Reza Chamani; Mehdi Vafakhah; Seyyed hamid reza Sadeghi
Abstract
Today, drought has become one of the hot topics of global concern, but its impact on the provision of services and functional health of watersheds in the face of this natural disaster has been less evaluated. Accordingly, in this study, the effect of drought on the Efin Watershed health has been evaluated ...
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Today, drought has become one of the hot topics of global concern, but its impact on the provision of services and functional health of watersheds in the face of this natural disaster has been less evaluated. Accordingly, in this study, the effect of drought on the Efin Watershed health has been evaluated based on changes in Reliability (Rel), Resilience (Res) and Vulnerability (Vul) indicators in the period 2005-2019. Based on this, the rainfall data of three rain gauge stations were interpolated using Inverse Distance Weighting (IDW) for the watershed and sub-watersheds. Standardized Precipitation Index (SPI) was then determined based on the mean and standard deviation of monthly data and was used to calculate the Rel, Res and Vul indicators. Finally, the overall health status of the watershed was determined by calculating the geometric mean of these indicators. The annual results showed that Efin Watershed in terms of Rel, Res and Vul indicators extends between 0.83-0.92, 0.17-0.33 and 0.24-0.54, respectively. The RelResVul index also has values between 0.37-0.53. The average watershed health indicator in this period was also calculated to be 0.42, which indicates mean watershed health condition. Spatial variations of watershed health also showed that Rel, Res and Vul indicators fluctuated between 0.85-0.86, 0.21-0.24 and 0.76-0.78 in different sub-watersheds. The results of rainfall analysis of the region, indicate that due to the relative stability of rainfall, the impact of human intervention and intensification of watershed health threatening factors, more than ever effect on the current situation and if not addressed will have harmful effects.
Bromand Salahi; Mahnaz Saber; Abbas Mofidi
Abstract
In this study, the perspective of reference crop evapotranspiration (ETo) in the southern part of the Aras River Basin under climate change condition was drawn using SDSM downscaling. For this purpose, meteorological data of selected synoptic stations located in this basin were used and after receiving ...
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In this study, the perspective of reference crop evapotranspiration (ETo) in the southern part of the Aras River Basin under climate change condition was drawn using SDSM downscaling. For this purpose, meteorological data of selected synoptic stations located in this basin were used and after receiving the downscaling outputs for the parameters required for estimating ETo by Penman-Monteith FAO-56, basin ETo was calculated for the near future (2021-2050). In this regard, daily reanalysis NCEP data and station daily data include: maximum and minimum temperature, wind speed, relative humidity and sunshine hours as well as output data on CanESM2 model under RCPs scenarios were used to generate future station data for estimate Aras Basin ETo. The studied stations included: Ahar, Ardabil, Parsabad, Jolfa, Khoy and Makoo and the base period for the data was considered 1985-2005. First, the efficiency of SDSM in simulating the parameters required for ETo estimation was evaluated by comparing NCEP simulated data with station data. Their comparison indicated the appropriate performance of the model in simulating data. Therefore, climatic parameters were simulated using the CanESM2 model under RCPs scenarios for the future. After calculating their monthly values, in CROPWAT was entered to estimate the basin ETo and trend of the variable for the next three decades were calculated. The results showed that the basin ETo in the future period compared to the base period will increase by an average of about 7 mm per year. In terms of stations, there will be an increase in Parsabad (102 mm) and Jolfa (66 mm). This increase also means an increase in the water needs of plants. Also, the future trends of ETo in Khoy, Makoo, Ahar and Ardabil will be decreasing.
Rahim Kazemi
Abstract
During the last two decades, there has been a lot of research on the base flow issue in the country, but so far, no comprehensive and specific article review of base flow research has been conducted, untill the various aspects of this issue be identified and the cases ignored, be introduced and addressed. ...
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During the last two decades, there has been a lot of research on the base flow issue in the country, but so far, no comprehensive and specific article review of base flow research has been conducted, untill the various aspects of this issue be identified and the cases ignored, be introduced and addressed. In this research, first, by literature review at the global and national level, the progress of studies in different fields of this issue were investigated and then dissertations, articles and reports published in international journals and related conferences have been classified and discussed for the past two decades. The main purpose of this research was to identify issues of research at base flow and to identify lesser and overlooked issues in country research. The articles reviewed in this research were analyzed based on spatial domain, research method, theory, data analysis techniques and topic. Results showed that research orientation in base flow in Iran can be divided into four general categories; 28.21% of studies related to applied orientation; 37.18% to comparison and introduction of proper baseflow separation method; 19.23% to investigation of factors affecting base flow and 15.38% to general use and description of hydrological conditions of the study area. The overall conclusion, indicates limited studies, lack of innovative, and focus on the use of conventional and repetitive methods and also lack of attention to this issue by scientific and research centers of the country.
Saeedeh Nateghi; Elham Rafiiei sardooi; Ali Azareh; Farshad Soleimani Sardoo
Abstract
Changes in water cycles in different parts of the world is one of the effects of climate change in recent decades. Evapotranspiration, as the part of the hydrological cycle, will also undergo these changes. Therefore, in the present study, the effect of climate change on potential evapotranspiration ...
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Changes in water cycles in different parts of the world is one of the effects of climate change in recent decades. Evapotranspiration, as the part of the hydrological cycle, will also undergo these changes. Therefore, in the present study, the effect of climate change on potential evapotranspiration changes in Halilrood Watershed, under RCP2.6, RCP 4.5 and RCP 8.5 scenarios using LARS-WG downscaling model and the output of the general circulation model of HadGEM2 in future (2021-2040) was studied and the rate of evapotranspiration at the basin scale was calculated based on the predicted climatic parameters using Tornthwaite method in future. According to the results of the LARS-WG model, in the study area, precipitation will decrease and the temperature will increase under all scenarios in future compared to the baseline period. Evapotranspiration will also increase based on the predicted temperature and precipitation. So that, at the basin scale, evapotranspiration will increase by 3.4, 6.8 and 8.5 under RCP 2.6, RCP 4.5 and RCP 8.5 scenarios in future (2040-2021), respectively. According to the results, the highest increase in temperature and evapotranspiration and the highest decrease in precipitation at the basin scale is related to the RCP 8.5 scenario. The results of this study can be used in studies related to water resources management, agricultural and environmental studies.
Sima Rahimi Bondarabadi; Saeed Jahanbakhsh; Behrooz Sari Saraf
Abstract
Any change in the concentration of greenhouse gases will upset the balance between the components of the climate system. But, the change in the concentration of these gases and how they will affect in the future is unknown. To study the effects of climate change on different systems in the future, climate ...
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Any change in the concentration of greenhouse gases will upset the balance between the components of the climate system. But, the change in the concentration of these gases and how they will affect in the future is unknown. To study the effects of climate change on different systems in the future, climate variables must first be simulated under changes in greenhouse gases (climate scenarios). There are several ways to do this, the most reliable of which is the use of climatic models. AOGCMs can simulate climate parameters globally in large scale, while these may not be suitable for small scales. One of the most important downscaling methods is dynamic methods that are based on increasing the resolution and analysis of planetary climate models. Here, in this research, climate change status in Karkheh River Basin where a major basin for water and agricultural yields is studied. For this purpose, the PRECIS model was used. PRECIS is an exponential dynamics downscaling model used to estimate the temperature and precipitation rates for the period of 2070 to 2100 under A2 and B2 scenarios. According to the results of climate change assessment under scenario A2, precipitation would increase up to 11% and up to five degree centigrade would rise in average maximum and minimum temperature while concerning B2 scenario, an increase in precipitation up to 7% and a rise in temperature rise up to three degree centigrade are estimated. However, under both the scenarios, despite, the fall’s precipitation is higher than the winter’s precipitation.
Sima Rahimi Bondarabadi
Abstract
Increasing the greenhouse gases not only has impacts on the weather parameters, but also, has impact on water resources, agriculture, environment, health and economy. Climate change has significant effects on water resources by changing the hydrological cycle. There are several simulation methods for ...
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Increasing the greenhouse gases not only has impacts on the weather parameters, but also, has impact on water resources, agriculture, environment, health and economy. Climate change has significant effects on water resources by changing the hydrological cycle. There are several simulation methods for investigating the effects of climate change on different systems in the future, like climate models. The AOGCM model is able to simulate global climate in an area of some ten dousant km2, but, while they are not suitable for regional scale. For this reason, downscaling methods such as dynamic methods are used. These methods are based on high resolution and analysis of climate models. In this research, the impact of climate change was investigated on the low flow of Karkheh Basin as one the most important basins due to its water product and agricultural point of view. For this purpose, the PRECIS which is exponential dynamics and downscaling model, was used to estimate the temperature and precipitation in the period of 2070 to 2100 under A2 and B2 scenarios. The SWAT model, a comprehensive and continuous hydrological model was also used to estimate the flow discharge for the watershed. After calibration and validation of the SWAT model, the amount of rainfall and temperature used as input for PRECIS model under different climate scenarios and finally the daily flow rate was estimated for sub-basins. Then the indices of low flow rates (Q75, Q90 and Q95) and low flow series frequency analysis of 10 and 30 days were assessed. Results showed that rainfall and flow rate have negative and temperature have positive trend. In general, the results of PRECIS model indicated that this model has a good estimate of temperature and precipitation in the region, but, it is not strong for rainfall in autumn and spring, due to the local nature of the precipitation. The climate change assessment under scenario A2, indicated the rise of low flow rate by 70 percent, and this increase of low flow was more in the northern parts of basin, while under the scenario B2 the low flow rate droped by 50 percent for the period of 2080. But, low flow distribution had no change compared to base period.Thus, sever droughts would happen in the central and some northern parts of basin. It can be concluded that under different scenarios, climate change has different impact on the low flow rate. Therefore, due to the different impacts of climate change on low flow rate under different scenarios, uncertainties of scenarios as well as regional economic and social status should be considered in the management plans.
Mehdi Ahmadi; Bagher Ghermezcheshmeh
Abstract
In the last decades, greenhouse gases in atmosphere have increased as a result of natural and human activities and thus, earth temperature has increased. Rising global temperature, in turn, leads to significant changes in related fields, especially water resources and agriculture. So, investigating and ...
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In the last decades, greenhouse gases in atmosphere have increased as a result of natural and human activities and thus, earth temperature has increased. Rising global temperature, in turn, leads to significant changes in related fields, especially water resources and agriculture. So, investigating and modeling climate changes can be considered as a very important factor in water resources management planning. Different studies have been done in the field of climate change issues in the world, but, at the moment, AOGCM model is the most reliable tool to generate climate scenarios. It is necessary to downscale AOGCM data using different techniques in station scale and compare linear and nonlinear downscaling models. In liner method SDSM and in nonlinear method ANN programming were used in MATLAB. For investigating the amount of error, mean biomass monthly and annual and for extreme data, variance and for analyzing uncertainty Man-Witney test were used in 95 percent level. Results showed the amount of mean monthly errors are 0.75, 12, 11 and 7 mm in Ghaemshahr, Babolsar, Ghoran Talar and Bandpey in SDSM model and 3, 2, 26 and 4 mm in ANN model and the amount of mean annual errors are 9, 146, 141 and 87 mm in SDSM model and 45, 32, 321 and 48 mm in ANN model (increased or decreased), respectively. Examining the performance of variance showed that ANN model was somewhat better than SDSM model. Also, results of uncertainty for 12 months in Ghaemshar, Babolsar, Quran Talar and Bandpey stations showed 8, 3, 6 and 4 in SDSM model and 4, 2, 2 and 3 in ANN model, respectively. In general, this study showed that in studies on climate change effects on runoff, uncertainty, and when limited data are available, SDSM model should be used and when the aim is investigating the flood and its minimum and maximum estimation, it is better to use ANN model.
Navid Ziaee; Majid Ownegh; Hamid Reza Asgari; Ali Reza Massah Bavani; Abdolrasoul Salman Mahini; Mohsen Hoseinalizadeh
Abstract
The effects of a change in the temperature and particularly precipitation around the world are not well known due to their complexity and spatial variations. In this research, the impacts of climate change on some climatic variables (temperature and precipitation) has been studied in Hableh Roud ...
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The effects of a change in the temperature and particularly precipitation around the world are not well known due to their complexity and spatial variations. In this research, the impacts of climate change on some climatic variables (temperature and precipitation) has been studied in Hableh Roud Basin due to ecological sensitivity and special situation of this area and HadCM3 model data were analyzed using LARS-WG model according to A2, B2 and A1B scenarios. The seasonal variations of precipitation, minimum and maximum temperature of the synoptic stations of Firouzkooh and Garmsar were investigated in two periods of 2030-2011 and 2046-2065. Results showed that precipitation between 0.23 to 0.48 mm will increase in the near future and will decrease between 0.08 to 0.15 mm in the middle future. The minimum temperature will increase between 0.5 to 0.67° C in near future and between 1.54 to 1.97° C for the middle future. Maximum temperature will increase in near future between 0.43 to 0.6° C and between 1.47 to 1.89° C in middle future. Finally, the climatic conditions of the Hableh Roud Basin will have a significant difference compared to current conditions in upcoming periods. Therefore, regarding to this issue, as well as awareness of the direct and indirect negative effects of climate change in the various parts of the basin (agriculture, water resources, environment, natural resources, health, industry and economics), long-term planning and strategic management of new situations is essential.
Razieh Saboohi; Hossein Barani; Morteza Khodagholi; Ahmad Abedi Sarvestani; Asghar Tahmasebi
Abstract
Climate change is one of the most important phenomena in recent years have been affected on natural resources and especially the communities whose livelihoods in relation to natural resources, as well as prediction of climate parameters in order to achieve future changes and regard to adaptations to ...
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Climate change is one of the most important phenomena in recent years have been affected on natural resources and especially the communities whose livelihoods in relation to natural resources, as well as prediction of climate parameters in order to achieve future changes and regard to adaptations to deal with climate change is interest of researchers. Therefore, in this study with purpose of previous trend analysis and prediction of precipitation, mean minimum and maximum temperature were used non-parametric Mann-Kendall test and General Circulation Models, HadCM3, respectively. For this purpose, the output data of HadCM3 with three scenarios A1B, A2 and B1 by LARS-WG model were downscale in Semirom region. The results showed that temperature parameters (mean temperature, mean minimum and mean maximum temperature) had increased trend in winter, autumn seasons and annual scale in six studied stations and temperature parameters showed different trend in spring and summer seasons and the annual precipitation is showed negative trend in most of the stations. Also, the results of minimum temperature prediction showed that minimum temperature will generally increase with three scenarios during 21 century and the largest increase in mean minimum temperature compared to the current period is observed in November with more than 0.8 °C increase. The maximum temperature prediction represents a change in the maximum temperature threshold and warming this century in all months of the year, except January and precipitation will increase in all months except June and September using all three scenarios.
Mehran Zand
Abstract
This research was designed and implemented with the aim of determining the Effectiveness of Reclamation Operations of watershed management implemented by the forest, rangeland and watershed management organization in increasing the carbon sequestration potential of the land and selecting the optimally ...
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This research was designed and implemented with the aim of determining the Effectiveness of Reclamation Operations of watershed management implemented by the forest, rangeland and watershed management organization in increasing the carbon sequestration potential of the land and selecting the optimally implemented patterns. In order to estimate the carbon sequestration of three basins were selected as three sites. Then, samples were weighed and their weighs were identified according to plot in each area and hectare. After that, 10 grams of each sample was transferred to the laboratory and the amount of sequestration was determined per unit area.The Research results show that sample basin of Rimeleh with 2025 kg per ha is the maximum carbon sequestration amount while control sample Abkandari Kohdasht with 122 kg has the minimum carbon sequestration among biological projects.From biological operations. point of view, seeding project with wheat in Rimeleh basic with 1064.56 kg per had the best performance in terms of carbon sequestration and was ranked highest. According to the results of experiments and analysis of data from the study sites, was determined In Bio-mechanical project of flood spreading Rumshkan, that they have been cultivated Eucalyptus species ,Conditions of carbon sequestration are better than the other varieties cultivated in Rimele and Koohdasht and the average rate is 37/31 ton/ha. The amount of soil carbon sequestration from mechanical operations was estimated to be 45.7, 45.4, 78.4, 54.8 ton / ha Respectively for the three catchment basins of Rimla, Rumshkan and Kohdasht, and the average of the control samples was 26 tons per hectare. Finally acccordind to results of this research Flood spreading Rumshkan project with carbon sequestration of almost 78 tons in each hectar is a successful project from carbon sequestration with a correct management and for mechanical and biological operations of watershed.
Ali Koulaian; Mojtaba Khoshravesh; Nima Mohammadigolafshani; Mohammadjavad Mirzaee
Abstract
Nowadays, the impacts of climate change evaluation on watershed hydrological resources is the most important task before any water resources planning. Stream flow trend was analyzed using non parametric Man-Kendall test conducted for 30, 40, 50 and 60 year periods in three, monthly, seasonal and annual ...
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Nowadays, the impacts of climate change evaluation on watershed hydrological resources is the most important task before any water resources planning. Stream flow trend was analyzed using non parametric Man-Kendall test conducted for 30, 40, 50 and 60 year periods in three, monthly, seasonal and annual time-scales and also peak discharge in Mazandaran Province watersheds. Results showed that the increase in Greenhouse gases and consequently climate change influenced severely on river stream flow which led to reduced river stream flows, especially in the eastern parts of the region the trend analysis results showed that most of hydrometric stations had significant downward trend especially in summer season and only they experienced positive trend in winter. It seems that increase in winter season is due to temperature rise and consequently melting of snow which led to increase of base-flow and upward trend during the studied period. Results of peak flow trend analysis showed that upward trend for recent four decades is due to changes in precipitation pattern. The research achievement may considerably help in forecasting the upcoming drought, irrigation planning and water resources management.
Milad Nouri; Mehdi Homaee; Mohammad Bannayan
Abstract
In this study, changes of aridity index (AI), reference evapotranspiration (ET0) and precipitation were investigated in six stations located in the west and northwest of Iran over 1966-2010, 2011-2040, 2041-2070 and 2071-2100 periods. The outputs of HadCM3 under A2 and B2 emission scenarios were downscaled ...
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In this study, changes of aridity index (AI), reference evapotranspiration (ET0) and precipitation were investigated in six stations located in the west and northwest of Iran over 1966-2010, 2011-2040, 2041-2070 and 2071-2100 periods. The outputs of HadCM3 under A2 and B2 emission scenarios were downscaled using statistical downscaling approach by Statistical downscaling model (SDSM). Mann-Kendall trend test was applied to assess the significance of trends of aridity index, reference evapotranspiration and precipitation in 1966-2010. The results of Mann-Kendall test revealed that there was a significant decreasing trend in AI and precipitation at the level of 95% over 1966-2010 in most of the surveyed stations. The negative trends of AI during winter, spring, summer and autumn were significant at five, four, zero and two of six surveyed stations, respectively. This indicates that reduced wintertime aridity index plays an important role in downward trend of annual aridity index in the studied area. The results also showed that AI, averaged across all stations, would decline by 8.0, 14.7 and 34.3% under A2 and 12.6, 12.5 and 20.1% under B2 over the early, middle and late 21st century relative to the baseline period (1966-2010), respectively, indicating a drier climate in northwest and west of country over the 21st century. On seasonal scale, the greatest decrease of AI is expected in summertime under A2 and springtime under B2 over the 21st century. AI, averaged over all stations, will most likely approach 0.2 indicating a severe reduction of aridity index in the studied area under A2. In some regions such as Tabriz, increased ET0 and decline of precipitation will cause a shift from semi-arid to arid climatic condition over the 21st century.
Bagher Ghermezcheshmeh; Aliakbar Rasuli; Majid Rezaei-Banafsheh; Alireza Massah; Alimohammad Khorshiddoost
Abstract
In the statistical downscaling methods which is based on the relationship between AOGCMs data and ground based climatic variables (such as rain and temperature), the future period of those variables are simulated. Since in the simulation, all effective parameters cannot be modeled, estimated values suffers ...
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In the statistical downscaling methods which is based on the relationship between AOGCMs data and ground based climatic variables (such as rain and temperature), the future period of those variables are simulated. Since in the simulation, all effective parameters cannot be modeled, estimated values suffers from be uncertainty. The outputs of downscaling models are used as inputs to agriculture and water resources models; therefore, identifying the models inputs’ error or uncertainty is essential to realize the reliability of obtained results. In this research, an attempt is made to investigate the uncertainty of Artificial Neural Network (ANN) as a downscaling model in a case study in the northwest of Iran. For this purpose, precipitation, minimum and maximum temperature variables were used in the designed ANN model, and the NCEP data was employed for its calibration and validation. The HadCM3 was the selected AOGCM in this study. Observed daily time series were gathered at all stations in the study period and on the basis of bootstrap method the 99% confidence interval was calculated for all the variables. In the next step, the simulated (downscaled) mean and variance of the variables by the ANN model, compared to the calculated confidence interval. To compare the results, the criterion of the number of station-month was used. The results showed that the average maximum temperature at 14 station-months were within the confidence interval. The results of monthly analysis showed that the accuracy of ANN model in summer was low and its uncertainty is more than the other seasons. In the simulation of minimum temperature based on this criterion, 18 station-months were within the confidence interval. The accuracy of ANN to estimate the minimum temperature in summer was low with high uncertainty in almost all the stations. Moreover, in June and August in any of the stations estimated values were not within the confidence interval. Due to the high variability of rainfall in relation to temperature, confidence range was very high, and in some stations was more than 50% of average monthly precipitation. Because of the high confidence rang of precipitation, in 53 Stations-month cases were within the confidence interval.
Bagher Ghermezcheshmeh; Aliakbar Rasuli; Majid Rezaei Banafsheh; Alireza Massah Bovani; Alimohammad Khorshiddust
Abstract
Increasing Green House Gases (GHG) may change the climate in different areas. Investigation of parameters are difficult due to induced changes in climate parameters, such as precipitation and temperature. For predicting global climate change, different climate scenarios are defined, using AOGCM models. ...
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Increasing Green House Gases (GHG) may change the climate in different areas. Investigation of parameters are difficult due to induced changes in climate parameters, such as precipitation and temperature. For predicting global climate change, different climate scenarios are defined, using AOGCM models. AOGCMs are able to simulate global atmospheric circulation patterns. However, the spatial resolutions of such models are coarse; for example HadCM3 has spatial resolutions of 3.75 and 2.5 in longitude and latitude, respectively. Therefore, to study climate change in a given area, the outputs of the used AOGCMs must be downscaled properly. For this reason, statistical and dynamical methods have been developed. Statistical methods establish a relationship between AOGCM outputs and climate parameters such as precipitation and temperature. For example, many statistical methods use multiple regressions to predict future climate parameters. However, the accuracy of downscaling procedure varies depending on the geographical position of the studied station in relative to the nearby AOGCM grids. In this research, the accuracy of SDSM was tested in different synoptic stations of northwest Iran. This area has a complex topography and climate due to intrusion of different rain bearing weather systems to the region. First of all, daily climate data (precipitation, maximum and minimum temperature) were collected and their time series created. HadCM3 data for the girds over the studied area was obtained and SDSM model was applied for each climate parameters of all synoptic stations in the region. Then, the difference between the SDSM outputs and observed parameters were evaluated for all the stations and the performance of the downscaled outputs were evaluated by comparing the mean and variance of the model outputs and those of the NCEP/NCAR for the present climate. The morpho-climatic parameters were derived for each station and their relations with the magnitude of the model error were evaluated. Results showed that the error in precipitation has significant relation with the distance to the grid center, whereas the error in maximum temperature is related to the difference between the elevation of a given station and the mean elevation of the HadCM3 grids. For example, in Urmia station, the error is the highest of 104 mm while in Saqez the error is the lowest of 9.4 mm. Also, the maximum temperature accuracy in stations with elevation near to mean elevation of the grid is higher. Pars Abad station with 32 m elevation and with high elevation difference with the grid mean elevation, showed 1.14 ºC of error and Tabriz station with less elevation difference to grid mean elevation, showed 0.0.08 ºC of error.
Zahra Jaberalansar; Morteza Khodagholi; Masoud Borhany; Hossein Arzani
Abstract
Rangeland ecosystems in semi-arid regions are vulnerable systems to climatic changes specially precipitation. In such conditions droughts are predictable. In this study the relationship between rangeland production and spatial and temporal changes of precipitation was investigated. Therefore, rangeland ...
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Rangeland ecosystems in semi-arid regions are vulnerable systems to climatic changes specially precipitation. In such conditions droughts are predictable. In this study the relationship between rangeland production and spatial and temporal changes of precipitation was investigated. Therefore, rangeland production through 10 years data set (1377-1387) in steppic bioclimatic of Esfahan province (Alavije, Muteh, Kalahrood and Gardaneshadian) using Standard Precipitation Index (SPI), the relationship between SPI series of 3, 5 and 8 month time scales, and rangeland production of 10 years. Thus Anova and correlation matrix between production and SPI factors were formed. Results indicated that the most severe drought has occurred in 1387 simultaneously, with the least production. A harmony between change trend of production and SPI in the sites showed that in most cases maximum and minimum production have occurred simultaneously with maximum and minimum of SPI series. Also, the production correlated with SPI series of three, five and eight months' time scales with correlation coefficients more than 63 percent which were significant in 1% and 5% level. Due to efficacy of production from spring precipitation and soil depth less than 30 cm in the sites, it is proposed to use SPI series of three months scale to evaluate drought in similar rangelands.
