نشریه مدل سازی و مدیریت آب و خاک
سال یکم شماره 4 (زمستان 1400)

Marls as the most sensitive geological structure against erosion and weathering have a major role in sediment yield of watersheds. Due to the lack of vegetation or sparse pattern of vegetation cover in the Marl Formations; by identifying suitable plants and establishing and propagating them in these areas, the amount of erosion can be reduced. it is difficult to carry out the implementation of erosion control structures in Marl lands due to their mechanical properties; therefore, erosion control using biological measures is necessary and this requires accurate identification of species diversity. Due to the importance of this issue, suitable plants for the conservation of marls were identified in the Tanghesorkh Watershed of Fars Province.

Eleven points with dominance and the presence of marl outcrops were selected as sampling points. The sampling method for studying vegetation in these areas was based on physiognomic-floristic method and using transects and plot methods. Samples were collected in early autumn 2019, late winter 2019 and spring and summer 2020 and using valid scientific methods and plant species were identified. Also, biological form, longevity, vegetation form and chorology were determined. Then, different plant characteristics (density, frequency, canopy and root and rhizome status, amount of litter produced, generation method and longevity) and ranking of plants were studied in order to stabilize and protect the marl soils.

Around 108 plant species belonging to 29 families and 88 genera were identified. Asteraceae family with 18 species, Papilionaceae family with 17 species and Poaceae family with 13 species, are in the first to third ranks, respectively, and 16.67, 15.74 and 12.03% of the number of species to allocate them. In terms of longevity, 40 annual species (16 species of grass and 24 species of forb) and 68 species of perennials (8 species of grass, 30 species of forb, 18 bushes, 2 trees and 10 shrubs) were identified. A total of 37.04 and 62.96% of the total species accounted for plant. Life form included therophyte (36.12%), hemicryptophyte (24.07%), camphite (17.59%), geophyte (11.11%) and phanerophyte (11.11%). 55 species with a specific chorotype specific to the Iran-Turani vegetation zone had the highest frequency (50.93%). According to botanical characteristics, 30, 38, and 40 species in the first to third ranks for conservation of marl in this watershed were introduced.

Species such as Astragalus susianus, Astragalus faciculifolious, Astragalus gossypinus, Artemisia Aucheri, Convolvuvlus acathocladus, Convolvuvlus leiocalycinus, Amygdalus scoparia, Acantholimon asphodelinum, Stipa barbata and Glycyrrhiza glabra is recommended for the establishment and reproduction of in marl-covered areas in this watershed. Also, due to the irregular exploitation of these lands, it is necessary to protect these areas by controlling and managing livestock grazing. Therefore, this conservation provides opportunities for regeneration and survival of valuable plant species in this watershed.

Introduction Landslide occurrence is caused by severe ground movement and fault fractures that lead to structural damage, road blockage, human death, and significant damage to other features. Landslide is one of the most destructive natural phenomena that can cause great damage to property and human loss. One of the basic measures to reduce potential damage is to identify landslide-prone areas. Due to the location of most cities in the mountainous and foothill areas and the topographic, geological, and geomorphological features, the natural conditions are vulnerable to a wide range of landslides. Tehran, as the largest city in Iran, has almost 12% of the total population of the country and is partly located in the foothills and mountainous areas. Tehran, has many important infrastructures, including crowded roads, and a large population, therefore, determining areas prone to future landslides is an important management issue. Also, debris flow is one of the main factors that cause serious damage to properties. Thus quantitative assessment and management are required to reduce the possible damages. In addition, technologies are needed to assess disaster prevention facilities and structures in disaster-prone areas. Therefore, using combined methods for landslide susceptibility areas can be very effective in managing the risk of reducing casualties.Materials and MethodsIn this study, the effective factors on landslide occurrence such as rainfall, earthquake, vegetation, land use, geology, river, fault, slope and aspect, and roads are employed using an integrated approach. Then, spatial analysis was performed in ArcGIS using Euclidean distance and Curvature functions. The Haraz and Lavasanat roads were selected as a case study, and each of the criteria was examined and classified using the Euclidean distance method and inverse distance weighted (IDW) technique.Results and Discussion The results showed that the areas facing northeast and southwest parts were ranked 1st and the rest of the area was ranked 0. The areas with slope values higher than 50%, had a higher risk of landslide. The curvature of the selected main and secondary roads was located in convex hillslopes indicating the areas at a high-risk level. These Haraz and Lavasan roads are at risk of slipping during rain, earthquakes, and other hazards. According to the area obtained from the regional statistical properties.Conclusion The mountainous roads of Tehran are vulnerable to landslide and debris flows due to the geographical location, and the existence of faults. The excessive interference in the nature and increase of additional load on the slopes and excessive influence on agricultural and road use are important reasons for instability in the slope and increasing the debris flow in these land uses. The controlling of landslide and debris flow phenomena depends on a comprehensive management plan. Factors such as population growth, land-use change, and climate change are intensifying the landslide and debris flow occurrence. Since rainfall is one of the accelerating the occurrence of natural disasters, the existence of a management system such as an early warning to the endangered population is necessary.

The pollutants have exceeded the environmental load capacity of the water resources due to the rapid development and expansion of urban areas, increased industrial production, agricultural activities, and discharging of the domestic sewage into the surface water runoff in recent years. These point and non-point source pollutions have decreased the water quality of the surface water. Water pollution has become a concerning management issue in quality control of the surface water in developing countries. Pollution of urban rivers seriously hinders sustainable economic and social development and threatens human health. Assessment of river water quality according to physical, chemical and biological parameters is the basis of health management of its ecological system. Water quality in any region is affected by two factors: natural processes and human activities such as the transfer of nutrients and heavy metals to surface waters. In this regard, freshwater pollution by heavy metals has become one of the main environmental concerns in recent decades.

This study is aimed to evaluate the water quality and the controlling mechanisms through calculation of Drinking Water Quality Index (DWQI) and four pollution indices (PLs). In this regard, the multivariate statistical analysis techniques such as partial least squares regression (PLSR), stepwise multiple linear regression (SMLR) were used, as well as the chemical type of the water has been determined using a three-line piper diagram. Therefore, 26 physicochemical parameters for eight surface water areas of the Talar River were analyzed in this research using standard analytical methods.

The results indicate that the surface water resources in this region are determined to be alkaline with Ca-Mg and Ca-Mg-Cl-SO4. According to the results of DWQI analysis, 19% of the total samples were good water, 56% poor and very poor, and 25% were inappropriate for drinking. Also the PI results demonstrate that the surface water is highly affected by Mn and Pb and are under a slight impact of Fe and Cr. The obtained SMLR models of the DWQI and PIs which developed according to the base ions and heavy metals represented the best estimates with R2=1 for QWQI and PIs. According to the Piper diagram, the surface water is affected by the interactions and weathering of rocks. According to Gibbs geochemical diagram, it was shown that surface water points are in areas with weathering and permeability. As a result, these factors have been proposed as the most important factors affecting the geochemistry of surface waters in the study area. The surface waters of the study area are polluted by heavy metals and this pollution increases from the beginning of the river to the station near the Caspian Sea.

The integration of DWQI and PIs is considered as a functional and distinguishing method in the assessment of the surface water quality, and the PLSR and SMLR models can be used to evaluate DWQI and PIs via chemical techniques application. Degradation and reduction of surface water quality can be attributed to the widespread use of agricultural pesticides, industrial activities and poor drainage network. The water quality amount has been severely reduced from upstream to downstream of the Talar River, due to the entry of agricultural effluent and passing through urban and industrial areas. The use of wastewater treatment methods before discharge to freshwater improves water quality and prevents its degradation.

Sustainable land management is defined as as “the use of land resources, including soils, water, animals and plants, for the production of goods to meet changing human needs, while simultaneously ensuring the long-term productive potential of these resources and the maintenance of their environmental function”. Undoubtedly, achieving comprehensive land management requires effective and coordinated communication, cooperation and synergy of all key stakeholders and stakeholders who have common goals but distinct tasks. The aim of this study is to investigate challenges and strategies for managing and combating dust storm using participatory appraisal among Sistan Institutional Stakeholders Network.

The aim of this research is participatory appraisal of challenges and strategies for managing, controlling and combating the dust phenomenon among 27 invited relevant key institutional stakeholders of Sistan network. Comprehensive studies of Sistan dust conducted by the Research Institution of Forest and Rangeland, and the considered challenges and strategies for managing, controlling and combating dust storm was assessed using a brainstorming technique in a collaborative way. So, the participants have been divided into 5 working groups, including Water-Agriculture, Economics-Development-Infrastructure, Environment-Natural Resources, Cultural-Social-Political, and Law-Policy Making. The challenges and solutions have been investigated.

some challenges stated by the groups are: limitation of water resources, depletion of groundwater table and the lack of optimal decision-making regarding the management of watersheds in western Sistan, the destruction of vegetation in northwestern Sistan, the lack of organizational cohesion and integrated attitude by land management authorities, the lack of communication between research and implementation, migration, insecurity due to the depopulation of villages, increasing poverty and unemployment, weak Iranian diplomacy regarding the Hamoon Wetland, strong dependence of the Sistan region on water resources and agricultural economy, lack of integrated management regarding the maintenance of wetlands. The presented solutions are: determining the extent of urban development based on the volume of available water, modifying the pattern of drinking water consumption, predicting the use of treated municipal effluents to control fine source of dust, the optimal use of precipitation to stabilize eroded areas, improve the Sistan river pathways, forming the Sistan Dust Working Group, evaluating the effectiveness of executive projects on watershed management, and education in schools.

In general, the challenges raised by various institutions indicate a weakness in comprehensive planning, integrated management and good governance based on community-based participatory management.

Drought is a natural disaster that occurs over a long period of time, and affects human societies through negative effects on water resources and agriculture, and consequently the economy. Forests are an important part of the ecosystem that covered about a third of the land surface. Occurrence of wild fires has been degraded the quantity and quality of the forest. The phenomenon of fire is one of the drought complications that cause irreparable damage to the ecosystems. The drought duration and its repetition have been reported more than other natural disasters. The definition of drought has continually been a key issuefor drought monitoring and analysis. The drought is a condition of insufficient moisture caused by a deficit in precipitation over some period of time. Difficulties are primarily related to the time period over which deficits accumulate and to the connection of the deficit in precipitation to deficits in usable water resources and the underlying impacts.

There are several indicators for drought identification and interpretation. The calculation of Keetch–Byram Drought Index (KBDI) requires a long series of meteorological data. When the data are available its calculation is straightforward. However, it is strictly valid for the location of the meteorological station and its immediate vicinity. The temporal and spatial characteristics of drought were investigated using Percent of Normal Precipitation Index (PNPI) and KBDI, at 4 stations in Rasht, Bandar Anzali, Astara and Manjil in Guilan province during a 30-year time period (1987-2017).

According to the results, the drought index KBDI, the monthly time series of the available data were categorized as follows; normal drought class, 96.3%, medium drought, 3.6%, and severe drought, 0.5%. On the other hand, by analyzing the PNPI index, the percentages of normal, moderate, severe and very severe drought classes were 68.9% and 8.1% and 7.5% and 15.4%, respectively, which are almost same as the KBDI results. Taking into account the cumulative percentages of the drought classes of the area, can be deduced from the normal dryness of the area. On the other hand, the most severe dry year, according to the KBDI index was observed in 1988, while 2010 year was the most severe drough year based on the PNPI index. The longest dry period was roughly the same in both indicators, which was determined between 2004 and 2007 years.

The results showed that the probability of severe drought based on the analysis of the past time series is widespread in the months of June and July, which is important in the management of water resources and vegetation. Also, the drought intensity in this province is gradually increasing. Considering the decreasing trend of rainfall in the region, we can expect more droughts in the future. It is recommended that the managers and experts pay special attention to the prevention and management of water resources and vegetation in the two months of July and August during their executive activities.

North Karun Basin is one of the snow-covered regions of Iran and its snowfall has a great role in the water supply situation in the central and southern regions of the country. In this research, an attempt has been made to investigate the changes in the snow-covered surface in the study basin. Access to this information in high and impassable areas is possible only with the help of remote sensing techniques. The MODIS sensor has multiple spectral bands, but the ETM+ sensor has a better spatial resolution. The purpose of this study is to monitor, compare and map snow-covered areas by MODIS and ETM+ data in the northern part of the Karun Basin.

The research has been conducted in the northern part of Karun Basin, as one of the snowy areas in Iran. This area is geographically between 31° 19' 9'' to 31° 39' 17'' northern latitude and 49° 33' 56'' to 51° 54' 23'' eastern longitude. The study basin is over 14802 square kilometers, about 90% of Chaharmahal and Bakhtiari Province and 23% of Karun Basin. The height of the study area is changing between 800 m at Karun No. 4 dam to 4440 m at the Peak of Zard Kooh Mountain. The satellite data included MODIS and ETM+ sensors over a period of 15 years (2000 to 2015) used to calculate NDSI. The satellite pass-times were at Julian day number 360, 333, 365, 355, 360, 363, 331, 350, 336, 355, 342, 345, 363, 334 and 1.

The minimum and maximum snow-covered areas produced by MODIS in 2010 and 2013 were 107,295 and 1,364,118 ha, respectively, and for ETM+ sensor, were 128,758 and 1,090,580 ha, in 2010 and 2006, respectively. The snow-covered areas estimated by MODIS in 14 dates were more than the corresponding values for ETM+. The exception was 2011 when the snow-covered area in the ETM+ was greater than MODIS (3067 ha or 1.36%). Based on the results in 15 years, the MODIS sensor overestimated the snow-covered area equivalent to 26.95% compared to ETM+. In a small snow-covered area, deviation from the 1:1 line was small but, by increasing snow-covered area, deviation increased. The overall difference in snow pixels in the 15 years between the two sensors was 26.95%. As MODIS pixels are 500 by 500 m, and ETM+ pixels are 30 by 30 m, the size of the pixels in ETM+ resized to 500 m by resampling method in which to use same pixel size for another comparison. After resampling, the slope of the regression line slightly dropped. However, there are no-significant differences. Using data from MODIS and ETM+ sensors had a good performance to monitor spatio-temporal and map snow-covered surfaces in North Karun Basin.

Due to spatio-temporal frequency in obtaining MODIS imageries via internet freely in temporal resolution of eight-days and one-day, and also at very wide area coverage, short-time monitoring is possible for hydrological studies, forecasting and flood warning. On the other hand, the ability and better spatial resolution of ETM+, small snowy fields could be estimated and mapped better than MODIS. Although it may be need to mosaic several ETM+ imageries to cover wide areas. However, paying attention to geographical characteristics and time of the study area, end user decides to choose one or both sensor data.