Exploitation Scenarios Research Articles

Scenario analysis for the sustainable development of agricultural water in the Wuyuer River basin based on the WEP model with a reservoir and diversion engineering module

Agricultural water use is increasing quickly with the rapid socioeconomic development observed in the Wuyuer River basin. Water withdrawal for agriculture over the past decade have seriously depleted the ecological water requirements in the basin and damaged the channel and downstream wetland ecosystems. Achieving sustainable development in the basin will require a balance between agricultural water exploitation and ecological water demands. In this paper, a reservoir and diversion engineering module was integrated with a dualistic distributed hydrological model (WEP model) to investigate the effects of agricultural water use on river discharge. Agricultural water shortages and yearly minimum river discharges between 2020 and 2050 under six agricultural water exploitation scenarios and one natural scenario were estimated based on the proposed model. The results showed that the dualistic hydrological process model was more suitable for basins with agricultural water resource exploitation and that the river discharge was significantly less than the natural discharge due to irrigation and reservoir filling, especially in drought years. Under the scenarios of high, middle and low water resource exploitation without ecological operations, agricultural development was unsustainable because of agricultural water shortages and ecological water scarcity. The evaluation of the guaranteed rates for the agricultural water supply and environmental flows showed that the low water resource exploitation scenario with ecological operations was the best option and that sustainable development could be achieved in the basin under this exploitation scenario in the future. However, implementing water management practices in the basin could result in certain economic losses. These losses could be offset by ecological protection funds for downstream wetlands. Overall, the model results could help to inform planning and investment decisions within the basin to improve the sustainable management of water resources.

Bio-economics of fisheries Assessment and management

The principles on which the evaluation of fisheries is based are described; a semblance is made of the initial stages that are required to satisfy the analysis of the dynamics of each population. The biological evaluation process requires the social and economic evaluation of each case study, in such a way that the maximum levels of biological, economic and social performance to be evaluated under certain fishing intensities together with the age of first catch. This evaluation offers useful exploitation scenarios for planning and decision-making aimed at conservation and sustainable exploitation of fisheries.

Clustering of Groundwater Wells and Spatial Variation of Groundwater Recharge in Sina Basin, India

A spatial and temporal analysis of groundwater levels, topography, and precipitation is required to properly manage the groundwater resource. The present paper explains it in two parts: (1) spatial analysis of groundwater levels and selection of suitable clustering approach for selection of representative wells and (2) spatial and temporal variations of groundwater recharge calculated by three numerical models: Chaturvedi model, Amritsar model and ERAS model. Four clustering techniques including K-Means clustering algorithm, Hierarchical clustering technique, canopy and expectation maximisation (EM) were used for the clustering of groundwater levels. Among these, the canopy technique presents more reliable results compared to the other techniques for the spatial analysis of groundwater levels and the formation of representative wells in the Sina basin. For the groundwater recharge estimation, Chaturvedi model and ERAS model values were found very close. The recharge values show consistency with the precipitation data and found that 15% of precipitation contributes to annual groundwater recharge. Spatio-temporal variation of groundwater recharge correlated with precipitation is also carried out for the selected basin. The results show a drastic decline in the groundwater recharge from the year 1990 to 2008. An empirical expression is also developed for groundwater recharge estimation in terms of groundwater level. This provides regional scale information about the basin and helps to understand the groundwater exploitation scenario for instance.

Scenarios to control land subsidence using numerical modeling of groundwater exploitation: Aliabad plain (in Iran) as a case study

The unconfined aquifer beneath the Aliabad plain is one of the few freshwater resources in northwestern Qom province in Iran. Land subsidence in the Aliabad plain is primarily the result of extensive overexploitation of groundwater resources and successive droughts. The harmful effects of overexploitation include significant socioeconomic consequences and severe damage to aquifers. The current study proposes an accurate scenario model that reduces the overall land subsidence by assessing different scenarios for future groundwater exploitation in the plain. The quantitative model consists of 120 time-steps over a period of 10 years (2006–2016). Model validation was achieved by comparing the calculated groundwater level variations with the results of piezometric evaluations in modeling. The results of the validated model were used to predict variations in the aquifer hydraulic head caused by changes in exploitation under different scenarios. Modeling of the Aliabad plain revealed that a 10% decrease in pumping will reduce and stabilize the groundwater decline and a 30% reduction will help recharge the aquifer. The model simulation was able to predict critical land subsidence of 35 cm by 2016. The geometric location of maximum land subsidence was predicted by comparing the geometric distribution of predicted land subsidence patterns with subsidence results from radar interferometry. Prediction of land subsidence by 2026 indicated that management of the exploitation of resources and strict aquifer stabilization programs can reduce the damage to the aquifer.

Escravidäo como un etno para matemáticas no Brasil

Diante da situação em que o mundo passou a vivenciar a partir da pandemia provocada pela Covid-19, naturalizou-se que este debate estivesse atrelado à Biologia, à Medicina, à Tecnologia, à Economia e, em menor grau, às Humanidades. Neste artigo, temos como intenção apresentar e discutir informações que indicam como a população negra, particularmente a população negra feminina, tende a suportar com maior prejudicialidade os efeitos da pandemia. Inicialmente, fizemos um levantamento de reportagens jornalísticas que circularam no país entre janeiro e maio de 2020 que traziam um recorte étnico-racial dos efeitos da pandemia. Em um segundo momento, e como principal objetivo, analisamos como as matemáticas presentes nessas reportagens fazem-nos refletir sobre o cenário histórico e atual de exploração e de extermínio da população negra no Brasil. Essa discussão nos permite situar o Etno da atualidade pandêmica brasileira, produtora de matemáticas, junto à escravidão, que torna a mulher negra mais vulnerável à contaminação pelo vírus pelos postos de trabalho que ocupa, seja como empregada doméstica da elite ou como funcionária do campo da saúde, particularmente das equipes de enfermagem. Por fim, propomos a emergência de um debate em Etnomatemática no contexto da desigualdade racial protagonizada por uma branquitude acrítica no mundo, reivindicando que o espaço científico-acadêmico, majoritariamente branco, assuma responsabilidades para a superação da invisibilização e da assimetria raciais nas pesquisas que promove.

Well spacing of the doublet at the Huangtsuishan geothermal site, Taiwan

The issue of thermal breakthrough is often encountered in the extraction of geothermal fluids with reinjection. This study analyzes the minimum safe distance between doublet wells that will maintain thermal productivity under various conditions at the Huangtsuishan geothermal site. A conceptual model is constructed and hypothetical exploitation scenarios are explored. The results show that a distance of 300 m is required to avoid a thermal break in 80 years with 120 tons/hour pumped and 90 % reinjected at the Huangtsuishan Geothermal site. A regression formula was provided as a guideline for the minimum required doublet distance for various pumping rates.

Heat and fluid flow dynamics of a stratovolcano: The Tacaná Volcanic Complex, Mexico-Guatemala

Mexico is the world's sixth-largest geothermal energy producer. To pursue its transition to renewable energy, other potential geothermal areas are under exploration. The Tacaná hydrothermal system is one of them. In this work, we developed a preliminary 2D numerical mass and heat flow model of the natural state of the Tacaná volcano in order to gain insight into fluid and rock properties at depth. A comprehensive set of simulations was performed involving various rock permeabilities, geometries, and upper and basal boundary conditions until the simulated data matched the measured data, including spring and fumarole temperatures at the surface and thermal spring discharge. Simulation results show that the temperature structure and the phase distribution at depth are partly controlled by the permeability distribution inside the volcano together with a low topography-driven downflow and the absence of elevated fluid pressures at shallow levels. The low topography-driven recharge may be related to a low-permeability layer, whereas low fluid pressures most probably related to a relatively deep water table. The deep thermal fluid source must be connected to the San Antonio fumarolic field by a high-permeability conduit to enhance the fluid upflow and the development of a boiling zone in the uppermost part of the cone. Furthermore, our results suggest that the (almost) total absence of hydrothermal manifestation in the NE part (Guatemala) of the volcano is controlled by the tilting of the basement rocks. Our model will be used as initial conditions for the modelling of several geothermal exploitation scenarios in future work.

Neanderthal lithic procurement and mobility patterns through a multi-level study in the Abric Romaní site (Capellades, Spain)

This study represents the first integrated approach to the lithic raw materials exploited by the Neanderthals that occupied the Abric Romaní site (NE Iberia). Focusing on chert as the most abundant raw material (>80% of the assemblages), we determine the potential procurement areas and the mobility patterns. Geo-archaeological surveys within a radius of 30 km from the site documented 32 primary locations with silicifications. The chert abundance ratio, a quantitative approach to the raw material availability, together with macroscopic and petrographic analyses, confirm the underexploitation of the local raw materials (<10 km).The main procurement areas are located between 16 km (Sant Martí de Tous chert) and 24 km (Panadella chert), indicating different procurement strategies and mobility patterns. Stone tool assemblages from levels M and Oa fall within a foraging radius, whereas level P, in part, suggests a logistical radius, demonstrating a complex scenario of extensive knowledge and intensive exploitation of the landscape among Neanderthals.

Numerical groundwater flow modeling for managing the Gabes Jeffara aquifer system (Tunisia) in relation with oasis ecosystems

The Gabes Jeffara aquifer system, in southeastern Tunisia, is essentially recharged by rainfall infiltration and by groundwater inflow from the Intercalary Continental aquifer in the northwest. The increase in groundwater pumping for irrigation in recent decades has induced a serious decrease in groundwater levels, depletion of springs and degradation of oasis ecosystems. A multidisciplinary study was carried out to better understand the behavior of oasis ecosystems and aquifer systems and to provide tools and recommendations for water resources management. An important part of the study was devoted to developing a hydrodynamic flow model of the Jeffara aquifer system, which can be used as a future groundwater management tool considering different recharge or exploitation scenarios. This model was built with Processing Modflow, gathering data on geology, hydrogeology, hydrology, rainfall, piezometry, withdrawals and spring flow rates. The model was calibrated in steady state with reference to the piezometric levels measured in 1970 and in transient state for the period 1972–2014, using records from more than 200 wells and piezometers. The analysis of current and future water consumption was carried out with existing data, processed satellite images and farmer surveys. This analysis was used to define water demand scenarios combined with scenarios of decreased groundwater withdrawal, reinforced groundwater recharge and use of alternative water resources. The scenarios tested with the model show that the situation will be critical in less than 25 years without radical measures to reduce groundwater withdrawals by at least 60 MCM/year.

Integrated valuation of alternative land use scenarios in the agricultural ecosystem of a watershed with limited available data, in the Pampas region of Argentina

Historically, Argentina has been among the world leaders in the production and export of agricultural products. The country is increasingly confronted with severe conflicts that originate from trade-offs between actors involved in the agricultural sector. This work presents an integrated valuation of alternative land use scenarios in the Carcarañá River Lower Basin, offering a way to link the various value domains by involving a broad set of multidimensional indicators and stakeholder concerns. Twenty-one indicators that address all three pillars of sustainability, environmental, economic and social, are selected and quantified. Three scenarios are analyzed: the Actual scenario, dominated by industrial-scale agriculture that primarily yields soybeans, maize and wheat; a Conservation Agriculture scenario, promoting permanent soil cover by crop rotation and the implementation of untreated buffer zones around the cities; and a Short Sighted Exploitation scenario, contributing to short-term profits for agribusiness but increasing pressure on the natural resources. A decision support system is implemented in the Driver, Pressure, State, and Ecosystem Services indicator framework. The Conservation Agriculture scenario is identified as the best option by stakeholders grouped into Regulatory State, Civil Society and Consensus perspectives. A ranking change occurs when the valuation is carried out from the Private Sector point of view and the Actual scenario comes in first position. We dare to say that the methodology presented in this work is a socio-technical innovation that can contribute to the process needed to achieve broad consensus among the agribusiness actors in Argentina.

Impact of time-varying productivity on estimated stock–recruitment parameters and biological reference points

Models with time-varying parameters are increasingly being considered in the assessment of fish stocks, but their reliability when used to derive biological reference points or benchmarks has not been thoroughly evaluated. Here, we evaluated stock–recruitment models with and without time-varying productivity in a simulation framework for sockeye salmon (Oncorhynchus nerka) under different scenarios of productivity and exploitation. Ignoring trends in productivity led to overestimates of productivity and underestimates of capacity when both exploitation rates and productivity declined over time, resulting in an underestimation on average of benchmarks of biological status. Despite being less biased, time-varying models had relatively poor fit based on AICc and BIC model selection criteria. Our simulation results were compared with empirical analyses of 12 Fraser River sockeye salmon stocks in British Columbia, Canada. Although benchmarks were less biased when based on time-varying models, underlying true benchmarks based on spawner abundances at maximum sustainable yield, SMSY, trend downwards when productivity declines, which may not be aligned with conservation objectives. We conclude with best practices when adapting biological benchmarks to time-varying productivity.

Estimation by Inverse Approach of a Transmissivity Field over the Entire Continental Terminal Aquifer of Abidjan

Hydraulic characterization of aquifer systems is important for the development of exploitation scenarios and groundwater management strategies. Especially in lithologically heterogeneous aquifers, local scale variations in transmissivity (T) may not be neglected. Field scale transmissivity values are usually derived from pumping tests, but in most cases their number and availability are rather limited. Thus, direct measurement of transmissivity over an entire aquifer is expensive and technically almost impossible. In such situations, inverse hydrodynamic modelling is the appropriate solution. In this article, the real transmissivity field of the aquifer of the Continental Terminal of Abidjan is investigated by a multi-scale parametrization that allows to bypass the problem of scale change and to determine this hydrodynamic parameter over the entire aquifer. This hydrogeological modelling of the Continental Terminal aquifer identified a structure of 153 nodes in size as the closest structure to that of the Continental Terminal aquifer. The transmissivity field associated with this optimal size, ranging from 5.4.10-5 to 1 m2s-1, has been compared with values published in other studies in Africa and the world. These identified values are plausible and have a good overall structure. The success of this modeling is strongly linked to the quantity, quality and spatial distribution of authentic informations on the parameters sought.

Decision-Making Challenges of Sustainable Groundwater Strategy under Multi-Event Pressure in Arid Environments: The Diyala River Basin in Iraq

A robust decision-making tool is needed to meet sustainability challenges and to manage water resources that are under development pressure, water scarcity, and climate change impact. To tackle such challenges, optimization modelling can be employed to explore regional sustainable management scenarios of groundwater exploitation. Multi-objective management modelling of various alternatives was developed for the Diyala River Basin in Iraq using Borg multi-objectives evolutionary algorithm (MOEA) and ε-DSEA algorithms. In almost all modelled cases, the upper aquifer storage is predicted to be depleted after 40 years due to large water demands and regional recharge scarcity. Hence, there is a need to develop a strategy to reduce water stresses by 45% to achieve sustainability within the next 25 years. Optimization modelling successfully generated future predictions that can be used by decision makers to manage the predicted groundwater shortages in the future.

Geothermische Nutzung eines alpinen Aquifers – Pilot Studie Davos

Topographically induced Alpine regional groundwater flow systems below the unconsolidated valley fillings constitute a substantial unused geothermal resource. Within the framework of the INTERREG VB project GRETA (shallow geothermal energy in the Alpine region), we developed a method to quantify the groundwater flux of complex alpine aquifers. The basis of the study is a regional-scale hydraulic groundwater model, which is based on a 3D tectonic model of the Davos region in Switzerland. Based on data from a large pumping test, we were able to calibrate the hydraulic model and to calculate basics for various usage scenarios of energetic exploitation for the Arosa Dolomite aquifer. Favourable conditions for an energetic exploitation are related to large-scale topography differences between groundwater recharge and potential exfiltration areas in the valleys, thanks to the 3D geometry of the large-area tectonic nappe units with their root zone located within river valleys. In general, the proposed concept could be applied to manifold similar geological and hydrogeological settings of the Alpine belt.

Life Cycle Assessment of a Biogas-Fed Solid Oxide Fuel Cell (SOFC) Integrated in a Wastewater Treatment Plant

This work assesses the environmental impacts of an industrial-scale Solid Oxide Fuel Cell (SOFC) plant fed by sewage biogas locally available from a Waste Water Treatment Plant (WWTP). Three alternative scenarios for biogas exploitation have been investigated and real data from an existing integrated SOFC-WWTP have been retrieved: the first one (Scenario 1) is the current scenario, where biogas is exploited in a boiler for thermal-energy-only production, while the second one is related to the installation of an efficient SOFC-based cogeneration system (Scenario 2). A thermal energy conservation opportunity that foresees the use of a dynamic machine for sludge pre-thickening enhancement is also investigated as a third scenario (Scenario 3). The life cycle impact assessment (LCIA) has shown that producing a substantial share of electrical energy (around 25%) via biogas-fed SOFC cogeneration modules can reduce the environmental burden associated to WWTP operations in five out of the seven impact categories that have been analyzed in this work. A further reduction of impacts, particularly concerning global warming potential and primary energy demand, is possible by the decrease of the thermal request of the digester, thus making the system independent from natural gas. In both Scenarios 2 and 3, primary energy and CO2 emissions embodied in the manufacture and maintenance of the cogeneration system are neutralized by operational savings in less than one year.

Assessment of Energy Production in the Deep Carbonate Geothermal Reservoir by Wellbore-Reservoir Integrated Fluid and Heat Transport Modeling

Geothermal energy is clean and independent to the weather and seasonal changes. In China, the huge demanding of clean energy requires the geothermal energy exploitation in the reservoir with depth larger than 1000 m. Before the exploitation, it is necessary to estimate the potential geothermal energy production from deep reservoirs by numerical modeling, which provides an efficient tool for testing alternative scenarios of exploitation. We here numerically assess the energy production in a liquid-dominated middle-temperature geothermal reservoir in the city of Tianjin, China, where the heat and fluid transport in the heterogeneous reservoir and deep wellbores are calculated. It is concluded that the optimal injection/production rate of the typical geothermal doublet well system is 450 m3/h, with the distance between geothermal doublet wells of 850 m. The outflow temperature and heat extraction rate can reach 112°C and 43.5 MW, respectively. Through decreasing injection/production rate lower than 450 m3/h and optimizing layout of the injection well and production well (avoiding the high permeability zone at the interwell sector), the risk of heat breakthrough can be reduced. If the low permeability zone in the reservoir is around injection well, it usually leads to abnormal high wellhead pressure, which may be solved by stimulation technique to realize stable operation. The methodology employed in this paper can be a reference for a double-well exploitation project with similar conditions.

A Survey of Exploitation and Detection Methods of XSS Vulnerabilities

As web applications become more prevalent, web security becomes more and more important. Cross-site scripting vulnerability abbreviated as XSS is a kind of common injection web vulnerability. The exploitation of XSS vulnerabilities can hijack users’ sessions, modify, read and delete business data of web applications, place malicious codes in web applications, and control victims to attack other targeted servers. This paper discusses classification of XSS, and designs a demo website to demonstrate attack processes of common XSS exploitation scenarios. The paper also compares and analyzes recent research results on XSS detection, divides them into three categories according to different mechanisms. The three categories are static analysis methods, dynamic analysis methods and hybrid analysis methods. The paper classifies 30 detection methods into above three categories, makes overall comparative analysis among them, lists their strengths and weaknesses and detected XSS vulnerability types. In the end, the paper explores some ways to prevent XSS vulnerabilities from being exploited.

The use of modeling in drawing up guidelines for the exploitation of the Khankala geothermal field (Chechen Republic)

Nowadays, geothermal waters have become an important form of energy and many researchers have put to the forefront the issue of “sustainability” of the geothermal reservoir development. Reinjection of the used fluid during exploitation allows minimizing the possible negative effect on the environment and maintaining the reservoir pressure and therefore the initial high flow rates. However, it has a major disadvantage—a gradual temperature decrease in an aquifer, which needs to be taken into account. The most effective methods assessing this disadvantage are based on numerical modeling, which has been actively implemented in all areas of science. In the current paper, mathematical modeling is applied for the Khankala geothermal field in the Chechen Republic to forecast changes in the temperature regime of the resource and define the optimal exploitation scenario to achieve its sustainable development.

Can the status of pelagic shark populations be determined using simple fishery indicators?

Calls to develop alternative methods of assessing the population status of pelagic shark populations have increased substantially in recent years. An interim solution has been the development of more subjective evaluation of data series (indicator-based analysis) rather than predictions from complex stock assessment models. This paper examines the reliability of indicators for predicting population status (i.e. whether it has been overfished) and the fishing pressure (i.e. whether overfishing is occurring) of large pelagic sharks, based on these fishery indicator trends alone. We simulate a variety of large pelagic shark populations under different exploitation scenarios using life history parameters, and measurable fishery indicators information (catch-per-unit of effort - CPUE; and average length - AL). Our simulation results, designed to be generalized (via sampling of realistic distributions) but based loosely on the shortfin mako shark, showed that the reliability of fishery indicators for establishing population status is dependent upon the length of the time series analyzed. These caveats are critical to the proper evaluation of population trajectories that underlie the most important conservation decisions being made for sharks today.

Limits and conditions for the exploitation of alluvial aquifers in the Brazilian semi-arid region

ABSTRACT Easily exploitable aquifers are formed along river beds in the Brazilian semi-arid region and present characteristics that enable the construction of underground dams. The estimate of the potential effective exploitation of these aquifers must take into account the pumping limits of the wells, the upstream groundwater inflows and the flows to downstream reaches and through the underground dam, whose reduction influences the downstream supply. The current research presents a real case study about an aquifer reach, with underground dam and wells, which was analyzed through computational model. We simulated the groundwater flow patterns according to different exploitation scenarios and found that there should be water extraction limitations to assure the required downstream flows. The limitations can be minimized through appropriate well locations and exploitation regimes, as well as through the implementation of underground dams. The definition of these measures becomes possible through the sound use of computational simulation, but their effective implementation will depend on negotiations among users at the basin scale, so that appropriate water permits can be issued.