Soil Conservation and Watershed Management Research Institute SCWMRI

Tehrān, Iran

Soil Conservation and Watershed Management Research Institute SCWMRI

Tehrān, Iran
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Raziei T.,Soil Conservation and Watershed Management Research Institute SCWMRI
Theoretical and Applied Climatology | Year: 2017

Monthly precipitation time series of 155 synoptic stations distributed over Iran, covering 1990–2014 time period, were used to identify areas with different precipitation time variability and regimes utilizing S-mode principal component analysis (PCA) and cluster analysis (CA) preceded by T-mode PCA, respectively. Taking into account the maximum loading values of the rotated components, the first approach revealed five sub-regions characterized by different precipitation time variability, while the second method delineated eight sub-regions featured with different precipitation regimes. The sub-regions identified by the two used methods, although partly overlapping, are different considering their areal extent and complement each other as they are useful for different purposes and applications. Northwestern Iran and the Caspian Sea area were found as the two most distinctive Iranian precipitation sub-regions considering both time variability and precipitation regime since they were well captured with relatively identical areas by the two used approaches. However, the areal extents of the other three sub-regions identified by the first approach were not coincident with the coverage of their counterpart sub-regions defined by the second approach. Results suggest that the precipitation sub-region identified by the two methods would not be necessarily the same, as the first method which accounts for the variance of the data grouped stations with similar temporal variability while the second one which considers a fixed climatology defined by the average over the period 1990–2014 clusters stations having a similar march of monthly precipitation. © 2017 Springer-Verlag Wien


Raziei T.,Soil Conservation and Watershed Management Research Institute SCWMRI | Raziei T.,University of Lisbon | Bordi I.,University of Rome La Sapienza | Pereira L.S.,University of Lisbon
Water Resources Management | Year: 2013

In the present paper, regional drought modes in Iran are identified applying the Principal Component Analysis (PCA) and Varimax rotation to the Standardized Precipitation Index (SPI) computed on different time scales. Data used include gridded monthly precipitation covering the period 1951-2007 retrieved from the Global Precipitation Climatology Centre (GPCC) archive with different spatial resolutions (2. 5, 1 and 0. 5° resolution). The objective of the study is twofold: (i) Investigate the stability of drought spatial modes as a function of the SPI time scales used for monitoring the different kinds of drought, (ii) Evaluate the impact of the spatial resolution of gridded data on drought regionalization. For the coarse spatial resolution of 2. 5°, results show four drought modes of distinct variability, which remain quite stable when the SPI time scale is varied from 1- to 24-month. Differently, for higher spatial resolutions drought modes appear more sensitive to the index time scale and become less spatially homogeneous as the time scale is increased. Moreover, the number of identified modes (sub-regions) may reduce to three or two, but in all cases the most well defined sub-region appears to be the southern one. This suggests that both the spatial resolution of precipitation data and the time scale may affect drought regionalization, i. e. the number of drought modes and their spatial homogeneity. © 2012 Springer Science+Business Media B.V.


Raziei T.,Soil Conservation and Watershed Management Research Institute SCWMRI | Raziei T.,University of Lisbon | Pereira L.S.,University of Lisbon
Agricultural Water Management | Year: 2013

Monthly data records of 40 Iranian stations distributed over the country, for the period 1971-2005, were utilized for estimation of reference evapotranspiration (ETo) using Penman-Monteith (PM-ETo), Hargreaves-Samani (HS) and FAO-PM temperature (PMT) methods. To estimate ETo with HS and PMT methods, appropriate kRs, an empirical radiation adjustment coefficient, were considered for each station, whereas Tmin was adjusted for estimation of Tdew and used only for PMT computation. It was found that the appropriate kRs for both HS and PMT methods are identical for a given station and it is generally smaller in sub-humid and humid than in semi-arid to hyper-arid climates. The performance of the PMT was further improved in both arid and humid climates when Tmin was adjusted. The result suggested that the HS and PMT methods appropriately predict ETo for all climatic regions of Iran if the appropriate kRs was utilized. However, the considered methods showed weak performances for some stations in arid and hyper-arid climates of eastern and southern Iran owing to the effect of extreme and variable wind speed inherent in the PM-ETo. Thus, the role played by wind speed in ETo estimation was examined; the result indicated that the existence of extreme winds, and also the time variability of wind speed, is responsible for the observed discrepancies between PMT and PM-ETo estimates. The spatial patterns of ETo computed with HS and PMT methods found to be identical and resemble to that of PM-ETo, all showing a gradual increasing from north to south, with the lowest ETo values observed over northern humid and sub-humid climates of Iran and larger ETo for arid and hyper-arid climates in the southern and eastern country. Results indicated that the HS and PMT methods are appropriate alternatives for estimation of ETo for all climatic regions of Iran. © 2013 Elsevier B.V.


Raziei T.,University of Lisbon | Raziei T.,Soil Conservation and Watershed Management Research Institute SCWMRI | Pereira L.S.,University of Lisbon
Agricultural Water Management | Year: 2013

Monthly averages of maximum and minimum temperature, mean relative humidity, sunshine duration and wind speed at 2m height, relative to 148 Iranian weather stations and period 1991-2005 were utilized for interpolation and gridding the variables to 1̊ in latitude and longitude. The Ordinary kriging method was used coupled with a spherical isotropic variogram. Monthly precipitation of the APHRODITE dataset was regridded to the same mesh grid for computing the aridity index jointly with the gridded variables. The required elevation for estimation of ETo at each grid node was extracted from the digital elevation map of Iran. The adequacy of gridded variables was proved through a set of statistical indicators applied to the cross-validated interpolation errors. The Penman-Monteith (PM-ETo) reference evapotranspiration (ETo) was estimated using the gridded variables and statistically compared with those of observational datasets relative to some stations covering all climatic regions of Iran. Results indicated that the PM-ETo computed using gridded variables well fitted the PM-ETo computed using observed full weather variables at those selected stations. ETo was also estimated by the Hargreaves-Samani (HS) and FAO-PM temperature (PMT) methods using gridded variables of minimum and maximum temperature (Tmin and Tmax). To estimate ETo with HS and PMT methods, appropriate kRs, an empirical radiation adjustment coefficient, were considered for each station, whereas Tmin was adjusted for estimation of the dew point temperature (Tdew) used for PMT computation. It was found that the appropriate kRs for both HS and PMT methods are identical all over the country and they are smaller in dry-sub-humid to humid areas and higher in semi-arid to hyper-arid climates. The result suggested that the HS and PMT methods appropriately predict ETo all over Iran if the appropriate kRs are utilized. The spatial patterns of ETo computed with HS and PMT methods found to be identical and resemble to that of PM-ETo, all showing a gradual increasing from north to south, with the lowest ETo values observed over northern humid and sub-humid climates of Iran and larger ETo for arid and hyper-arid climates in the southern and eastern country. Results indicated that the HS and PMT methods are appropriate alternatives for estimation of ETo for all climatic regions of Iran, either when using observation or gridded data. © 2013 Elsevier B.V.


Samadi S.,University of South Carolina | Carbone G.J.,University of South Carolina | Mahdavi M.,University of Tehran | Sharifi F.,Soil Conservation and Watershed Management Research Institute SCWMRI | Bihamta M.R.,University of Tehran
Water Resources Management | Year: 2013

Linear and non-linear statistical 'downscaling' study is applied to relate large-scale climate information from a general circulation model (GCM) to local-scale river flows in west Iran. This study aims to investigate and evaluate the more promising downscaling techniques, and provides a through inter comparison study using Karkheh catchment as an experimental site in a semi arid region for the years of 2040 to 2069. A hybrid conceptual hydrological model was used in conjunction with modeled outcomes from a General Circulation Model (GCM), HadCM3, along with two downscaling techniques, Statistical Downscaling Model (SDSM) and Artificial Neural Network (ANN), to determine how future streamflow may change in a semi arid catchment. The results show that the choice of a downscaling algorithm having a significant impact on the streamflow estimations for a semi-arid catchment, which are mainly, influenced, respectively, by atmospheric precipitation and temperature projections. According to the SDSM and ANN projections, daily temperature will increase up to +0. 58 0C (+3. 90 %) and +0. 48 0C (+3. 48 %), and daily precipitation will decrease up to -0. 1 mm (-2. 56 %) and -0. 4 mm (-2. 82 %) respectively. Moreover streamflow changes corresponding to downscaled future projections presented a reduction in mean annual flow of -3. 7 m^3/s and -9. 47 m^3/s using SDSM and ANN outputs respectively. The results suggest a significant reduction of streamflow in both downscaling projections, particularly in winter. The discussion considers the performance of each statistical method for downscaling future flow at catchment scale as well as the relationship between atmospheric processes and flow variability and changes. © 2012 Springer Science+Business Media Dordrecht.


Sharifi F.,Soil Conservation and Watershed Management Research Institute SCWMRI | Samadi S.Z.,University of Cardiff | Wilson C.A.M.E.,University of Cardiff
Natural Hazards | Year: 2012

In August 2001, the worst flash flooding event of the Caspian Sea regions in over two centuries claimed over 300 lives after a weekend of heavy rainfall and brought about a devastating disaster in the Mother-Soo catchment, province of Golestan, Iran. As a result of this event, a series of site investigation were carried out to identify the pertinent factors that led to a flood of this magnitude. This paper identifies the fundamental causes of the frequent floods and debris flow occurrence in the area prone to flooding and analyzes the main runoff mechanism of these events. The maximum observed 24-h rainfall depths and maximum peak discharges at the existing gauges were compared with the depths of rainfall and the peak values corresponding to the August 2001 flood respectively. For the majority of the rain gauges, the rainfall depth exceeded those of historical recorded events. In Golestan dam, an increase of 7. 5 times the maximum value observed in the past 20 years was noted. The flood height was 10-15 m while passing through the middle subcatchment area of Golestan National Park. The preliminary evaluation indicates the existence of bare soil in the catchment, movable material, steep slopes, high rainfall intensity, deterioration of pasture and forest land, and inappropriate agriculture and development practices as well as climate change were the main factors for the occurrence and the extent of the August 2001 disaster. Finally, due to the likelihood of flooding and debris flow events in future, some countermeasures are proposed. © 2011 Springer Science+Business Media B.V.


Saadat H.,McGill University | Adamowski J.,McGill University | Bonnell R.,McGill University | Sharifi F.,Soil Conservation and Watershed Management Research Institute SCWMRI | And 2 more authors.
ISPRS Journal of Photogrammetry and Remote Sensing | Year: 2011

Accelerated soil erosion, high sediment yields, floods and debris flow are serious problems in many areas of Iran, and in particular in the Golestan dam watershed, which is the area that was investigated in this study. Accurate land use and land cover (LULC) maps can be effective tools to help soil erosion control efforts. The principal objective of this research was to propose a new protocol for LULC classification for large areas based on readily available ancillary information and analysis of three single date Landsat ETM+ images, and to demonstrate that successful mapping depends on more than just analysis of reflectance values. In this research, it was found that incorporating climatic and topographic conditions helped delineate what was otherwise overlapping information. This study determined that a late summer Landsat ETM+ image yields the best results with an overall accuracy of 95%, while a spring image yields the poorest accuracy (82%). A summer image yields an intermediate accuracy of 92%. In future studies where funding is limited to obtaining one image, late summer images would be most suitable for LULC mapping. The analysis as presented in this paper could also be done with satellite images taken at different times of the season. It may be, particularly for other climatic zones, that there is a better time of season for image acquisition that would present more information. © 2011 International Society for Photogrammetry and Remote Sensing, Inc. (ISPRS).


Raziei T.,Soil Conservation and Watershed Management Research Institute SCWMRI | Mofidi A.,Ferdowsi University of Mashhad | Santos J.A.,Royal University | Bordi I.,University of Rome La Sapienza
International Journal of Climatology | Year: 2012

The relationships between large-scale atmospheric circulation types and seasonal regimes of daily precipitation over Iran are assessed using daily precipitation from a high-resolution gridded dataset provided by the Asian Precipitation-Highly Resolved Observational Data Integration Towards the Evaluation of Water Resources (APHRODITE) Project. Regional spatial modes of daily precipitation variability were identified by S-mode Principal Component Analysis (PCA) with Varimax rotation, applied to the subset of days when at least 10% of all grid-points over Iran received precipitation ≥ 5 mm. The study refers to the period 1961-2004 and is carried out for each season (excluding summer) separately. To characterize the dynamical features associated with each regional precipitation regime (PR), composites of daily atmospheric fields are computed by only averaging days with rotated PCA scores ≥ 1.5 (strong positive phase). In autumn and winter, Iran is divided into five PRs, while four PRs are identified in spring. Results suggest that the spatial distribution of precipitation over Iran is largely governed by the geographical position of both the mid-tropospheric trough over the Middle East and the Arabian anticyclone. In fact, in almost all PRs, the trough, as a pre-conditioning factor, leads to regional-scale ascending motions, whereas the Arabian anticyclone induces low-tropospheric moisture transports from southern water bodies into the cyclonic systems near Iran, triggering rain-generating conditions. © 2011 Royal Meteorological Society.


Heydarian S.A.,Soil Conservation and Watershed Management Research Institute SCWMRI
Irrigation and Drainage | Year: 2013

Irrigation management transfer (IMT) has already been implemented in over 60 countries. The project has faced different challenges and achieved various results in each country. Use of global experience in implementing IMT projects is highly recommended. Considering that the success of IMT is affected by various parameters, the present study has been conducted with the aim of finding the key indicators and strategic issues on the local, national and global levels. For this purpose, the data from four studies already carried out by the author (and his colleagues) on the local (the Moghan and Qazvin irrigation networks in Iran) and national scale (Iran) as well as global research by the Food and Agricultural Organization (FAO) were used. Currently Iran is at the rudimentary stages of IMT, and the two selected pilot studies deal with distinctive social and organizational features, operation time, irrigation method, physical status, conducted method and duration of IMT. The method of the study is descriptive correlation and the sample society consists of farmers on the pilot level and experts on the national level. The results reveal that the indicator of 'clarity on roles, responsibilities and authority of public sectors' has a low score. Although the effects of neglecting the said indicator are clearly manifest on the local level, and global experience has already established the fact, the significance of this indicator is not greatly recognized on the national level because of the limited IMT experience and simplicity-minded strategies in Iran. Key factors such as 'pilots, study tours and information sharing significance', 'severe deterioration of infrastructure' and 'financial capacity of water users' associations (WUAs)', on the other hand, are more important on the national level. This study enabled the author to develop an initial strategic framework for better utilization of the related experience in the field of IMT. © 2013 John Wiley & Sons, Ltd.


Nikkami D.,Soil Conservation and Watershed Management Research Institute SCWMRI
Turkish Journal of Agriculture and Forestry | Year: 2012

Significant errors when sampling from collection tanks installed at the lower end of soil erosion plots may lead researchers toward wrong conclusions. Limited research has been found on sampling accuracy. In this study, a cylindrical sampler is introduced as a new sampling device and its sampling accuracy is investigated and compared with 2 other manual methods, namely bottle and pipette. Three target sediment concentrations were prepared in separate 213.5-L collection tanks as 3 replications with 3 mixing periods. The results using the bottle and pipette in all mixing periods and all target sediment concentrations showed that the concentration of sediment increases with the depth of the tank, which implies that making a uniform sediment concentration in the collection tank for sampling is impossible. The results indicated that the cylindrical sampler had the highest sampling efficiency of 88.68%. Computed sampling efficiencies in tanks of 20, 40, 60, and 80 cm in depth were 34.76%, 43.94%, 54.45%, and 67.21% for the bottle and 34.58%, 43.05%, 49.20%, and 56.42% for the pipette, respectively. The ere was no significant difference between sampling from the center and from the side of the collection tank and among mixing periods of 1, 2, and 5 min. In order to maximize the accuracy of the sampling, a 10-L bucket was placed in the collection tank to trap the coarse material. Weighing collected coarse material and adding the sampled part improved the accuracy by 9.45%. In fact, using a cylindrical sampler and a bucket together resulted in 98.13% sampling accuracy. © TÜBİTAK.

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