inorganic nitrogen concentrations increased. We found that δ15 N of macrophytes, but not of POM, increased as N load increased. The δ15 N values of macrophytes and groundwater NO3 tracked the percent of wastewater contribution linearly. This research confirms that δ15 N values of macrophytes and NO3 can be excellent indicators of anthropogenic N in aquatic systems.
Water Resources Research - Tập 41 Số 1 - 2005
Daily spatiotemporal precipitation simulation using latent and transformed Gaussian processes A daily stochastic spatiotemporal precipitation generator that yields spatially consistent gridded quantitative precipitation realizations is described. The methodology relies on a latent Gaussian process to drive precipitation occurrence and a probability integral transformed Gaussian process for intensity. At individual locations, the model reduces to a Markov chain for precipitation occurrence and a gamma distribution for precipitation intensity, allowing statistical parameters to be included in a generalized linear model framework. Statistical parameters are modeled as spatial Gaussian processes, which allows for interpolation to locations where there are no direct observations via kriging. One advantage of such a model for the statistical parameters is that stochastic generator parameters are immediately available at any location, with the ability to adapt to spatially varying precipitation characteristics. A second advantage is that parameter uncertainty, generally unavailable with deterministic interpolators, can be immediately quantified at all locations. The methodology is illustrated on two data sets, the first in Iowa and the second over the Pampas region of Argentina. In both examples, the method is able to capture the local and domain aggregated precipitation behavior fairly well at a wide range of time scales, including daily, monthly, and annually.
Water Resources Research - Tập 48 Số 1 - 2012
Methods for predicting peak discharge of floods caused by failure of natural and constructed earthen dams Floods from failures of natural and constructed dams constitute a widespread hazard to people and property. Expeditious means of assessing flood hazards are necessary, particularly in the case of natural dams, which may form suddenly and unexpectedly. We revise statistical relations (derived from data for past constructed and natural dam failures) between peak discharge (Q p V 0 ) or drop in lake level (d ) but assert that such relations, even when cast into a dimensionless form, are of limited utility because they fail to portray the effect of breach‐formation rate. We then analyze a simple, physically based model of dam‐breach formation to show that the hydrograph at the breach depends primarily on a dimensionless parameter η=kV 0 /g l/2 d 7/2 , where k is the mean erosion rate of the breach and g is acceleration due to gravity. The functional relationship between Q p k , and thus η, can be estimated. The theory thus provides a rapid means of predicting the plausible range of values of peak discharge at the breach in an earthen dam as long as the impounded water volume and the water depth at the dam face can be estimated.
Water Resources Research - Tập 33 Số 10 - Trang 2337-2348 - 1997
Chlorine 36 dating of very old groundwater: 2. Milk River Aquifer, Alberta, Canada The Milk River aquifer in southern Alberta, Canada, consists of sandstone interbedded between thick shale units. The groundwater is confined and discharges by both upward and downward leakage through the shales. The concentration of Cl− increases by about 2 orders of magnitude downgradient through the aquifer. This Cl− increase complicates 36 Cl dating of the system. Climatic changes, flushing of connate water, introduction of Cl− from older water below the aquifer, and ion filtration have been proposed as possible explanations for the increase. The 36 Cl data show a consistent decrease of the 36 Cl/Cl ratio downgradient, but an increase in the 36 Cl concentration downgradient in certain parts of the aquifer. Dates calculated from the 36 Cl/Cl ratio show a reasonable distribution in light of the hydraulic controls on the system, whereas dates calculated from the 36 Cl concentration give negative ages. This suggests that ion filtration is responsible for the Cl− increase and that the 36 Cl/Cl dates are to be preferred. We estimate water ages to be more than 2 m.y. near the distal end of the aquifer.
Water Resources Research - Tập 22 Số 13 - Trang 2003-2016 - 1986
Chlorine 36 dating of very old groundwater: 1. The Great Artesian Basin, Australia Chlorine 36 has many advantages as a dating tool for very old groundwater. These advantages include a suitable half‐life (3.01 × 105 years), simple geochemistry, conservative behavior in groundwater, and a general absence of subsurface sources at levels comparable to the atmospheric input. Recent advances in tandem accelerator mass spectrometry have permitted the analysis of 36 Cl at the low abundance expected following residence in the subsurface for 106 years or more. In order to test the suitability of 36 Cl for dating very old groundwater, the 36 Cl/Cl ratios of 26 groundwater samples from the Great Artesian Basin of Australia have been measured. Groundwater ages calculated from the 36 Cl data compare favorably with ages computed independently from hydrodynamic simulations.
Water Resources Research - Tập 22 Số 13 - Trang 1991-2001 - 1986
A closed‐form equation for effective stress in unsaturated soil We propose that the recently conceptualized suction stress characteristic curve represents the effective stress for the shear strength behavior of unsaturated soil. Mechanically, suction stress is the interparticle stress called tensile stress. The working hypothesis is that the change in the energy of soil water from its free water state is mostly consumed in suction stress. We demonstrate that the suction stress lies well within the framework of continuum mechanics where free energy is the basis for any thermodynamic formulation. Available experimental data on soil water characteristic curves and suction stress characteristic curves are used to test the hypothesis, thus validating a closed‐form equation for effective stress in unsaturated soil. The proposed closed‐form equation is intrinsically related to the soil water characteristic curve by two pore parameters: the air entry pressure and pore size spectrum number. Both semiquantitative and quantitative validations show that the proposed closed‐form equation well represents effective stress for a variety of earth materials ranging from sands to clays. Of important practical implications are (1) the elimination of the need for any new shear strength criterion for unsaturated soil, (2) the elimination of the need for determining the Bishop's effective stress parameter χ because the new form of effective stress is solely a function of soil suction, and (3) the ready extension of all classical soil mechanics work on limit equilibrium analysis to unsaturated soil conditions.
Water Resources Research - Tập 46 Số 5 - 2010
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