جستجوی مقالات مرتبط با کلیدواژه « vensim » در نشریات گروه « آب و خاک »

Recently, the increase in water demand and the pollution of water resources have threatened groundwater resources. The purpose of this research is to investigate the impact of the conservative scenarios of groundwater resources and its effect on the restriction of the aquifer volume reduction process using the system dynamics approach in Marvdasht-Kharameh plain.The current conditions of the aquifer during the statistical period of 2005-2018 were simulated and recalibrated according to the observed values of the aquifer volume. The scenarios have been applied in three ways to investigate the effect of climate change, changing the amount of water allocated to farmers from Doroudzan dam and changing the cultivation pattern under the scenarios SSP1-2.6 and SSP5-8.5 on the volume of the aquifer. In order to investigate the effect of climate change on Marvdasht-Kharameh aquifer in the period from 2021 to 2046, the rainfall data of GFDL-ESM4 model under two scenarios SSP1-2.6 and SSP5-8.5 were considered. The study of the impact of climate change and the release of the Darudzen dam showed that the volume and recharge of groundwater will decrease in the scenario SSP1-2.6 (50 and 49 million cubic meters respectively), and in the scenario SSP5-8.5 (54 and 67 million cubic meters respectively),. Also, by removing the rice crop from the cultivation pattern of Marvdasht-Kharameh plain in the future climate conditions under two scenarios SSP1-2.6 and SSP5-8.5, which will add 495 and 207 million cubic meters to the aquifer volume respectively, the greatest effect on increasing the aquifer volume will be achieved. It will have 30 and 50 percent reduction in the area under rice cultivation. Therefore, in order to manage and preserve groundwater resources, it is necessary to change the cultivation pattern and replace high consumption crops with low consumption crops.

available water resources and their management are very important in preserving and sustaining the development plans of a country, along with providing foodstuffs. Meanwhile, the main tributaries and flooded rivers of a country play a vital role. There are also very important rivers in Iran, one of which is Ghezel Ozan. This river originates in Kurdistan province and it reaches Gilan province after it passes through downstream provinces and joins Sefid-Rud river after which it is called Qezel Ozen of Sefid-Rud river and enters the great dam of Sefid-Rud. In the meantime, considering small details of the area, modeling will provide a faster and more accurate investigation so that managers can use it. In this regard, there are two views, dynamic and linear. In this research, the mechanistic view was used as a decision support system due to the available feedback, holistic thinking, and the possibility of using the model. Then the problems of the region were evaluated by identifying generic archetypes. The current research has dealt with the dynamic simulation of the surface water resources allocation in upstream Sefid-Rud basin during the years 1990 to 2019 in two annual and monthly scales. During 1990 to 2011 when the dams had not yet started to operate, simulation was conducted by considering about 30 intervals in the mainstream of the rivers and tributaries of Kurdistan province, part of Zanjan province, and a small area of Hamadan province precipitation, discharge and ground waters as well as all agricultural products, domestic and industrial amounts as input. The annual scale of the model structure, with MAE, RMSE, and R2 scales of 0.098, 0.087, and 0.980, respectively, confirmed the accuracy and precision of the model along with the test of the limit conditions that are specific to the dynamic system. Due to the construction of dams, since 2010, monthly simulations were carried out in two sections, before and after the dams' operation. Before the operation of the dams, the values of MAE, RMSE, and R2 were equal to 0.052, 0.103, and 0.940, respectively, confirming the high efficiency of the model. From 2011 to 2019, modeling was defined so as during the first 6 months of water year, water withdrawal was done from the river and during the second 6 months it was done from the dam. All the specifications of the dams along with the needs of the region were simulated in all intervals on a monthly scale. In the meantime, according to the dynamic simulation, the feedback and causal loops formed by them formed patterns that corresponded to the generic archetypes of the region. With the start of the dams, the escalation archetype, limits to growth archetype, and fixes that fail archetype were activated and the increase in water withdrawal was observed in all intervals, whether with the construction of the dam or not.The results showed that despite the drop of aquifers to an average amount of 30 meters in the whole period and 6.35 meters after the construction of dams, in addition to a 90% reduction in discharges, there was an increase in water withdrawal and despite the severe reduction of water resources, the area under cultivation in dealing with escalation archetype has increased by four times, and following the limits to growth archetype, there has been a very sharp decrease to about 3 times. On average, in the region, the area under cultivation has increased by 2.8 times, at the highest value by 4 times and at the lowest value by 1.6 times. The results indicate that, dam construction led to inappropriate exploitation in the region.

Due to rapid expansion of population, there is an increase in the number of water users. As a result, optimal water allocation has become a pivotal issue. System dynamics is a suit methodology for simulating and representing of water availability in complex condition and impacts of water resources usage over time. In this study, a dynamic water allocation model within Vensim GUI was developed for the agricultural and environmental water resources of Khamiriza catchment.

The model consists of two separate sections; the first part is a water balance module which is designed to provide surface water and groundwater simulations; the other part is a water allocation sub-model. After the development of the model, the water balance simulation optimized by optimizing the surface water and groundwater against observed data.

The water use policy includes the conjunctive use of groundwater and surface water to meet drinking, industrial, agricultural, and environmental demands. The results suggest that under current situation the quantity of available surface and groundwater could be insufficient to meet the demands of different sectors within the basin. Therefore, a scenario containing improved irrigation efficiency and 30% of the land in fallow may lead to the allocation vulnerability.

The results of this application indicate that system dynamics can be considered as an innovative tool in the planning and allocating water resources. Moreover, conjunctive use of groundwater and surface water resources may lead to a better water allocation policy.

One of the most critical challenges of the twenty-first century is to resolve water crisis. This crisis is characterized by scarcity of water, the destruction of natural ecosystems, and food shortages. In spite of extensive efforts made to ensure food security, human societies still have trouble feeding their populace. This problem is most likely due to their inability to access healthy and safe water resources (Kijne, 2003). The solution to the water crisis can be expressed as better development and proper management of water resources systems. Various technical and managerial solutions should be taken such as upgrading and improving irrigation systems, introducing new irrigation methods, deficit irrigation, optimizing the cropping pattern, improving the efficiency of irrigation networks, etc. to improve water productivity in agriculture. The system dynamics methodology is a modeling and simulation technique and is specially designed for long-term, chronic, and dynamic management issues (Vlachos et al., 2007). Crop pattern scenarios, crop production, and agricultural pollution in a region in southern Turkey have been studied by Saysel et al. (2002) with a system dynamics approach. Also, the system dynamics approach was applied in the study of integrated water management at the catchment scale by Soltani and Alizadeh (2017). In this study, the systems dynamics approach, which is a suitable method for studying complex water systems, was applied in water productivity investigation in the Qazvin irrigation network.

One of the most important issues for mankind in the present century is access to water resources. Increasing population growth and expanding industry have made agricultural development in arid and semi-arid regions a major challenge. The depletion of water resources and the critical situation in the drinking, agricultural, industrial and environmental sectors are a major problem. An essential principle is the relative balance of water supply and demand that emerges with the creation of a comprehensive water management system.

The present study was carried out in Hirmand catchment in Sistan area, focusing on the issue of Hirmand river flow and the volume of Chah Nimeh. In order to control the alignment of Chah Nimeh, modeling steps were developed and the basis of the problem was investigated in the process of forming flow-storage diagrams. Using Vensim software, the effect of each variable was simulated on the problem and the calibration and model validation were fitted to different methods such as statistical tests.

The results of the tests show that the model corresponds to reality and the model behavior is consistent with the behavior of the system in reality. According to the statistical tests performed, between the observed and simulated values for the well reserves variable, the coefficient of determination is equal to 0.84, the root mean square error (RSME) is equal to 0.25 and the Nash-Sutcliffe criterion is equal to It is 0.77 in 2019. According to the findings, the demand for various agricultural, drinking and environmental needs will increase in the coming years. The total demand in 1410 will increase from 1350.01 to 1515.93 million cubic meters, which will be impossible to meet the needs despite the reduction of system resources. The largest increase in demand will be in the agricultural and drinking sectors.The results of the scenarios show that the policies of 70% irrigation efficiency in the agricultural sector and reduction of water losses (reduction of evaporation by 50%) based on the proposed scenarios were implemented by the model.

The results show that the irrigation efficiency policies of 70% in the agricultural sector and the reduction of water losses (reduction of evaporation by 50%) based on the proposed scenarios were implemented by the model. Examining the results of these scenarios, it is seen that each of these solutions will reduce water shortage in the coming years, but the best result has been achieved in the first scenario (70% irrigation efficiency in the agricultural sector). In general, the findings show that the continuation of the current consumption trend and, consequently, the continued withdrawal of water resources with the same trend, will have irreparable effects. In this situation, modeling optimal consumption in different sectors, observing limit conditions and creating a culture based on non-extravagance is one of the key issues in crisis management and is one of the most basic foundations of consumption management.

Quality and quantity of drainage water in saline lands, which require primary leaching is continuously changing from the beginning of irrigation and drainage network operation before reaching a more or less equilibrium state. The time to reach a state of equilibrium in areas with saline groundwater may take several years. Therefore in this paper, the system dynamics technique that is one of the object oriented approach was used to simulate farms of irrigation and drainage network, and determine model performance to simulate the drainage water salinity and discharge of subsurface drains. To validate the results of the model, data collected in the 2004 and 2005 cropping years from ARC2, ARC4, ARC6 and ARC8 farms was used in the research area of ​​Sugar Center Research Center (Amir Kabir Agro Industrial Development Unit of Sugarcane Development Company, Khuzestan Province). To statistical analysis and calculating, the root mean square error (RMSE), standard error (SE) and correlation coefficient (R2), were used. In this regard, the RMSE statistical index for drainage discharge of ARC2, ARC4, ARC6 and ARC8 farms were 6639, 8546, 7950 and 8207 m3/day respectively. Also, the RMSE for drainage water salinity of the farms were 2.25, 4.86, 2.04 and 7.98 dS/m respectively. The results showed that the model is capable of simulating the drainage outflow and its salinity in saline and shallow water table region

Due to the growing population, crop production is one of the essential needs of the society. Since soil and water salinity can have a great impact on the crop yield loss; so, the appropriate irrigation method can be applied to reduce these effects. In this study, the system dynamics model was developed using VENSIM. The model simulated the effect of salinity and water stress on the crop yield, moisture and salinity of the root zone. In order to calibrate and validate the model results, 9 treatments data were collected from the Right Abshar Irrigation Network, on the Zayandehrud basin. After statistical analysis and calculation of RMSE index and the standard error, the fit between the measured and simulated crop yield, the moisture and salinity of root zone was calculated. The average of these indexes for all treatments was 2776.98 kg/ha and 0.07 for crop yield, 0.026 and 0.09 for soil moisture and final, 0.54 dS/m and 0.08 for the salinity of root zone, respectively. The results showed that the model could be calibrated accurately and completely in estimating the crop yield with the reasonable accuracy.

In this study allocation of water resources Choghakhor dam after the operation of the water transfer project Sabzkouh to Choghakhor using system dynamics approach is discussed. For this purpose, the inputs discharg to the reservoir and evaporation rates using SARIMA model to forecast for period 2014-2019 and The best model fitted to the data for input to reservoir and evaporation has been respectively SARIMA (1,0,3)(1,1,1) and SARIMA (1,0,1)(1,0,1). In this way all the factors affecting the volume of water in the dam as well as the interaction of supply and demand for drinking water, industry, agriculture and environmental was modeling in programming VENSIM. Then 9 scenarios was defined for the future allocation of water resources. The results showed that the optimal scenario of the dam is able to provide 4,300 hectares of agricultural land in the state percentage water supply, drinking, industry, agriculture and the environment demands, respectively, 98, 90, 87 and 94. In addition, by changing of the irrigation system from surface irrigation to pressurized system and increasing irrigation efficiency by 30% the cultivated area, can be developed up to 3900 hectares.

Nowadays, due to increased water consumption and demands, optimum water allocation should be taken as a serious need. In this research, WEAP and Vensim softwares are used to plan and manage the water resources and demands in Nazloo River basin, located in West-Azarbaijan province. By use of these softwares, two models were prepared: One for supplying water demands of the region using river flows (without Nazloo dam) and the other one with the same condition but by considering the Nazloo dam operation effect. Water demands of the region were assessed up to 2016, river flow of the past 40 years was analyzed, and river discharge of 2013-2016 was estimated by ARIMA method. Results showed that average differences between the results of WEAP and Vensim softwares were 3.74% and 8.91% for the with-dam and no-dam options, respectively. The highest water deficiency was in water supply to agricultural demand in September, which with construction of the dam, the average supply in this month increases from 15.8% to 94% of the demand amount. To verify the obtained results of the unmet water demand in various years, the SPI index was used, which in 72.5% of the cases it was consistent with the results of the softwares. In general, without constructing the dam, water needs of industry and environment will be mainly supplied, but there would be some deficiencies in water supply for agriculture. For water supply, instead of constructing a dam with a storage capacity of 154 MCM, a dam with a capacity of 100 MCM will be enough.

Today, widening the gap between supply and demand serious attention to the principles of allocation and management of water supply and water demand is inevitable is necessary.In this regard Vensim model based on the theory of dynamic systems for planning and management of water resources and uses in the catchment of Nishapur in the KhorasanRazavi province were used. Finally policy scenarios are based on the proposed model was implemented. Results analysis of running various scenarios over the next 25 years in Nishabur plain to study the aquifer water level changes due to pressur irrigation systems development was done, so that the development of the first scenario (normal rainfall conditions) showed an increase in annual acreage about 1.38, acreage constant 0.95 and reduce the acreage of about 0.77 m drop in water table of the aquifer will see annual drowdown in aquifer levels over the course of the simulation and reality (about 0.87 m), respectively, an increase of 58 percent, an 8 percent increase and 12% decrease at will. So if fixing reduced acreage of agricultural land and ground water storage can be increased somewhat, and the severe decline in aquifer water level to prevent, however, the use of pressurized irrigation systems coupled with increased acreage loss of aquifer water level will be intensified.

In The comprehensive management of water resources in the basin level, the interaction of components within the system and the interaction of different systems should be considered comprehensively. This Study levels has been done in the basin of neyshabour, with an emphasis on problem solving of process decline annual in groundwater in this plain. To control the level of the aquifer, the modeling steps were developed and roots of problem examined in the formation process of flow- storage diagram. By using Vensim software, effect of each variable on the simulated problem and validity of the model were examined via different methods such as sensitivity analysis, statistical tests, etc. Results of tests show that the model has a good accordance with reality and behavior of model has accordance with reality. According to The statistical tests between the observed values and estimated values of rise and fall aquifer level via model, the coefficient of determination equal to 0.8 and root of the mean square error was 0.21. Different tests were also carried out that results confirmed the simulated model. Finally, policies was implemented based on the proposed scenarios by model.