جستجوی مقالات مرتبط با کلیدواژه « بهره وری آب » در نشریات گروه « علوم پایه »

The current situation of water resources in Iran, the trend and trends governing it, as well as considering the inappropriate spatial and temporal distribution of water per capita and its excessive consumption, show the necessity of demand management. In this regard, improving the efficiency of water consumption, especially in the agricultural sector, is considered as an opportunity to save more water. Optimum water management requires a great change and to ensure the sustainability of these resources, integrated and systematic management should be applied in line with optimal processing and exploitation with the application of new technology for maximum utilization of these resources in planning. Improving the efficiency of water consumption has been introduced as one of the most important ways to reduce water consumption, but it can be seen that the aforementioned improvement does not necessarily reduce water consumption to the saved amount and sometimes leads to no change or even an increase in water consumption. only the use of new and efficient irrigation methods cannot be effective in adjusting the consumption and balancing the supply and demand of water. In explaining why water consumption has not decreased despite the large investment in the field of modern irrigation technology, the concept previously expressed in the field of energy consumption, i.e. the rebound effect, can be useful. The rebound effect, which is more prominent in the literature of energy economy, in the field of water, can be considered a mechanism that causes a part of the water saved due to the improvement of water efficiency to be reused and, as a result, leads to a reduction in the amount of water saved. In simpler terms, the return effect can be defined as a percentage of the potential water savings resulting from water efficiency improvement, which reflects the difference between the potential and actual savings in water consumption. The return effect is usually defined in relation to different forms of energy, such as fuel or electricity, but in this research, an attempt is made to investigate the return effect for agricultural water.

the price of agricultural water is determined by the government in most countries according to the nature of agricultural goods and its importance for the society and is kept almost constant. Therefore, the price elasticity method is not a suitable method to estimate the return effect of agricultural water. According to these materials, in this research, the direct comparison method has been used to estimate the effect of agricultural water return at the macroeconomic level. In equation 1, the estimation of the return effect requires the estimation of the expected water storage (EWS) resulting from the increase in efficiency and the estimation of the return water used (RWU) resulting from the reduction of water cost. The relationship between water consumption and partial water productivity can be considered as follows: W="Y" /"WP" In which, W represents total agricultural water consumption, Y represents total agricultural production, and WP represents agricultural water productivity at the macroeconomic level. If it is assumed that agricultural water consumption, agricultural production and water productivity in year t are W_t, Y_t and WPt, respectively. According to the equation, the change in agricultural water consumption from year t-1 to year t is represented by (∆w_t), which can be decomposed as follows ∆wt = Wt- W (t-1) = Yt/(WPt ) - Y (t-1)/(WP (t-1) ) = (Yt ∆WPt)/(WPt WP (t-1) ) + (∆Yt)/( WPt-1) According to this equation, the change in agricultural water consumption (∆wt) can be divided into two parts: the change in agricultural water consumption due to the change in water productivity ((Yt ∆WPt)/(WPt WP (t-1) )) and the change to The reason for the growth of agricultural production ((∆Yt)/(WP (t-1) )). Changes in agricultural water use in addition to growth in agricultural production can be due to technological progress. ρ is assumed to be the rate of change due to technological advances. Therefore, return water use (RWU), which represents the return (or surplus) of water as a result of increasing water productivity, is equal to (ρ∆Yt)/(WP (t-1)) and EWS, which represents the expected water savings ( calculated or predicted) after increasing irrigation efficiency is equal to (Yt ∆WPt)/(WPt WP (t-1)). It can be concluded that the formula for the return effects of water in year t is:WRE=(∑ (ρ∆Yt)/(WP (t-1) ) )⁄(∑ (Yt ∆WPt)/(WPt WP (t-1) ) )×100 According to the above equation, the return effect of water is the increase in the ratio of water consumption due to the growth of agricultural production to the reduction of the expected water reserve through the improvement of water efficiency. Here, both the improvement of water productivity and the growth of agricultural production are created by methods of improving irrigation efficiency. Based on equation 6, another important factor in estimating the return effect is to estimate the exact contribution of technological progress (ρ). For this purpose, according to the production function of Cobb Douglas Hicks-Neutral, which is as follows :"Y" _"it" "=" "A" _"it" 〖" W" 〗_"it" ^"α " "X" _"1it" ^"β" " " "X" _"2it " ^"γ" … X_nit^ω=A_i e^rt 〖 W〗_it^(α ) X_1it^β " " "X" _"2it " ^"γ" … "X" _"nit" ^"ω" By taking the logarithm from the above equation, we can reach equation:Ln"Y" _"it" =ln A_i+rt+ α ln"W" _"it" +β lnX_1it+γ lnX_2it+…+ ωlnX_nit In this way, by using the estimation of this equation based on the provincial data during the studied period, the r coefficient can be extracted. Now the participation rate of technological progress (ρ) can be calculated as follows:"ρ= r/gy r: represents the growth rate of technology and (gy) represents the growth rate of agricultural production. Finally, by using equation, the effects of agricultural water return can be calculated at the macroeconomic level and in the agricultural sector.

The return effect of agricultural water in Kurdistan province was 106.25%, which has the highest return effect during the studied period. And the second rank belongs to Bushehr province with a rate of 91.19%, the lowest rate of return effect is for East Azarbaijan, Golestan and Tehran provinces (1.45), (2.63) and (3.50) respectively. The return effect is greater than 100% only in Kurdistan Province by 106.25%, these results show that measures to improve water efficiency in Kurdistan Province can increase agricultural water consumption in this province, which is the phenomenon of "Jones' Paradox".In some cases, the amount of return effect is negative, in other words, the measures taken to improve the efficiency of the new irrigation system have caused the predicted water savings to exceed the actual amount of water savings. It should be noted that, theoretically, this phenomenon is only It occurs in the case of a decrease in the production of agricultural products. Therefore, in the provinces where the return effect is negative, according to the data used, the amount of agricultural production in the desired year was less than the previous year, or the water productivity in year t was less than year t-1, this situation can be due to the change in water conditions and The country's weather, such as drought or extreme cold, and the decrease in agricultural production compared to the previous year, or due to the country's structural changes from agriculture to industrial mode.The results show that a partial rebound effect is evident in Iran in the studied years. Water savings have not fully met expectations and some of the expected water savings have been reused. It can be seen that the highest return effect is in 2018 and also in 2013 it has experienced a negative return effect, the negative return effect indicates the existence of savings in this period, but as it was said, this result can be affected by the reduction of agricultural production due to changes in the use of agricultural water, so the negative return effect alone is not a reason that the water efficiency improvement system is affected, in addition, the lowest return effect is in 2013, which is 11%, which shows that 89% of the stored water and only 11% of it is used again. So, in fact, the annual return effect is sensitive to changes in agricultural water use and depends to some extent on natural factors, such as rainfall. In general, the findings indicate that the agricultural water savings due to the improvement of irrigation system efficiency has been reduced by 15.29% due to the increase in demand for irrigation. In fact, this largely shows the success of the policy of increasing water efficiency in order to reduce water consumption.The results of the findings showed that during the studied period, the return effect for Iran was on average 15%, which indicates that about 15% of the water saved due to the increase in agricultural water efficiency was reused in this sector. In other words, about 85% of water has been saved, which somehow shows that the policy of increasing agricultural irrigation efficiency can have positive effects on Iran's water reserves in the long run.

Due to the geographical location of Iran and its location in the arid and semi-arid belt of the earth, water has been very valuable from the past to the present. The Iranian have always tried to use favorable measures to create appropriate structures for water storage, use, collection, distribution and distribution due to limited access to water. The purpose of this study is to investigate the methods of traditional water supply management in the city of Robat Karim. This study was conducted in the city of Robat Karim and the data for the present article were collected by two methods. First, by using library documents that include books on water and irrigation sciences, arid and semi-arid regions, history, travelogues and biographies, as well as reviewing research and resources that include related articles, documents, and reports, along with exploring cyberspace. In the second step, unstructured interviews were conducted using qualitative content analysis method with 20 elderly people in Robat Karim who were purposefully selected. In fact, first a list of qualified people was prepared and interviews were conducted according to their desire and possibility of access. The results showed that the traditional method of water supply in the city of Robat Karim was possible through glacier, water storage, water well, small water basin, aqueducts and permanent and seasonal rivers. Prior to the construction of Amirkabir Dam, with the increase in the number and intensity of rainfall, the Karaj River became more watery and a large volume of water flowed to downstream areas such as Robat Karim, which strengthened the groundwater aquifer and raised its level, which caused prosperity. Agriculture has been especially vineyards. Knowing the traditional methods in water resources management system in different regions of Iran can provide valuable tips that can be used to meet this challenge and water management.

Increasing greenhouse gases will have different effects on crop yields, so that the interaction of these effects may increase or decrease yields. Crop simulation models have been used to investigate different levels of crop and environmental managements. The aim of this study was to investigate the AquaCrop model based on past, present and future climate in Rasht city located in Guilan province to achieve maximum water productivity and rice grain yield.

In order to study the changes in rice yield, water balance and productivity in Rasht city located in Gilan province under the past, present and future climate, the AquaCrop model was used. For this purpose, long-term data (over 30 years) were used to evaluate the yield and water balance in rice cultivation in the past and present climate. Also, using LARS-WG6 software, meteorological data for the next 83 years were generated based on the available daily meteorological data. The AquaCrop model was evaluated in the past, present and future climates based on daily data of minimum and maximum temperatures, precipitation and sun hours. The studied treatments included four levels of irrigation including 55, 70, 85 and 100% of water requirement and the planting dates were April 21st, May 11st and May 31st. By examining the effect of different treatment levels based on RCP 4.5 and RCP 8.5 climate change scenarios, the rate of changes in grain yield, evapotranspiration and water productivity based on evapotranspiration in the past, present and future climates were investigated. Also, the best irrigation treatment and planting date were introduced to increase rice yield and reduce water consumption.

The evaluation results showed that the LARS-WG6 model is able to simulate the climatic components including temperature, precipitation and radiation with high accuracy. The results showed that the minimum and maximum temperatures increased during the climate change scenarios and the amount of radiation and precipitation decreased. The result of rice biomass and grain yield under RCP 4.5 and RCP 8.5 showed that the highest grain and biomass yield was obtained in irrigation of 100% of water requirement and planting date on April 21st. The study of water productivity showed that irrigation treatment of 100% of water requirement and planting date of May 31st had an effective role in increasing soil water storage and reducing evapotranspiration from the soil surface. The highest water productivity in grain production based on evapotranspiration was obtained in irrigation of 100% of water requirement and planting date was May 31st.

According to the obtained results, considering the water consumption productivity and yield and problems that will exist in the future including water shortage, it seems that late cultivation of rice in conditions of water shortage is a good solution, but under conditions where there is no water shortage, early cultivation of rice, such as April 21, can increase production. The study of irrigation levels showed that grain production is the most effective factor in increasing water use productivity and the use of low irrigation levels will not play an effective role in increasing water productivity.

In order to evaluate effect of water superabsorbent application on yield and some physiological characteristics and water productivity of common bean (Phaseolus vulgaris L.), sesame (Sesamum indicum L.) and maize (Zea mays L.) in water stress conditions, a split plots experiment based on RCBD design with three replications was conducted during 2015-2016 growing season, in Research Farm of Ferdowsi University of Mashhad, Iran. Irrigation levels (50 and 100 percent of water requirement) and application (80 kg.ha-1) and non-application of water superabsorbent assigned to main and sub plots, respectively. The results showed that in bean, the highest seed yield (2191kg.ha-1), dry matter yield (4588 kg.ha-1), weight seed per plant (10.89 g), height plant (97 cm), LAI (9.39), CGR (8.35 g.m-2.day-1), soil nitrogen (0.163%), phosphorous (0.0082%) and pH (9.68) obtained in treatment of 100 percent of water requirement and application of water superabsorbent. In sesame, application of water superabsorbent in drought stress conditions (50 percent of water requirement) increased seed weight per plant (22.17 g), plant height (91 cm), LAI (9.70), CGR (6.58 g.m-2.day-1) and soil nitrogen (0.101%), phosphorous (0.0063%) and pH (9.32) by 24, 30, 32, 59, 20, 44 and 17 percent compared to control, respectively. In maize, the highest seed yield (22522 kg.ha-1), dry matter yield (39502 kg.ha-1), seed weight per plant (332 g), plant height (194 cm), LAI (8.10), CGR (9.43 g.m-2.day-1) and soil nitrogen (0.095%) and pH (9.70) observed in treatment of 100 percent of water requirement and application of water superabsorbent.

From the perspective of many experts and decision makers, advances in irrigation technology are the main cause of reducing water consumption. Despite these comments, many experts are skeptical of this conclusion. Despite the improvement of irrigation, drainage technologies and improvement of resistant species, the expected reduction in water consumption have never occurred. Can the water rebound effect (WRE) phenomenon be responsible for the lack of reduction in water intake? What is the situation in Iran? This study sought to answer these questions.

First, it was necessary to determine the impact of technology on the agricultural sector in the provinces using panel data. The data for the years 1370 to 1396 were used for this purpose. In the next step, using information about water consumption and agricultural sector products over the years under consideration along with the estimated model, the factors of agricultural growth rate, water consumption growth rate, and expected and ongoing savings were calculated. The results of these calculations indicated the rate of water rebound effect in the agriculture sector for 31 provinces and made it possible to discuss the effect of WRE on different regions with a simple comparison. To help policy-makers, the five divisions of the Ministry of Interior was used.

The rate of participation in the development of technology was at a high level of significance (0.043). The agricultural WRE amount in Iran was 319.9%. This study confirmed the effect of WRE on agriculture in the country. The effect of water rebound on all regions of the country was also clearly visible and even some industrial provinces such as East Azerbaijan and Khuzestan were more severely affected by this phenomenon. The highest intensity of WRE was observed in the 3rd region of the country, including the provinces of East Azerbaijan, West Azerbaijan, Ardabil, Zanjan, Gilan and Kurdistan, and the lowest was in the 5th area including Razavi, Southern and Northern Khorasan, Kerman, Yazd, and Sistan and Baluchestan. The intensity of the WRE in the southern and eastern regions of the country was lower than in the northern and western regions. The reason for the relatively lower intensity of this phenomenon in the southern and eastern regions was the limited access to water resources, lack of funding to change the irrigation technology, high-quality land, and specialized labor. Although less intensely, it could be clearly seen that more than 80 percent of the saved water across the country was due to the improvement of technology, which was significant in the field of irrigation technologies, by the same agricultural sector. This it indicates the intensity of the WRE phenomenon on the country's agriculture.

The trend of increasing water use in agriculture in the country after applying government support policies and the development of irrigation technologies along with the calculated WRE indicated that improving irrigation technologies, due to the increased productivity, initially reduces water consumption, and also, higher profitability can be achieved by reducing water consumption costs. Increased profit is a motive to expand the crop area, which will increase water consumption, in some cases, more than initial consumption. At this very moment, it is necessary that the authorities focus on controlling the water rebound phenomenon, in addition to the concept of reducing water consumption in the agricultural sector.

The most important issues and challenges facing humanity in the 21st century are the phenomenon of climate change and its effects on increasing the temperature and amount of water consumption. This phenomenon has begun due to the increase in greenhouse gas emissions since the 1850s, following the industrialization of the planet, so that the temperature of the Earth's atmosphere has risen by about 1 degree. This increase in temperature causes changes in other climate variables and in recent decades has had a different impact on systems that are interfacing with or without interacting with the Earth's atmosphere. Therefore, it was necessary for each region to take different measures to reduce greenhouse gases and adaptation strategies for climate change. In this research, by identifying the strengths, weaknesses, opportunities and threats of water resources in the country, their SOWT model and their weighting with the ANP model were determined as the best national strategy for water consumption and adaptation to climate change in Iran. Based on the results, two models can be mentioned. Model No 1, entitled "Control, Reduction and Gradual Decrease in Sustainable and Unhealthy Consumption Volumes", and Model No. 2 "Management, Improvement and Increased Sustainable Water Consumption Resources", stabilize the system of sustainable consumption of water consumption in Iran in order to adapting the climate change in the medium to long term.