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

Water crisis in the Middle East has made water security the main issue in national security. Water security is a vital element in supply of energy security and food security. Water security is one of the concepts that examines the situation of countries and watersheds in terms of access to water resources, and has emerged in response to the challenging nature of the global water crisis. Various hydrological, structural, institutional, political, social, economic and environmental factors are involved in water security. The present study is an attempt in investigation on the hydrological factors affecting the water security of the western sub-basin Lake Urmia. For this purpose, water availability, water use intensity, monthly runoff variability and portion of irrigated land to cultivated land as the selected indicators in assessing the water resource and consumption security in the western sub-basin of Lake Urmia by study areas Salmas, Urmia, Naqadeh, Oshnavieh, Mahabad and Bukan in the 5-year time period including 2006 and 2011. The results showed that the water resource and consumption security in the western parts of the Urmia Lake basin have relatively similar conditions and included in the weak and middle class. The score of water resource and consumption security for the whole western sub-basin of Lake Urmia for the years 2006 and 2011 is equal to 0.4 (medium) and 0.32 (weak), respectively. This is due to the reduction of total renewable water resources per capita and increasing the water use intensity in the western sub-basin of Lake Urmia, which requires a review in managing water consumption in different sectors.

Rapid population growth and the expansion of urbanization in large parts of the world have increased the need for various facilities and resources, of which water is undoubtedly the most important or one of the most important. This need, which is associated with the heterogeneous distribution of water resources and rainfall in the world, has caused numerous tensions in the field of water supply. It has also made the issue of "water security" an emerging challenge in the field of national and international security. Water security is one of the concepts that examines the situation of countries and watersheds in terms of access to water resources, and has emerged in response to the challenging nature of the global water crisis. Various hydrological, structural, institutional, political, social, economic and environmental factors are involved in water security. The present study wants to investigate the hydrological factors affecting water security in the western sub-basin of Lake Urmia and to provide an overview of the state of water resources and consumption security in the study areas.

One of the most common methods used to assess water security is the use of indicators so that they can express large amounts of complex information in a simple and understandable way. The method of assessing the status of water security using indicators is a new method that is proposed to countries to assess the current state of their water security in this way. In the present study, the state of water resources and consumption security in the western sub-basin of Lake Urmia (by study areas of Salmas, Urmia, Naqadeh, Oshnavieh, Mahabad and Bukan) in 5-year periods including 2006 and 2011 have been investigated. For this purpose, water availability, water use intensity, monthly runoff variability and Portion of irrigated land to cultivated land are considered as selected indicators in evaluating water security in terms of water resources and consumption. Due to the unit differences of the indicators, in order to facilitate the interpretation of the water security situation, the indicators are normalized in the range of 0 to 1 and based on the threshold / reference values. Then, using the weighted average method, the score of water resources and consumption security is calculated for each of the studied areas. At the end, based on the water resources and consumption security score, all areas are classified as "very poor", "poor", "average", "good" and "very good".

The results of the study showed that the water resource and consumption security situation in the western parts of the Urmia Lake basin has relatively similar conditions and is in the middle and poor class. None of the study areas in the western sub-basin of Lake Urmia have very high or even high water security. The score of water resource and consumption security for the whole western sub-basin of Lake Urmia for the years 2006 and 2011 is equal to 0.4 (medium) and 0.32 (weak), respectively. The best water security situation is in Bukan area and the worst situation is in Naqadeh area. The decreased water resource and consumption security over time periods has been due to the reduction access to water and increasing the Water use intensity in the western sub-basin of Lake Urmia, which requires a review in managing water consumption management in different sectors.

According to the results of the study, it can be stated, the trend of water security changes in the western sub-basin of Lake Urmia is decreasing and the root of water insecurity is different in each of the studied areas. This indicates the high need of the basin to make economic and infrastructure investments and increase the institutional capacity of the basin to manage and plan water resources, which shows the need for attention of planners and officials in the water sector.

The date bunch fading disorder causes huge loss on farmers' incomes and damages to economy of date producing regions. Thus it is important to find a way for controlling the disorder or reducing its economic damages. It seems that the water losses of the tree under critical environmental conditions, such as high temperature and very low air relative humidity, cause date bunch fading disorder especially when is accompanied by regional warm wind. According to the scientific literatures, the use of different covers on bunches, high-frequency irrigation, foliar application of mineral nutrients and anti-transpiring substances, and soil mineral fertilization can affect date palm bunch fading disorder. Superabsorbent polymers have great capability for storage water and can be used in soil to improve its water retention and increase soil available water under drought conditions. On the other hand, potassium has important roles in metabolism of carbohydrates, plant water relations as the major element in action mechanism of stomata, and plant water osmotic potential. Organic matter can also improve soil physical properties, i.e., soil structure and soil available water as well as soil fertility and bioavailability of mineral nutrients. Because of mentioned roles of these three factors, the effects of them on date palm bunch fading disorder were investigated in this research.

The effects of superabsorbent, potassium fertilizer, and manure on yield and date bunch fading disorder of "Mazafati" date palm cultivar were investigated in Jiroft, Kerman province, south of Iran. An experiment was conducted in factorial randomized complete block design. The factors were included superabsorbent polymer A200 in 0 (S1), 200 (S2), and 300 (S3) g.tree-1 levels, potassium sulfate fertilizer in 0 (K1), 2 (K2), and 3 (K3) kg.tree-1 levels, and cow manure in 0 (O1), 65 (O2), and 130 (O3) kg.tree-1 levels. Treatments were applied in February in three blocks and harvest was done at the first half of August. The yield of intact fruits, the yield of dried and dropped fruits (collected in an elastic silicone wire cloth cover), and total yield were determined at the harvest time and date bunch fading disorder was calculated as weight percentage (the dried fruits weight was divided by the total fruits weight and multiplied by 100, in each plot). Weight, diameter, and length of fruits were measured and determined from a random sample containing 30 intact fruits per each plot (a tree). Statistical analysis was done by IBM SPSS Statistics version 25.

According to the results, the block had no significant effect on any of studied parameters, on the other hand, the results showed significant effects of all three factors on all of the measured parameters including percentage of date bunch fading disorder, total fruits yield, intact fruits yield, fruit weight, fruit diameter, and fruit length, except fruit length by the manure factor, by ANOVA at the 0.01 level. Three factors interaction significantly affected only the fruit characteristics including weight, diameter, and length of fruit. About the intact and total fruits yield and date bunch fading disorder, interactions between superabsorbent and two other factors were statistically significant. The highest means of intact fruits yield were observed in S3K3 and S3O3 treatments (28.9 and 28.7 kg.tree-1) increased by 98% and 93% compared to S1K1 and S1O1 treatments, respectively; and they were also significantly higher than those of all other treatments. The maximum means of total yield were found in S3K3 and S3O3 treatments (35.0 and 26.8 kg.tree-1) increased by 33% and 28% compared to S1K1 and S1O1 treatments, respectively. The mean percentage of date bunch fading disorder was significantly decreased by increasing the levels of superabsorbent, potassium fertilizer, and manure factors in interactions between superabsorbent and two other factors (SK and SO interactions), thus the lowest mean of date bunch fading disorder percentage in both interactions was found in third levels of each factor (S3K3 and S3O3 treatments), decreased by 60% and 63% compared to S1K1 and S1O1 treatments, respectively. The lowest and the highest mean of fruit weight, fruit diameter, and fruit length parameters were observed in S2K1O3 and S3K3O3 treatments, respectively. Negative significant correlations were found between percentage of date bunch fading disorder and total fruits yield, intact fruits yield, fruit moisture, fruit weight, fruit diameter, and fruit length, while the last six parameters had positive significant correlations with each other. In addition to common positive effects of three factors on water supply improvement, they can influence plant progress in different ways, such as carbohydrate metabolism and activation of some enzymes by potassium, and increasing of mineral nutrients availability and soil microbial activities by organic matter and manure. Therefore, these three factors could have some positive interactions on their effects on control of the disorder, increasing the yield, and improvement of weight and size of fruit. An observed decrease in weight and size of fruit by using 2nd level of superabsorbent and 3rd level of manure can be resulted from significant decrease in percentage of disorder and finally competition between safe fruits for potassium in carbohydrate metabolism and so on.

According to the results of this research, applying of superabsorbent polymer (300 g.tree-1), potassium fertilizer (3 kg.tree-1), and manure (130 kg.tree-1) together can be recommended to improve qualitative parameters of date palm fruits (weight, length, and diameter). Applying the 3rd levels of these factors together can also control date bunch fading disorder cv. Mazafati, and increase the economic income because of qualitative improvement of fruits.

The complexity of the concept of soil water availability has led to the emergence of a variety of methods to estimate it, which have always been changing, refining, and replacing. Among those, the conventional method of plant available water (CPAW=FC-PWP) due to convenient measurement has received more attention. In theory, however, the methods of Integral Energy (EI) and Kirchhoff Potential (Mh0) have been considered due to the interference of soil properties and plant ability for water uptake. In this  study, the available water was calculated with CPAW, E I and Mh0 concepts in a wide range of soils (72 samples) with various physical properties and results were compared. Also, different upper limits were tested to determine the water availability and the new field capacity moisture coefficient was used as the upper limit of the concept of water availability. Despite the weak correlation between EI and Mh0, the trend of their variations in different soils is somewhat similar, indicating their similarity in the estimation of available water for plants. In contrast, the lack of a clear relationship between EI and Mh0 with CPAW confirmed their lack of correlation in explaining water availability of the plant. The convenience of using CPAW makes it even more preferable to study the variability of soils in terms of hydraulic properties. On the other hand, the use of EI and Mh0 results will be useful for explaining the available water content but still needs to be modified in terms of determining threshold limits.

In most countries, agricultural sector is the main user of water resources (surface and ground water). The process of exploitation of water resources to explain the sustainability and continuity of exploitation in each region, especially in arid and semi-arid areas, which is faced with the shortage and severe competition of water resources use in different sectors is necessary. The purpose of this study was to investigate the status of water resources in the Marvdasht-Kharameh range (covered by two modern irrigation networks in Dorodzan and traditional Korbal) in Fars province during the statistical period of 2006-2016, based on the stability analysis indexes proportional to the volume of water allocated in comparison with excessive withdrawal of groundwater resources, as well as the relationship between rainfall and the amount of variations in the level of stagnation. For this purpose, by using Dorodzan weather data and Persepolis stations, as well as Kheirabad, Pulkhan and Zarghamabad hydrometric stations and the irrigation networks data, the available water resources in terms of surface and groundwater were estimated. According to the average level of stagnation and changes in aquifer volume, excess water harvesting were calculated in two areas covered by Dorodzan and Korbal irrigation networks. The amount of runoff coefficient in plain, altitudes and total range was calculated to be 6.9, 14.1 and 9.9 percent, respectively. The average amount of excess withdraw in the area covered by two modern Dorodzan and Korbal networks is 96.33 and 16.2 MCM /year, which according to available water resources is 8.2% and 5.2%, respectively. The Average standardized precipitation-evaporation-transpiration12-month SPEI index for Droodzan and Persepolis stations was calculated to be -0.33 and -0.43, indicating the mild drought in the area and during the proposed time period, and this is in good agreement with the Water table drawdown. The result of linear regression between the independent variable of rainfall and the dependent variable of the average water table changes showed a significant increasing linear relationship (p < 0.001) with R2 = 0.95 and RMSE = 0.99. This result for the independent variable of rainfall with the dependent variable of water allocation volume, indicated an incremental linear relationship (P = 0.110), with R2 equal to 0.29 and RMSE equal to 245.6. Indicators of water resource sustainability analysis, such as Falcon Mark (FI), United Nation (UN) and Water Tension Index (WSI), were calculated for the region. The values of the Indicators of water resource sustainability analysis including Falcon Mark (FI), United Nation (UN) and Water Tension Index (WSI) were 1983 cubic meters per person, 210 percent and 2.93, respectively. By comparing the values of these indexes, it was found that based on the FI index, the area is close to tension. The UN and WSI indicators are indicative of the fact that the study area is under severe crisis and excessive use of water resources and the pattern of exploitation of water resources should be managed in order to eliminate surplus withdrawals and sustainability of water resources.