Extraction, processing, production and display of geographic data
Seyed Hossein Mirmousavi
Abstract
Extended Abstract
Introduction
In hydrological drought, water scarcity spreads through the hydrological cycle and can subsequently reduce groundwater levels, surface water and lake levels, and this means that hydrological drought dominates those areas, leading to long-term effects. In addition, due ...
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Extended Abstract
Introduction
In hydrological drought, water scarcity spreads through the hydrological cycle and can subsequently reduce groundwater levels, surface water and lake levels, and this means that hydrological drought dominates those areas, leading to long-term effects. In addition, due to climate changes and rainfall and temperature anomalies, droughts have increased in frequency and severity in many regions of the world. The predicted changes for the coming years show that climate variables will not have uniform changes in all regions and regional changes in the amount of precipitation may lead to the creation of hydrological patterns much different from the current conditions.
The present study was also carried out with the aim of spatial analysis of drought effects on water level changes in the catchment area of Bakhtegan, Tashk and Maharlo lakes. In this research, an attempt has been made to identify temporal and spatial patterns of changes in the level of this lakes by using satellite images and spatial analysis models.
Materials and Methods
In the present study, Landsat 5(TM), 7(ETM+) and Landsat 8(OLI) satellite images with a resolution of 30 meters have been used in the period of 2000-2021 to investigate water level changes. Due to the fact that the water level of the studied lakes changes drastically with the rainfall of different months, therefore, it is difficult to determine the amount of water cover for a year without considering the fact that a part of this cover is seasonal and when the rainfall decreases, a part of the lake Dry may not provide accurate results. Based on this, in the present study, one image was used for each month for each year studied to evaluate the changes in the water level of the lakes in all months of the year.
Conclusion and Discussion
The investigation of the changes in the water level of Maharlo Lake shows that in the drought of 2108 and 2017, the permanent water level of the lake has decreased to 1.8 square kilometers. Meanwhile, in the severe and very severe drought of 2005 and 2004, the permanent water level reached 170.4 square kilometers. Examining the changes in the area of Tashek Lake in 15 years of drought shows that the area of the waterless part of this lake has increased more than the seasonal and permanent water. The highest amount in this field was in 2021 with a very severe drought, which shows that this lake has more critical conditions in terms of permanent dryness than Maharlo Lake. This lake has been in a terrible state for 5 years. Comparing the changes in the area of Bakhtegan lake in different years shows that this lake has a more critical situation than its neighboring lakes (Maharlo and Tashk), so that in a significant number of years (12 years) the lake lacked permanent water and only With monthly or seasonal rains, some water has been temporarily collected on its surface, but it has a short shelf life between 2 to 6 months (November to May).
Results
The results of the evaluation and analysis of the role of drought in the water level changes of the Bakhtegan, Tashk and Maharlo catchment lakes showed that the area of these lakes has decreased significantly during the studied period, so that over time the area of the water area has decreased. It has been permanently reduced and added to the dry and waterless area. The maximum decrease in the water level of all three investigated lakes occurred during a 6-year drought between 2008 and 2013, in such a way that the area of the part with permanent water was greatly reduced and the area of the dry part of the lakes was increased.
Saeed Farzaneh; Reza Shahhoseini; Iman Kordpour
Abstract
Introduction Drought is considered to be one of the most widespread natural disasters, ranking second in terms of damages. Due to the complex relationship between hydrological cycle parameters and atmospheric observations, predicting or modeling drought lacks the necessary precision. One of the most ...
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Introduction Drought is considered to be one of the most widespread natural disasters, ranking second in terms of damages. Due to the complex relationship between hydrological cycle parameters and atmospheric observations, predicting or modeling drought lacks the necessary precision. One of the most significant problems in drought monitoring is lack of proper spatial coverage for the collected data (due to unavailibility of field data in some regions) and also lack of a suitable time scale (observations and thus drought estimation is not always possible). Since satellite observations do not face challenges like lack of spatial scale which is quite common in field observations, remote sensing satellites can provide a better estimate of droughts. However, satellite observations alone are not capable of accurately estimating the occurrence of droughts. Therefore, a combination of field and satellite observations has been used recentely to reach a better estimate of hydrological problems. Materials & Methods Temporal and spatial complexity of droughts have made a new global index combining ground-based and satellite-based observations quite necessary. Given the kind of data used in MDI index, we cannot expect it to be global. However, its performance is still acceptable in similar environments and climates, and thus it has been used in the United States (Texas). Datasets selected for the present study have different temporal and spatial scales and thus, a common scale must be found before calculating the index. Data received from GRACE satellite and MODIS sensor were downloaded monthly, but precipitation data were collected on a daily basis. Thus, aritmatic mean of precipitation data was calculated to reach a monthly avarage. Regarding the spatial scale, one-degree precipitation data were received from GRACE and MODIS while precipitation data extracted from synoptic stations had a point-based nature. Therefore, Inverse Distance Weighting (IDW) method was used to produce a one-degree network. Three types of observations were used in the present study including data received from synoptic stations of Iran meteorological organization, GRACE mission satellite-based gravity data and MODIS remote sensing satellite-based data. These were selected to identify droughts over a 14-year time series. Results & Discussion The present study has calculated MDI drought index on a one-degree spatial scale and monthly temporal scale for 168 months using Precipitation, NDVI, and TWS data. Severe droughts in northwestern and central areas of Iran from 2004 to 2014 have led to a shortage of water in reservoirs. In addition to drought, too much water harvesting in northwestern Iran has resulted in a decrease in groundwater level and thus, increased water harvesting from rivers and canals leading to the Urmia Lake and reduced water level in this lake. The results of MDI drought index calculated for Iran over the period of 2000 to 2014 show a high correlation with the results of standardized precipitation-evapotranspiration drought index. According to the type of data used to calculate MDI index, it is expected to have a strong correlation with PDSI index due to its sensitivity to precipitation, area temperature and soil moisture content. Since GRACE and MODIS satellite-based data, and data received from synoptic stations were used, a strong correlation with MDI is also expected. It should be noted that PDSI index is higher than MDI index in Iran, although both show the drought trends accurately. For example according to PDSI index, the worst drought of the last two decades in Iran has occurred in 2008, and MDI index shows the same year. Conclusion The present study has introduced a new drought index using a combination of precipitation data, GRACE_TWS and NDVI. These data were selected because of their high sensitivity to drought. GRACE_TWS observations monitor hydrological drought and include surface and subsurface water sources. NDVI observations are mostly used to identify photosynthetic activities of vegetation cover and are therefore very useful for detecting agricultural drought. Precipitation value shows the amount of surface water in the study area. Precipitation can have relatively rapid effects and is therefore useful for monitoring meteorological drought. MDI index has identified several droughts in each region of the country in the period of 2003 to 2016. These identified droughts have generally covered the country over time. However, each drought has had a different impact on ecosystem. In Iran, the most severe droughts have occurred during 2008 to 2009 and 2011 to 2012. Since MDI correlates well with PDSI, both show a drought in these years. In order to develop the proposed algorithm, the effect of different zoning of the study area on MDI index can be studied.
Sepehr Honarparvar; Mohammad Reza Malek
Abstract
Introduction
In recent decades, rapid climate changes in the Middle East have led to the rapid growth of drought phenomenon. Given the recent observations and surveys in the countries of the region, the rate of evaporation of surface water has increased. In addition, water consumption has increased ...
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Introduction
In recent decades, rapid climate changes in the Middle East have led to the rapid growth of drought phenomenon. Given the recent observations and surveys in the countries of the region, the rate of evaporation of surface water has increased. In addition, water consumption has increased dramatically in recent decades due to various causes, including industrial and agricultural development and population growth. Apart from the natural causes, the lack of proper management and planning of water resources is one of the main reasons for drought occurrence in the country. It’s obvious that every program needs reliable and updated information to help planners make decisions. Therefore, information onthe volume changes and the amount of water is of great importance in the management of the limited water resources. This information is usually obtained using conventional methods of remote sensing, surveying and photogrammetry which require significant amount of time and money. On the other hand, obtaining information from people is very beneficial due to the high speed, low cost of preparation and high volume of shared information. Volunteered Geographic Information provides an environment for the acquisition of spatial information from ordinary and expert people.Recently, many researcheshave been carried outon geography, natural resources and geosciencesin relation to the voluntary applications of spatial information in crisis management, and it has been proved that these data are suitable for managing long-term and short-term crises. Regarding the water management in particular, researches have been carried out on collecting water pollution information through sharing the location and the type of water pollution. The issue of drought in water resources has not been taken into consideration in this category of investigations.Another category of the researches is about the type of architecture used to obtain popular information from the volunteered spatial information, while the quality of this information has been ignored. In another category of the researches, users identify and report the rate of changes in water resources using remote sensing and aerial images but, this method is indirect and does not share information instantaneously and directly.
Materials and methods
The aim of this paper is to design and develop a Volunteered Geographic Information system for receiving and updating drought information on natural water resources. To do so, users send the information on water volume and its changes as well as the location, to the drought information spatial database. The case study of this paper is the water resources of the rivers and lakes of the TashkBakhteganMaharloubasin. TashkBakhteganMaharlou is a basin region in the province of Fars in Iran,and the reason for choosing this basin as a case study isthe abundance and diversity of water resources in the area. A Web-based mobile application has been developed to receive the popular information of water resources. Users can share information based on the level of access. This level of access is determined based on the level of users’ expertise and occupation relative to water sciences. In order to implement this system, a client - server architecture was employed, in which SQL Server was used as the updating and managing system of the spatial database, ArcGIS Server as a spatial server, WCF Service to receive thematic information, JSON as the format of exchanging data and Android as the client’s development language.
Discussion and results
In order to evaluate this system,the spatial accuracy, descriptive accuracy and the integrity of the Volunteered Geographic Information were measured. After the evaluation, a spatial accuracy of 12.5 meters, a descriptive accuracy of 67%, and the integrity of 75% were obtained. Moreover, 80% of the Volunteered Geographic Information hadan area of more than 1 Hectares,representing the interest of the users in sharing lakes with wider areas. Meanwhile, 65% of the Volunteered Geographic Information has a density of 27 lines per Hectare, indicating that people are willing to share rivers with denser branches.
Conclusion
Since the datawas collected by smartphones’ GPS,this amount of spatial accuracy was predictable. Descriptive accuracy obtained is relatively low due tothe ambiguity in the naming of received data. The high integrityindicatesthe capability of the system in updating drought spatial database over a short period of time. Therefore, it seems that the Volunteered Geographic Informationon drought is generally acceptable for completing the water resources database and for the management and making decisions on the planning of conserving water resources in a short time with low cost.
mahdieh soltani Gerdfaramarzy; gholamali mozafari; Shahab Shafie
Abstract
Extended Abstract Introduction Droughts are one of the most common climatic changes that occur in many arid and semi-arid regions of the world with high intensities every few years. In many years, the occurrence of droughts is also unknown for a while, therefore, the identification of drought itself, ...
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Extended Abstract Introduction Droughts are one of the most common climatic changes that occur in many arid and semi-arid regions of the world with high intensities every few years. In many years, the occurrence of droughts is also unknown for a while, therefore, the identification of drought itself, is considered as a valuable finding for managing the water resources in areas such as Iran, most of which are formed by arid and semi-arid regions. Precipitation is the most important determinant variable in drought conditions among climatic variables. Rainfall is the most important variable whose variations are directly reflected in soil moisture and surface runoff, variations in underground water reservoirs and others. The purpose of this research is to investigate the best method of drought interpolation in the Yazd-Ardakan plain, to identify areas at risk of this phenomenon and to identify its spatial distribution, and also to investigate the relationship between drought and the salinity of groundwater and the spatial distribution of saline water in the Great Plain of Yazd – Ardakan. Materials & Methods In this research, regarding the lack of long-term statistical period of some stations and considering the distribution of stations in this basin, the annual precipitation data of meteorological stations of Yazd - Ardakan plain during 2 long term period of 7 meteorological stations (1346-1391), and short term precipitation and salinity period of 41 meteorological stations and 47 underground water wells (1375 to 1391) have been used all together. The standardized drought index for the determining drought condition and descriptive statistics methods in SPSS software has been used to describe the state of groundwater salinity using Excel software. The Pearson, Man-Kendhal, and Spearman correlation analyses were also used to determine the relationship between drought and the state of salinity of groundwater. Finally, the Geographic Information System (GIS) was also used to map the zoning of groundwater salinity. Results & Discussion The results of the assessment showed that in the correlation analysis with all 3 Pearson, Man-Kendhal, and Spearman statistics, a negative trend along with inverse correlation is observed between the precipitation (SPI) and salinity based on the Z grade,, in none of which the significant level is observed. The existence of a strong correlation between these two parameters with a one year delay was among the other results of this research. Using GS+ and GIS, the best variogram model was selected and the maps of drought, groundwater salinity and salinity variations were also drawn. Generally, in most stations with negative precipitation trend, a positive trend of underground water salinity is observed, and groundwater quality has also changed more strongly in areas with more drought outbreak and its salinity has also increased. Conclusion The occurrence of droughts, on the one hand, increasing water demand in the area, on the other hand, exacerbate the shortage and need for water. Therefore, the monitoring of future droughts and wet years should be considered very important in terms of management strategies of the region. Passing such crises require the efficient management of water resources under present conditions, especially during drought periods. Usually, during such a period, the region’s water shortage, are provided from the groundwater resources and through increasing the water extraction from wells, to meet basic needs such as drinking. Therefore, in such cases, the quality issue of the extracted water from these wells becomes more important. The available statistics show that the water quality in the Yazd-Ardakan plain (electrical conductivity) is a function of annual precipitation (as the most important feature of droughts in the region), and with the annual precipitation increasing and decreasing, the groundwater quality also undergoes changes. In general, the results of the analysis of the studied parameters indicated that the climate of Yazd-Ardakan plain was associated with a rainfall reduction trend, which is one of the important factors of drought, so that, its consequences have also affected the level and quality of water resources. It has been observed in this research, that droughts have had a considerable effect on the salinity of groundwater in most of the areas. Therefore, it is generally stated that the groundwater quality has changed more strongly in areas with more drought outbreaks and its salinity has increased.
Nasrin Nikandish; Abbasali Arvin; Vajiheh Shahsavari; Farshad Soleymani
Volume 22, SEPEHR , July 2013, , Pages 23-29
Abstract
Drought is a global phenomenon which can happen nearly everywhere and result in major economic, social and environmental costs and losses. In this study, annual precipitation data of 7 synoptic stations and 8 pluviometric stations in a 20 year period (1986-2005) were applied to investigate climatic droughts ...
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Drought is a global phenomenon which can happen nearly everywhere and result in major economic, social and environmental costs and losses. In this study, annual precipitation data of 7 synoptic stations and 8 pluviometric stations in a 20 year period (1986-2005) were applied to investigate climatic droughts in Hormozgan province. After preparation of data, the intensity of drought was calculated using two statistical indices (percent index of normal precipitation and annual precipitation metric). Then, the results in each station were compared with its corresponding precipitation to select the best zoning method.
Finally, percent index of normal precipitation was selected as the best index for zoning drought. Results of the zoning indicated that in 1992, 1997, 1996, 1995 wet year was dominant in the area, while in 1993, 1994, 2000, 2004, 2005 average dry year covered a large part of the area and in 2001, 2003 very dry and extremely dry year was dominant. Drought does not show a specific trend considering its continuation, intensity and extent and lacks a homogeneous temporal and spatial distribution.
Majid Montazeri
Volume 20, Issue 80 , February 2012, , Pages 23-28
Abstract
In order to assess the climatic drought trend in 23 sub-basins of the Caspian Sea, monthly precipitation data were converted to the zoned data by interpolation method. Then, based on the coordinates of the basins, the monthly precipitation of each basin was separated. The Standard Precipitation Index ...
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In order to assess the climatic drought trend in 23 sub-basins of the Caspian Sea, monthly precipitation data were converted to the zoned data by interpolation method. Then, based on the coordinates of the basins, the monthly precipitation of each basin was separated. The Standard Precipitation Index (SPI) method was used to assess climatic droughts and this index was calculated monthly for each basin. According to the parametric test, linear regression of 23 sub-basins of Caspian Sea in January, May and December do not show any significant trend at 95% confidence level. Five sub basins in the months of February and July have a positive trend and 11 sub basins show negative trend in March and September. By applying non-parametric Mann-Kendall test on the SPI matrix of the 23 Caspian sub basin, it was found that no baseline shows significant trend in May. The highest trend in six sub-basins have been in the months of July and August.
Ali Baratian (Compilation)
Volume 10, Issue 38 , August 2001, , Pages 60-64
Abstract
Drought is lack or inadequacy of rainfall over a long period of time, so that it leads to a lack of moisture in soil and reduces the flowing waters, thereby interrupting human activities and plant and animal life. The time between last rainfall and observation of tangible decrease in rivers’ water ...
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Drought is lack or inadequacy of rainfall over a long period of time, so that it leads to a lack of moisture in soil and reduces the flowing waters, thereby interrupting human activities and plant and animal life. The time between last rainfall and observation of tangible decrease in rivers’ water and soil moisture is not the same in different climates. Therefore, a precise and comprehensive definition of drought cannot be provided. For this reason, experts have each proposed a different definition of drought from different points of view.
In this paper, eleven meteorological factors that play a role in severity of dryness and drought have been selected and their effects on determination of dry years have been classified. Among these factors, six factors of precipitation, maximum daily rainfall, number of rainy days, dew point, relative humidity and cloudiness have been selected as factors reducing drought severity, and factors of maximum temperature, average temperature, sunny hours and evaporation as those intensifying drought; these factors have been classified at the synoptic meteorological station of Hamedan during the statistical period from 1989 to 1997 using the scalogram model. This classification can be applied to more factors and longer periods at each station, so that in determination of drought years, efforts will not be limited to the amount of precipitation, and other factors will be involved in calculations according to their priority.
According to the classification and use of the tables at Hamadan station, eleven meteorological factors were selected which can be named in terms of priority as follows:1. Maximum temperature 2. Minimum temperature 3. Average temperature 4. Rainfall 5. Maximum daily precipitation 6. Number of rainy days 7. Dew point 8. Relative humidity 9. Cloudiness 10. Sunny hours 11. Evaporation
