Water2015, 7(9), 4701-4723; doi:10.3390/w7094701 (registering DOI) - published 28 August 2015 Show/Hide Abstract
Abstract: In many Mediterranean countries, users store water resources in private tanks, which are typically located on rooftops. These local reservoirs are generally connected directly to the water distribution network (WDN). This installation scheme causes a disconnection of the WDN from the users, and thus, the users’ water supply is no longer linked to their consumption, which changes the network operating conditions from the designed conditions. For WDNs characterized by the presence of several private tanks, specific models have to be developed to correctly simulate the operation of the WDN while accounting for reservoirs located between the hydraulic network and users. Some mathematical models that are able to reproduce the tank emptying/filling cycles have already been developed, which combine a tank continuity equation with a float valve emitter law. In the present work, a new emitter law is proposed that improves the predictability of actual models. The new formulation takes into account the variation of the emitter coefficient and of the discharge area during the phases of the filling process of private tanks. Specifically, hyperbolic tangent laws were adopted. A comparison between the proposed mathematical model and the experimental data demonstrated the ability of the new law to estimate the flow discharging into private tanks independently of the float valve branch and of the pressure in the network. The developed model can easily be implemented in hydrodynamic models to take private tanks into account.
Water2015, 7(9), 4685-4700; doi:10.3390/w7094685 - published 27 August 2015 Show/Hide Abstract
Abstract: Long-term observations of lake water level are essential to our understanding of the evolution of Tibetan lake system. CryoSat-2 radar altimetry data over the Tibetan Plateau (2010–2014, P2) is used to extend lake level measurements from ICESat laser altimetry (2003–2009, P1). This study evaluates the performance of CryoSat-2 data by comparing with gauge-based water levels that are calibrated by ICESat-observed water level time series, and quantifies the uncertainty of water-level change rate estimates from satellite altimetry measurements. We completely investigate the 131 lakes that were observed by both ICESat and CryoSat-2. The mean change rate of water level for all of examined lakes in P2 (0.19 ± 0.03 m·year–1) is slightly lower than that (0.21 ± 0.02 m·year–1) observed in P1. The extended lake level time series also indicates that, in the past few years, lakes in the Northern Changtang (especially in Hol Xil) showed accelerated growth; and that the extensive lake level rises north to the Gangdise Mountains, during 2003–2009, were found dampened during the CryoSat-2 observation period. The spatio-temporal heterogeneity of precipitation observed from weather stations can be used to partly explain the observed temporal pattern of lake level changes over different sub-zones of the plateau.
Water2015, 7(9), 4657-4684; doi:10.3390/w7094657 - published 27 August 2015 Show/Hide Abstract
Abstract: The importance of water security has gained prominence on the international water agenda, but the focus seems to be directed towards water demand. An essential element of water security is the functioning of public organizations responsible for water supply through direct and indirect security approaches. Despite this, there has been a tendency to overlook the water security strategies of these organizations as well as constraints on their operation. This paper discusses the critical role of water supply in achieving sustainable water security and presents two case studies from Central Asia on the management of water supply for irrigated agriculture. The analysis concludes that existing water supply bureaucracies need to be revitalized to effectively address key challenges in water security.
Water2015, 7(9), 4638-4656; doi:10.3390/w7094638 - published 27 August 2015 Show/Hide Abstract
Abstract: Hard-rock aquifers, which constitute a water supply source in many countries, are highly heterogeneous and defining a realistic model of an aquifer can be extremely complex. The objective of this study was to hydraulically characterize a metamorphic aquifer in a representative area of Italy and to identify the most appropriate approach for tapping of groundwater in this challenging environment. The results of surface fracture surveys, injection tests, pumping tests, and a simplified numerical model were compared. From the surface fracture survey, a model of the rock mass characterized by a well-developed discontinuity network and by a high frequency of discontinuities resulted. The injection tests showed the extreme heterogeneity and the lower hydraulic conductivity of the rock mass in comparison with the results of the pumping tests. The independent estimate of the hydraulic parameter resulting from numerical model highlighted a range of values higher than those resulting from the pumping tests. The study demonstrated that the continuum medium approach can be used in the case of hard-rock aquifers with a dense network of discontinuities. The multi-scale approach is recommended for investigating hydraulic heterogeneity and significantly helps to identify the most promising areas for well locations and their characteristics in relation to the style of fracturing.
Water2015, 7(9), 4622-4637; doi:10.3390/w7094622 - published 27 August 2015 Show/Hide Abstract
Abstract: In cities with problems of aridity and a shortage of drinking water supply, there is an urgent need to establish alternatives for an adequate water management program. This study proposes an estimation through which users can select a rainwater harvesting system for non-drinking water consumption. For the cities of Pachuca and Mineral de la Reforma, State of Hidalgo, Central Mexico, the historical record of rainfall analyzed covers a period of 33 years (1980–2013). We calculated the monthly volume of rainwater harvestable from roof areas (VR, m3) with household roof areas (Hra) of 45 m2, 50 m2, 100 m2 and 200 m2. It is proposed to replace in each single house the flush toilets and washing machine with ecological devices with consumptions of 4.8 L/flush and 70 L/load, respectively. Furthermore, a maximum and a minimum consumption of eight and six flushes/day/person (flush toilets) and five and four loads/week (washing machine), respectively, are proposed. From these considerations, our estimations of the harvestable rainwater showed that households with Hra of 45 m2 and 50 m2 would depend on the water supply system of the public network during part of the year. On the other hand, households with Hra of 100 m2 and 200 m2 might be able to store enough water to meet other needs besides toilet flushing and laundry.
Water2015, 7(9), 4605-4621; doi:10.3390/w7094605 - published 25 August 2015 Show/Hide Abstract
Abstract: A new approach is investigated utilizing light guidance capabilities of optical pure quartz glass in order to maximize drinking water disinfection efficiency with UVC-light-emitting diodes (LEDs). Two experimental setups consisting of soda-lime AR® glass (VWR, Darmstadt, Germany) or HSQ® 100 quartz glass (Heraeus, Wasserburg, Germany) reactors were designed to compare disinfection rates with and without total reflection of UVC radiation along the reactor walls. Each reactor was filled with 9 mL bacteria samples containing either E. coli DSM (Deutsche Sammlung von Mikroorganismen) 498 or B. subtilis DSM 402 strains (concentration 1–3 × 106 colony forming units (CFU)/mL) with and without additional mixing and irradiation periods of 10, 40, and 90 s. Disinfection rates were increased up to 0.95 log10 (E. coli) and 0.75 log10 (B. subtilis) by the light guide approach in stagnant samples. The same experiments with mixing of the samples resulted in an increased disinfection efficiency of 3.07 log10 (E. coli) and 1.59 log10 (B. subtilis). Optical calculations determine that total reflection is achieved with the applied UVC-LED’s viewing angle of 15°. Furthermore measurements show that HSQ® 100 quartz has a transmittance of 92% at 280 nm UVC irradiation compared to the transmittance of soda-lime glass of 2% (1 mm wall thickness).