Constant Water Volume Research Articles

Numerical simulation of mixed aseismic/seismic fault-slip induced by fluid injection using coupled X-FEM analysis

Fluid injection into a rock mass from industrial processes can cause perceivable seismic events that may raise public concern. This seismicity can be caused by injection-induced fluid pressure in the rock mass causing slip on faults. Here we provide a method to distinguish between aseismic and seismic mobilisation and to predict fault movement due to anthropogenic fluid injection. This was achieved by extending a two-dimensional fully coupled fluid and mechanical loading extended finite element model (X-FEM) via development of a dynamic analysis module as a standalone code in Matlab . This code considers fluid flow along the fault as well as into the rock mass and uses a directly proportional equivalent injected flow rate into the fault as the input. This model was validated by comparing the resultant pressure and normal and shear displacements calculated at the centre of the fault against observations from a decametre-scale in-situ experiment. The main results were that not only the mechanics of the fault could be simulated using this approach, but that the simulation correctly predicted the onset of seismicity and transition to dynamic analysis and at similar seismic magnitudes to observations. Parametric studies investigated the influence of the flow rate (when injecting a constant volume of water) and the effect of rate and state frictional parameters in representing modes of seismicity. The main conclusion is that this modelling technique using X-FEM provides an accurate method in accurately predicting modes, location and timing of fault remobilisation due to fluid injection inclusive of important precursory aseismic fault movements. These results are important, since they demonstrate the applicability of this X-FEM approach in accurately predicting the mechanics of fault reactivation and the resultant seismicity, aiding in the design and scheduling of fluid injection operations and in the optimisation of operational parameters . • An in-situ fluid injection experiment was simulated using a coupled static and dynamic X-FEM approach. • The simulated response closely represented observed in situ response, using history matching. • This calibrated model predicted the main seismic event and its magnitude during the in-situ experiment. • This was achieved by considering rate and state friction with frictional degradation due to fault slip.

Diversidad y patrón de emergencia de libélulas en un hábitat léntico del Jardín Botánico Nacional de Cuba

The transference of biomass to terrestrial ecosystems is carried out in part by the adults of aquatic insects after their emergence from water, as it is in the case of odonates. The aim of this study is to characterize the emergence pattern of an odonate assemblage in an artificial lentic habitat of the National Botanical Garden of Cuba, from the harvest of exuviae. Fifty two samplings were carried out with a frequency of once a week, and an interval of seven to nine days, in four transect of 8 m2. To characterize the emergence, the seasonal climate model was considered: rainy, poorly rainy and transition seasons. The change in climatic variables and habitat characteristics was registered, and was related to the emergence pattern. The variation in the use of resources during emergence was described. The emergence with a constant volume of water turned out to be asynchronous, with a predominance of accidental species and unequal abundance distribution. The rainy period was the season with the highest percentage of emergence, in which rainfall and relative humidity were the factors that most influenced the emergence pattern. The plants were the most used emergence substrate, and the decrease in vegetation cover corresponded to the alternative use of other substrates. Citation: Lim, G. & Trapero-Quintana, A. 2020. Diversidad y patron de emergencia de libelulas en un habitat lentico del Jardin Botanico Nacional de Cuba. Revista Jard. Bot. Nac. Univ. Habana 41: 119-130. Article history: Received: 17 February 2020. Accepted: 15 June 2020. Online: 4 November 2020. Editor: Luis Manuel Leyva

Modelling of the Complex Groundwater Level Dynamics during Episodic Rainfall Events of a Surficial Aquifer in Southern Italy

We analyzed the complex dynamics that are involved the groundwater level variations due to the episodic rainfall supply in the Ionian coastal plain surficial aquifer located in Southern Italy. In this aquifer, as a consequence of the particular hydrogeological framework, both direct and lateral recharge mechanisms coexist. Hence, the dynamics of groundwater level variations are quite complex and strongly non-linear. Our focus was essentially on the short-term behavior of groundwater levels, with a specific analysis on episodic rainfall events. To model these dynamics, due to the presence of the preferential pathways in the infiltration processes, a kinematic dispersion wave model was used. Specifically, a one-dimensional and non-linear particle-based numerical model was developed. It uses ideal particles with constant water volume travel, according to celerity and hydraulic dispersion, to simulate the infiltration rate wave through the vadose zone. The infiltration rate that reaches the water table represents the input function to evaluate the aquifer groundwater level fluctuations. As a consequence of the special lithological and storage capacity characteristics of the surficial layers, groundwater flow conditions change from unconfined to confined. The developed model analyzes the direct groundwater supply under natural conditions, including episodic rainfall, and it has been validated using a high-resolution time series of rainfall data and groundwater level obtained from the monitoring station Terra Montonata.

Experimental Study of Heat Transfer Enhancement in Double-Pipe Heat Exchanger Integrated with Metal Foam Fins

The influence of adding fins of copper foam on the characteristics of heat transfer in a double-pipe heat exchanger is investigated experimentally. The test rig consists of two concentric pipes (copper and Perspex) to form the required double-pipe heat exchanger. The metal foam fins of 40 PPI are made from copper and set at 30° angle with the tube entrance and are distributed in sections inside the annular gap around the inner copper tube to guide the fluid flow and to disturb its structure inside the annular gap. The Reynolds number range for air is from 616 to 2343, with a constant water volume flow rate (2 lpm) in these experiments. The inlet water temperature is controlled at three values (80 °C, 85 °C, and 90 °C). Both parallel and counterflows are examined in this study. The comparison is made between the two cases of with and without insertion of copper foam fins and between parallel and counterflow mode. Results show that the average heat transfer coefficient and the average Nusselt number are increased as the Reynolds number increased, and their largest values are obtained in case of copper foam fins insertion and for counterflow mode. The important finding is no significant pressure drop is found with the enhancement of heat transfer throughout the annular gap of heat exchanger. Results also showed that the effectiveness values are doubled in case of insertion of the copper foam fins. The counterflow pattern is the most efficient flow pattern than the parallel flow.

Effect of desiccation on mosquito oviposition site selection in Mediterranean temporary habitats

1. Hydroperiod duration has been identified as the main factor determining the faunal composition and structure of aquatic communities in temporary habitats. It is hypothesised that desiccation will positively affect mosquito oviposition habitat selection during the post‐drought period due to the lack of antagonists.2. An experiment was carried out in outdoor mesocosms to assess whether desiccation events have post‐drought effects on community richness and mosquito oviposition.Three different treatments were randomly assigned to the mesocosms: (i) eight mesocosms were left dried for a week and then reflooded; (ii) eight mesocosms stayed dry for 4 weeks before they were reflooded; (iii) eight mesocosms were maintained at a constant water volume of 30 litres during the entire experiment as controls. Mosquito oviposition and invertebrate community richness were monitored in every mesocosm, along with environmental parameters [water temperature, pH, conductivity, dissolved oxygen, total suspended solids (TSS) and chlorophyll a concentration].3. Post‐drought mosquito oviposition and larval abundance were higher in the short‐drought and long‐drought pools than in the control. Desiccation negatively affected the biomass of the filter feeder invertebrates in both desiccation treatments. Chlorophyll a concentrations were higher in the long‐drought pools than in controls. The negative impact of desiccation on zooplankton led to a post‐drought increase in algae, associated with an increase in mosquito oviposition.4. Despite immediate negative effect on mosquitoes, pulsed disturbances can benefit mosquitoes as they favour oviposition during the post‐disturbance recovery period due to a lower abundance of mosquito antagonists and higher food resources for their offspring.

A Hybrid Dynamical Modelling and Control Approach for Energy Saving of Central Air Conditioning

Currently in China, energy conservation and emission reduction are important initiatives for society. Because of its large proportion of building energy consumption, several methods for building energy conservation have been introduced for central air conditioning. This paper presents a hybrid system for a modelling and control approach. By analysing the cooling capacity transfer process and the electromagnetic properties of pumps, the modelling is performed in a hybrid system framework. Pumps are classified as fixed-frequency pumps, variable-frequency pumps, and switchable pumps; a switch control strategy is used in the chilled water system for supplying cooling capacity. In order to adjust indoor temperature and save electrical energy, the cooling capacity allocation and average temperature methods are presented, which satisfy the goal of optimal control of real-time energy consumption. As a numerical example, the temperature variation and cold regulation processes are simulated. Three rooms are the control objects that lower the setting points, and pumps waste as little electrical energy as possible. The results show 49.4% of water pump power consumption when compared with constant water volume technology. The modelling and control approach is more advantageous in ensuring the success of reconstruction projects for central air conditioning.

The relationships between washing parameters, fabric movement, and wrinkling in a top-loading washer

Easy care for clothing is increasingly important, but the major problem is still the severe wrinkles formed on garments after machine washing. In this research, orthogonal tests and the analysis of variance (ANOVA) at a 95% confidence level were used to determine the critical parameters that affect fabric smoothness. We developed a video capturing and processing system for dynamic measurements of fabric in a top-loading washer to find the relationship between fabric movement and wrinkling performance during laundering. The ANOVA results showed that the smoothness of woven cotton fabrics was mainly affected by the washing load and the drum rotating speed, with p values of 0.000 and 0.036, respectively. Additionally, a relation models for fabric movements suggested by a curvilinear regression analysis indicated that the main causes of fabric wrinkling during top-loading washing were liquor ratio and the centrifugal force imposed on the fabric. The smoothness grade increased with the decrease of washing load and drum rotating speed, since these settings led to lower liquor ratio with a constant water volume and less stress on the fabric. The results of this study provide valuable information for the optimization of washing programs for fabric smoothness.

Estimation of Infiltration and Hydraulic Resistance in Furrow Irrigation, with Infiltration Dependent on Flow Depth

Abstract. Estimation of infiltration and hydraulic resistance model parameters from furrow irrigation evaluation data was investigated. A semi-physical, flow-depth dependent furrow infiltration model was used for the analysis. Macropore infiltration was modeled empirically as a constant volume of water per unit area that is absorbed instantaneously. The estimated infiltration parameters were the saturated hydraulic conductivity and the macropore constant. Hydraulic resistance was modeled with the Manning equation; thus, the estimated resistance parameter was the Manning coefficient. The estimation procedure uses volume balance calculations and unsteady flow simulation. Estimation of the flow-depth dependent infiltration parameters requires first the estimation of an empirical infiltration function, via volume balance, and of the resistance parameter, via unsteady flow simulation. Simulated flow depth hydrographs as a function of distance are then used as inputs for a second set of volume balance calculations with the semi-physical infiltration model. This procedure takes advantage of the fact that similar surface flow conditions (advance and recession times, flow depths, and runoff rate) can be predicted with different infiltration functions. The procedure was tested with two irrigation data sets, each consisting of three furrows. With both data sets, the semi-physical infiltration model fitted the measured volume balance data as well as empirical infiltration models. For each group of furrows, estimates of the hydraulic conductivity were of comparable magnitude and were consistent with published values for the particular soil texture. Likewise, estimates of the macroporosity parameter were consistent for each group of furrows. Estimates of the Manning coefficient suggest very uniform hydraulic resistance. Finally, results show that the effect of flow-depth dependent infiltration on irrigation distribution uniformity depends on soil and hydraulic conditions. For one of the data sets, distribution uniformity computed with the proposed infiltration model was only slightly different from the uniformity computed assuming that infiltration depends only on opportunity time, because of the large macropore flow contribution and the shallow flow conditions. Keywords: Distribution uniformity, Furrows, Green-Ampt, Hydraulic conductivity, Hydraulic modeling, Hydraulic resistance, Infiltration, Inverse modeling, Irrigation, Parameter estimation.

The promoting effect of natural sand on methane hydrate formation: Grain sizes and mineral composition

Investigations regarding the effects of particle size on gas hydrate growth are commonly carried out using glass beads, silica powder, and various clay minerals. Comparisons of different grain sizes of sands are less common as are natural samples. Since the highest gas hydrate saturations and possible energy resource targets are associated with natural sandy sediments, the presented experiments address the possible effects of different grain sizes from a natural sand sample on methane hydrate formation. Influences on the kinetics of hydrate formation in natural deposits are of particular interest in hydrate production or carbon dioxide sequestration in methane hydrates. In both cases an undesired secondary hydrate formation may occur on short time scales, usually under non-equilibrium conditions.The static small-volume experiments are carried out far within the methane hydrate stability field (7MPa/274K) using five different grain size classes of a natural quartz sand: <125μm, < 250μm, 250–500μm, 500–1000μm, and 1000–2000μm. A constant volume of water or salt water is added to saturate the sediment sample and pressure is built up using methane gas. Pressure and temperature are continuously recorded and a glass window allows for microscopic observation and Raman spectroscopy to verify methane hydrate formation.For the chosen experimental set-up there is a strong particle size effect on the kinetics of methane hydrate formation. A high concentration of fine sands with a grain size <125μm led to explicitly faster gas hydrate formation compared to coarser sand or a small fraction of fine particles diluted in a sample of coarser sand grains. Our article discusses possible causes in conjunction with changes of the mineral surface. These include accelerated hydrate nucleation or growth due to the surface area (1) or mineral composition (2) and changes in dissolution kinetics (3) caused by enhanced dissolution rates or changes in the ratio of bound to bulk water volumes. The addition of salt significantly increased induction times but did not supplant the particle size effect.

Carbon Dioxide Sequestration: Influence of Porous Media on Hydrate Formation Kinetics

In the present study, CO2 sequestration by hydrate formation in porous sediments has been discussed. Two siliceous materials with high porosities, pumice and fire hardened red clay (FHRC), have been used as packing materials in a fixed bed setup to study hydrate formation kinetics. The results obtained using the aforementioned materials were compared with those obtained using silica sand and quartz. Carbon dioxide hydrate formation kinetics was studied at 3.0 MPa pressure and 274 K temperature. Two different types of experiments were conducted: (a) using a constant volume of water and (b) maintaining a constant bed height. These experiments were conducted using the different porous media individually as packing materials. It was observed that pumice as the porous medium showed better hydrate formation kinetics resulting in 46 mol % water to hydrate conversion in 5 h. Moreover, kinetics was enhanced with decrease in the bed height of pumice; this suggests that at field scale adaptation of CO2 sequestration...

フィールド試験による変流量制御を導入したシステム性能の実証&lt;br&gt;少水量対応地中熱ヒートポンプビルマルチシステムの開発に関する研究(第2報)

Field test of the Ground Source Heat Pump (GSHP) system applying variable water volume (VWV) control and multi-split heat pump has been carried out in order to demonstrate the effect of reduction of circulation pumps' electric power consumption. It was confirmed that the constant differential temperature control is practicable method as the VWV control method. As the result of field test, the GSHP system applying VWV control could reduce approximately 80 % of circulation pumps' electric power consumption compared to the GSHP system applying constant water volume. Seasonal performance factor of the GSHP system was 4.51 and this result achieved the target value of more than 4.5. During the heating operation, seasonal performance factor of the GSHP system was 3.61 and the value was higher than the one of conventional system. In addition, it was shown that the decrease of system COP of GSHP system using antifreeze solution as heat carrier fluid is less than 15 % compared to the one of GSHP system using water.

Escória de aciaria na redução da solubilidade e lixiviação de manganês em áreas contaminadas

A escória de aciaria é um rejeito da produção do aço e possui propriedade corretiva da acidez do solo, podendo reduzir consequentemente a mobilidade de elementos traço. O trabalho objetivou avaliar a capacidade do resíduo industrial escória de aciaria em reduzir a solubilidade e lixiviação de Mn em resíduos contaminados. No Laboratório de Poluição de Solos da UFRRJ (Seropédica-RJ), foram realizados ensaios de lixiviação em colunas usando três resíduos contaminados com Mn, denominados G1, G2 e G3 e duas doses de resíduo inertizante (escória de aciaria). Nas colunas, foi aplicado um volume de água conhecido e constante que simula a precipitação máxima ocorrida nos últimos 17 anos na região onde foi coletado o resíduo. A maior dose do resíduo de escória de aciaria (6%) reduziu a solubilidade do Mn a valores inferiores ao limite máximo permitido pela ABNT, nos grupos G1, G2 e G3, sendo que o tratamento com 6% escória de aciaria + barreiras químicas foi o mais eficiente na redução da lixiviação de Mn em todos os grupos de resíduos estudados. Portanto, os resultados evidenciaram a eficiência da escória de aciaria na redução da solubilidade e lixiviação do Mn, em todos os resíduos.

A three-year time-series of dust deposition flux measurements in Gran Canaria, Spain: A comparison of wet and dry surface deposition samplers

A three-year dataset of particle deposition flux measurements in Gran Canaria, Canary Islands, is presented. As part of this work, a comparison between wet and dry surrogate surfaces to estimate dry deposition fluxes was carried out over a period of more than two years in order to compare the particle collection efficiency of both devices. The selected recipients were buckets placed in two commercial samplers (ARS 1000, MTX Italy) equipped with a rain sensor; one of which was modified to maintain a constant volume of water during the collection time. No relationship was found between dry deposition fluxes and meteorological conditions (such as wind speed), the volume of the deposition container, or the number of days sampled. Dry deposition measurements made using a wet plate were 94% (±7%) of the corresponding measurements made by dry plate, and therefore are no better for the collection of particles. While both systems showed consistent results, with no significant differences in the estimation of total flux, the use of wet plates increased the uncertainty in the measurements and the complexity of the sampling method.During 2009–2012, wet and dry deposition fluxes showed a marked seasonality with a maximum in spring. Dry deposition dominated the particle fluxes (more than 93% of the total flux) and a value of 25.0 ± 0.3 mg m−2 d-1 was measured. Estimated dry deposition velocity was 0.85 ± 0.38 cm s−1, in good agreement with previously reported values.

Reducing Set Retardation in High-Volume Fly Ash Mixtures with the Use of Limestone

High-volume fly ash (HVFA) concretes are attractive not only because they reduce cement content and the associated greenhouse gases, but also because they avoid landfilling excessive quantities of fly ash. These sustainability benefits are often tempered by practical constructability limitations that may exist for HVFA concretes: retardation and diminution of the early-age reaction, delay in setting (and finishing operations), and lower early-age strength. This paper explores the alleviation of these deficiencies in HVFA mixtures by the incorporation of fine limestone powders into ternary blends. Isothermal calorimetry and Vicat needle penetration measurements are employed to assess reaction rates and setting times, respectively. A systematic variation of the content and fineness of the limestone powder in mixtures containing either a Class C or a Class F fly ash indicates that setting times are linearly correlated with the surface area supplied by the limestone. Comparison of a limestone system to a system containing an inert titanium dioxide of similar particle size indicates that the acceleration and amplification effects of the limestone can be attributed to both physical (nucleation) and chemical (additional calcium ions) processes. The results indicate that ternary blends with 40% of the cement by volume replaced by 30% to 35% fly ash and 5% to 10% limestone at a constant water volume fraction can be achieved without significant delay in setting.

Effects of larval stocking density and feeding regime on larval rearing of giant freshwater prawn ( Macrobrachium rosenbergii)

A series of larval rearing experiments were conducted to investigate the effect of larval stocking density and feeding regime on larval development, survival, and larval quality of Macrobrachium rosenbergii (de Man). For larval density, fixed initial stocking densities (50, 100, 150 and 200 larvae l − 1 ), as well as treatments where larval density changed during the rearing period (in function of the rearing volume), were tested. In the latter trial, initial densities ranged between 100 and 400 larvae l − 1 . For the factor feeding regime (based on Artemia nauplii), the effect of both feed ration (1.5, 2, 3 and 4 times the standard feed ration) and feeding frequency (2 or 6 times per day) on larval performance was tested. The results of the experiments showed that larval stocking density and feeding regime strongly affected larval development, survival, and duration of the rearing cycle, as well as larval quality. The best initial larval stocking density when using a constant water volume was 100–150 l − 1 , which could be increased up to 400 l − 1 if the water volume was increased during culture. A feeding frequency of 6 times per day using first-stage Artemia nauplii, was more effective than feeding only twice daily. Production efficiency in terms of the number of postlarvae produced per unit rearing volume, and the number of Artemia nauplii used per postlarva produced in the different treatments is discussed. These optimized larval stocking densities and feeding regimes are expected to render freshwater prawn larval rearing more profitable and improve larval quality.

Effects of temperature and volume of water on the growth and development of tadpoles of Pleurodema diplolister and Rhinella granulosa (Amphibia: Anura)

The capacity of tadpoles to reduce their metamorphosis time and body size in response to fluctuations in environmental variables of temporary ponds has been recorded in field and laboratory studies. The main alterations in this habitat are related to the decrease of the water level and increase in temperature. However, few studies tried to dissociate the effect of these two variables. The aim of the present study was to analyze simultaneously the effects of water volume reduction and temperature on the development and growth in tadpoles of Pleurodema diplolister (Peters, 1870) and Rhinella granulosa (Spix, 1824) - species that use temporary ponds for reproduction. The tadpoles of these two species were subject to four treatments: (1) constant volume of water of 2000 ml and constant temperature of 26oC; (2) gradually decreasing water volume from 2000 ml to 200 ml or 150 ml and constant temperature of 26 oC; (3) Constant water volume as in (1) and constant temperature of 30 oC or 33 oC and (4) Decreasing water volume (as above) and constant temperature as in the treatment (3). There was no interaction between both tested variables on the growth and development of tadpoles of both species. Tadpoles of P. diplolister and R. granulosa responded to high temperature by decreasing development time. Tadpoles responded to decreasing volume of water by metamorphosing into smaller size. Tadpoles of P. diplolister maintained at 30oC showed growth reduction. Tadpoles of R. granulosa increased their body size when subject to the treatment at 30oC.

The acidic mine pit lakes of the Iberian Pyrite Belt: An approach to their physical limnology and hydrogeochemistry

This study examines some relevant limnological and hydrogeochemical characteristics of 22 mine pit lakes of the Iberian Pyrite Belt (IPB). The studied pit lakes include some of the largest and historically most important mines of the IPB (including Corta Atalaya and Cerro Colorado in Riotinto, Filón Norte, Filón Centro and Filón Sur in Tharsis, Aznalcóllar, or San Telmo) and many other of minor size. As a whole, these lakes constitute, at present, a large volume of highly acidic and metal-polluted water. Some of these pit lakes are very recent (e.g., Corta Atalaya, 2.5 a; Los Frailes, 6 a) and present a continuous hydrological and geochemical evolution, although many others were abandoned decades ago and show nearly constant water volume. Depth profiles obtained in several pit lakes (e.g., San Telmo, Confesionarios, Cueva de la Mora, Concepción) indicate that many of them have developed meromixis and show, at present, a permanent thermal and chemical stratification with a well defined chemocline separating an anoxic, Fe(II)-rich monimolimnion, and a well mixed, oxygenated and Fe(III)-rich mixolimnion. In the upper layer, the bacterial oxidation of Fe(II) competes with photoreductive processes which take place in the surface water, thus provoking diel cycles of Fe(II) concentration. The observed water chemistry reflects the oxidation and dissolution of pyrite and other sulphides and gangue aluminosilicates from the country rock. The pit lakes of the IPB cover a wide range of water compositions, from circumneutral and relatively low-metal (e.g., Los Frailes, pH 7.2, 0.07 mg/L Fe, 3.8 mg/L Mn, 30 mg/L Zn), to extremely acidic and metal(loid)-rich (e.g., Corta Atalaya, pH 1.2, 36.7 g/L Fe, 6.7 g/L Zn, 1.3 g/L Cu, 159 mg/L As). Most pit lakes, however, are comprised within the pH range of 2.2–3.6 and appear to be strongly buffered by the hydrolysis and precipitation of Fe(III) in the form of schwertmannite, which forms colloids that can sorb trace elements from the aqueous phase.

Water Extractable Trace Elements in Poultry Litters and Granulated Products

Poultry litter contains many trace elements such as As, Cu, and Zn, and its land application may lead to the accumulation of these elements in soils, especially near the soil surface. The objectives of this study were to determine the total amount of trace elements and evaluate the effect of litter granulation and various litter to water extraction ratios on water extractable trace elements in 8 raw and granulated litter products. Granulated litters that contained urea, dicyandiamide, or hydrolyzed feathermeal had significantly lower contents of total As, B, Cu, Mn, and Zn than untreated litters because of the dilution of litters with additives. Trace element concentrations (mg/L) in the water extracts of the various poultry litters generally decreased when extraction ratios (litter to water) shifted from 1:10 to 1:250, or as the amount of poultry litter decreased with a constant water volume (200 mL). But, the water extractable content of trace metals (mg/kg) generally increased from an extraction ratio of 1:10 to 1:200, with values similar at 1:200 and 1:250 extraction ratios. Based on our results, we suggest using a 1:200 extraction ratio when evaluating water extractable As, Cu, and Zn in poultry litters. The estimated land application rates of trace metals, when poultry litter is applied on the basis of total P content, were considerably lower than the trace metal loadings allowable under the current environmental regulations governing biosolids and other materials with measurable amounts of trace metals. The laboratory water extractions of poultry litters and granulated products have increased our understanding of the potential risks to water quality posed by the land application of poultry litter and will contribute to the development of base knowledge needed to define land application practices that are protective of soil and water quality.

Economic assessment of acquiring water for environmental flows in the Murray Basin*

This article is an economic analysis of reallocating River Murray Basin water from agriculture to the environment with and without the possibility of interregional water trade. Acquiring environmental flows as an equal percentage of water allocations from all irrigation regions in the Basin is estimated to reduce returns to irrigation. When the same volume of water is taken from selected low‐value regions only, the net revenue reduction is less. In all scenarios considered, net revenue gains from freeing trade are estimated to outweigh the negative revenue effects of reallocating water for environmental flows. The model accounts for how stochastic weather affects market water demand, supply and requirements for environmental flows. Net irrigation revenue is estimated to be 75 million less than the baseline level for a scenario involving reallocating a constant volume of water for the environment in both wet and dry years. For a more realistic scenario involving more water for the environment in wet and less in dry years, estimated net revenue loss is reduced by 48 per cent to 39 million. Finally, the external salinity‐related costs of water trading are estimated at around 1 million per annum, a quite modest amount compared to the direct irrigation benefits of trade.

Effects of Pumping on Entomopathogenic Nematodes and Temperature Increase within a Spray System

Exposure to hydrodynamic stresses and increased temperature during hydraulic agitation within a spray system could cause permanent damage to biological pesticides during spray application. Damage to a benchmark biopesticide, entomopathogenic nematodes (EPNs), was measured after a single passage through three different pump types (centrifugal, diaphragm, and roller) at operating pressures up to 828 kPa. No mechanical damage to the EPNs due to passage through the pumps was observed. Separate tests evaluated the effect of pump recirculation on temperature increase of water within a laboratory spray system (56.8-L spray tank) and a conventional-scale spray system (1136-L spray tank). A constant volume of water (45.4 L) was recirculated through each pump at 15.1 L/min within the laboratory spray system. After 2 h, the temperature increase for the centrifugal pump was 33.6°C, and for the diaphragm and roller pumps was 8.5°C and 11.2°C, respectively. The centrifugal pump was also evaluated within the conventional spray system, under both a constant (757 L) and reducing volume scenario, resulting in an average temperature increase of 3.2°C and 6.5°C, respectively, during the 3-h test period. When comparing the number of recirculations for each test, the rate of temperature increase was the same for the conventional spray system (for both the constant and reducing volume scenarios), while for the laboratory spray system the temperature increased at a greater rate, suggesting that the volume capacity of the spray tank is the primary factor influencing the temperature increase. Results from this study indicate that thermal influences during pump recirculation could be more detrimental to EPNs than mechanical stress. Results show that extensive recirculation of the tank mix can cause considerable increases in the liquid temperature. Diaphragm and roller pumps (low-capacity pumps) are better suited for use with biopesticides compared to the centrifugal pump, which was found to contribute significant heat to the spray system.