Water Discharge Rate Research Articles

Direct measurement of denitrification activity in a Gulf coast freshwater marsh receiving diverted Mississippi River water

Wetland loss along the Louisiana Gulf coast and excessive nitrate loading into the Gulf of Mexico are interrelated environmental problems. Nitrate removal by soil denitrification activity was studied in a ponded freshwater marsh receiving diverted Mississippi River water for the purpose of reversing or slowing wetland loss. Labeled 15N-nitrate was applied at 3.8 g N m −2 into four replicate study plots after removing above ground vegetation. Nitrogen gas (N 2) and nitrous oxide (N 2O) emissions from the plots were determined by isotope ratio mass spectrometry (IRMS). Nitrous oxide emissions were also compared with the results determined by gas chromatograph (GC). Results showed that it took 2 weeks to remove the added nitrate with N 2O emission occurring over a period of 4 d. The apparent denitrification dynamics were assumed to follow the Michaelis–Menten equation. The maximum denitrification rate and K m value were determined as 12.6 mg N m −2 h −1, and 6.5 mg N l −1, respectively. Therefore the maximum capacity for nitrate removal by the marsh soil would be equivalent to 110 g N m −2 yr −1, with more than 30% of nitrogen gas evolved as N 2O. For typical nitrate concentrations in Mississippi River water of about 1 mg N l −1, nitrate would be removed at a rate of 14.7 g N m −2 yr −1 with N 2O emission about 1.5%. A denitrification dynamic model showed that the efficiency of nitrate removal would largely depend on the water discharge rate into the ponded wetland. Higher discharge rate will result in less retention time for the water in the marsh where nitrate is denitrified.

Optimal multi-reservoir network control by augmented Lagrange programming neural network

An approach based on augmented Lagrange programming neural network (ALPNN) is proposed for the optimal operation of multi-reservoir network control problems. The main objective here is to find out the optimal hourly water releases from each hydro-plant in the interconnected hydro system to minimize the energy deficit and to distribute uniformly the energy deficit if any in each time interval. The interdependence between water discharge rate variables is very apparent in multi-reservoir network control problems. This proposed method takes into account the concurrent interaction among all the water discharge rate variables of the problem. This approach is based on the Lagrange multiplier theory and search for solutions satisfying the necessary conditions of optimality in the state space. The network equilibrium point satisfies the Kuhn-Tucker condition for the problem and corresponds to the Lagrange solution of the problem. This technique has been applied to a standard 10-reservoir interconnected network in which each hydro-power plant has a linear generation model and discretized time varying river inflows. Results obtained from this approach are compared with those obtained by the conventional discrete maximum principle method. It is observed from the results that the proposed method is very effective and provides better results with respect to constraint satisfaction.

Fuzzy rule-based modelling for human health risk from naturally occurring radioactive materials in produced water

Produced water, discharged from offshore oil and gas operations, contains chemicals from formation water, condensed water, and any chemical added down hole or during the oil/water separation process. Although, most of the contaminants fall below the detection limits within a short distance from the discharge port, a few of the remaining contaminants including naturally occurring radioactive materials (NORM) are of concern due to their bioavailability in the media and bioaccumulation characteristics in finfish and shellfish species used for human consumption. In the past, several initiatives have been taken to model human health risk from NORM in produced water. The parameters of the available risk assessment models are imprecise and sparse in nature. In this study, a fuzzy possibilistic evaluation using fuzzy rule based modeling has been presented. Being conservative in nature, the possibilistic approach considers possible input parameter values; thus provides better environmental prediction than the Monte Carlo (MC) calculation. The uncertainties of the input parameters were captured with fuzzy triangular membership functions (TFNs). Fuzzy if-then rules were applied for input concentrations of two isotopes of radium, namely 226Ra, and 228Ra, available in produced water and bulk dilution to evaluate the radium concentration in fish tissue used for human consumption. The bulk dilution was predicted using four input parameters: produced water discharge rate, ambient seawater velocity, depth of discharge port and density gradient. The evaluated cancer risk shows compliance with the regulatory guidelines; thus minimum risk to human health is expected from NORM components in produced water.

Export rate of dissolved organic matter from paddy fields during cultivation-activity events

The aim of this study is to quantify the dissolved organic carbon (DOC) of drainage water from paddy fields in agricultural areas of Tottori prefecture, Japan. In four experimental paddy fields, DOC concentration varied much from 1.1 to 10.1 mg C l−1, and was the highest during heavy runoff that occurred in April when there was a non-agricultural period. However, variation in DOC concentration did not always correspond to rainfall, but depended more on cultivation-activity events such as tilling, planting, draining in summer, and final draining in autumn. The water discharge rate from each experimental field was estimated by using a hydrologic model (the Tank Model and a genetic algorithm). Daily DOC export rate per unit area of three experimental paddy fields was calculated to be 0.0074, 0.0052, and 0.0081 kg a−1 day−1, respectively. The daily DOC export rate showed large seasonal variation with the highest value in May and June. It can be concluded that DOC export from paddy fields can be a substantial source of DOC in receiving waters, and the export rate depends much on cultivation method practice. It might be suggested that DOC export from paddy fields can be controlled by a better water management practice of farmers.

Eruption of the dacite to andesite zoned Mateare Tephra, and associated tsunamis in Lake Managua, Nicaragua

The dacite to andesite zoned Mateare Tephra is the fallout of a predominantly plinian eruption from Chiltepe peninsula at the western shore of Lake Managua that occurred 3000–6000 years ago. It comprises four units: Unit A of high-silica dacite is stratified, ash-rich lapilli fallout generated by unsteady subplinian eruption pulses affected by minor water access to the conduit and conduit blocking by degassed magma. Unit B of less silicic dacite is well sorted, massive pumice lapilli fallout from the main, steady plinian phase of the eruption. Unit C is andesitic fallout that is continuous from unit B except for the rapid change in chemical composition, which had little influence on the ongoing eruption except for a minor transient reduction of the discharge rate and access of water to the conduit. After this, discharge rate re-established to a strong plinian eruption that emplaced the main part of unit C. This was again followed by water access to the conduit which increased through upper unit C. The lithic-rich lapilli to wet ash fallout of unit D is the product of the fully phreatomagmatic terminal phase of the eruption. A massive well-sorted sand layer, the Mateare Sand, replaces laterally variable parts of unit A and lowermost part of unit B in outcrops up to 32 m above present lake level. The corresponding interval missing in the primary fallout can be identified by comparing the composition of pumice entrained in the sand, and pumice from the local base of unit B on top of the sand, with the compositional gradient in undisturbed fallout. The amount of fallout entrained in the sand decreases with distance to the lake. The Mateare Sand occurs at elevations well above beach levels and its widespread continuous distribution defies a fluviatile origin. Instead, it was produced by lake tsunamis triggered by eruption pulses during the initial unsteady phase of activity. Such tsunamis could threaten areas not affected by fallout, and represent a hazard of particular importance in Nicaragua where two large lakes host several explosive volcanoes.

An augmented Lagrange programming optimization neural network for short-term hydroelectric generation scheduling

An approach based on augmented Lagrange programming neural networks is proposed for determining the optimal hourly amounts of generated power for the hydro-units in an electric power system. This methodology is based on the Lagrange multiplier theory in optimization and searches for solutions satisfying the necessary conditions of optimality in the state space. The equilibrium point of the network satisfies the Kuhn–Tucker condition for the problem. The equilibrium point of the network corresponds to the Lagrange solution of the problem. The proposed technique has been applied to a multi-reservoir cascaded hydro-electric system with a non-linear power generation function of water discharge rate and storage volume. The water transportation delay between connected reservoirs is also taken into account. Results obtained from this approach are compared with those obtained from the two phase optimization neural network and the conventional augmented Lagrange multiplier method. It is concluded from the results that the proposed method provides better results with respect to constraint satisfaction and is very effective in yielding optimal hydro-generation schedules.

Evaluation of time‐space distributions of submarine ground water discharge

Submarine ground water discharge (SGD) rates were measured continuously by automated seepage meters to evaluate the process of ground water discharge to the ocean in the coastal zone of Suruga Bay, Japan. The ratio of terrestrial fresh SGD to total SGD was estimated to be at most 9% by continuous measurements of electrical conductivity of SGD. Semidiurnal changes of SGD due to tidal effects and an inverse relation between SGD and barometric pressure were observed. Power spectrum density analyses of SGD, sea level, and ground water level show that SGD near shore correlated to ground water level changes and SGD offshore correlated to sea level changes. SGD rates near the mouth of the Abe River are smaller than those elsewhere, possibly showing the effect of the river on SGD. The ratio of terrestrial ground water discharge to the total discharge to the ocean was estimated to be 14.7% using a water balance method.

The application of simple methods using remote sensing data for the regional validation of a semidistributed hydrological catchment model

Simulation runs of a semidistributed hydrological conceptual catchment model were performed using a spatial data set from a mesoscale catchment located at the moraine landscape of North–East Germany. The simulation quality of the model was estimated by comparing measured daily actual evapotranspiration rates, soil water contents and discharge rates with the corresponding simulated model outputs. Additionally, six Landsat-TM5-subsets covering the catchment were used to calculate the Normalized Difference Vegetation Index (NDVI). These NDVI-distributions were compared with the corresponding simulated regional distributions of actual evapotranspiration (ETr) rates. A visual analysis of the spatial distribution patterns of the NDVI and of the simulated ETr-rates shows some correspondences. However, the spatial variability of the NDVI-patterns was distinctly higher in comparison with the variability of the ETr-rates calculated by the model. We analyzed the coefficients of correlation R between the patterns of the NDVI and the simulated ETr-rates separately for the land cover classes arable land, meadows, coniferous, deciduous and mixed forests. For arable land R ranged within 0.77 and 0.10, for meadows within 0.79 and 0.10, for coniferous forests between 0.73 and 0.10, for deciduous forests between 0.88 and 0.10 as well as for mixed forests between 0.67 and 0.10. The spatial distributions of simulated high and low ETr-rates were mainly correlated with the spatial distributions of forest areas, arable land, water bodies and settlements.

Ground Water Recharge and Discharge in the Central Everglades

AbstractRates of ground water recharge and discharge are not well known in the central Everglades. Here we report estimates of ground water recharge and discharge at 15 sites in the Everglades Nutrient Removal Project and in Water Conservation Area 2A (WCA‐2A), along with measurements of hydraulic properties of peat at 11 sites. A simple hydrogeologic simulation was used to assess how specific factors have influenced recharge and discharge. Simulations and measurements agreed that the highest values of recharge and discharge occur within 600 m of levees, the result of ground water flow beneath levees. There was disagreement in the interior wetlands of WCA‐2A (located > 1000 m from levees) where measurements of recharge and discharge were substantially higher than simulated fluxes. A five‐year time series (1997 to 2002) of measured fluxes indicated that recharge and discharge underwent reversals in direction on weekly, monthly, and annual timescales at interior sites in WCA‐2A. Ground water discharge tended to occur during average to moderately dry conditions when local surface water levels were decreasing. Recharge tended to occur during moderately wet periods or during very dry periods just as water levels began to increase following precipitation or in response to a pulse of surface water released from water‐control structures by water managers. Discharge also tended to occur at sites in the wetland interior for ∼1 week preceding the arrival of the surface water pulse. We conclude that ground water recharge and discharge vary cyclically in the interior wetlands of the central Everglades, driven by the differential responses of surface water and ground water to annual, seasonal, and weekly trends in precipitation and operation of water‐control structures.

Advection Within Shallow Pore Waters of a Coastal Lagoon, Florida

AbstractGround water sources can be a significant portion of a local water budget in estuarine environments, particularly in areas with high recharge rates, transmissive aquifers, and permeable marine sediments. However, field measurements of ground water discharge are often incongruent with ground water flow modeling results, leaving many scientists unsure which estimates are accurate. In this study, we find that both measurements and model results are reasonable. The difference between estimates apparently results from the sources of water being measured and not the techniques themselves. In two locations in the Indian River Lagoon estuarine system, we found seepage meter rates similar to rates calculated from the geochemical tracers 222Rn and 226Ra. Ground water discharge rates ranged from 4 to 9 cm/d using seepage meters and 3 to 20 cm/d using 222Rn and 226Ra. In contrast, in comparisons to other studies where finite element ground water flow modeling was used, much lower ground water discharge rates of ∼0.05 to 0.15 cm/d were estimated. These low rates probably represent discharge of meteoric ground water from land‐recharged aquifers, while the much higher rates measured with seepage meters, 222Rn, and 226Ra likely include an additional source of surface waters that regularly flush shallow (< 1 m depth) sediments. This resultant total flow of mixed land‐recharged water and recirculated surface waters contributes to the total biogeochemical loading in this shallow estuarine environment.

The validation of a modelling system for calculating water balance and catchment discharge using simple techniques based on field data and remote sensing data

In a regional case study, simulation runs of a simple hydrological conceptual catchment model were performed using a spatial data set, which covers a mesoscale catchment located at the moraine landscape of North-East Germany. This data set consists of a soil map, rivernet, landuse map, digital elevation model as well as meteorological time series. Furthermore for 3 years, a survey of the actual crop distribution in the catchment were carried out. The simulations cover the time period from 1993 to 1997. At first, the simulation quality of the model was estimated by comparing measured daily evapotranspiration rates, soil water contents and discharge rates with the corresponding simulated model outputs. Additionally, four Landsat-TM-Scenes covering the catchment were used to calculate the Normalized Difference Vegetation Index (NDVI). The NDVI was used for the estimation of the spatial distributions of transpiration rates. These data were used to check the simulated regional distributions of transpiration rates. The transpirations rates estimated by NDVI and simulated by the model were in different ranges of 0–1.8 and 0–6.5 mm day −1, respectively. However, the spatial distribution patterns of areas with high and low transpiration rates estimated by NDVI and simulated by the model were identical.

The Effect of Water Mist on Burning Rates of Pool Fire

The present study aims to investigate the interactions between water mists and fires and show the influence of water mist on burning rates of pool fires. Experiments are extensively performed for various sizes of fire source with different discharge rates of water. From the experimental observations, it is noted that the fuel burning rate is substantially changed when the water mists are interacted with fires and its difference with and without water mist increases with the discharge rate of water and decreases as the fire intensity increases. In addition, the interactions of water mists with pool fires are simulated by the FDS (Fire Dynamics Simulator; Ver. 3.0) program with the measured burning rates as input data in the present study. Considering the influence of water mists on burning rates, better predictions are yielded compared with experimental data for the suppression time and the mean ceiling temperature.

Sediment accumulation in newly constructed vegetative treatment facilities along a new major road

The A34 Newbury bypass was opened in England in November 1998. This 15 km of roadway has nine constructed vegetative treatment systems incorporating oil separators, silt traps, grass filters for primary filtration and chemical absorption, reed wetlands for secondary biofiltration, a deep water pool and outflow device to control the rate of water discharge into existing watercourses. Two of these facilities discharge stormwater into the Lambourn sites of special scientific interest (SSSI) river. An evaluation of the heavy metal levels in these two ponds (Ponds J and K) has been undertaken in the 39-month period after the opening of the bypass. Motorway-derived contaminants including Pb, Cd, Cu and Zn were evaluated within pond sediment throughout these treatment facilities. Results reveal that heavy metal levels within the treatment system that possesses a well-established reed bed system decrease rapidly though the facility. It is postulated that the high reed biomass within this facility may be primarily responsible for reducing hydraulic flow thus allowing a greater residence time for sedimentation, filtration and bioaccumulation processes.

Export of Dissolved Inorganic Nitrogen in a Partially Cultivated Subtropical Mountainous Watershed in Taiwan

A spatial and temporal investigation of dissolved inorganic nitrogen (DIN; NO3, NO2 and NH4) was conducted under various water discharge conditions in Lanyang-Hsi, a subtropical mountainous stream, which drains through distinct degrees of agriculture-influenced sub-watersheds. In both the cultivated and non-cultivated sub-watersheds, NO3 was the most abundant species accounting for >80% of total DIN, while NH4 and NO2 accounted for <15% and 5% of DIN, respectively. Agricultural activities along the riverbank led to significantly higher NO3 concentrations (13–246 μM) and DIN yields (1300–3800 kg N km−2 yr−1) in main channel when compared to those of non-cultivated tributaries (9–38 μM for NO3 and 550–740 kg N km−2 yr−1 for yield). The much lower and less variable DIN yields observed in tributary stations (mean = 660 ± 120 kg N km−2 yr−1) are considered as the present day background of DIN yield, which is significantly higher than those of most natural watersheds in other regions. Elevated atmospheric DIN deposition is likely the cause for the high background DIN yield. Human activity within the watershed results in additional DIN yield, which accounted for 49% of total N export. However, the reported atmospheric DIN input in northern Taiwan (∼1800 kg N km−2 yr−1) is much higher than the background DIN yield implying that a major fraction (70%) of atmospheric inputs are retained or processed within the watershed. A dilution pattern occurred in the main channel where high NO3 concentrations from the upstream sources decreased significantly in downstream direction due to inputs of NO3-diluted water from non-cultivated areas. We adopted a two-source mixing model to predict the NO3 dilution pattern. This model revealed a third yet not recognized N source in the lower part of watershed. Model results also indicated the importance of water discharge rate in regulating the relative contribution to total DIN export among these sources.

Impact of biological clogging agents on filter and emitter discharge characteristics of microirrigation systems

AbstractWater application efficiency of microirrigation systems (MIS) may depend, at least partially, on algae and protozoa (biological clogging agents, BCAs) induced filter and emitter clogging. In this study we assessed the impact of BCA‐induced changes on water discharge rate and distribution uniformity from (i) emitters with different water flow cross‐section (CS) area, pressure compensation (PC) systems, and inbuilt filtration areas (FAs), and (ii) filters either made of urethane, sand, or disk in the Tohaku irrigation project in Japan. In a field experiment, four types of on‐line emitters on each of four laterals and four types of in‐line emitters on each of another four laterals were assessed for BCA‐induced emitter discharge performance without using filters in the field irrigation line. The emitters' discharge rate increased with increasing CS, FA, and working pressure (WP) and decreased when the emitters were on‐line in the laterals and with increasing BCA counts. Because BCAs are the only dynamic variable in the above relationship, we conclude that BCA‐induced clogging is a major issue when filters were not installed in field irrigation lines. The filter performance assessment based on the number of backwashings required to restore the working pressure to the recommended level indicated that BCA filtering by the sand filter was highest, followed by disk and urethane, respectively. Copyright © 2004 John Wiley &amp; Sons, Ltd.

A fuzzy global efficiency optimization of a photovoltaic water pumping system

This paper presents an on-line fuzzy optimization of the global efficiency of a photovoltaic water pumping system driven by a separately excited DC motor (DCM), a permanent magnet synchronous motor (PMSM), or an induction motor (IM), coupled to a centrifugal pump. The fuzzy optimization procedure stated above, which aims to the maximization of the global efficiency, will lead consequently to maximize the drive speed and the water discharge rate of the coupled centrifugal pump. The proposed solution is based on a judicious fuzzy adjustment of a chopper ratio which adapts on-line the load impedance to the photovoltaic generator (PVG). Simulation results show the effectiveness of the drive system for both transient and steady state operations. Hence it is suitable to use this fuzzy logic procedure as a standard optimization algorithm for such photovoltaic water pumping drives.

Transformation of dissolved and particulate materials on continental shelves influenced by large rivers: plume processes

The world's ten largest rivers transport approximately 40% of the fresh water and particulate materials entering the ocean. The impact of large rivers is important on a regional/continental scale (e.g. the Mississippi drains ∼40% of the conterminous US and carries approximately 65% of all the suspended solids and dissolved solutes that enter the ocean from the US) and on a global scale (e.g. the Amazon River annually supplies approximately 20% of all the freshwater that enters the ocean; e.g. approximately 85% of all sedimenting organic carbon in the ocean accumulates in coastal margin regions). River plume processes are affected by a suite of complex factors that are not fully understood. It is clear however, that the composition, concentration and delivery of terrestrial materials by large rivers cannot be understood by simply scaling up the magnitudes and impacts of dominant processes in smaller rivers. Because of high rates of particulate and water discharge, the estuarine processes associated with major rivers usually take place on the adjacent continental shelf instead of in a physically confined estuary. This influences the magnitude and selectivity of processes that transform, retain or export terrestrial materials. Buoyancy is a key mediating factor in transformation processes in the coastal margin. In this paper we review and synthesize current understanding of the transformation processes of dissolved and particulate organic and inorganic materials associated with large river (buoyant) plumes. Chemical and biological activities are greatly enhanced by the changed physical and optical environment within buoyant plumes. Time and space scales over which these transformation processes occur vary greatly, depending on factors such as scales of discharge, suspended sediment loads, light and temperature. An adequate understanding of transformation processes in these highly dynamic, buoyancy-driven systems is lacking. In this paper, we review the biogeochemical processes that occur in large river plumes.

Distribuição da água no solo para o dimensionamento da irrigação por gotejamento

O objetivo do dimensionamento de um sistema de irrigação por gotejamento é escolher adequadamente o "layout" e os componentes do sistema para promover a distribuição precisa da água (e fertilizante) para todas as plantas, ao longo do campo. Com vistas a este propósito, avaliaram-se as contribuições capazes de fornecer elementos básicos para o dimensionamento da irrigação por gotejamento, utilizando-se sondas de TDR. Assim, o estudo experimental foi dividido em duas partes; na primeira, tem-se o efeito de irrigações sucessivas nas dimensões dos raios horizontal e vertical do bulbo molhado, analisado em condições de laboratório e, na segunda, o processo de distribuição da água na formação do bulbo molhado em campo. Com os resultados apresentados nesta pesquisa pôde-se concluir que: a umidade inicial do solo, o volume aplicado, a vazão do gotejador, o disco saturado e a condutividade hidráulica, são elementos importantes e devem ser conhecidos para o dimensionamento e o manejo adequado da irrigação.

Nutrient transfer from soil to surface waters: Differences between nitrate and phosphate

Nitrate (NO3 –) and soluble reactive phosphorus (SRP), the two major dissolved N and P species available to aquatic biota, respond differently to varying water discharge rates (Q) in agricultural drainage pipes and rivers (Fig. 1): SRP concentrations are positively related to Q, whereas NO3 – concentrations decrease with increasing discharge rates. In addition, NO3-N concentrations exceed (in mass units) SRP concentrations up to 700-fold even though the liquid manure applied to agricultural fields has a N:P ratio equal to only about 5. Preferential flow of rainwater across the soil column and different affinities of the two nutrients for the soil matrix explain these differences in behaviour and mobility: i. Concentrations of substances that have a high sorption affinity for the soil matrix (such as SRP) tend to increase in drainage pipes and streams as water discharge increases. ii. Concentrations of species that are not retarded by sorption processes (such as NO3 –) and, hence, do not accumulate in the topsoil, tend to be negatively related to discharge rate. Differences in the availability and pool size of NO3 – and SRP in the topsoil explain the different hysteresis patterns if NO3 – and SRP concentrations are plotted versus the corresponding discharge rate during precipitation events (Fig. 2).

Radioactive contamination in the upper part of the Techa river: stirring-up of bottom sediments and precipitation of suspended particles. Analysis of the data obtained in 1949-1951.

A hydrodynamic model of the upper part of the Techa river was developed on the basis of the river valley geometry as well as data of hydrological conditions and of the granulometric composition of bottom sediments. The model describes the transport of radioactivity by suspended sediments with different granulometric compositions (clay, silt) in the early 1950s. It includes the stirring-up of bottom sediments and the precipitation of suspended sediments as a function of water discharge rate and water level in the investigated part of the river. The results allow to specify the development of the river system contamination as a result of inflow of suspended sediments contaminated with radionuclides. In the period of liquid radioactive waste (LRW) discharges, the water of the Techa river contained a large fraction of finely dispersed particles of less than 5 micro m diameter. At the site of LRW discharge 80% of the discharged activity was adsorbed to these particles. Depending on the water flow, 40-80% of the suspensions precipitated at the bottom of subsequent sedimentation reservoirs. A total of about 1.6 MCi adsorbed to the suspended particles entered the open hydrographic system of the Techa river. The conclusion that the largest part of the activity was adsorbed on the suspended particles contradicts the assumption in the Techa river dosimetry system, TRDS-2000, that most of the released activity entered the Techa river in soluble form. For a correct reconstruction of the doses received by the Techa river population it is, therefore, essential to consider hydrodynamic models that take into account the transport of radionuclides adsorbed on the suspended particles.