مجله مهندسی و مدیریت آبخیز
سال دهم شماره 4 (زمستان 1397)

Rainfall erosivity factor is the first noticeable point in soil erosion issues that plays very important role in detachment of soil particle from the origin bed. Hence, investigation of rainfall erosivity factor trend is necessary in decision-making and planning in order to manage soil and water resources. However, studies on various aspects of erosivity like trend and in interaction with precipitation and SPI index have not been attended well. The present study therefore aimed to investigate the rainfall erosivity factor trend based on the Fournier index in 28 stations throughout North-Khorasan Province during the period of 1987 to 2006 by using the Mann-Kendall test. In addition, the SPI and precipitation trend were comprehensively investigated for better characterization of erosivity trend analysis. Results showed that Noushirvan, Faruj, Ayerqayeh and Gholaman stations had decreasing trend and other study stations (71.85%) had increasing trend in the modified Fournier erosivity index. The SPI and precipitation in the study area indicated that most of the stations (89.28%) excluding Khartot, Noushirvan, Faruj and Ayerqayeh had increasing trend. The maximum and the minimum values of modified Fournier erosivity index with 70.97 and 33.44 mm were also assigned to Darkesh and Abiary Bojnourd stations, respectively.

Determination of time to runoff and runoff volume in watershed response management against rainfall are the key parameters in watershed system management. Among different factors of effect on time to runoff and runoff volume, the rainfall intensity is one of the most important factors. In this study, the effect of rainfall pattern on variables of time to runoff, runoff volume and coefficient was studied under simulated rainfall in the southeastern Noshahr city, Mazandaran province. To achieve the study purposes, four rainfall patterns, each with three changes in rainfall intensity (I: Low-Medium-High, II: Low-High-Low, III: High-Medium-Low, IV; High-Low-High) were simulated. Then, the time to runoff, runoff volume and runoff coefficient were measured for each rainfall pattern. The measured data were analyzed in Excel and SPSS 23 softwares to determine the relationship between the rainfall pattern and variables of time to runoff, runoff volume and runoff coefficient. The results showed that there was a significant difference (P≤0.05) in variables time to runoff, runoff volume and runoff coefficient resulted rainfall patterns. Also the results showed that, in all of rainfall patterns between mean amounts were the significant differences on time to runoff, runoff volume and runoff coefficient in level of 99 percent. The results showed that the rainfall pattern I had the longest time to runoff and rainfall pattern III had the largest amounts of runoff volume and runoff coefficient. The average time to runoff in rainfall patterns of I, II, III was 5.90, 4.24, 0.71 and 1.25 min, respectively. Also, the average runoff coefficient in rainfall patterns of I, II, III and IV measured 30.03, 49.63, 88.82 and 75.16 percent, respectively.

Banketing and artificial afforestation are effective processes for soil carbon storage and removal of carbon from the atmosphere. In this research, land use change and its effects on carbon storage has been studied in Pakal Basin in Markazi Province. Rangeland was selected as a witness for comparing soil carbon storage with areas with banketing operations and planted with almonds (biomechanical activity) . Soil was sampled on transect and plot in systematic random samplingFor this purpose, three plots were used randomly, along each transect. Soil samples of one kilogram were taken from 0-15 and 15-30 cm depth of each plot. . Soil physico-chemical properties such as bulk density, organic carbon and soil texture were analyzed. Resalts showed that total carbon stored in the soils of bio-mechanical operation is 33.65 t.ha-1 from which 30% belongs to above and underground biomass, 2% litter,38.9% in the depth of 0-30 and 29.1% in the depth of 15-30 cm. Also, the the results showed theamount of soil organic carbon of 30.16 t.ha-1 in witness area from which 4% belongs to above and underground biomass, 3% litter, 62% in the depth of 0-15 and 31% in the depth of 15-30 cm.. As a result, biomechanical operations are more effective in carbon sequestration compared to rangelands as witness areas.

Due to lack of surface water, the most important option for water supply in arid and semi-arid areas is from groundwater resources and one of the engineering measures to use the floods for improving groundwater resources is the implementation of artificial recharge systems. The purpose of the present study is to provide a model-based framework based on several quantitative indicators such as recharge efficiency and flood attenuation rate for assessing the performance of artificial recharge systems. Considering the capabilities of hydrological, hydraulic and seepage models, the combination of these models was used to estimate the parameters of the indicators. Finally, by determining the indices for floods with different return periods, their average values were determined using the expected value. The studied system (Emamzade Abdollah, Sorkheh) had a good performance based on recharge efficiency and flood attenuation rate indicators in events with frequency of more than 0.2, and the average value of these two indicators was 0.54 and 0.93, respectively. Due to the model based characteristic of the proposed framework, it has the potential to be used in similar cases.

Investigation of drought event has a great importance in the natural resources management and planning water resources management. In this research, the drought characteristics in the selected synoptic stations in northwest of Iran, including Ardebil, Khoy, Oroomieh, Tabriz, Zanjan, Sanandaj and Saghez were investigated using the Deciles Index. First, after rebuilding monthly missing data in the period of 1977-2014, time series of precipitation in each station normalized using Box-Cox Transformation. Then, the Deciles Index in different time scales of monthly, seasonal and yearly was calculated based on the normalized monthly precipitation of stations in the period of 1977-2014 by MATLAB and DIP softwares. Then, the drought characteristics, including intensity, duration and frequency were calculated in each synoptic station. In this research, to find the trend of precipitation in the 38 years, 1977-2014, First, trends of the selected stations were determined using Mann-Kendall trend test at the different time scales of the 19 year period, 1977-1995, then compared with trend of the 38 years and finally, determined the changes of the mean precipitation values in two subsequent periods, 1977-1995 and 1996-2014. Obtained results show that the mean annual precipitation at the all stations was decreased in the second period than base period. The results also show that the drought occurrence with different intensity, duration and frequency occurred in selected synoptic stations in northwest of Iran. The results also indicate that there is the decreasing trend of precipitation at the synoptic stations of Saghez and Sanandaj in yearly time scales. Although the stations of Saghez and Zanjan have no trend in the period of 1977-1995, they have decreasing and increasing trends in some time scales in the period of 1977-2014.

River bed materials are of great importance in construction works as one of the most valuable resources due to their economical costs and ease of extraction. This has caused the rivers to be subjected to profound changes due to excessive, improper and non-standard harvesting by effective activities of human apart from their natural changes. Hence, replacement of river resources with other resources such as mountain mines can be considered as an essential way to protect the rivers. Considering the importance of this issue, the present study has evaluated the potential of sediment production and delivery in Qaen and Ferdows’ rivers sub-basins using a combination of GIS and geomorphological models. The results obtained from the studied basins indicated that the geomorphologic models are capable of identifying areas susceptible to sediment production. According to calculations performed by the geomorphologic model, the southern and south-western parts of Ferdows and northern parts of Qaen Basins in Southern Khorasan Province have good potential for harvesting. Moreover, sediment quality assessment showed that most of materials in these areas are coarse grains and therefore require far less processing.

Historically, flood control and artificial recharge are one of the most important objectives in spreading in arid and semi-arid systems. Therefore, determining suitable locations for floodwater spreading systems based on different criteria and indicators is of great importance. In this study, seven information layers (slope classes, runoff volume, transmissibility in alluvium, thickness of unsaturated zone, surface infiltration rate, quality of water and land use) were combined in GIS using AHP model and weights of each factor were determined based on membership function of each responsible factor. Then AHP map of each factor was incorporated to have the flood spreading map based on the most susceptible AHP model. The results indicated that land use (39%) was the most important criterion in suitable location mapping for floodwater spreading and runoff volume, slope classes, surface infiltration rate, thickness of unsaturated zone, transmissibility in alluvium and quality of water were in second to seventh order. The results of integration of maps showed that 70% of the study area is suitable for flood spreading.

The human interventions role, particularly land use changes, is investigated in this research in Kor River hydromorphologic state (upstream of Dorudzan Dam, Fars). Within the steps of this research, there are discrete methods frameworks such as hydrologic model using HEC-HMS, to investigate the effect of land use changes on flood characteristics and Rosgen geomorphologic evaluation model to investigate the effect of land use changes s on environmental resources and geomorphologic changes of the river. Results of hydrologic studies by HEC-HMS indicated that in the studied time interval, the number and the value of peak discharges are increased and the delay time and concentration time are reduced. Through simulation results for 1993-2013, this indicated that land use changes have increased the amount of flood discharge by 15% in this region and these findings are corresponds with observed floods. The results of Rosgen geomorphologic evaluation model, indicated that during studied time interval, maximum hydromorphologic changes in level 1 and 2 of Rosgen model were related to spatial ranges 1 and 2 and then ranges 4, 5 and 3 followed. In all studied spatial intervals, there are numerous transversal and longitudinal changes due to erodible boundaries and maximum changes are related to 2, 1, 3, 4 and 5 spatial intervals, respectively. The transversal changes were due to slope change, hydrologic regime, suspended and bed load, aggression to riparian lands and constructing dams.

A side weir is a structure which is set in a side of main channel and used for discharge of additional flow, diverting excess water and water level control of channels and in irrigation and drainage systems. Due to difficulties presented in mountainous regions, lateral ‘piano key weirs’ could be used in arc-shaped channels. In addition, curved channels, which are commonly used in mountainous areas, are places that can be used to locate the side piano key weirs. In this research, experimental investigation was performed on side piano key weirs type B, type c and sharp crest side weir on flow in the 30 degree curved channel. Among the findings of the above survey, one could point out to the equality of the specific energy on the two edges of piano key lateral weirs, the changes of which equal 0.277% for type C piano key lateral weir and 1.98% for type B weir. Also, focusing on the empirical analyses, it becomes evident that the coefficient of discharge for piano key weir bears a higher quantity considering the more effective length corresponding to rectangular weir. Comparing the coefficient of discharge of the two weir types C and B, it becomes evident that type B weir has a better functioning in relation to type C.

In mountainous watersheds, snow melt can have a significant impact on the water balance and at certain times of the year it could have the most important contribution to runoff. In many parts of the world snow acts as a natural reservoir that can play an important role for water supply. Specifically, high-altitude basins in semi-arid regions with a significant snow component can have a large capability to balance and distribute scarce water resources. In this study the spatially distributed process-oriented hydrological model J2000g was used for the 431 km² large Latyan catchment in Iran. The target was to derive spatially distributed estimates of the quantity and timing of hydrological balance terms and state variables like rainfall, runoff, snow water equivalent (SWE) and snow melt. The model uses the distribution concept of Hydrological Response Units (HRU) to take the spatial variability in the basin into account. The comparison of the separate SWE models resulted in values between 0.28-0.68 for NSE and values between 0.53-0.83 for R². For the catchment models the comparison of the simulated runoff with measured data showed NSE values between 0.78 and 0.82. By these values it can be stated that the hydrological dynamics and the snow processes of the sub-basins within the Latyan catchment could be simulated sufficiently well with J2000g. It can be summarized that the single modules and in particular the snow components of J2000g along with the HRU distribution approach can be considered as suitable for the given project objectives i.e. the assessment of the hydrological dynamics of the Latyan catchment. Hereby, the model can be used to elaborate important hydrological information for a sustainable management of the water resources.

Evaporation as a natural parameter due to the release of water from the upper part of mankind has always been of interest to scholars and researchers. In this study, we try to apply the artificial neural network model to estimate evaporation from the Amir Kabir dam and to evaluate the model accuracy. In this context, 18 years data from 1997 to 2014 were used and after consecutive try and error, the best structure for computing the amount of evaporation from the surface of the dam was selected. This structure has five neurons in the first, fourth and second layers that showed the best result in 1000 replications. Also, statistical coefficients obtained from the analysis using artificial neural network was considered in choosing the best structure with the amount of 0.9365 which was the highest amount among other tests and the amount of test and training data error were 0.0321 and 0.0311, respectively. In addition, general trend of effective data on evaporation was determined, using Mann-Kendall test on 15 years daily data. In Mann-Kendall method, temperature changes, wind speed and precipitation graphs had no significand trend and showed -1.69< U

Watershed planning and management of water resources requires various data including base flow and its index. This parameter is influenced by Morphometric, geologic, hydrologic and climatologically factors and has always been one of the most important issues in hydrology. In this research, the Domarton method was used to map the climate of Iran with the use of temperature and precipitation data. Then, using daily stream flow data and after controlling for time series, base flow and related index, using two parameter the recursive digital filter were extracted in selected catchments of six climatic zones including; arid, semi-arid, humid and semi-humid and very wet and Mediterranean. Hydrological and climatically parameters of the basins measured and physiographic factors were extracted in the digital environment. To identify independent factors affecting base flow, factor analysis were down using 14 parameters in each climate zone and then effective factors were analyses. The results showed that more than 80 percent of the variance of parameters was explained by selected parameters. The intrinsic factors related to the penetration and retention of water in all climate zones are in the first importance order with the weight more than 45 percent. Flow duration curve indices in very humid, humid, semi-humid and semi-dry climatic zones respectively with 45, 53, 52, and 53 percent and in the dry and Mediterranean climate zones parameter of storage capacity, Respectively with 49 and 58 percent have the greatest influence over the base flow. The results showed that the weight of the factors affecting base flow, vary depending on the type of climate.

Erosion is always a major concern for farmers, engineers and policy makers due to economic and environmental impacts. Slope is one of the most important indicators on soil erosion, therefore, the aim of this study is investigation of slope steepness and its aspect on sediment and surface runoff on Gonbad Watershed located in Hamadan, Iran. To this regard, three standard experimental plots installed at southern, northern, and eastern aspects of the basin. The plot dimensions were 1.8×24 meters installed in the relatively uniform slope with different values. Runoff and its sediments were collected in spatial containers. 16 rainfall events (2010-2013) were sampled. Effect of slope steepness, its aspect as well as their interactions were analysed using a factorial experiment by SAS 9.4 software. Results indicated significant roles of slope, its aspect and their interactions in surface runoff volume. Based on the results, small slope has carried out slope steepness significantly on runoff rate, that have more significant effect on smallest steep compared to higher steepness. This is because of land use and vegetating cover and also higher average infiltration rate as well as the recent soil moisture content on the high steep. This is important to note that the slope steepness have not significant effect on runoff sediment rate. The aspect also has significant effect just on 6.25% of the events. The interaction of slope steepness and its aspect also was significant on 18.75% of the events.

On areas with highly eroded soils, where vegetation is absent or negligible, runoff generation and erosion processes can greatly be affected by the nature of parent material. This research was carried out to investigate the effects of lithology and soil parent material on erosion and soil loss, using rainfall simulator in Sangerd Drainage Basin which is located in Khorasan Razavi Province. To do this research, 11 homogeneous soil units (map units) with the same slope (20%), land use (rangeland), different lithology (marls and conglomerate) and erosion facies (sheet-rill, rill and rill-gully) were selected. A rainfall simulator producing 36 mm h-1 rainfall intensity and 30 minute duration was used at 33 locations over soil erosion plots. The amount of sediments was measured. In order to investigate factors affecting on soil erosion and sediment yield, soil was sampled from 0-15 cm depth of plot adjacent areas. For statistical analysis, SPSS 22 was used. Results showed that soil erosion and sediment yield have meaningful differences in different lithologies. Eem-RG and Plc-SR soil units with 260.9 and 45.1 gr m-2 have the most and the least sediment yield, respectively. It was found that the sediment yield had positive correlation with some soil properties such as silt, Ec, pH, SAR and antecedent soil moisture and negative correlation with sand, OC, NPV, vegetation and rock fragment cover.

In this study, marls ofsouth of Hassan Abad and Varamin in Tehran Province, including the marls of Upper Red Formation unit M3 and Pliocene marls of unit Plm in slopes of five5, 20 and 40 percents were evaluated in terms of shape and intensity of erosion, physical, chemical, engineering and dispersion features. Accordingly, 20 samples were taken from mentioned marl formations. To achieve predetermined goals, granulometry, Atterberg limits, chemical analysis such as cations and anions, SAR, TDS, EC and double hydrometery and pinhole were tested. Results of double hydrometery tests on 18 samples indicated that only three have low dispersion degree Which are related to marls of unit M3 in undisturbed samples of station 1 with the form of gully erosion, station 2 with 40% slope and surface erosion and station 5 with 5% slope and channel erosion. According to the pinhole test, from 17 samples, 12 samples were classified as non dispersive and five samples as low to moderate dispersive classes. In this test, the majority of the samples with channel erosion and some samples with gully erosion showed low to moderate dispersion rate. Other erosion forms such as surface and rill erosion showed non-dispersive behavior. Based on chemical properties of the Total Dissolved Solids (TDS) and Sodium Percentage (PS), in Casagrande chemical graph, the majority of samples are clssified as dispersive soil, one sample with surface erosion in the boundary of dispersion and one sample with rill erosion as dispersive with the probability of 50%. In modified Sherard chemical method, all samples are classified as non dispersive soils. These results have no conformity with other physical and chemical methods so this classification is not acceptable. African chemical method showed better results compared to other chemical methods. In this method, half of the samples were classified as dispersive and the other half as non-dispersive. According to chemical and physicalstandards, dispersion phenomenon has been seen in all forms of surface, rill, gully and channel erosion. It has been concluded that marl soils are potentially dispersive under the influence of chemical and physical factors, even if they show surface and rill erosion forms, at the time of sampling. In other words, if the necessary conditions such as slope sleepness and runoff concentration occure in these soils, surface and rill erosion forms can be developed to dispersive forms such as channel and gully erosion types.

Dust storm is a meteorological phenomenon which is common in arid and semi-arid regions. Dust storms are also one of the environmental concerns in Iran. There are different methods to control this phenomenon which some of them have limitations. Application of mulches is one of the ways to control and prevent dust storms. This study, aims to evaluate the behavior of biological, chemical and mineral mulches during one week in laboratory conditions and six months to stabilize the source of dust storm and improve the persistence of these mulches in Ilam Province. In order to study dust storm stabilization by these mulches, different tests were carried out including wind tunnel test, light and temperature stress effect on strength, pressure resistance, aggregate stability and soil loss. Wind erosion resistance determined in laboratory conditions by wind erosion simulation in 25 m s-1 for 15 minute of each treatment for both, one week and six months. According to the results, strength, pressure resistance, aggregate stability and wind tunnel simulation, three formulation of F4, F13 and F14 (zantan polymer-calcium carbonate, polyvinyl acetate-calcium carbonate and zantan-polyvinyl acetate) were recommended for stabilization of dust storm in Ilam Province. Generally, for soil stabilization suitable formulation based on climatic, soil physical and chemical properties are needed for each region.

Various factors such as rainfall intensity and slope affect hydrological processes such as infiltration and runoff. Study on rainfed soils is very important because of intense degradation and sensitive ecosystem. The present research was conducted to investigate the effect of rainfall intensity and slope gradient on infiltration and surface runoff using rainfall simulator in rainfed lands of Kalaleh region, Golestan Province. To achieve the study purposes, four rainfall events with the intensities of 33, 64, 80 and 110 mm hr-1 and duration of 15 min were simulated. Three slope gradients of 6, 12 and 25% were selected and infiltration and surface runoff were measured in four 25×25 cm2 plots. The results showed that the infiltration average rate and runoff average coefficient were increased with increasing rainfall intensity and slope gradient. The main and interaction effects of rainfall intensity and slope gradient on infiltration and surface runoff were significant (p≤0.01). The results of subgroups of rainfall intensity and slope gradient using Duncan test showed that two turning points in hydrological response of plot are distinguishable, one between rainfall intensities of 64 and 80 mm hr-1 and another between slope gradients of 12 and 25%. In other words, at the rainfall intensity more than about 70 mm hr-1 and the slope gradient more than about 15%, average infiltration rate and average runoff coefficient were significantly decreased and increased, respectively. These results emphasized on land use management via avoiding change from rangeland to rainfed land especially when the slope is more than 15%. Agricultural and land cover management was also emphasized especially in high rainfall intensities (more than 70 mm h-1).

Gully erosion is an important challenge in natural resource management and sustainable development that often has severe environmental, economic, and social consequences. Thus, the objective of the present study is to assess the capability of maximum entropy (ME) model for spatial prediction of gully erosion susceptibility at Kashkan-Poldokhtar Watershed, between Lorestan and Ilam provinces, Iran. At first, a gully erosion inventory map was produced using GPS in field surveys. The gully conditioning factors including lithology, soil texture, land use, drainage density, distance to streams, topographic wetness index, altitude, slope percent, slope aspect, plan curvature, and distance from road were selected, and their maps were prepared in geographical information system (GIS). A total of 65 gully locations were divided into two groups (1) training of the model (45 gully occurrences), and (2) validation of the model (20 gully occurrences). The prediction of gully susceptibility and variables importance analysis were carried out based on maximum entropy model using MAXENT software. Finally, the validation of the prediction results was conducted based on the receiver operating characteristic (ROC) curve method, and the area under the curve (AUC) was calculated using MedCalc software. Results indicated that highest gully erosion susceptibility is located on the center parts of the study area. According to validation results, the resulting map of areas susceptible to gully erosion obtained by ME model has a prediction accuracy of 90.7%. In addition, the results demonstrated soil texture, drainage density, lithology, and distance to streams are most important factors and their variable importance index (VII) 23, 18, 15.2, and 15.1 were obtained, respectively. However, altitude, distance from road, slope aspect, land use, topographic wetness index, and plan curvature have a less influence on gully erosion occurrence. Therefore, it was established in current study that the ME is promising of make accurate prediction in gully erosion susceptibility.

Zayandeh Rood Basin has a vital role in Iran's poetry, biomass, agriculture, industry and tourism, faced with drought problems. Clustering approach can be a management approach to reduce drought risk impacts which groups the members with regard to the division based on the Euclidean distance of stations. In this research, the approach of determining the spatial-temporal distribution of drought clusters in watersheds is used to express variations based on precipitation precipitation index (SPI) parameters of stations, which depends on the probability of precipitation for any time scale. Since the maximum spatial distribution of the meteorological stations in the region and the maximum time period of the long-term and possible long-term statistical period were considered the same, the data of 26 stations from 12 years (2003 to 2014) was used as reference data. In this regard, the12 months SPI index was first calculated. Then, the 12-month SPI index, which ended in December, was used for cluster analysis of the SPI, and then 144 data were clustered into four groups. Further, zoning analysis was performed on data clusters. Then, the relationship between elevations as an effective landform factor in drought with SPI drought index cluster was investigated using correlation of variables. SPI correlation with mean height of each cluster stations was studied and the results were compared and analyzed. The results of the SPI drought fluctuation chart showed a very severe drought in 2008 and 2009 and 2010, and severe drought in 2010 and mild drought in 2003, 2005 and 2013. Also, 12-month SPI drought data showed a high and negative correlation with height data. Consequently, spatial-temporal monitoring of drought indicators clusters is recommended as a way to manage the impacts of drought risk.

Flood spreading is an effective way to increase the groundwater level, rectify the critical conditions of groundwater, and prevent flooding at Naeim-Abad, Fars Province. The most important step in the successful implementation of artificial recharge is the selection of recharge areas in the studied region. In this research, the GIS technique and Analytical Hierarchical Process (AHP) method have been used. We considered nine factors–land, slope, and distance from the road, altitude, thickness of the alluvium, distance from the stream, surface permeability, land use, and fault for analysis in this research. Each layer was prioritized using the AHP method and the different layers were integrated. Expert Choice software was used to prioritize nine considered factors. The results showed that 3.6% of the Naeim-Abad area was suitable for flood spreading based on the AHP method and GIS technique. In this research, hydrologic factors with a weight of 0.687 had the most impact among the main criteria for locating areas prone to flood spreading. Among the sub-criteria of this criterion, surface permeability with a weight of 0.558 had the greatest influence. In addition, the sub criterion of land use was weighted equal to 0.701, which had the highest weight among the sub criteria. The lowest weight among the sub criteria was attributed to the distance from the road with a weight of 0.106, which indicated the least influence on locating suitable areas for flood spreading.